System Designing

Post Graduate Diploma in Piping Design

Semester I

System Designing

This book is a part of the course by uts, Pune.This book contains the course content for System Designing.

© uts, PuneFirst Edition 2011

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Website : www.utsglobal.edu.inTel : +91-20-41034800, +91 9011067684

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Index

Content .................................................................................................................................................................. IIList of Figures ....................................................................................................................................................... VList of Tables ........................................................................................................................................................VIAbbreviations ......................................................................................................................................................VIICase Study ......................................................................................................................................................... 131Bibliography ...................................................................................................................................................... 135Self Assessment Answers ................................................................................................................................... 138Book at a Glance

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Contents

Chapter I ....................................................................................................................................................... 1Role of Piping Engineering and Needs of Various Process Industries .................................................... 1Aim ................................................................................................................................................................ 1Objectives ...................................................................................................................................................... 1Learning outcome .......................................................................................................................................... 11.1 Introduction .............................................................................................................................................. 21.2 Piping Design ........................................................................................................................................... 31.3 Piping Engineering ................................................................................................................................... 31.4 Piping Engineer: Roles and Responsibilities ........................................................................................... 31.5 Design Planning ....................................................................................................................................... 41.6 Basic Engineering Documents ................................................................................................................ 41.7 Detailed Engineering Documents ............................................................................................................ 71.8 Miscellaneous Documents ....................................................................................................................... 71.9 Review of P and IDs ................................................................................................................................ 81.10 Review of Other Documents .................................................................................................................. 91.11 Pipe Stress Analysis ............................................................................................................................ 101.12 Piping Designing Tools ........................................................................................................................ 13Summary ..................................................................................................................................................... 17References ................................................................................................................................................... 17Recommended Reading ............................................................................................................................. 17Self Assessment ........................................................................................................................................... 18

Chapter II ................................................................................................................................................... 20Interdepartmental Interactions and Plot Plan ........................................................................................ 20Aim .............................................................................................................................................................. 20Objectives .................................................................................................................................................... 20Learning outcome ........................................................................................................................................ 202.1 Introduction ............................................................................................................................................ 212.2 Information Sharing ............................................................................................................................... 212.3 Stages of Data Generation .................................................................................................................... 222.4 Nature of Problems in Interface Areas ................................................................................................... 232.5 Mitigation of the Problems in Interface Areas ....................................................................................... 242.6 Guidelines for Plot Plan ........................................................................................................................ 252.7 Criteria for Facility Location ................................................................................................................. 31Summary ..................................................................................................................................................... 33References ................................................................................................................................................... 33Recommended Reading ............................................................................................................................. 33Self Assessment ........................................................................................................................................... 34

Chapter III ................................................................................................................................................. 36Process Piping and Instrumentation Diagram (P and ID) ..................................................................... 36Aim .............................................................................................................................................................. 36Objectives .................................................................................................................................................... 36Learning outcome ........................................................................................................................................ 363.1 Introduction ............................................................................................................................................ 373.2 Piping and Instrumentation Diagram (P and ID) .................................................................................. 37 3.2.1 Operation ............................................................................................................................... 37 3.2.2 Start-Up .................................................................................................................................. 38 3.2.3 Maintenance ........................................................................................................................... 38 3.2.4 Safety ..................................................................................................................................... 38 3.2.5 Aesthetics ............................................................................................................................... 393.3 Process P and ID Preparation ................................................................................................................. 393.4 Basic Instrument Symbols ..................................................................................................................... 42

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Summary .................................................................................................................................................... 48References ................................................................................................................................................... 48Recommended Reading ............................................................................................................................. 48Self Assessment ........................................................................................................................................... 49

Chapter IV .................................................................................................................................................. 51Steam Tables and Mollier Diagram .......................................................................................................... 51Aim .............................................................................................................................................................. 51Objectives .................................................................................................................................................... 51Learning outcome ........................................................................................................................................ 514.1 Introduction ............................................................................................................................................ 524.2 Steam: Formation and Properties ........................................................................................................... 52 4.2.1 Formation of Steam ............................................................................................................... 52 4.2.2 Properties of Steam ................................................................................................................ 534.3 Steam Tables .......................................................................................................................................... 534.4 Mollier Diagram ..................................................................................................................................... 56 4.4.1 Dryness Fraction Lines .......................................................................................................... 56 4.4.2 Constant Specific Volume Lines ............................................................................................ 56 4.4.3 Constant Pressure Lines ......................................................................................................... 56 4.4.4 Constant Temperature Lines .................................................................................................. 564.5 Piping for Steam Distribution ................................................................................................................ 574.6 Heating Media ........................................................................................................................................ 63 4.6.1 Steam Utilisation in the Large Complex ................................................................................ 64 4.6.2 Steam Quality ........................................................................................................................ 654.7 Selection of Steam Pressures ................................................................................................................. 694.8 Pressure Drop Factor ............................................................................................................................. 694.9 Steam Pipe Sizing and Design .............................................................................................................. 704.10 Thermal Insulation ............................................................................................................................... 72Summary .................................................................................................................................................... 75References ................................................................................................................................................... 75Recommended Reading ............................................................................................................................. 75Self Assessment ........................................................................................................................................... 76

Chapter V .................................................................................................................................................... 78Slurry Piping Systems................................................................................................................................ 78Aim .............................................................................................................................................................. 78Objectives .................................................................................................................................................... 78Learning outcome ........................................................................................................................................ 785.1 Introduction ............................................................................................................................................ 795.2 Slurry Piping Systems ............................................................................................................................ 795.3 Line Sizing and Pressure Drop .............................................................................................................. 805.4 Special Considerations ........................................................................................................................... 845.5 Pump for Slurry...................................................................................................................................... 855.6 Instrumentation ...................................................................................................................................... 87Summary ..................................................................................................................................................... 88References ................................................................................................................................................... 88Recommended Reading ............................................................................................................................. 88Self Assessment ........................................................................................................................................... 89

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Chapter VI .................................................................................................................................................. 91Pumps .......................................................................................................................................................... 91Aim .............................................................................................................................................................. 91Objectives .................................................................................................................................................... 91Learning outcome ........................................................................................................................................ 916.1 Introduction ............................................................................................................................................ 926.2 Centrifugal Pumps ................................................................................................................................. 926.3 Applications of Centrifugal Pump ......................................................................................................... 936.4 Calculation of Flow Required ................................................................................................................ 946.5 Calculation of Pump Head ..................................................................................................................... 956.6 Classification of Centrifugal Pump ........................................................................................................ 966.7 Specific Speed ........................................................................................................................................ 966.8 Power and Efficiency ............................................................................................................................ 976.9 Shut in Pressure...................................................................................................................................... 996.10 Expanding the Pump Capacity ............................................................................................................. 996.11 Importance of Low Discharge Flow .................................................................................................. 1006.12 NPSH (Net Positive Suction Head) ................................................................................................... 1016.13 Importance of Low NPSH ................................................................................................................. 1046.14 Pump Safety Tips ............................................................................................................................... 104Summary ................................................................................................................................................... 106References ................................................................................................................................................. 106Recommended Reading ........................................................................................................................... 106Self Assessment ......................................................................................................................................... 107

Chapter VII .............................................................................................................................................. 109Pneumatic Conveying Terms CEMA Standard No. 805....................................................................... 109Aim ............................................................................................................................................................ 109Objectives .................................................................................................................................................. 109Learning outcome ...................................................................................................................................... 1097.1 Introduction ...........................................................................................................................................1107.2 List of Pneumatic Conveying Terms .....................................................................................................1107.3 Material Characterisation ......................................................................................................................1117.4 Basic Terms and Definitions .................................................................................................................115Summary ....................................................................................................................................................117References ..................................................................................................................................................117Recommended Reading ............................................................................................................................117Self Assessment ..........................................................................................................................................118

Chapter VIII ............................................................................................................................................. 120Cross – Country Pipe – Line ................................................................................................................... 120Aim ............................................................................................................................................................ 120Objectives .................................................................................................................................................. 120Learning outcome ...................................................................................................................................... 1208.1 Introduction .......................................................................................................................................... 1218.2 Pipeline System .................................................................................................................................... 1218.3 Limitations of Modes of Transport ...................................................................................................... 1228.4 Advantages and Disadvantages of Cross-Country Pipe-Lines ............................................................. 1228.5 Preliminary Work for a Cross-Country Pipe-Line Project ................................................................... 1238.6 Salient Steps in Detail Engineering ..................................................................................................... 127Summary ................................................................................................................................................... 128References ................................................................................................................................................. 128Recommended Reading ........................................................................................................................... 128Self Assessment ......................................................................................................................................... 129

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List of Figures

Fig. 1.1 Large-scale piping system ............................................................................................................... 2Fig. 1.2 Piping engineering factors ................................................................................................................ 4Fig. 1.3 Process of piping system design ....................................................................................................... 9Fig. 1.4 Object diagram of piping system .................................................................................................... 10Fig. 1.5 Stress-strain curve ............................................................................................................................11Fig. 1.6 Stress analysis tool.......................................................................................................................... 15Fig. 1.7 Routing process of main pipes ........................................................................................................ 16Fig. 2.1 Interaction between different departments in an industry .............................................................. 21Fig. 2.2 Data transfer from piping to other departments / clients / agencies ............................................... 23Fig. 2.3 Plot plan .......................................................................................................................................... 26Fig. 2.4 Plot plan and road ........................................................................................................................... 27Fig. 2.5 Location map of project site .......................................................................................................... 29Fig. 2.6 A typical plot plan drawing ............................................................................................................. 30Fig. 3.1 Process and instrument symbols ..................................................................................................... 42Fig. 3.2 Process and instrument symbols (continued) ................................................................................. 43Fig. 3.3 Process and instrument symbols (continued) ................................................................................. 44Fig. 3.4 Use of P and ID symbols ................................................................................................................ 45Fig. 3.5 Tag descriptors ................................................................................................................................ 45Fig. 3.6 Tag numbers .................................................................................................................................... 46Fig. 3.7 Process flow diagram (PFD) ........................................................................................................... 47Fig. 4.1 Mollier diagram .............................................................................................................................. 57Fig. 4.2 Resistance of valves and fittings to flow of fluids .......................................................................... 59Fig. 4.3 Recommended take-off point with branch drainage ....................................................................... 60Fig. 4.4 Drain and vent ................................................................................................................................ 61Fig. 4.5 Relaying to higher level .................................................................................................................. 61Fig. 4.6 Ineffective and proper drainage point ............................................................................................. 62Fig. 4.7 Steam line reducer .......................................................................................................................... 62Fig. 4.8 Automatic air vent located opposite the steam inlet on the jacketed pan ....................................... 67Fig. 4.9 Steam separator ............................................................................................................................... 68Fig. 4.10 Pressure reducing valve ................................................................................................................ 69Fig. 4.11 Pressure drop in stream pipes ....................................................................................................... 70Fig. 5.1 A typical graph for slurry specific gravity ...................................................................................... 81Fig. 5.2 A typical graph to calculate NRec .................................................................................................. 82Fig. 5.3 Slope of line .................................................................................................................................... 84Fig. 5.4 Wear Prone Zone ............................................................................................................................ 84Fig. 5.5 Centrifugal pump ............................................................................................................................ 85Fig. 5.6 Piston and plunger pump ................................................................................................................ 86Fig. 6.1 Liquid flow path inside a centrifugal pump .................................................................................... 92Fig. 6.2 Components of centrifugal pump ................................................................................................... 93Fig. 6.3 Efficiency relative to different blade shapes .................................................................................. 97Fig. 6.4 Types of impeller ............................................................................................................................ 98Fig. 6.5 Shut in pressure .............................................................................................................................. 99Fig. 6.6 Low discharge flow ...................................................................................................................... 101Fig. 6.7 Effect of NPSH on pump .............................................................................................................. 102Fig. 6.8 NPSH ........................................................................................................................................... 103Fig. 6.9 Design of vortex braker ............................................................................................................... 104Fig. 8.1 Typical mode-wise transportation of petroleum products ............................................................ 121Fig. 8.2 Modes of transportation of petroleum-A comparison ................................................................... 122Fig. 8.3 Product transportation ................................................................................................................... 124

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List of Tables

Table 2.1 L:B ratios and actual area relationship ......................................................................................... 28Table 3.1 Major steps for the preparation of any process P and ID ............................................................. 39Table 3.2 Details of the documents for preparation of P and ID .................................................................. 41Table 4.1 Example of saturated water and steam (temperature) table ......................................................... 54Table 4.2 Saturated water and steam (pressure) tables ................................................................................ 55Table 4.3 Approximations of equivalent length of fittings .......................................................................... 58Table 4.4 Steam pipe sizing (carrying capacity in kg/h) .............................................................................. 63Table 4.5 Comparison of heating media with steam .................................................................................... 65Table 4.6 Pipe NB according to different surface temperatures .................................................................. 73Table 4.7 Heat loss from fluid inside pipe (W/m)........................................................................................ 73Table 6.1 Different types of impellers and their rotative speed ................................................................... 97Table 6.2 Multiplication factor and absorbed power for pump motor ......................................................... 98Table 7.1 The individual particle shape descriptions ..................................................................................112Table 7.2 The general compositions found in a bulk material ....................................................................113

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Abbreviations

ACFM - Actual Cubic Feet per MinuteAPI - Active Pharmaceutical IngredientsBHP - Brake HorsepowerBOM - Bill of Materials CEMA - Conveyor Equipment Manufacturers AssociationDG - Diesel GeneratingETP - EffluentTreatmentPlantFAD - Free Air DeliveredHAZOP - Hazard and OperabilityHVAC - Heating, Ventilating and Air ConditioningICFM - Inlet Cubic Feet per MinuteMCC - Motor Control CenterMTO - Material Take Off NB - Nominal BoreNPSH - Net Positive Suction Head NPSHa - Available NPSHP & IDs - Piping and Instrumentation Diagrams PCC - Power Control CenterPFD - Process Flow DiagramROW - Right of WaySCFM - Standard Cubic Feet per MinuteUFD - Utility Flow Diagram WHP - Water Horsepower

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Chapter I

Role of Piping Engineering and Needs of Various Process Industries

Aim

The aim of this chapter is to:

definepipingsystem•

explain concept of piping engineering•

illustrate the role of piping engineers•

Objectives

The objectives of this chapter are to:

describe the pipe stress analysis•

explain the piping designing tools•

state the advantages of system designing software•

Learning outcome

At the end of this chapter, the students will be able to:

examine various statutory bodies involved in piping system design•

analyse the stress analysis process•

describe the documents in piping system design•

System Designing

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1.1 IntroductionPiping is an asset for any project. Piping is a system of pipes (hollow, cylindrical tubes) used to pass on liquids, gases and other materials often under pressure and thermal loads, from one location to another within industrial facilities such as petroleumrefineries, chemical and petrochemical manufacturing, natural gas processing, electricity-generating power plants and many others.

Industrial plant piping and the accompanying in-line components can be manufactured from various steel alloys, titanium, aluminium, copper, glass or various plastics. These in-line components are known as fittings and valves. Process control systems use in-line sensors and control valves installed in the piping to monitor and regulate the desired temperatures, pressures, flow rates andprocessvessel liquid levels of thefluidsbeing transported andprocessed. Piping and control systems are referred to as piping and instrumentation diagrams.

Fig. 1.1 Large-scale piping system (Source: http://www.equityeng.com/piping.php)

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1.2 Piping DesignPiping system includes:•

pipe �fittings(e.g.elbows,reducers,branchconnections,etc.) �flanges,gaskets,bolting �valves �pipe supports �

Theroutingandlayoutofthepipesfittingsinacomplexpipingsystemisknownaspipingsystemdesign.This•is typically done by experienced piping draftsmen known as piping designers. Piping system design constitutes a major part of the design and engineering effort in any facility. The discipline •of piping design requires good technical skills such as:

the principles and practice of drafting and creating isometric drawings �familiarity and experience with computerised drafting programs �the ability to visualise and develop an industrial facility plot plan �abasicunderstandingoffluidflow,pipingmaterialsandpipingspecifications �an extensive knowledge of piping standards and codes as well as process safety codes and practices �aknowledgeofthevarioustypesofpipeconnectionssuchasthreaded,weldedandflangedconnections �a knowledge of the various types of valves and their use �a good understanding of pipe stress analysis �

1.3 Piping EngineeringPiping engineering is a specialised branch of engineering dealing with design & layouts of piping network •along with the equipments in a process plant. These layouts form a complete blue print of the plant & are used for plant construction at site. The most important factors to be considered are process requirements, safety, operations, maintenance, compliance •with statutory requirements & economy.

1.4 Piping Engineer: Roles and ResponsibilitiesA piping engineer is a mechanical engineer who specialises in disciplines which deal with the design, planning and installation of various plumbing and piping systems for a wide variety of industries. The responsibilities of piping design engineer begins with:

preparationofplotplan,equipmentlayoutspipingstudies,pipingspecification•review of process package•giving inputs to civil, vessel, electrical or instrumentation groups for various purposes•

Goes through:preparation of piping layouts, isometrics, support drawings•stress analysis•procurement assistance•preparation of drawings for statutory approvals•preview of vendor drawings•coordination with various engineering groups & site•

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Ends with:completion & commissioning of plant•

Process Equipments

Operations

Safety

Economy

Statutory requirements

Process Package

Plant Designs and Layout

Maintainence

Piping Engineering

Fig. 1.2 Piping engineering factors

1.5 Design PlanningFollowing information is required for planning the various design activities:

contract instructions •project design basis & scope of work•basic engineering documents•site design data including facilities around the plot•contour & survey drawing•applicable codes, standards & statutory regulations•project schedule & network•

1.6 Basic Engineering Documents The main documents covered by design engineer are:Equipment layout

These include the documents showing layout of all equipments satisfying the process requirements, safety & •statutory regulations, operations, ease of maintenance and economy.

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Equipment layout including tanks, vessels, process pumps and other rotating machinery, must show the •following:

package items �pipe racks �electrical & instrument cable trays �control rooms �A/C ducting �offices&maintenanceareas �buildingfeaturesincludingcolumns,beams,walls,flooropenings,staircases,passagesetc � .show tube removal space for heat exchangers �show monorails lifting bays & hoists etc. �

Consideration must be given to the following while•developing equipment layouts �process requirements �operations & maintenance requirements �hazardousareaclassification �safety requirements �factory inspector’s requirements �civil requirements �erection / dismantling requirements �future provisions �

Piping layoutsTheseincludedocumentsshowinglayoutsofpipingnetworktocarryfluidsfromoneequipmenttoanotherin•a process plant.Piping layouts is required by site for construction to prepare isometrics.•Pipinglayoutsmustconsiderprocessrequirements,operationsandmaintenancerequirements,areaclassification,•safety requirements, factory inspector’s requirements, civil requirements, erection or dismantling requirements, future provisions etc.Document required while developing piping layout are:•

equipment layouts �process piping and instrumentation diagrams (P & IDs) �utility piping and instrumentation diagrams (P & IDs) �line designation list �pipingspecification �equipment data sheets or vendor drawings �civil drawings �inline instrument details �insulation requirements �

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Following points should be kept in mind while developing piping layouts •process requirements, e.g. slopes, vents & drains, barometric leg for vacuum lines �instrumentrequirementse.g.straightlengthforflowmeasurement �location of control valves, safety valves �safety requirements �operations & maintenance �accessibility �service stations, safety showers �

Plot planItincludesarrangingallplantunitsinalogicalmannertotakecareofmaterialflow,statutoryrequirementsandgood engineering practices.

Plot plan shows overall areas & locates the co-ordinates of:•process unit �raw material storages �finishedproductstorage �utility generation areas �pipe racks �electrical receiving and distribution substation �facility blocks e.g. work shop ,weigh bridge, canteen �administration lock, security, car or lorry park etc. �flaresystem �effluenttreatment �green belt �future requirements etc. �

Following documents are required to develop the plot plan:•plot boundary and contour survey �access by transportation modes (road, rail ) �incoming utilities e.g. electrical, power, water �feed stock etc. �wind direction �facilities around the plot etc. �

The following factors should be kept in mind while developing the plot plan:•Statutory requirements, e.g. factory inspector, chief controller explosives, tariff advisory committee, pollution �board,localbodies,aviationauthorities,hazardousareaclassification.sitecontour,drainage,effluentdisposal,plantroads,spaceforpiperack,undergroundlinesetc. �process & clients requirements �material movement & workers management �

The following should be ensured while developing the plot plan:•utilities are closer to process plant to cut down the length of pipes & cable racks �rawmaterialandfinishedproductwarehouseareclosertoaccessroadorrail �utility areas are kept near to each other as utility operators are common �wind direction is taken care of while locating chimneys cooling tower etc. �effluentdisposalistowardsnaturalplotgradient �hazardous tank ages are at safe distance from process plant �

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Pipe rack study sketchesThese are prepared taking into account requirements of piping, electrical & instrument cable trays to be routed between various plant areas. These documents are used by civil, piping, electrical and instrument group to prepare detailed construction drawings.

Study piping layoutsThese are prepared to show routing of critical process lines which could affect functioning of plant. This document is reviewed by process licensor and forms basis of detailed piping layout drawings.

Piping specificationsThese documents specify in detail all piping items required for the plant. Various piping items required for a particular dutycondition,dependingontypeoffluidsuchaslinepressureandtemperature,arelistedunderonespecificationclass.

Utilityflowdiagram(UFD)•This document is similar to P&ID’s•Prepared based on utility summary•Prepared based on utility summery furnished by process group•Shows utility generation and distribution in the plant.•

Line numbering and line listAll process and utility lines appearing in P&IDs and UFDs are given unique serial numbers on these documents. The operating, design and test conditions, insulation and painting requirements are listed on line list.

Critical line listAll line requiring stress or vibration analysis etc. are listed in this document.

1.7 Detailed Engineering DocumentsThese mainly cover the following documents:

piping layouts drawings•material take off (MTO) or bill of materials (BOM) for piping items•nozzle orientation for fabricated equipments•stress analysis•piping isometric drawings•piping support drawings•firefightingspecification•drawings for statuary approvals•

1.8 Miscellaneous DocumentsThese mainly cover the following documents:

review of drawings for machinery & other brought-outs•review of drawings for special piping items•specificationsforbellows,spring,hangersetc.•specificationforinsulationandpaintingofequipments&pipingitems•updating of P&IDs based on detailed engineering•scheme for the erection of equipments in consultation with site engineer•

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1.9 Review of P and IDsA piping and instrumentation diagram (P and ID) is a schematic illustration of functional relationship of piping, •instrumentation and system equipment components. P and ID shows all of piping including the physical sequence of branches, reducers, valves, equipment, •instrumentation and control interlocks. The P and IDs are used to operate the process system. •Following information should be available in P and IDs:•

legends, notes, abbreviations �locationofchangeinpipingspecification �specificrequirementslikeslope,elevationdifference,minimumrunninglength,processdrainsandvents �type of heating (jacketing, steam or electric heating) �proper symbols for piping items �equipments and nozzle numbers �all instrumentation and control valves �continuation sheet numbers �instrumentation and designations �mechanical equipment with names and numbers �allvalvesandtheiridentifications �processpiping,sizesandidentification �miscellaneous-vents,drains,specialfittings,samplinglines �permanentstart-upandflushlines �flowdirections �interconnection references �control inputs and outputs, interlocks �interfaces for class changes �seismic category �quality level �computer control system input �vendor and contractor interfaces �identificationofcomponentsandsubsystemsdeliveredbyothers �intended physical sequence of the equipment �

A P and ID should not include:•instrument root valves �control relays �manual switches �equipment rating or capacity �primary instrument tubing and valves �pressuretemperatureandflowdata �elbow,teesandsimilarstandardfittings �extensive explanatory notes �

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1.10 Review of Other DocumentsThese include:

Utility summary• : This document reflectsthevariousutilitiesconsumedbyeachoftheequipmentwithconditionslikepressure,temperate,flow,stateoffluidandcriticalfactorlikefreezingpointetc.Conceptual equipment layouts• : This document gives the general arrangement of the equipments considering the process requirements like inter-distances and approximate elevations of the equipments.Piping material specification• :Basicmaterialforpipingitems,valvespecifications,specialflanges&gasketsrequired etc.Type of storage required• :Thisdocumentshallmentionthestateofthefluidandtypeofequipmentstobeusedforthestoragelikeactivepharmaceuticalingredients(API)tank,dehumidifiedatmosphere(warehouse)etc.Hazard classification• :Thisdocumentmentionsthetypeofhazardforthefluidsbeinghandled(e.g.classa/b/c,flammabilitytoxicityetc.)andthespecialprecautionstobetakencareof.Future expansion requirements• : These are to be mentioned by the client and to be taken care for the space requirement during the layout stage.

Design Modification

Building Spec.

System Design

Hull Structure Information

Production/ Installation Technology

Empirical Knowledge

Maritime Regulation

OutfittingInformation

3-D Modeling

2-D Drawing

2-D Arrangement

Drawing

Production DrawingDetail DesignFunctional

DesignBasic Design

Production Design

3-D Model

Design Modification

DesignModification

Fig. 1.3 Process of piping system design(Source: http://icad.kaist.ac.kr/~msh/ARS/cad-ars.htm)

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Piping_Systems

Equipments

Connectors Points

Pipe_Routes

Catalogs Piping_Components

Pipe_Lines

Aux_Piping_Systems Main_Piping_Systems

Str_pipes

Valves

Elbows

Reducers

Flanges

Sleeve_Joints

Loops

Sliding-Joints

a_kind_of

reference_to

reference_to

consist_of consist_of

consist_of

consist_of

connected_with

connected_with

reference_to

reference_to

reference_toreference_toreference_to

a_kind_of

Fig. 1.4 Object diagram of piping system(Source: http://icad.kaist.ac.kr/~msh/ARS/cad-ars.htm)

1.11 Pipe Stress Analysis Stress of a material is the internal resistance per unit area to the deformation caused by applied load.•Strain is the unit deformation under applied load.•Stress• – strain curve is a curve in which unit load or stress is plotted against unit elongation, technically known as strain.

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O – A represents the stress is directly proportional to strain, and point A is known as � proportional limit.Point B represents � elastic limit beyond which the material will not return to its original shape when unloaded but will retain a permanent deformation called permanent set.Point C is called � yield point and is the point at which there is an appreciable elongation or yielding of the material without any corresponding increases of load.Point D is ultimate stress or � ultimate strength of material.Point E is the stress at failure known as � rupture strength.

Ultimate strength

Actual rupture strength

Rupture strength

Elastic limit

Yield pointSTRESS

STRAIN

Proportional limit

BA

O

ED

C

Fig. 1.5 Stress-strain curve(Source: http://civil-engg-world.blogspot.com/2008_10_01_archive.html)

Stress analysis is a critical component of piping design through which important parameters such as piping •safety,safetyofrelatedcomponentsandconnectedequipmentandpipingdeflectioncanbeaddressed.Piping stress analysis is a term applied to calculations, which address the static and dynamic loading resulting •fromtheeffectsofgravity,temperaturechanges,internalandexternalpressures,changesinfluidflowrateandseismic activity. Codes and standards establish the minimum requirements of stress analysis.•The objective of pipe stress analysis is to prevent premature failure of piping and piping components and ensuring •that piping stresses are kept within allowable limits.

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Why stress analysis?•Stress analysis is carried out for all lines covered in critical line list. �This is toensureflexibilityof linesoperatingat elevated temperaturesandalso toensure that loadon �equipment nozzles is within remissible limits due to expansion of piping. Stress sketches are prepared in isometric form on stress sheet showing location of all supports. �

Stress analysis ensures•integrityofpipeandpipingcomponentsagainstpressureanddeadweight(fixedweightofastructureor �piece of equipment on its supports)flexibilityofpipefromthermalexpansion �safety of nozzles to the connected critical equipments �proper supporting against dead weight, thermal expansion & occasional loads �properselectionandspecificationofspecialsupportslikespringhangersandexpansionjoints �

Stress categories•The major stress categories are primary, secondary and peak stresses.

Primary stresses � These are developed by imposed loading and are necessary to satisfy the equilibrium between external and internal forces and moments of the piping system. Primary stresses are not self-limiting.Secondary stresses � These are developed by the constraint of displacements of a structure. These displacements can be caused either by thermal expansion or by outwardly imposed restraint and anchor point movements. Secondary stresses are self-limiting.Peak stresses � Unlike loading condition of secondary stress which causes distortion, peak stresses cause no significantdistortion.Peakstressesarethehigheststressesintheregionunderconsiderationandare responsible for causing fatigue failure.

The piping engineers can provide protection against some of the failure modes by performing stress analysis •according to piping codes. There are various failure modes that could affect a piping system such as:

Failure by general yielding � : failure is due to excessive plastic deformation.Yielding at sub elevated temperature � : body undergoes plastic deformation. Yielding at elevated temperature: � after slippage, material re-crystallises and hence yielding continues without increasing load. This phenomenon is known as creep.Failure by fracture: � Body fails without undergoing yielding.

– Brittle fracture: Occurs in brittle materials.– Fatigue: Due to cyclic loading initially a small crack is developed which grows after each cycle and

results in sudden failure.How Stress analysis is carried out?•

Stress analysis is carried out using softwares. �Output data is tabulated on stress sketch. �A typical stress sketch giving input and output data is enclosed. �Nozzle loadings on equipments are transmitted to mechanical group for approval if it exceeds permissible �limit.Piping stress analysis process includes: �stress sketch report �support arrangement �design conditions �material code �pipe size, insulation thickness �

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nozzle displacements �loadings �code compliance stress �nozzle loads �loads on supports �piping movements �

Statutory approvals•Various statutory bodies whose approvals are necessary in piping system designing are:

Chief inspector of factories �Chief inspector of boilers �Chief controller of explosives �Petroleum act & rules ( for storage tanks) �Gas cylinder & static & mobile pressure vessel rules �Oil industry safety directorate �Tariff advisory committee �Pollution control board �Local bodies (municipal or district authority, port authority, aviation authority, highway authority etc.) �electrical inspection �town planning authority �

Responsibility of piping engineering onsite•List of the major activities onsite includes:

supervision of fabrication & erection of equipments and piping �co-ordinationwithclients,contractors,&detailengineeringoffice �planning & monitoring the work for timely completion of the project �conductweldingprocedure&performancequalifications �assure the quality of work done by contractors �maintain QA or QC records �assure the lifting equipments tools & tackles are in proper condition �check the alignments of equipments �assure the work is carried out as per P & IDs, layouts drawings & isometrics �check critical pipe supports �check visual inspection & radiography of weld joints �checkinsulation&paintingasperthespecifications �

1.12 Piping Designing ToolsAdvances in computer technology are providing better tools to simplify the tasks faced by engineers, especially •thoseresponsiblefordesigningandmanagingprocesslinesthathandlefluidsandgases.Tools such as spreadsheets can be used to reduce errors in calculations. Spreadsheets, however, are generally •tailoredforveryspecificproblems.Softwaretoolshelptoavoidsuchengineeringerrors.Computer-aided design (CAD) is the use of computer technology for the process of design and design-•documentation. CAD softwares provide the user with input-tools for the purpose of streamlining design processes; drafting, •documentation, and manufacturing processes. CADoutputisoftenintheformofelectronicfilesforprintormachiningoperations.•

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Software tools used for piping design are:•2D design tools like Microstation, AutoCAD etc. �3D design tools like PDS (Plant Design System), PDMS (Plant Design and Management System) �CAESAR II �CAEPipe �AFT IMPULSE �

AutoCAD or Micro Station are useful for piping applications:•P&IDs �Plot plans �Equipments layouts �Piping plans �Isometrics �Piping support drawings �

Salient features of 3D design tools are:•3D software inputs data via forms and menu �3D model, easy conceptualise �ing of plant layouts �On line clash detections �Various information obtained through PDS/PDMS are: �– Piping layouts– Ducting layouts– Cable tray layouts– Isometrics and material take-off

Customisation �Ability to get inputs from various engineering disciplines �Pipingspecificationinusersformat �

The advantages of piping design tools are:•replacement of drawing board �neat drawings �fastmodifications �copying of identical parameters �time saving �accurate results �fast problem solving �– can solve problems with number of anchors and number of piping branches which by manual method

is unimaginable– can solve problems of occasional loads and various combinations of loads

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Fig. 1.6 Stress analysis tool(Source: http://www.cadalyst.com/aec/aec-from-ground-up-plant-and-piping-software-2867)

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START

END

Set Design Environment

Decide Design Procedure of Piping Sys.

Decide Typical Section

Decide Main Pipes Based on Priorities

Visualization of the Design

All the Main Pipes Designed

Design Rules Satisfactory?

ModificationofDesign Factors

YES

NO

NO

(1)

(2)

(3)

(4)

Fig. 1.7 Routing process of main pipes(Source: http://icad.kaist.ac.kr/~msh/ARS/cad-ars.htm)

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SummaryPiping is an asset for any project. •Piping is a system of • pipes (hollow, cylindrical tubes) used to pass on liquids, gases and other materials often under pressure and thermal loads, from one location to another within industrial facilities. Piping engineering is a specialised branch of engineering dealing with design & layouts of piping network •along with the equipments in a process plant. These layouts form a complete blue print of the plant & are used for plant construction at site. Pipinglayoutsincludedocumentsshowinglayoutsofpipingnetworktocarryfluidsfromoneequipmentto•another in a process plant.Plot plan• includesarrangingallplantunitsinalogicalmannertotakecareofmaterialflow,statutoryrequirementsand good engineering practices.Equipment layout include the documents showing layout of all equipments satisfying the process requirements, •safety & statutory regulations, operations, ease of maintenance and economy.Stress of a material is the internal resistance per unit area to the deformation caused by applied load. Strain is •unit deformation under applied load.Stress –strain curve is a curve in which unit load or stress is plotted against unit elongation, technically known •as strain.Piping stress analysis is a term applied to calculations, which address the static and dynamic loading resulting •fromtheeffectsofgravity,temperaturechanges,internalandexternalpressures,changesinfluidflowrateandseismic activity. Codes and standards establish the minimum requirements of stress analysis.•Advances in computer technology are providing better tools to simplify the tasks faced by engineers, especially •thoseresponsiblefordesigningandmanagingprocesslinesthathandlefluidsandgases.Tools such as spreadsheets can be used to reduce errors in calculations. Spreadsheets, however, are generally •tailoredforveryspecificproblems.Softwaretoolshelptoavoidsuchengineeringerrors.CAD softwares provide the user with input-tools for the purpose of streamlining design processes; drafting, •documentation, and manufacturing processes.

ReferencesFundamentals of Pipe Stress Analysis with Introduction to CAESAR II• [Online]. Available at: < http://www.idc-online.com/pdf/training/mechanical/SA.pdf>. [Accessed 5 April 2011].Stress analysis for process piping• [Online]. Available at: <http://www.pipingdesign.com/stressanalysis.pdf>. [Accessed 5 April 2011].P&ID - Piping and Instrumentation Diagram• [Online]. Available at: <http://www.engineeringtoolbox.com/p&id-piping-instrumentation-diagram-d_466.html>. [Accessed 5 April 2011].

Recommended ReadingKellogg, 1964. • Design of Piping Systems, 2nd ed., John Wiley & Sons Inc.Nayyar, M. L., 2000. • Piping Handbook, 7th ed., McGraw-Hill.Towler, G. P., & Sinnott R. K., 2008. • Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design, Butterworth-Heinemann.Weaver, R., 1986. • Process piping drafting, 3rd ed., Gulf Pub Co.

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Self AssessmentPiping system does not include __________.1.

pipea. flangesb. valvesc. logical gatesd.

Piping system design is typically done by experienced piping draftsmen known as __________.2. piping designersa. administratorsb. managersc. chemical engineerd.

Which of these is not an important factor to be considered in piping engineering? 3. process requirementsa. safety and operationsb. social ethicsc. maintenanced.

The responsibilities of piping design engineer does not begin with ________.4. preparationofplotplan,equipmentlayoutspipingstudies,pipingspecificationa. review of process packageb. giving inputs to civil, vessel, electrical or instrumentation groups for various purposesc. stress analysisd.

The responsibilities of piping design engineer end with ________.5. procurement assistancea. completion & commissioning of plantb. preparation of drawings for statutory approvalsc. preview of vendor drawingsd.

Equipment layout does not show___________.6. package itemsa. pipe racksb. future provisionsc. A/C ductingd.

Which of the following statements is FALSE?7. Piping layouts is required by site for construction to prepare isometrics.a. Piping layouts must consider process requirements, operations and maintenance requirements.b. Pipinglayoutsincludedocumentsshowinglayoutsofpipingnetworktocarryfluidsfromequipmenttoc. another in a process plant.Piping layouts include the documents showing layout of all equipments satisfying the process requirements, d. ease of maintenance and economy.

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Which point is not included while developing piping layouts?8. process requirementsa. instrument requirements b. aestheticsc. safety requirementsd.

_______ are prepared taking into account requirements of piping, electrical & instrument cable trays to be 9. routed between various plant areas.

Pipe rack study sketchesa. Piping layoutsb. Pipingspecificationsc. Utilityflowdiagramd.

Critical line list includes ____________.10. all line requiring stress or vibration analysis etca. all process and utility lines appearing in P&IDs and UFDsb. documents specifying in detail all piping items required for the plantc. piping layouts drawingsd.

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Chapter II

Interdepartmental Interactions and Plot Plan

Aim


defineplotplan•

describe interaction between different departments in an industry•

state the role of information sharing•

Objectives


describe the mitigation of the problems in interface areas•

explain the major roles of plot plan•

enlist the guidelines for plot plan or layout engineering•

Learning outcome


examine various criteria for facility location•

illustrate the steps involved in preparation of a plot plan•

explain the nature of problems in interface areas•

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2.1 IntroductionIn general, every activity or work, whether big or small, personal or social, urgent or routine, is successfully executed by a team. The teamwork includes the co-ordinated efforts of all the participants. In particular, engineering of a project is a task of a team. The success of a project depends on various factors. Knowledge, skills and resources can notbebeneficialforsuccessfulcompletionoftheproject,ifitlacksproperco-ordination.Inanytask,therearetwocategories of the responsibilities resting with each individual member of the team and interface areas.

Individual responsibilities are solely to be executed by the individual, using his own knowledge, skills, efforts, data resources. Responsibilities in interface areas are those where each individual has to interact with one or more of the other team members or departments. This is done by sharing of the information, understanding each other’s problemsandresolvingorarrivingatthebestcompromiseonconflictingrequirementstoachievethebestresults.But there should not be any compromise in product or process quality, requirements and schedule. Inordertoachievethecommongoaloftheteam,therehastobeappropriateandefficientinteractionbetweenvariousdepartments, agencies, clients and technology licensors. As a result, the transfer of data, documents and information between individual team members can be made in very comprehensive, rational and effective manner.

The diagram below shows how the departments at a typical manufacturing company interact with each other during production. The product is developed by the three departments. The researchers gather information on the new and improved materials that can be machined. Then, the new product system is developed using complex engineering softwaresuchasAutoCAD.Theproductsaretestedonthecomputersystem.Thedesignerstakethefindingsfromthe research and development stage. All three departments work very closely together and meet at least on a daily or weekly basis. Sometimes they work in teams made up of researchers, development managers and designers.

RESEARCH

DEVELOPMENT

DESIGN

PRODUCTION PLANNING

PRODUCTION CONTROL

QUALITY CONTROL

STORAGEHANDLING AND DISTRIBUTION

CUSTOMERS

MARKETING

PRODUCTION

PRODUCT DEVELOPMENT

Fig. 2.1 Interaction between different departments in an industry(Source: http://www.technologystudent.com/vocat/intact1.htm)

2.2 Information SharingBroad responsibilities of piping engineer are to:

receive or study basic engineering package �receiveorstudyequipmentlayouts,P&IDs,specifications �prepare general plot plan of all facilities �prepare layouts of each individual units �prepare underground coordination plan �prepare piping study drawings �

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prepare piping plans or layouts �preparepipingspecifications �prepare piping design or stress analysis or support systems �prepareMTOorBOMforpipesorpipefittingsorvalvesetc. �prepare piping isometrics �prepare or co-ordinate material handling systems with the designers or suppliers �prepareorco-ordinatefire-fightingsystem �

For the purpose of execution of the above responsibilities, piping engineer has to send as well as receive lots •of data. This data-exchange forms the interface area. In order to enable other departments to execute their individual responsibilities, piping has to initiate certain •documents and send to others, so as to receive the required inputs from them.

2.3 Stages of Data Generation Generally, it is neither possible nor necessary to generate all design data in one stroke. The data gets built up as •the engineering, ordering and detailing are in progress. Hence piping engineer must know :

What data is required? �In what sequence it is required? �Which data is required by whom? �At what stage a particular data is required? �What is preliminary data? �Whatisfinaldata? �

For the above purpose, the following guideline should be followed:•preliminary data for overall knowledge of everyone �data for preliminary estimates (may be with ± 30% accuracy) �data for obtaining comments/mark- ups etc. from others �data for preliminary design �data for sending enquiries or tenders to suppliers or contractors �data for approval of clients or licensors �data for design and detail engineering �data for construction �dataforfinaldocumentation �

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Vendors

Contracts Procurement cost

EstimationConstruction

Project Manager Planning

Clients

Process

Instruments Piping Department Mechanical

Instruments / Cable Routing

Control loops /On-line Equipment Loads

Nozzle details

PipingMTO+Specification Issue of construction

Co -ordination / Schedule

Drawing & MTO

Issue of construction drawings

& problems on delays

+ Tech. R

ecomm. F

or

Purchas

e orde

rP

& ID

’s /S

pec.

Proc

ess d

escr

iptio

nVe

ndor

s

Release

of co

nstruc

tion

Drawing

s

Layout/Specific

requir

ement

s

Fig. 2.2 Data transfer from piping to other departments / clients / agencies

2.4 Nature of Problems in Interface AreasTheefficientandeffectiveengineersdependontheco-ordinatedteamefforts.•Hence any problem in interaction areas can be a serious issue to the project. The problems within the departments •can be resolved quickly as they are seen or noticed in day-to-day work by the working and supervising persons. But the problems in interface zone go concealed or hidden many times until some serious situations arise. This •can create crisis, hasty actions and decisions and can lead to many more problems, delays and mistakes.Hence all must know what are the likely problem areas and their nature in the interface zone.•Piping engineer, being at the focus of engineering data coordination must carefully avoid these problems, by •using proper systems, data banks, communication methods and timely action.The nature of problems arising in the interface areas can be listed below:•

Acceptance and use of incomplete or unapproved data can lead to incorrect down-stream activities which �canleadtounprofitableworkorredoing,andthuswastageoftimeandefforts.Incomplete study of data received from others and sending incomplete comments to others can mislead �others who proceed with their work and return incomplete data for piping engineering, resulting in many more to -and- fro communications on the same topic and delaying everyone’s work.Sending data in inappropriate sequence will disturb the sequence of work to be executed by others. �Not sending the revisions in frozen data that is already transferred to others for detail engineering, will erase �thepartorentireworkdonebyothersinoffice.

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Not incorporating the comments or mark-ups sent by others will lead to incomplete or incorrect engineering �and also delays, at a very late stage of the project.Hasty action on data generation to meet the stipulated schedule dates will involve mistakes or errors leading �to wrong data.Undefinedorgreyareasarecertainportionsoftheprojectwhicharenotfoundcoveredinthescopeofany �department.Ifthisisnotidentifiedataveryearlystagebyprojectmanagerornotbroughttoanybody’snotice by the noticing individual, it can lead to a very serious situation. Due to its omission, ordering and the material, equipment or building required for project completion will be delayed. A small thing not executed on account of this reason can hold up the commissioning of the whole or part of the plant.Long delivery items are some of the critical equipments that take long period (10 to 18 months) for delivery �by the supplier. Such items have to be tackled at a very early stage of the project. Hence, data for such items have to be generated much earlier and transferred to the concerned disciplines for their early actions. If there is delay on such matters then the entire project can be delayed.Not transferring the data in written form, sketches or drawings can be problematic. Sometimes, a telephonic �conversation becomes essential between the two engineers interacting on a particular data. Certain clarifications,dimensionsordetailsareclarifiedorcommunicatedontelephone.Thisisacceptableasfaras immediate actions are concerned. But the same should be instantly put in writing or on drawing and sent by the piping engineer to the others to use the data.Bad written communication is also a serious issue in interaction between departments. If the hand-drawn �sketches or hand-written notes are used for transfer of data, then they should be neat and clear for reading and interpretation by the receiver. Not signing and getting an approval is another issue. Whenever experienced or inexperienced engineer �works and prepares data, it should be signed and got approved by the seniors who can point out and correct the mistakes caused by the misconceptions or ignorance of the juniors. If this is not done, serious mistakes will lead to further chain reaction through all others concerned and using the wrong data that has been received.Bye-passingtheQAsystemcanbeerror-prone.Specificorcontractrelatedqualityassuranceproceduresare �made for each project. While transferring the data, if the steps are omitted or the procedures are violated by taking shortcuts, then such non-compliance can result in use of wrong data or outdated information.

2.5 Mitigation of the Problems in Interface AreasThe problems in interface areas can be either mitigated or prevented. The above mentioned problems arise due •to different sources listed below:

improper and/or lack of communication �casual approach to the serious nature and importance of the interaction �not understanding the QA procedures �notion that QA procedures are an unnecessary burden and bye-passing it �conflictingsituations,differenceofopinionsleadingtonoacceptablesolution �not following the priorities or not prioritising the work and generating data in wrong sequence �not bothered of others’ problems, disciplines, norms, codes or practices �likes and dislikes for persons and type of work �lack of cost consciousness or knowledge �ignorance or tendency to hide ignorance �shyness to interact with the superiors or colleagues �

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To prevent or minimise the problems in interface areas, following points should be considered by the •engineer:

Clear thinking �Clear and complete communication �Studying or understanding the job under execution �Habit of listing down the doubts or queries while studying the basic data received �Making a checklist of the data or information required by and to be received from others �Following the QA and other departmental and interdepartmental procedures strictly �Checking the correctness and completeness of the data by the receiver and rejecting or returning to the �sender for completion. Incompleteness can be in respect of bad non-readable documents or no signatures and approval or missing dimensions or details, no revision numbers on the documents etc.Full preparation in co-ordination meetings to sort out most of the mutual problems �Understanding the problems of others whenever there is difference of opinions on technical matters; resolving �and arriving at common decisionAwareness of the fact that all future problems, delays, mistakes, errors, re-doing, dismantling and extra �unnecessary costs to clients and consultants, have their root causes deeply burred in the interaction phase of the project. If interaction is made in rational or serious manner, most of the future problems can be prevented at the root-level.Therefore, during interactions, the individual should be prompt, correct, neat, clear, precise, brief, timely, �compromising and serious while generating, sending and receiving the data, documents or information.

2.6 Guidelines for Plot Plan A plot plan is a scale drawing that gives an overview (top view) of the entire plant. •Plot plan is the drawing of land detail with adjacent reference points, where project is to take or taken place. •This is dimensional drawing.Plot plans are considered to be the key documents of projects and are normally initiated in the pre-contract, •conceptual and development stages of a proposal. After the contract is awarded for engineering, plot plans are developed at a rather rapid pace with very limited •information. This early stage plot plan usually is very limited in information, containing only enough dimensional datatodefinetheouterlimitsoftheavailablepropertyselectedforplantdevelopment.The equipment sizes and shapes are pictorially positioned in a rough manner, along with anticipated pipe rack •configurations,structureshapeandroughsizes.The plot plan at this level is then used for constructability evaluation and submitted to the client for approval.•

Major roles of a plot planPlot plans are essential for obtaining permits and determining environmental and personnel safety. They are the •keydocumentsusedinassessingfireprotection.During the engineering and construction phases, many owners use the plot plan as a basis for evaluating the level •of completeness of work agreed upon. The document can be used as a measure of the progress payments.Prevailing winds and tower and structure heights must be considered in developing a plot plan. Although wind •direction is never constant, prevailing wind is used as a basis to evaluate safety. Climatic considerations also play a major role in plot plan development. •Thus, for preparation of plot plan of any plant, the concerned engineer has to proceed in a logical and sequential •manner, before actually putting the unit-blocks on the drawing sheet.

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The basic steps involved in preparation of plot plan are:Preparation of preliminary plot plan

preliminary equipment layout or arrangement•preliminary arrangement of structures, building & other facilities•

Study on preliminary plot planstudy on safety instances•study on pipe rack width•study on routing for main piping & cables•study on construction & maintainability•study on operation accessibility & operability•study on underground obstruction•

Completion of plot plandetermination of dimension between equipment, structures etc.•modificationasaresultofpipinglayout•

Fig. 2.3 Plot plan(Source: http://www.epcpj.com/preparation-of-plot-plan/)

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Fig. 2.4 Plot plan and road(Source: http://www.epcpj.com/preparation-of-plot-plan/)

Elaborating the steps involved in preparation of a plot plan:STEP1: The list of all units and the sizes of the plots to accommodate each unit is prepared. The information can also be made available from process engineer.

STEP 2: The total area occupied by the present and future facilities is ‘A’ sq. m. The area required for general facilities like roads, drains, underground services (cable trenches, drains, storm water pipes, chambers, manholes, parking places etc.)hastobeadded.Unitplotplansaregenerallydefinedbyimaginarylinescalledbatterylimits. Thumb-Rule: For total space requirement to accommodate all facilities, double the area calculated i.e., (2A) sq. m.

STEP 3: Having known that the total plot size required to accommodate all the facilities including process plant, off sites, utilities, non-plant buildings general facilities, is ‘2A’ sq. m, we can now approximately calculate, the project-plot size.

For square plot, size is 2• A ×2AFor rectangular plot and different ratios of L: B (length : width) can be calculated by assuming L:B-ratio like •1.25, 1.50, 1.75, 2.e.g. if, L:B= 1.25: 1 and L x B = 2A, then (1.25) B• 2 = 2A

L= 1.25 B =

And the plot size is

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Sl. No. L:B ratio L (m) B (m) Actual area Check

1 1 245 245 60025 √

2 1.25 274 219 60006 √

3 1.5 300 200 60000 √

4 1.75 324 185 59940 √

5 2 347 173 60031 √

Table 2.1 L:B ratios and actual area relationship

STEP 4:Next step is to select the portion of the entire land belonging to the owner, which will be developed to accommodate theproposedplantfacilities.Forthispurpose,firstthe‘greenbeltzone’isdemarcated.Minimumwidthofgreenbelt differs according to different states and countries.

For selecting the most optimum portion of the total land, following checklist of governing factors can be used.Preferably rectangular (or square) shape should be chosen near one of the corners of the land.•It should be nearest to the following public facilities, e.g.•

approach road (state or district highway) �water-supply line or other water-sources such as well �power-supply transmission line (or the location where it can enter the land from the nearest source) �disposal channel for storm-water disposal �

Proximity to ideal locations formain switchyardor substation, effluent treatmentplant andwater storage-•tanks.Wind-direction•Existing tree-plantation•Suitability for future expansion of the same plant or other projects in the land•Landconfiguration:Basedonabovecriteria,ifthebestlocationselectedhappenstobeaverylowlyingarea•needing4to6mfilling,tobringittothesafelevelabovehighfloodlevel,thenanotherareaadjacenttoitisselected,whichinvolvesminimumcostoffillingwork.Suitability of access road location from main adjacent state-road•

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PROPO

SED

PROJEC

T SITE .

STATE HIGHWAY .

RIVER .

E '

DD ' P

QC'C

E

AA'

B' BWATER LINE .

66 K

M O

.H.TR

ANSM

ISSIO

N LI

NES .

300

m

277

m217 m

100 m

500 m

440 m470 m

Fig. 2.5 Location map of project site

Total Boundary of owners’ land ABCDE (say, 2,50,000 m• 2)Green Belt width, all around 30 m (say, 57,600 m• 2)Plot available for locating the proposed project A’B’C’D’E’•Total Land area within A’B’C’D’E’ = (ABCDE) - Green Belt Area • = 2, 50,000 - 57,600 = 1, 92,400 m2

Total area required for the proposed plant = 60,000 m• 2

Balance available for future projects = 1,92,400 - 60,000 = 1,32,400 m• 2

Plot selected for the project C’D’PQ = 277 * 217 = 60,109 m• 2

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STEP 5:Having located the portion of the land based on the factors in Step 4, the area ‘C’D’PQ’ (277 x 217 m) can be blown up to a suitable scale, generally 1:331/3, or 1:50 or 1:100 for a very big-plot on sheet as given below:

NO . UNIT . SIZE . NOTES :-

REFERENCE DRAWINGS :-

LIST OF UNITS & SIZES .

KEY PLAN .

REV.TABLE .NAME PLATE .

TRUE .

PLANT .

N =

0 .

N =

50

.

N =

100

.

N =

150

.

N =

200

.

N =

217

.

W = 0

W = 50

W = 100

W = 150

W = 200

W = 250

W = 277N =

30

.

1)2)

Fig. 2.6 A typical plot plan drawing

Draw grid-lines on 100 m * 100 m spacing as shown in STEP 4.•Draw grid- lines on 50m * 50m spacing as shown in STEP 5.•Draw Name-plate, key-plan, N- lines, table for list of unit no., unit - name and plot-size.•On key plan, hatch the portion of whole land, selected for plot-plan as in STEP 4.•Show all other features as indicated above.•

STEP 6:For locating different units (blocks onto the scaled-drawing as in STEP-5, the best way is to use a CAD facility. •If not available, pieces of cardboard can be cut and used to required size and shape, drawn to the same scale as the plot drawn on drawing as in STEP 5. Also, the strips for roads between adjacent plots can be cut. Approximately, width of the strips will be:•(Road=6m) + (Shoulders (2×2) = 4m) + (Drain (l×2) = 2m) + (Additional space (4m×2) = 8m) Total = 20 mThepieceswithinthespecifiedplotisarranged,(277×217intheSTEP5example),givingconsiderationto•following points

Approximate main road spacing �Locating main-process-plant at appropriate place, away from front boundary- line of the plot. �Imposing the constraints on the layout and locating the respective units accordingly. �

Vastuconstraints(e.g.waterbodynearN-E-corner,firebodynearS-Ecorneretc.)asspecifiedby- clientsAccess roads from main roads- Gate house, admin or canteen block- Flare-stack as per wind-direction- Closeness of certain units like (main substation-incoming line, water -tank – incoming water line, - process-plant-control building room etc.)

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Keeping the blocks and road strips adjusted until all blocks are arranged, satisfying all conditions of - space requirements, space-constraints, mutual relationship etc.Finalising the locations and drawing the plot boundaries, roads, drains (double lines) etc. -

Numberofunitsineachplotwithreferencetothetableintheabovefigure.Numbertheroads,preferably �as given below

All N-S roads are numbered by odd no. 1,3,5,7 ... etc. with Rd. 1, closest to the boundary- All E-W roads are numbered by even no. 2, 4, 6 ... etc. with Rd. 2 closest to south boundary which - forms part of project boundary tooSub-roadsorin-plantroadstobesuffixedbyA,B,Cetc.e.g.roads4and6tobenumberedasRd.- 4A, Rd. 4B..... etc. Roads between 3 and 5 to be numbered as 3A, 3B etc.-

** While preparing plot-plan, due consideration to the following should be given to avoid interference of unit-areas.

road turning radius •storm-water, cables and underground pipe-crossings near the junction area•statutory & safety requirements, safe distance etc.•

2.7 Criteria for Facility LocationFollowing are the criteria for facility location:Utilities boiler house

roads(6m minimum) close to process plant, at least from two sides •minimum pipe run to avoid excessive steam condensation high temperature lines•downwindtononplantprocessplantfirehazardoustankfarmsshouldbelocated•proper ventilation and light should be provided•sufficientspaceoraccess(buildingopeningheightandnearbypiperackheight)forboilererectionshouldbe•providedspace for future boiler house and erection space or access for boiler should be provided•sufficientspaceor• access (near by pipe rack height) for chimney erection should be providedother facilities like water treatment plant, furnace oil storage or coal storage, • effluenttreatmentplant etc. should be located as per good engineering practices

Water treatment plantnear to boiler house•space for acid , alkali storage or separate acid, alkali tank farm should be considered•minimum pipe run (of bigger water lines) should be taken into account•road(minimum4.5m)ononesideissufficient,butfirefightingspaceneedstobeprovided•

Utility building (with compressor, chillers etc)closetoprocessplantbutlocationawayfromadmin,office,residentialcomplexes(toavoidnoisetrouble)•air (pressure) vessels outside the building in open area•if required noise dampening should be provided•road(minimum4.5m)ononesideissufficient,butfirefightingspacetobeprovided•

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Cooling towerslocated close to end user to have minimum pipe run •downwind to process plant; other plant buildings should be located in open (ventilated) area•water drift should not obstruct visibility on roads and corrode the adjacent plants•crosswinddirectionshouldbelocatedtoavoidsuctiondischargemixingandefficiencyreduction•cooling water headers should be preferably run underground•road(minimum4.5m)ononesideissufficientbutfirefightingspacetobeprovided•

2 Pole/4 Pole structureclose to the plot boundary and incoming HT cable (HT means more than 500V)•awayfromfireproneareaslikefirehazardtankfarmcoal/bagassestorage•pathway (1m or 1.5m) should be provided if required (road is not required)•

Mitch-yard /MCC (motor control center), PCC (power control center) room/ DG (diesel generating) roomclose to process plant or utility area (can be combined with utility block)•minimum cable run•providesufficientspace,piperackheightroad(min4.5m)forDGpanelerection•locationathighergradeandabovefloodlevel•DGroomshouldbelocatedawayfromadmin,officeorresidentialcomplex;ifrequirednoisedampeningshould•be provided

Raw water/ Fire water storage and pump houseclose to plant entry, in safe area near to water battery limit or tube well•locationathighergradeelevationandhighfloodlevel•minimumpipeorcablerun,firefightinglinesnormallyunderground•road(min4m)ononesideissufficient,butfirefightingspacetobeprovided•sufficienterectionandmaintenancespaceshouldbeprovided•

Effluent treatment plantlocation in low lying area at remote place away from process (main) plant ,non plant building ensure proximity •to industrial estate ETP lineminimum pipe or cable run pipes or cables are run underground•pathwayononesideissufficientbutfirefightingspacetobeprovided•

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SummaryThe teamwork includes the co-ordinated efforts of all the participants. In particular, engineering of a project is •a task of a team.Inordertoachievethecommongoaloftheteam,therehastobeappropriateandefficientinteractionbetween•various departments, agencies, clients and technology licensors.For the purpose of execution of various responsibilities, piping engineer has to send as well as receive lots of •data. This data-exchange forms the interface area. Generally, it is neither possible nor necessary to generate all design data in one stroke. The data gets built up •as the engineering, ordering and detailing are in progress.Theefficientandeffectiveengineersdependontheco-ordinatedteamefforts.Henceanyproblemininteraction•areas can be a serious issue to the project.Piping engineer, being at the focus of engineering data coordination must carefully avoid the problems, by using •proper systems, data banks, communication methods and timely action.Hasty action on data generation to meet the stipulated schedule dates will involve mistakes or errors leading •to wrong data.Not transferring the data in written form, sketches or drawings can be problematic.•Bye-passingtheQAsystemcanbeerror-prone.Specificorcontractrelatedqualityassuranceproceduresare•made for each project. While transferring the data, if the steps are omitted or the procedures are violated by taking shortcuts, then such •non-compliance can result in use of wrong data or outdated information.Plot plan is the drawing of land detail with adjacent reference points, where project is to take or taken place. •This is dimensional drawing.Plot plans are considered to be the key documents of projects and are normally initiated in the pre-contract, •conceptual and development stages of a proposal. For preparation of plot plan of any plant, the concerned engineer has to proceed in a logical and sequential •manner, before actually putting the unit-blocks on the drawing sheet.As a result, the transfer of data, documents and information between individual team members can be made in •very comprehensive, rational and effective manner.

ReferencesWormer, R. V., • Plot plan design [Online]. Available at: <http://www.spedweb.com/index.php/sped-technical/plot-plans.html>. [Accessed 6 April 2011.]Preparation of Plot Plan• [Online]. Available at: < http://www.epcpj.com/preparation-of-plot-plan/>. [Accessed 6 April 2011.]Basic and Detailed Engineering • [Online]. Available at: <http://www.technip.com/en/about-us/range-services/basic-and-detailed-engineering>. [Accessed 6 April 2011.]Design Guide for Layout and Plot Plan• [Online]. Available at: <http://www.chagalesh.com/snportal/Uploads/chagalesh/karafarinan%20farda/jozveh/piping/6.pdf>. [Accessed 6 April 2011.]

Recommended ReadingBausbacher, E., & Hunt R. W., 1993. • Process plant layout and piping design, PTR Prentice Hall.Weaver, R., 1986. • Process piping drafting, 3rd ed., Gulf Pub. Co.Parisher R. A., Rhea, R. A., 2001. • Pipe Drafting and Design, 2nd ed., Gulf Professional Publishing.

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Self AssessmentWhich of these do not include the responsibilities in interface areas?1.

sharing of the informationa. understanding each others’ problems b. resolvingorarrivingatbestcompromiseonconflictingrequirementsc. compromising in product or process qualityd.

Product development process does not include ________.2. production planninga. researchb. developmentc. designd.

Long delivery items are some of the critical equipments that take long period of _______ for delivery by the 3. supplier.

10 to 18 monthsa. 20 to 30 monthsb. 1 weekc. 1 yeard.

The data shared by piping engineer between departments should not be in form of _______ until immediate 4. actions are concerned.

written forma. sketchesb. telephonic conversationc. drawingsd.

Which of these is not problematic in interface areas?5. improper and/or lack of communicationa. casual approach to the serious nature and importance of the interactionb. not understanding the QA proceduresc. checklist of the data or informationd.

Which of these describe the activities in completion of plot plan?6. determination of dimension between equipment, structures etc.a. study on routing for main piping & cablesb. study on construction & maintainabilityc. study on operation accessibility & operabilityd.

For total space requirement to accommodate all facilities, _____ the area is calculated.7. triplea. doubleb. halfc. one-fourthd.

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All _______roads are numbered by odd no. 1,3,5,7 ... etc. with Rd. 1, closest to the boundary8. N-Sa. E-Wb. N-Ec. S-Ed.

Which of the following is FALSE?9. Acceptance and use of incomplete or unapproved data can lead to incorrect down-stream activitiesa. Acceptanceanduseofincompleteorunapproveddatacanleadtounprofitableworkorredoing,andthusb. wastage of time and efforts.Sending data in appropriate sequence will disturb the sequence of work to be executed by others.c. Not sending the revisions in frozen data that is already transferred to others for detail engineering, will erase d. thepartorentireworkdonebyothersinoffice.

Which of the following is FALSE?10. Individual responsibilities are solely to be executed by the individual, using his own knowledge, skills, a. efforts, data resources.Responsibilities in interface areas are those where each individual has to interact with one or more of the b. other team members or departments.Knowledge,skillsandresourcesarebeneficialforsuccessfulcompletionoftheproject,ifitlacksproperc. co-ordination.The transfer of data, documents and information between individual team members can be made in very d. comprehensive, rational and effective manner.

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Chapter III

Process Piping and Instrumentation Diagram (P and ID)

Aim


definepipingandinstrumentationdiagram•

describe operational sequence of the process P and IDs•

explain the steps in preparation of process P and IDs•

Objectives


describetheprocessflowdiagrams•

explain the use of P and ID symbols•

discuss the importance of maintenance during process P and IDs •

Learning outcome


examine various aspects during the preparation of process P and ID•

explain the importance of safety in process P and IDs•

analyse basic instrument symbols•

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3.1 IntroductionThe successful conversion of a conceptual idea into actual execution of process industry is the basic aim of any process engineer. Normally, a project passes through various phases, viz. basic engineering, detailed engineering, equipment fabrication or procurement, civil or structural work, erection and commissioning. The conceptual idea, either from the process development cell (for new processes) or from the marketing engineer (as per the customer’s requirement), is converted to executable documents during basic engineering stage, and thus governs the successful completion of the project.

3.2 Piping and Instrumentation Diagram (P and ID) P and ID is one of the important and basic engineering documents in the form of drawing, which truly represents •the process plant.It shows the pipelines, interconnecting all equipments, instruments, control systems, valves, etc. for the •completeness of the process plant.Since detailed engineering work for any process plant depends more on the P and ID, its correctness and •completeness is very much essential. Any wrong information provided in the P and ID at the initial stage may bring a big disaster or may entail heavy expenses later on. Hence, great attention is required for the preparation of error-free P and ID.Good quality P and ID may cut the engineering main hour requirement for the successful completion of a •project. Normally process plants have static equipments like storage tanks, columns, heat exchangers etc. and rotating •equipments like pumps, blowers, etc. These equipments are connected to each other by a complicated pipeline network for the completeness of the process. Measuring instruments like thermocouple for temperature measurement and controlling devices like temperature •control valves are mounted on the equipments or pipelines for operating the plant at desired conditions. Although a single step process like blending of two compounds can be represented in a single piping & •instrumentationdiagram(PandID),aprocesshavingalargenumberofprocessingstepslikereaction,filtration,drying, etc. would need to have many P and IDs for the complete representation of the process plants. For an ease of understanding, the complete process plant is functionally divided into various units. For example, •a reactor with the other related equipments, pipelines and instruments required for carrying out a reaction process maybecoveredinoneunitwhilefiltrationoperationmaybespecifiedwithanotherunitnumber,accordingtothe individual units.In a big chemical process industry, the processing units are spread over a large area. Although two different units •farawayfromeachother,areconnectedbypipelinesorthecontinuousflowoffluidfromoneunittoanother.Interconnection between two units is represented by interconnecting P and IDs. •Similarly, another engineering document, utility P and IDs, provides information regarding the distribution of •utilities like water, steam, fuel etc. in the required locations.Process P and ID provides detailed information of the process plant like type of equipment, the details of pipelines •i.e.,sizeofmaterial,identificationnumber,typesofinstruments,controllingdevicesetc.Operation, start-up, maintenance, safety and aesthetic aspects are mainly considered during the preparation of •process P and ID.

3.2.1 Operation

Process P and ID is prepared by following the operational sequence of the process. For example, a process •needssteplikechemicalreaction,followedbyfiltrationanddryingoftheproduct.ProcessPandIDshowsthecorrespondingequipmentlikereactor,filteranddryerinthesameorder.Allequipmentsaretobeshownconnectedwithpipelines,fittingsandinstrumentsnecessarytocarryoutthe•process. Clear understanding of the process is very much essential for the preparation of a good quality process.•

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Process P and ID provides detailed information of the process plant like type of equipment, the details of pipelines, •i.e.,sizematerial,identificationnumber,typesofinstrumentsandcontrollingdevices,etc.PandIDelevationofallequipmentarenormallyfixedinthepriorstage.EquipmentintheprocessPandID•are shown at different levels with marked elevations. For example, head tank for reactant is shown above the reactorinprocessPandIDforrepresentingthegravityflowofreactantfromheadtanktothereactor.Similarly,other equipments like critical pipelines, instruments, control valves etc. are shown at the appropriate elevations. Normally, heavy rotating equipments like pumps, compressors etc. are located at lower elevation i.e., ground floor.Therefore,rotatingequipmentisplacedatalowerintheprocessPandIDalso.

3.2.2 Start-Up

Start-up of any process plant may need some additional steps which are not required for the normal run. •Special care should be taken for such steps at the initial stage of P and ID preparation. For example, safety seals •inthecriticalgaseouslinesneedtobefilledwithliquidbeforeinstallationoftheplant.ValvewithconnectionsshouldbeshownintheprocessPandIDforliquidsealfilling.•Critical equipment is bypassed using temporary pipeline connections during water test run to avoid contamination. •Thus, process P and ID is marked with such types of requirements for the plant start-up.

3.2.3 Maintenance

Maintenance is an important aspect during the preparation of process P and ID. For example, electric elevator •required for lifting heavy equipment is shown in it. Regulating valve in bypass line of control valve is provided for maintenance without affecting the running •plant. Sometimes,itismarkedinthePandIDtoprovidesufficientroomforcut-outinthefloorabovetheverticaltube•bundle from the heat exchanger body. If such type of information is not provided initially, it may be missed out in the various engineering stages and may lead to problems at the later stages. To avoid such possibilities, process P andID, should be critically examined from the maintenance point of view •during preparation stage.

3.2.4 Safety

For the successful operation of any process plant, safety measures cannot be ignored. Hence, the preparation •of process P and ID needs the attention of safety aspects too. Hazard and operability (HAZOP)• study is carried out keeping in view, each and every safety and operation step. A hazard and operability (HAZOP) study is a structured and systematic examination of a planned or existing •process or operation in order to identify and evaluate problems that may represent risks to personnel or equipment, orpreventefficientoperation.For example, the exhaust of obnoxious gases near the plant operators is harmful to their health. Such gases •are diffused in the atmosphere at a higher elevation. These safe elevations are normally marked in the process P and ID.Safety interlocks are provided to ensure safe operation of the process plant. For example, failure of a running •pump for a critical operation may disturb the complete process plant. To avoid this situation, the stand-by pump should be started without any time lag. Necessary interlock is shown in the process P and ID. Some metallic pipelines and the equipments handling •hotfluidsareinsulatedforbodyprotection.Here,heatsavingmaynotbeanimportantcriteriafortheselectionof insulating, but it is essential for the operator’s safety. Such safety requirements are clearly marked in the P and ID. Requirementofsafetyvalvesinpressurisedsystem,minimumflowlinesforcentrifugalpumps,highandlow•alarms etc. are to be critically seen during the preparation of process P and ID.

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3.2.5 Aesthetics

Though it is not concerned with the plant operation, aesthetic look of process P and ID is important for better •presentation of the document and ease of understanding for the user.Complex presentation of the pipelines i.e., lots of cross-crossing, may even lead to wrong pipeline routing and •hence due attention should be paid to the aesthetic aspect during the preparation of process P and ID.

3.3 Process P and ID PreparationAlthough experience plays a major role, systematic approach is equally essential for producing error-free process •P and ID. Table 3.1 highlights the major steps for the preparation of any process P and ID.

STEP No.1: Show all equipment as per equipment list and layout.

STEP No.2: Connect all equipment with necessary pipings to carry out process.

STEPNo.3:Showallrequiredvalvesandfittings.

STEP No.4: Show all required instruments.

STEPNo.5:Marksizefluidcode,materialcode&identificationnumberofallpipelines.

STEP No.6: Mark interlock number as per interlock description.

STEP No.7: Review P& ID considering all operational steps.

STEP No.8: Review P& ID considering start-up requirements.

STEP No.9: Review P& ID for safety considerations following HAZOP analysis.

STEP No.10: Review P& ID in reference to the maintenance.

STEP No.11: Review P& ID for its aesthetic look.

Table 3.1 Major steps for the preparation of any process P and ID Following documents are essentially required for the preparation of any process P and ID:

Process Flow Diagram (PFD)•Equipment list•Fluid list•Equipment layout•Interlock description•Vendor information (for related equipment)•

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Details of these documents are given in Table 3.2 below.

TYPE:SHELL - Cylindrical/Spherical/Rectangular/ OtherENDS - Flat /Conical/ Spherical /OtherORIENTATION - Vertical/Horizontal/Other

NOZZLE:SIZES–Inlet/Outlet/Vent/Drain/Overflow/Instrument/SpareLOCATION – Shell/Top/BottomELEVATION:As per equipment layoutAGITATION:Is agitation required?Type of Agitation – Air/ Mechanical

HEATING/ COOLING:Is heating or cooling required?Arrangement – Internal coil/Jacket/Limpet coil /other

INSULATION:TYPE – Cold/Hot/Body Protection; ThicknessINSTRUMENTATION:Necessary for parameters like pressure, level, temperature, etc.TYPE:Centrifugal/Reciprocating /Positive displacementDRIVE:Electric Motor/Steam Turbine /Pneumatic DriveQUANTITY:Working + StandbyFLUSHING PLAN:NecessarypipingasperflushingplanrecommendedbypumpvendorPIPING:Sizes of suction and discharge linesRequirement of reducers at suction and discharge ports of pumpVenting, drawing, degassing arrangementsAnt vibration bellows; Suction line strainer especially for gear, screw pumpsPulsation dampener for positive displacement pumpsPulsation dampener for positive displacement pumps (if required)

SAFETY:Minimum bypass line for centrifugal pumpsPressure safety valve /switch for positive displacement pumpNon-return valve discharge line of auto start of centrifugal pump

PROCESS LINES

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All process lines are correctly connected to equipment.

UTILITY LINESRequired utility line are shown.

LINE DETAILSSize,fluidcode,materialcode,identificationnumberinsulatingthickness(ifrequired).

HEATINGPURPOSE – Process requirement / Freeze protectionTYPE – Steam /Electric / Thermal/ Fluid /OtherRequirement of line Jacket

VALVES AND SPECIAL PARTSType of valve – Regulating /Isolating /Check /OtherSpecialparts–Strainer/restrictionorifices/inserttubespraynozzle

IMPORTNT INFORMATIONSlop in the lines; critical elevation differences; required liquid seal in gas linesPipeclassbreakageasperthesuitabilityoffluidtomaterial;Flushingconnectionforslurryfluids,etc.

TYPE OF MEASUREMENTFluidpressure/temperature/flowers/pH/other

TYPES OF INSTRUMENTSuitableinstrumentforselectedvariable,forexample:rotameterforflowratemeasurement.INTERLOCKINGFor representing control action, alarm, switch, operation

CONTROL VALVEType –Flow /Level/Temperature /OtherFail Safe Position – Failure to close /Open/ last statusBypass valve or hand wheel requirementsSize of control valve, reducer requirement

SIGNAL TYPEField /PLC/DCS/Local panel

NECESSARY INSTRUCTIONSTapconnectionsizeformountingtransmitter;ensurepropercontactoffluidtotheanalyzerprobe,e.g.forpHmeasurement, etc.

Table 3.2 Details of the documents for preparation of P and ID

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3.4 Basic Instrument SymbolsProcess technicians use P and IDs to identify all of the equipment, instruments and pipings found in their •units. Knowing and recognising these symbols is important for an engineer. The chemical processing industry has •assigned a symbol for each type of valve, pump, compressor, steam turbine, heat exchanger, cooling tower, basic instrumentation, reactor, distillation column, furnace, and boiler. There are symbols to represent major and minor process lines and pneumatic, hydraulic, or electric lines.•

Reboiler

Shell & Tube Heat Exchanger

Single PassHeat Exchanger

U-TubeHeat Exchanger

HEAT EXCHANGERS

Bin

Tank

Tower

Drum or Condenser

Mixer

Mixing Reactor

Minor Process

Pneumatic

Hydraulic

Capillary Tubing

Electromagnetic Signal

Electric

X X X X X X

L L L

VESSELS

Furnace

Hairpin Exchanger

CondenserHeater

Towerwith Packing

LINE SYMBOLS

Major Process

Future Equipment

Induced-Draft Cooling Tower

Forced-Draft Cooling Tower Flow Indicator

Flow Transmitter

Flow Recorder

Pressure Indicator

Pressure Transmitter

Pressure Recording Controller

FI

FT

FR

PI

PT

PRC

Te mp Indicator

Te mp Transmitter

Te mp Recorder

Level Indicator

Level Transmitter

Level Controller

TI

TT

TR

LI

LT

LC

Fig. 3.1 Process and instrument symbols(Source: http://webtools.delmarlearning.com/sample_chapters/1418030678_ch12.pdf)

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GlobeValve

GateValve

Three-WayValve

Check ValveBleederVal ves

PneumaticOperated

CentrifugalPumps

RotaryCompressor

ManualOperated

ValveGauge

VacuumPumpReciprocating

Compressor

Turbine

PneumaticOperated

Compressor &Silencers

SafetyPSV

Ball

SolenoidValve

CLOSED

S

VALVES

PUMPS & TURBINECOMPRESSORS

Liquid RingCompressor

Centrifugal Compressor

Centrifugal Compressor(Turbine Driven)

T

Gear Pump

Ve rtical

Screw Pump

Rotameter

Four-WayNeedle Angle

Plug

Diaphragm

M

H

Hydraulic BackPressureRegulator

BackPressureRegulator

MotorReliefPRV

Fig. 3.2 Process and instrument symbols (continued)(Source: http://webtools.delmarlearning.com/sample_chapters/1418030678_ch .pdf)

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ariable Being

Flow Indicator

Flow Transmitter

Flow Recorder

Pressure Indicator

Pressure Transmitter

FI

FT

FR

PI

PT

Temp Indicator

Temp Transmitter

Temp Recorder

Level Indicator

Level Transmitter

Level Controller

TI

TT

TR

LI

LT

LC

F I C55

VMeasured

Remote Location(board mounted)Control Loop

Instrument

Remote Location(behind control panel)

Field Mounted

LR Level Recorder

TC Temp Controller

PR Pressure Recorder

Pressure ControllerPC

65 55

5565

65 55

Flow ControllerFC

PIC

PRC

LA

105

40

25

IP

Transducer

Pressure IndicatingController

Pressure RecordingController

Level Alarm

FE Flow Element

TE Temperature Element

LG Level Gauge

AT Analyzer Transmitter

What It Does

Fig. 3.3 Process and instrument symbols (continued)(Source: http://webtools.delmarlearning.com/sample_chapters/1418030678_ch12.pdf)

The P and ID use symbols and circles to represent each instrument and how they are inter-connected in the •process.

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Thermometer

TemperatureSensing Bulb

Temperature Transmitter

Temperature Controller and Recorder

Pneumatic Control

Valve

Fig. 3.4 Use of P and ID symbols(Source: http://www.lle.rochester.edu/media/omega_facility//documents/P&ID.pdf)

Tag DescriptorsTag “numbers” are letters and numbers placed within or near the instrument to identify the type and function of the device.

123

X Y Z

The first letter is used to designate the measured variable

The succeeding letter(s) are used to designate the function of the component, or to modify the meaning of the first letter.

Pressure

Level

Flow

Temperature

Indicator

Recorder

Controller

Transmitter

Fig. 3.5 Tag descriptors(Source: http://www.lle.rochester.edu/media/omega_facility//documents/P&ID.pdf)

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FCV206

emperature ecording T R Controller

Temperature Transmitter

Temperature Indicator

TemperatureSensing Bulb

TRC206

TT206

TI206

Fig. 3.6 Tag numbers(Source: http://www.lle.rochester.edu/media/omega_facility//documents/P&ID.pdf)

Process Flow Diagrams (PDF)Processflowdiagramstypicallyincludethemajorequipmentandpipingpathwhichtheprocesstakesthrough•the unit. Some symbols are common among plants; others differ from plant to plant. •Thesymbolsusedinthischapterreflectawidevarietyofpetrochemicalandrefineryoperations.•ThePFDgivenbelowshowsthebasicrelationshipsandflowpathsfoundinaprocessunit.Theflowdiagram•isbrokendownintosections:feed,preheating,theprocess,andthefinalproducts.Thissimpleleft-to-rightapproach allows a technician to identify where the process starts and where it will eventually end. The feed section includes the feed tanks, mixers, pipings and valves. •Inthesecondstepofpreheating,theprocessflowisgraduallyheatedforprocessing.Thissectionincludesheat•exchangers and furnaces. In the third section, the process is included. Typical examples found in the process section could include •distillation columns or reactors. The process area is a complex collection of equipment that works together to produceproductsthatwillbesenttothefinalsection.

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Furnace

Feed Tank

Bottoms Tank

Boiler

Cooling Tower

Reactors

ProductTank

2

ProductTank

1

Vacuum Pump

Column

Drum

Fig. 3.7 Process flow diagram (PFD)(Source: http://webtools.delmarlearning.com/sample_chapters/1418030678_ch12.pdf)

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Summary Normally, a project passes through various phases, viz. basic engineering, detailed engineering, equipment •fabrication or procurement, civil or structural work, erection and commissioning. In a big chemical process industry, the processing units are spread over a large area. Although two different units •farawayfromeachother,areconnectedbypipelinesorthecontinuousflowoffluidfromoneunittoanother.Clear understanding of the process is very much essential for the preparation of a good quality process.•Process P and ID provides detailed information of the process plant like type of equipment, the details of pipelines •i.e.,sizeofmaterial,identificationnumber,typesofinstrumentsandcontrollingdevices,etc.Complex presentation of the pipelines i.e., lots of cross-crossing, may even lead to wrong pipeline routing and •hence due attention should be paid to the aesthetic aspect during the preparation of process P and ID.A hazard and operability (HAZOP) study is a structured and systematic examination of a planned or existing •process or operation in order to identify and evaluate problems that may represent risks to personnel or equipment, orpreventefficientoperation.

ReferencesDesign guide for layout and plot plan • [Online]. Available at: <http://webtools.delmarlearning.com/sample_chapters/1418030678_ch12.pdf>. [Accessed 6 April, 2011].Process diagrams • [Online]. Available at: <http://www.lle.rochester.edu/media/omega_facility//documents/P&ID.pdf >. [Accessed 6 April, 2011].P&ID - Piping and Instrumentation Diagram • [Online]. Available at: <http://www.engineeringtoolbox.com/p&id-piping-instrumentation-diagram-d_466.html >. [Accessed 7 April, 2011].Symbols for Process Flow Diagrams and Engineering Line Diagrams• [Online]. Available at: <http://www.roymech.co.uk/Useful_Tables/Drawing/Flow_sheets.html>. [Accessed 7 April, 2011].I• nterpreting Piping and Instrumentation Diagrams [Online]. Available at: < http://chenected.aiche.org/plant-operations/interpreting-piping-and-instrumentation-diagrams-part-2-of-5/>. [Accessed 7 April, 2011].

Recommended ReadingGoettsche, L. D., 2005. • Maintenance of instruments & systems: Practical guides for measurement and control, 2nd ed., ISA.Blevins, T. L., 2010. • Mark Nixon Control Loop Foundation: Batch and Continuous Processes, 2nd ed., ISA.Thakore, 2008. • Introduction to Process Engineering and Design, Tata McGraw-Hill Education.

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Self AssessmentWhat cannot be at all ignored for the successful operation of any process plant?1.

Safety measuresa. Maintenanceb. Operationsc. Aestheticsd.

What is not concerned with the plant operation?2. Maintenancea. Aestheticsb. Operationsc. Start-upd.

________of the process is very much essential for the preparation of a good quality process.3. Clear understandinga. Equipmentsb. Identificationnumberc. Controlling devicesd.

_______withconnectionsshouldbeshownintheprocessP&IDforliquidsealfilling.4. P and IDa. Valveb. Instrument symbolsc. Instrument sized.

__________ study is carried out keeping in view, each and every safety and operation step.5. Hazard and operability a. Equipment layoutsb. Plot planc. Pipingspecificationsd.

WhichoftheseisthefinalstepforthepreparationofanyprocessPandID?6. Show all equipment as per equipment list and layout.a. Showallrequiredvalvesandfittings.b. Review P and ID considering start-up requirements.c. Review P and ID for its aesthetic look.d.

Which is not the necessary parameter of instrumentation?7. Pressurea. Levelb. Temperaturec. Lightd.

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Which of these is not a method of heating in a manufacturing industry?8. Steam a. Solarb. Electric c. Thermald.

Which of these is not a type of valve used in piping?9. Regulating valvea. Isolating valveb. Check valvec. Rotating valved.

Which of the following statement is FALSE?10. Process technicians use P and IDs to identify all of the equipment, instruments and pipings found in their a. units. There are symbols to represent major and minor process lines and pneumatic, hydraulic, or electric lines.b. The P and ID use symbols and circles to represent each instrument and how they are inter-connected in the c. process.P and ID are letters and numbers placed within or near the instrument to identify the type and function of d. the device.

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Chapter IV

Steam Tables and Mollier Diagram

Aim


definesteamtables•

describe properties and formation of steam•

explain the Mollier diagram•

discuss the steam distribution piping system•

Objectives


describe the typical steam distribution system•

explain the use of P and ID symbols•

understand the steam main and branch lines•

Learning outcome


examine various heating media used in industries•

highlight the importance of steam quality•

get an overview of steam tables and Mollier diagram•

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4.1 IntroductionIn oil and chemical plants, of all types and sizes, energy is used for process heating. It may also be used for space heating and for power, generating electricity and driving pumps and compressors. Process applications include product heating in stills, evaporators, feed heaters, boilers, reaction vessels and dyers.

Maintenance of product temperature is often required in storage tanks, tracer lines jacketed pipes and valves. Particularly in the large complex, steam remains an obvious choice for heating. Although steam is the traditional means of conveying heat, there are now a number of alternatives. These include high or medium pressure hot water and heat transfer oils. In some cases, it is more convenient to use electricity, especially for tracing and for the mechanical agitation for storage tanks.

Where electric power is generated, exhaust steam is an essential component of the overall heat balance. It is use directly as a constituent in many chemical reactions and it provides, though waste heat boiler, an obvious way of recoveringheatfrommanyexothermicreactions.Inmanyrefineries,primarysteamisobtainedbyburningwasteproducts in the boiler and thus, it costs low.

Steam is usually generated in a central boiler used and distributed around the site, often at a number of different pressures,byanetworkofsteammainswhichplaysavitalpart intheefficientrunningoftheplant.Ithastheadvantagethatitcanbeusedforpowerandheatingbutitsmainvirtueisitsflexibility.Thoughmanychemicalplantsmay have a limited life, their overall cost will be reduced if they are applied from steam services on a permanent basis. Another great virtue of steam is that it can be regulated to give varying heat levels through reducing valves or to give temperature control through simple two-way valves.

4.2 Steam: Formation and PropertiesSteam is the vapour form of water. It does not obey the laws of perfect gases, until it is perfectly dry. When the dry steam is further heated, it behaves more or less like a perfect gas. The steam is generally used as a working substance in the operation of steam engines and steam turbines.

4.2.1 Formation of SteamWhen any liquid is heated at constant temperature, it i. starts changing in vapour condition. A vapour is a mixture of gasandliquidparticlesinsuspensionanditcanbeliquefiedbymoderatechangesofpressureor temperature. Theprocessofvapourformationfromliquidstatehassomedefinitecharacteristicstofollowinsteamii. engine.The heat supplied during the process of vaporisation changes its state gradually from liquid to gaseous iii. state.The vapour is said to be dry saturated when the process of vaporisation takes place at constant pressure iv. and temperature or when the liquid is completely evaporated.The vapour is calledv. superheated when the heat is added to the dry saturated vapour state. At superheated state, the temperature will rise gradually.During the process of superheating, the volume of vapour at constant pressure increases approximately vi. in proportion to the absolute temperature, which indicates that the vapour is approaching the state of perfect gas.The temperature at which the evaporation process is taking place increases when the pressure on the vii. liquid surface is increased. The latent heat of vaporisation decreases with the increase of pressure and temperature but the enthalpy increases under this condition.

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The total heat (enthalpy) of dry saturated vapour increases with increase in saturation temperature. After viii. certain saturation temperature, the rate of increase in enthalpy is less than the rate of decrease in latent enthalpy and hence, the enthalpy of dry saturated vapour decreases. This will continue to happen until the saturation temperature is reached when the latent enthalpy becomes zero and the enthalpy of dry saturated vapour becomes equal to the sensible heat. This saturation temperature is called as critical temperature and the corresponding pressure is called critical pressure and the state of substance is called its critical state.Steaix. m can not exist as saturated vapour above its critical temperature. At any temperature higher than the critical temperature (374.14°C), the vapour can only exist as a gas without any effect of pressure. At criticaltemperature,thespecificvolumeofdrysaturatedvapourbecomesequaltothespecificvolumeof the liquid from which it is being formed.

4.2.2 Properties of SteamThe followings properties of steam are always needed for the calculations of its various parameters, which are required in the operation of steam engines and steam turbines.Specific volume of steam

It is the volume occupied by the steam per unit mass at a given temperature and pressure. •It is expressed in m/kg and is the reciprocal of the density of steam. •Thespecificvolumeofsteamincreaseswith the increase in temperatureanddecreasewith the increase in•pressure.

Specific enthalpy of steamIt is the total heat absorbed by the steam per unit mass from the freezing point of water (0°C or 273 K) to the •saturation temperature (100°C or 373K) plus the heat absorbed during evaporation. It is expressed in kJ/kg. •Thespecificenthalpyofsteamincreaseswiththeincreaseintemperatureandpressure.•

Specific entropy of steamIt is a theoretical value of heat energy, which can not be transformed into mechanical work under the given •conditions of temperature or pressure. It is also called degree of disorder of the system. •It is expressed in kJ/kg K.•Thespecificentropyofsteamdecreaseswithanincreaseintemperatureandpressure.•The most common term used is the change of entropy, which is mathematically given as:•

4.3 Steam TablesSteam tables are tables of thermodynamic data for steam, used often by engineers and scientists in design and •operation of equipment where thermodynamic cycles involving steam are used. Thevariouspropertiesofsteam(suchasspecificenthalpyandentropy)ofdrysaturatedsteamandsuperheated•steam vary with the variations of temperature and pressure.Thesevalueswerecarefullydeterminedbyobservationsandcalculationfirstin(FootPoundSystem)F.P.S.•system and were made available in tabular form known as steam tables. Later on, these values were converted in to M.K.S. units and then in to S.I. units.

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It is a general practice to give the following tables for some important values:•Saturated water and steam (temperature) table �Saturated water and steam (pressure) table �Superheated steam table �Supercritical steam table �

Saturated water and steam (temperature) tableIt contains values of :•

absolute pressure (in bar) �specificvolume(inm � 3/kg)specificenthalpy(inkJ/kg) �specificentropy(inkJ/kgK)from0ºCto374.15ºC(criticaltemperature) �

A sample of this table is given below:•

Temperaturein0C(t)

Absolutepressure

in bar(p)

Specificvolumeinm3/kg

Specificenthalpyin kJ/kg

Specificentropyin kJ/kg K

Water(vƒ)

Steam(vg)

Water(hƒ)

Evaporation (hƒg)

Steam(hg)

Water(sƒ)

Evaporation (sƒg)

Steam(sg)

0510

0.006 110.008 720.012 27

0.001 0.001 0.001

206.16147.16106.43

0.021.042.0

2501.62489.72477.9

2501.62510.72519.9

0.0000.070.151

9.1588.9518.751

9.1589.0278.902

Table 4.1 Example of saturated water and steam (temperature) table

The use of this table is given in the following example.

Example 1: Calculatethespecificenthalpyandspecificentropyof1kgofsteamat100ºCwhenitsdrynessfractionis0.8.Solution:

Given: •Mass of steam (m) = 1 kg; �Temperatureofsteam(t)=100ºCand �dryness fraction of steam (x) = 0.8 �

Fromsteamtables,correspondingtoatemperatureof100ºC,wefindthat•h � ƒ = 42.0 kJ/kgh � ƒg = 2477.9 kJ/kgs � ƒ = 0.151 kJ/kg K s � ƒg = 8.751 kJ/kg K.

Specificenthalpyofsteam•Weknowthatspecificenthalpyofsteamis,

h = m [h � ƒ + x hƒg] = 1 × [42.0 + (0.8 × 2477.9)] = 2024 kJ

Specificentropyofsteam•Wealsoknownthatspecificentropyofsteamis,

s = m [s � ƒ + x sƒg] = 1 × [0.151 + (0.8 × 8.751)] = 7.1518 kJ/kg K

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Saturated water and steam (pressure) tablesItcontainsthevaluesoftemperature(inºC),specificenthalpy(inkJ/kg)andspecificentropy(inkJ/kgK)from•0.0061 bar (critical pressure). A sample of this table is given below:•

Absolutepressure

in bar(p)

Temperature in

0C(t)

Specificvolumeinm3/kg

Specificenthalpyin kJ/kg

Specificentropyin kJ/kg K

Water(vƒ)

Steam(vg)

Water(hƒ)

Evaporation (hƒg)

Steam(hg)

Water(sƒ)

Evaporation (sƒg)

Steam(sg)

0.0100.0200.030

6.9817.5124.10

0.001 0.001 0.001

129.2167.01245.670

29.373.5101.0

2485.02460.22444.6

2514.42533.62545.6

0.1060.2610.354

8.8718.4648.224

8.9778.7258.578

Table 4.2 Saturated water and steam (pressure) tables

The use of this table is given in the following example.

Example 2:Whatisthespecificenthalpyandspecificentropyof1.5kgofsteamatapressureof0.030bars,whenitsdrynessfraction is 0.6?Solution:

Given: •Mass of steam (m) = 1.5 kg �Pressure of steam (p) = 0.030 bar and �Dryness fraction of steam (x) = 0.6 �

Fromsteamtables,correspondingtoapressureof0.030bars,wefindthat•h• ƒ =101 kJ/kgh• ƒg = 2444.6 kJ/kgs• ƒ = 0.354 kJ/kg K and s• ƒg = 8.224 kJ/kg KSpecificenthalpyofsteam•Weknowthatspecificenthalpyofthesteam,

h = m [h � ƒ + x hƒg] = 1 × [101 + (0.6 × 2444.6)] = 1567.76 kJ

Specificentropyofthesteam•Wealsoknowthatspecificentropyofthesteam,

s = m [sƒ + x sƒg] = 1.5 × [0.354 + (0.6 × 8.224)] = 7.9326 kJ/kg K �

Superheated steam tablesThesetablescontainvaluesofspecificvolume,specificenthalpyandentropyofsuperheatedsteamfroman•absolutepressureof0.02bar(criticalpressure)atvarioustemperaturesfrom100ºCto800ºC.Thevalueofspecificvolume,specificenthalpyandspecificentropyofsteamaredirectlyreadfromtheconcerned•tables. However, the value at any other pressure or temperature (not mentioned in the tables) is obtained by •interpolation.

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Supercritical steam tablesThesetablesalsocontainthevaluesofspecificvolume,specificenthalpyandspecificentropyofsupercritical•steamfromanabsolutepressureof250barto1000baratvarioustemperaturesfrom400ºCto800ºC.Inthesetablesalso,thevaluesofspecificvolume,specificenthalpyandspecificentropyofsteamaredirectly•read from the concerned tables. However, the value at any other pressure or temperature (not mentioned in the table) is obtained by •interpolation.

4.4 Mollier DiagramThe Mollier diagram is a graphic representation of the relationship between air temperature, moisture content •and enthalpy, and is a basic design tool for building engineers and designers. Itisagraphicalrepresentationofsteamtables,inwhichspecificentropy(s)isplottedalongthecoordinate•(Y-axis)andspecificenthalpy(h)alongtheabscissa(Xaxis).It is sometimes known as the h-s diagram.• The diagram is divided into two portions by a somewhat horizontal line termed as saturation curve. •The lower portion (i.e., wet steam region) contains the values of wet steam, whereas the upper portion (i.e., •superheated steam region) contains the values of superheated steam. A Mollier diagram has the following lines.•

Dryness fraction line �Constantspecificvolumelines �Constant pressure lines �Constant temperature lines �

4.4.1 Dryness Fraction Lines

These lines are drawn in the wet steam region. i.e., only below the saturation curve (which represent dryness •fraction equal to unity). These lines represent the condition of wet steam between various values of enthalpy and entropy. •The dryness fraction lines are slightly curve in horizontal direction.•

4.4.2 Constant Specific Volume Lines

These lines are drawn in both the wet steam region and superheated steam region.•Theselinesrepresentthespecificvolumeofsteambetweenthevariousvaluesofenthalpyandentropy.•The lines are straight in the wet steam region, i.e., below the saturation curve, but are curved upward in the •superheated region i.e., above the saturation curve.

4.4.3 Constant Pressure Lines

These lines are also drawn in both the wet steam region and superheated steam region. •These lines represent the pressure of steam between various values of enthalpy and entropy. •The pressure lines are also straight in the wet steam region, i.e., below the saturation curve, but are curved •slightly upwards in the superheated region i.e., above the saturation curve.

4.4.4 Constant Temperature Lines

These lines are drawn only in the superheated steam region i.e., above the solution curve. •These lines represent the temperature of steam between various values of enthalpy and entropy. •The temperature lines are slightly curved in the horizontal direction.•

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Specific volume line Pressure line

Temperature line

Ent

hapl

y

Saturation line

Superheated steam (x = 1)

Wet steam (x < 1)

Dry saturated steam (x = 1)

Dryness fraction line

H

H1x

H2

Fig. 4.1 Mollier diagram(Source: http://www.transtutors.com/university-yale/mollier-diagram-application-6.htm)

4.5 Piping for Steam DistributionIn large size plants, steam is used for one or more of applications such as power generation (steam turbine), process heating in vacuum device (steam ejector) etc.

Typical steam distribution systemA typical steam distribution system consists of:

Boiler, for steam generation.•Steam using equipments such as turbine, evaporator, reaction vessel, ejector etc.•Interconnecting pipelines.•Pressure reducing station (PRS) with desuperheater (PRDS) or without desuperheater.•Condensatereturnpipingsystemwithorwithoutflashsteamrecoverysystem.•

Heating or space heating applicationsFor process or space heating options, other forms of steam are available viz. water (sometimes at high pressure) andthermicfluids(includinghightemperatureoils)areused.

Line size for steam pipeThelinesizeforsteamdistributionisdecidedbythesteamflowrateandpermissiblepressuredrop.However,incase of steam piping, a few things are to be considered such as:

quality of steam (dry saturated / wet exhaust / superheated)•main supply line (often referred to steam header) or branch line (pipeline form steam header to user •equipment)

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Unwin equation (using metric units)Unwin equation is used for calculation of pressure drop for steam service. The equation is given below:

where,theunitsforsteamflowrate(W),internalpipediameter(d)anddensity(ν) are:W - Kg / hr•d - mm•ν-Kg/m• 3

Equivalent length of fittingPressuredropthroughfittingssuchasbend,reducer,valveetc.Fluidsufferspressuredropasitpassesthroughfittings.Theresistanceofferedbyfittingcanbecorrelatedtolengthofstraightpipeofferingsameresistanceintermsofpressuredrop.Suchlengthofstraightpipeisdesignatedasequivalentlengthofthefitting.Foranysegmentofpipeline,totalequivalentlengthisthetotaloflengthofstraightpipeplusequivalentlengthofallfittings.Nomographisusedforfindingequivalentlengthoffittings.Someapproximationscanbeseenasbelow.

Fitting Equipment length in m (d-pipe NB in mm)

Gate valve-full open 0.01

Globe valve-full open 0.35

Long radius bend 0.03

Tee connection 0.07

Table 4.3 Approximations of equivalent length of fittings

Equationsforpressuredropbasedonrigorousmathematicsareavailableforisothermalaswellasadiabaticflowconditions. However, certain empirical equations based theoretical consideration has proved adequate for the practical purpose. For steam applications, Unwin equation is widely used.

Where,W=steamflowinlbs/minv=sp.vol.incubft/lb•d = pipe ID in inches•D• p= actual pressure drop (psi per 100 ft pipe)

Conversion in metric units is:

Various units of pressure measurement are:1 atm - 1.033 Kg / cm2 = 1.013 bar = 14.7 psi

- 1.02 Kg / cm2 = 1 bar = 14.5 psi - 1 Kg / cm2 = 0.981 bar = 14.23 psi

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LONG RADIUS90 BEND0LONG RADIUS90 BEND0

SHORT RADIUS90 BEND0

Fig. 4.2 Resistance of valves and fittings to flow of fluids(Source: http://www.pipingguide.net/2010/01/piping-for-steam-distribution.html)

Economic Velocity for deciding line sizeFor given mass or volume, increasing pipe diameter (ID) would reduce the velocity. The effect of change in pipe size could be seen as below:

Pipe size (ID) Velocity Pressure drop Heat-loss

Higher Lower More

Lower Higher Higher Less

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A compromise has to be reached between these opposing factors of initial cost, pressure drop and heat loss. Velocity of steam which offers optimum solution is referred to as economic velocity. For standard steam service, the recommended velocities are:

Exhaust wet steam 15 - 25 m /s•Dry saturated steam 25 - 35 m/s•Superheated steam 35 - 45 m/s•

At these velocities the pressure drop would be about 1 psi /100 ft or about 0.2 bar / 100 m.

where,m=massflowrateofsteaminkg/hr•EV = economic velocity m/s•SPV=specificvolumecubm/kg•d = pipe diameter ( ID) in mm•

For purpose of deciding pipe sizes for steam service, the steam pipe lines could be broadly grouped into two categories viz. steam main and branch lines.

Steam mains• are large size line spanning considerable distance. They have to deliver steam of required quantity to various steam using devices. The pressure drop is, therefore, an important consideration. The design procedure, therefore, involves selecting steam velocity closest to, if not within economic range, which gives pressure drop within permissible limits. Branch lines• are much shorter in length. Thus, the pressure drop is not of substantial magnitude. Therefore, branch lines are sized on the basis of velocity of 25 - 35 m/s.

Main

Shut-Off Valve

Trap Set

Fig. 4.3 Recommended take-off point with branch drainage

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Drain

Vent

Steam Main

Fig. 4.4 Drain and vent

steam

drain points

Foll 1/70 Relay to higher level

30-50 m

Fig. 4.5 Relaying to higher level

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Correct

Steam

Steam

Condensare

Incorrect Steam Trap

Steam Trap

Pocket

Fig. 4.6 Ineffective and proper drainage point

Correct

Steam

Incorrect

Condensare

Fig. 4.7 Steam line reducer

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PressureBar

Velocity m/s

15mm

20mm

25mm

32mm

40mm

50mm

65mm

80mm

100mm

125mm

150mm

200mm

250mm

300mm

0.4 152540

71017

142535

244064

3762102

5292142

99162265

145265403

213384576

3946751037

6489721670

91714572303

160628064318

259041016909

367859389500

0.7 152540

71218

162537

254568

4072106

59100167

109182298

166287428

250430630

4317161108

68011451712

100615752417

170828164532

2791146297251

3852620410323

1.0 152540

81219

172639

294871

4372112

65100172

112193311

182300465

260445640

4707301150

69411601800

102016602500

186430994815

281448697333

4045675110370

2.0 152540

121930

254364

4570115

70112178

100162275

182295475

280428745

4106561010

71512151895

112517552925

158025204175

281448157678

4545742511997

62771057516796

3.0 152540

162641

375687

60100157

93152250

127225375

245425595

3856321025

5359101460

92515802540

150524804050

204034405940

3983677910476

62171026916470

87431431622950

4.0 152540

193049

4263116

70115197

108180295

156270456

281450796

4327421247

63510801825

116619803120

168529254940

246042257050

4618786612661

71211222519663

103581730427816

5.0 152540

223659

4981131

87135225

128211338

187308495

352548855

5268851350

77012651890

129521103510

210535405400

283551507870

5548886513761

85861426823205

119472005132244

6.0 152540

264371

5997157

105162270

153253405

225370595

4256581025

63210651620

92515202270

155525304210

252542506475

340061759445

66541062916515

102971710827849

143282404238697

7.0 152540

294976

63114177

110190303

165288455

260450690

4457851210

70512051865

95217502520

18153025458 5

276548157560

3990690010880

73901228819141

120151937730978

160962708043470

8.0 152540

325484

70122192

126205327

190320510

285465730

4758101370

80012602065

112518703120

199032405135

302552208395

4540712012470

80421314021247

126252160033669

177283321046858

10.0 152540

4166104

95142216

155257408

250405615

372562910

6269901635

101215302545

146522053600

249538256230

399562959880

5860899514390

9941596626621

161722586041011

227133589057560

1 4.0 152540

5085126

121195305

205331555

310520825

4657401210

81013752195

127020803425

187031204735

322052008510

5215850013050

73901256018630

129212172035548

205383413954883

290164721876534

Table 4.4 Steam pipe sizing (carrying capacity in kg/h)

4.6 Heating MediaThere are a number of heating media used in industries.Water systems

Watersystemsfindonlylimitedapplicationinthechemicalindustrybuttheyareusedparticularlywherethe•high temperatures associated with steam will damage the product. They involve relatively large pipes and large heating surfaces. •

High temperatures oilsTheoilandchemicalindustrieswereamongthefirsttoutilisehightemperaturefluidsasheattransfermedia.•These are extremely useful where high process temperatures are required and where the high pressure associated •withsteamwouldcausedifficulties.Mostofthesefluidsareveryexpensive,butrecentlyhydrocarbonoilshaveprovidedamoreviableanswer.•Hydrocarbon oils are used increasingly for the medium range temperatures associated, for example, with •bitumen plants.However,theinflexiblenatureofhightemperatureoilsystemsuggeststhatitwilltaketimetobeconsidered•as a complete alternative to steam.

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Electric heatingWhether electricity is generated or purchased from the national grid, electric heating is almost invariably more •expensive than other forms of heating. Therefore, it is rarely used for build heating but can sometimes be usefully employed on the heat loads associated •with tracing. Electric tracing is a system used to maintain or raise the temperature of pipes and vessels. •Electrical heat tracing may be described as an insulated electrical heating cable, which is spiralled around •theprocessfluidpipe,afterwhichthepipeandtracingisinsulatedwiththeappropriatetypeandthicknessofinsulation lagging material.It is useful for overcoming cold start up conditions before steam is available or perhaps at remote points where •there is no steam service.Ontheotherhand,anelectricsupplysystemisfrequentlylessflexiblethanasteamsystem.•Although, the old tapping from a steam system can usually be used to provide steam tracing, the random use •of electric tracing can soon produce overloading of supply cables and switchgear, and produce unsatisfactory load factors. Electricheatingisoftenavoidedonsiteswherefireorexplosionriskscallforspecialflame-proofing.•

Mechanical agitationFrom time to time, steam heating coils are used in storage tanks, not to maintain temperature, but simply to •provide convection currents and thereby avoid the settling out of various fractions. As an alternative, mechanical agitators or stirrers are sometimes used, powered by electric motors. The electric •motors used on large tanks are sizeable.

4.6.1 Steam Utilisation in the Large Complex

Inarefinerychemicalcomplex,thereisagreatdemandforelectricalpower.Thisislargelymetbygenerating•electricity on site, utilising turbines fed by superheated steam from a central boiler plant. Saturated steam will condense rapidly on any surface which is at lower temperature, giving up a large proportion •ofitstotalheatcontent.Oncondensation,thechangeinvolumeencouragestheflowofsteamtowardstheheatexchange surfaces and enables-high heat transfer rates to be maintained.Ontheotherhand,withsuperheatedsteam,theflowofheatfromthecoreofthesteamtotheheattransfersurface•is only by conduction and thus, much slower.Thedrygasactsasinsulatingfilm,resistingtheflowofheat.•

Sl. No. Steam Hot Water High Temperature Oils

1High heat content.Latent heat approximately2100 kJ / kg 900 Btu /b

Moderate heat content.Specificheat–4.19kJ/ kg°C, 1 Btu/lb°F

Poor heat contentSpecificheatoften1.69 – 2.93kJ/ kg°C, 0.4 -0.7 Btu/lb°F

2 Cheap but some watertreatment cost

Cheap .Onlyoccasional dosing Expensive

3 Good heat transfercoefficients

Moderate heattransfercoefficients

Relatively poor heattransfercoefficients

4 High pressure required forhigh temperatures

High pressurerequired

Low pressures onlyto get hightemperatures

5 No circulating pumprequired

Circulating pumprequired

Circulating pumprequired

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6 Small pipes Large pipes Large pipes

7 Easy to control with 2-wayvalves

Less easy – 3 wayvalves or differentialpressure valves may be required

Less easy – 3 wayvalves or differentialpressure valves may be required

8 Temperature breakdowneasy through reducing valve

Temperaturebreakdown lesseasy

Temperaturebreakdown lesseasy

9 Steam traps required No steams traps No steams traps

10 Condensate to be handled No condensatehandlings

No condensatehandlings

11 Flash problems Noflashproblems Noflashproblems

12 Blow down loss No blow down loss No blow down loss

13 Corrosion problems Less corrosion Negligible corrosion

14 Reasonable pipe-workrequired

Searching medium,weldedorflangedjoints usual

Very searchingmedium, welded orflangedjointsusual

15 Nofirerisk Nofirerisk Fire risk

16 Systemflexible Systemlessflexible Systeminflexible

Table 4.5 Comparison of heating media with steam

4.6.2 Steam Quality

For most process applications, dry saturated steam is required.•Anidealconditioncouldbeachievedbydistributingthesteamfromtheboilerhouse,withsufficientsuperheat•to cater mains losses, so that the steam arrived at the point of usage having lost its superheat, be in a dry state. Inpractice,suchaconditionisdifficulttoachieve.Variations in lengths of travel and ambient air conditions make it impossible to reach the extract ideal of having •dry saturated steam at each and every point of usage. Therefore, steam quality varies around the industrial complex.This can even be the case where very high-pressure and high temperature superheated steam is being used.•On the start-up of such a system, the superheated steam enters the cold steam pipe work and gives up its superheat, •until it condenses rapidly at the saturated steam temperature. For such start-up conditions, it is a conventional practice to blow down the steam main through valves so that •thiscondensateisremoved.Asthesteammaincomesuptothefinalworkingpressureandtemperature,thesevalues are closed.However, depending upon the superheat temperature, the travel length of the steam main, the quality of insulation, •weatherconditionsandthequantityofsteamflowingundercertainconditions,itispossibleforthesteamtogive up its superheat and begin to condense. Therefore, at these remote points, provisions should be made for automatically draining out such condensate •using a steam trap. This is absolutely essential for the batch process applications, where for short periods, there isnosteamdemandandhencenoflowsofsteamdownthepipe.Undersuchcircumstances,operatorsshouldnot rely upon opening and closing drain valves.Steam at the point of usage is seldom dry and unsaturated. •

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In chemical plant, steam is being generated within a boiler and thus, is in contact with water. Further, it leaves •water through a surface which is turbulent, throwing up droplets of water into the steam space and producing wet steam. It depends on factors such as water level below the off-take (point of beginning of water channel), pressure on water surface, solids content of water and effect of peak loads.Any of the factors, one or in combination, can make it possible for droplets of water to be carried over with the •steam into the distribution system. These droplets entrained with the steam, carry no latent heat.Theyaddtothethicknessoftheresistantfilmofwaterontheheatexchangersurfaceandslowdowntherate•of heat transfer. The problem lies to improve steam quality by removing these moisture particles. The solution can be achieved, •simply by installing a steam dryer or separator into the pipe line.A steam separator is an in-line piece of equipment that is used to remove entrained condensate particles.•Any moisture particles carried along with the steam will impinge on a plate, and drain to bottom of the unit •leaving the dry steam to pass on to the processing plant.Thewaterisfinallyseparatedoutanddrainedoffbymeansofasteamtrap.Itisagoodthingtofitseparatoron•the branch line to every steam user, thus ensuring a dry steam supply.Theefficiencyofseparatorsisabigquestion.Agenerallyhighfiguremaybequotedsuggestingthatalmostall•freewaterisremoved.Suchfiguresaremisleadingontwocounts.Firstly, the performance of the separator varies with the conditions such as total moisture content, droplets size •and particularly, the steam velocity.Secondly, the measurement of results is the main tentative block. Although calorimeters are available for •measurement of dryness fraction, it is almost impossible to take representative sample from the steam pipe either upstream or downstream of a separator. Steam at the centre of a pipe will travel at the highest velocity and will be relatively free of water droplets. Towards the pipe wall, the velocity will be lower. This part of thesteamflowwillcarrymoremoisturewhilethepipewallmaybecoveredbyafilmofwaterbeingdraggedalong at some lower velocity. Results will depend on the point from which the sample is taken. It is, therefore, difficulttogetanyclearview.Upontraditionalexperienceofinstallations,particularlythosewithwidevariationsinconditions,thebaffle•plate type of separator, provides better plant performance by supplying steam using equipment with high quality dry steam. Moisture,eitherbeingcarriedalonginthesteamfloworpresentasafilmofcondensateonthewallsofsteam•pipe, is not the only factor affecting steam quality. There are factors like air and incondensable gases. Consider a plant which has been shut down for a period of time. The steam trapped in the pipe is condensed and •itsplacetakenbyairdrawninthroughflangedjoints,unions,valveglands,etc.Whenthetimecomestore-startthe plant, this air has to be pushed out of the pipe work by the incoming steam acting like a piston. This applies once a year for some plants which are in continuous operation, when the plant is restarted after •annual shutdown. If, because of lack of provision for air venting, 50 plant operators are waiting for minimum half an hour for •their plant to warm up, then 25 valuable man hours are lost to production. In such cases, the operator will invariably open the steam inlet valve to plant during this period. Air pushed •along the steam mains, is now passed into the steam spaces of the plant.So, particularly in those cases where steams distribute systems are shut down at frequent intervals, adequate •provisions for air venting on start up is a must. Coupled with air, there can be presence of other incondensable gases which enter the steam system, especially •from decomposition of carbonate and bicarbonate ions from salts in the boiler feed water. These ions release carbon dioxide within the boiler, and this gas as well as the oxygen and nitrogen are carried by the steam into the distribution system.

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Even where desecrators are in use, very small amounts of gases remain in solution in the feed water and over •moderate periods of use, it accumulates in the steam lines and in the heat exchangers. Only when the partial pressureofthegaseshasbuiltuptoasufficienthighlevel,theydissolveinthecondensate.Whenthishappens,corrosion problems usually occur swiftly and in the meantime, the gases form an insulating barrier between the steam and the heat exchanger surfaces, reducing the plant output. Even if the appropriate chemicals are added to the boiler feed water to deal with oxygen and carbon dioxide, •the nitrogen dissolved in the water is usually ignored. Automatic air vents are the simple way of dealing with these problems.•

Steam in

Air pushed along by steam

Condensate return lineFloat-thermostatic trap set

Condensate

CondensateCondensate

Air Air Air

Steam in Steam inAir vent located

opposite steam inlet

Fig. 4.8 Automatic air vent located opposite the steam inlet on the jacketed pan(Source: http://www.spiraxsarco.com/resources/steam-engineering-tutorials/steam-traps-and-steam-trapping/air-

venting-theory.asp)

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Fig. 4.9 Steam separator(Source: http://arab-training.com/vb/t8022.html)

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4.7 Selection of Steam PressuresSteam should be distributed at high pressure because it occupies less space and this in turn means that smaller, •less costly mains can be used. The smaller mains have less heat-losing surface and better quality steam is likely to result.For process or space heating purposes, steam should be used at the lowest possible pressure. Low pressure steam •offersthemaximumamountoflatentheatperpoundandtheproblemsofflashsteamfromthecondensatearereduced. This means less back pressure in condensate systems and less wasteful vapour at collecting tanks or from trans-discharging to atmosphere. This vapour can also be dangerous if it reduces visibility or freezes in cold weather. But there are factors that limit how far pressure can be reduced. The amount of heating surface in the plant will usually determine how low the pressure can be before the •corresponding reduction in temperature head adversely affects outputs.Some products must be processed at a particular temperature and this will require a certain steam temperature •and pressure. The choice of pressure is a compromise and can only be decided in the light of all the factors.When the steam pressure required in the distribution system, a reducing valve must be used to break down the •pressure from a high pressure main and a good quality valve should be chosen providing a consistent supply of steam, regardless of load changes.A reducing valve of the self-contained relay type is more than adequate for many applications, but it is to provide •accurate control.The use of a reducing valve will not normally convert wet steam into a superheated condition but will simply dry •out some of the entrained water and give drier and, therefore, better quality steam reaching the reducing valve.

High pressure steam in

Separator

Safety valve

Low pressure steam out

Condensate

Pressure reducing

valve

Fig. 4.10 Pressure reducing valve(Source: http://www.spiraxsarco.com/resources/steam-engineering-tutorials/control-applications/pressure-

control-applications.asp)

4.8 Pressure Drop Factor Steam may be thought of as a medium to convey heat from the boiler to the point where it is needed. •Asthetemperatureofsaturatedsteamisfixedinrelationtothepressure,therequiredtemperatureinanyprocess•can be controlled by the steam pressure. But, for instance, a 20% reduction in designed steam pressure to a calorifiermayresultina15%dropinoutput.Therefore, while producing steam at the correct pressure and quantity in the boiler house is important.•While distribution pipework cannot be too big, the extra capital cost would not be acceptable. If pipework is •too small, then the increased steam velocity will cause noise and erosion and the excessive pressure drop may starve the equipment of steam. Velocity should be designed to be below 15 metres/sec or 50 ft/sec.In practice, sizing the pipework to produce a known pressure drop, works best. There are many programs, graphs •andtablesavailablethatmakeuseofthesimplifiedformula:

F= (P1 - P2)/ L

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where,F = Pressure drop factorP1 = Factor at inlet pressureP2 = Factor at a distance of L metresL = Equivalent length of pipe (m)

4.9 Steam Pipe Sizing and Design Anymodificationandalterationintheexistingsteampiping,forsupplyinghigherqualitysteamatrightpressureand quantity must consider the following points:

Pipe Sizing The objective of the steam distribution system is to supply steam at the correct pressure to the point of use. •Pressure drop through the distribution system is an important feature. Proper sizing of steam pipelines helps in minimising pressure drop. •The velocities for various types of steam are: •

Superheated : 50-70 m/sec �Saturated: 30-40 m/sec �Wet or Exhaust: 20-30 m/sec �

Forfluidflow,theremustbemoreenergyatPoint1thanPoint2.•Thedifferenceinenergyisusedtoovercomefrictionalresistancebetweenthepipeandtheflowingfluid.•

Pipe Diameter (D)

Length (L)

hf

h2

h1

Point 1 Point 2

Flow Velocity (u)

Fig. 4.11 Pressure drop in stream pipes

This is illustrated by the equation:

=

Where,hf = Head loss to friction (m)f = Friction factor (dimensionless) L = Length (m) u = Flow velocity (m/s) g = Gravitational constant (9.81 m/s²) D = Pipe diameter (m)

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It is useful to remember that: Head loss to friction (• hf) is proportional to the velocity squared (u²). The friction factor (• f)isanexperimentalcoefficientwhichisaffectedbyfactorsincluding:

Reynolds Number (which is affected by velocity) �

TheReynoldsNumberisanondimensionalparameterdefinedbytheratioofdynamicpressure(ρu2) and shearing stress (μu/L) and can be expressed asRe = (ρ u2) / (μ u / L) = ρ u L / μ = u L / ν

Where,Re = Reynolds Number (non-dimensional)ρ=density (kg/m3, lbm/ft3)u = velocity (m/s, ft/s)μ= dynamic viscosity (Ns/m2, lbm/s ft)L = characteristic length (m, ft)ν= kinematic viscosity (m2/s, ft2/s)

Reciprocal of velocity � ²

Because the values for ‘f’ are quite complex, they are usually obtained from charts. •

Example - Water pipe Determine the difference in pressure between two points 1 km apart in a 150 mm bore horizontal pipework system. Given:thewaterflowrateis45m³/hat15°Candthefrictionfactorforthispipeistakenas0.005.

=

=

= 3.43 0.34 bar

In practice, whether for water pipes or steam pipes, a balance is drawn between pipe size and pressure loss. •The steam piping should be sized, based on permissible velocity and the available pressure drop in the line. •Selecting a higher pipe size will reduce the pressure drop and thus the energy cost. However, higher pipe size •will increase the initial installation cost. By use of smaller pipe size, even though the installation cost can be reduced, the energy cost will increase due to higher-pressure drop. It is to be noted that the pressure drop change will be inversely proportional to the 5th power of diameter change. •Hence, care should be taken in selecting the optimum pipe size.

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Pipe redundancy All redundant (piping which are no longer needed) pipelines must be eliminated, which could be, at times, up •to 10-15 % of total length. Thiscouldreducesteamdistributionlossessignificantly.•The pipe routing shall be made for transmission of steam in the shortest possible way, so as to reduce the pressure •drop in the system, thus saving the energy. However,careshouldbetakenthat,thepiperoutingshallbeflexibleenoughtotakethermalexpansionandto•keep the terminal point loads, within the allowable limit.

4.10 Thermal InsulationPiping plays a central role in many industrial processes in chemical or petrochemical installations such as •power plants, as it connects core components such as appliances, columns, vessels, boilers, turbines etc. with oneanotherandfacilitatestheflowofmaterialsandenergy.Pipe insulation is thermal or acoustic insulation used on pipework.•There are many reasons for insulating a pipeline, most important being the energy cost. •

Purpose of pipe insulationThe functions of correct thermal insulation for piping includes: •

Condensation contro � lReduction of CO � 2 emissions Reduction of heat losses �Frost protection in � pipesProcess control: ensuring stability of the process temperature �Cost savings �Energy savin � gProtection against extreme temperature � sNois � e reduction

Adequate thermal insulation is essential for preventing both heat loss from hot surfaces of ovens/furnaces/piping •and heat gain in refrigeration systems. Inadequatethicknessofinsulationordeteriorationofexistinginsulationcanhaveasignificantimpactonthe•energy consumption. The material of insulation is also important to achieve low thermal conductivity and also low thermal inertia. •Developmentofsuperiorinsulatingmaterialsandtheiravailabilityatreasonablepriceshavemaderetrofittingor re-insulation a very attractive energy saving option.The simplest method of analysing whether you should use 1” or 2” or 3” insulation is by comparing the cost of •energy losses with the cost of insulating the pipe. The insulation thickness, for which the total cost is minimum; is termed as economic thickness. •However, in plants, there are some limitations for using the results of economic thickness calculations. Due to •space limitations, it is sometimes not possible to accommodate larger diameter of insulated pipes.By optimum pipe thickness, heat loss can be reduced to 5- 10 % of heat loss from bare surface or brought down •to 50 -100 k cal / hr m3.

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According to Petroleum Conservation Research Association (PCRA) recommended thickness of pipes are given •in the table below:

Surface temp (°C)Pipe Nominal bore (NB)

25 50 80 100Recommended thickness (inch)

100 1.0 1.5 1.5 2.0200 2.0 3.5 3.5 3.5300 3.0 4.5 4.5 5.0

Table 4.6 Pipe NB according to different surface temperatures

Heat loss from 1/2” to 12” steel pipes at various temperature differences between pipe and air can be found in the table below.

Nominalbore Temperature Difference (o C)

(mm) (inch) 50 60 75 100 110 125 140 150 165 195 225 280

15 1/2 30 40 60 90 130 155 180 205 235 280 375 575

20 3/4 35 50 70 110 160 190 220 255 290 370 465 660

25 1 40 60 90 130 200 235 275 305 355 455 565 815

32 11/4 50 70 110 160 240 290 330 375 435 555 700 1000

40 11/2 55 80 120 180 270 320 375 420 485 625 790 1120

50 2 65 95 150 220 330 395 465 520 600 770 975 1390

65 21/2 80 120 170 260 390 465 540 615 715 910 1150 1650

80 3 100 140 210 300 470 560 650 740 860 1090 1380 1980

100 4 120 170 260 380 5850 700 820 925 1065 1370 1740 2520

150 6 170 250 370 540 815 970 1130 1290 1470 1910 2430 3500

200 8 220 320 470 690 1040 1240 1440 1650 1900 2440 3100 4430

250 10 270 390 570 835 1250 1510 1750 1995 2300 2980 3780 5600

300 12 315 460 670 980 1470 1760 2060 2340 2690 3370 4430 6450

Table 4.7 Heat loss from fluid inside pipe (W/m)(Source: http://www.energymanagertraining.com/CodesandManualsCD-5Dec%2006/BEST%20PRACTICE%20

MANUAL-FLUID%20PIPING.pdf)

Factorsinfluencingperformance•Therelativeperformanceofdifferentpipeinsulationonanygivenapplicationcanbeinfluencedbymanyfactors.The principle factors are:

Thermalconductivity(“k”or“λ”value) �Surface � emissivity(“ε”value)Watervapourresistance(“μ”value) �Insulation thickness �

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Densit � yOtherfactors,suchasthelevelofmoisturecontentandtheopeningofjoints,caninfluencetheoverall �performance of pipe insulation.

Insulating material •Calcium silicate �Fiber glass �Mineralwoolorfibre �Polyethylene �Perlite �Silica � AerogelPhenolic foam �Flexible elastomeric foams �

Condensate load occurs when heat loss after insulation leads to condensate formation in lines carrying saturated •steam.

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Summary Though many chemical plants may have a limited life, their overall cost will be reduced if they are applied from •steam services on a permanent basis. Another great virtue of steam is that it can be regulated to give varying heat levels through reducing valves or •to give temperature control through simple two-way valves.Steam is the vapour form of water. It does not obey the laws of perfect gases, until it is perfectly dry.•The steam is generally used as a working substance in the operation of steam engines and steam turbines.•Steam can not exist as saturated vapour above its critical temperature. •Atcriticaltemperature,thespecificvolumeofdrysaturatedvapourbecomesequaltothespecificvolumeof•the liquid from which it is being formed.Steam tables are tables of thermodynamic data for steam, used often by engineers and scientists in design and •operation of equipment where thermodynamic cycles involving steam are used. The Mollier diagram is a graphic representation of the relationship between air temperature, moisture content •and enthalpy, and is a basic design tool for building engineers and designers. The temperature lines are slightly curved in the horizontal direction.•Thelinesizeforsteamdistributionisdecidedbythesteamflowrateandpermissiblepressuredrop.•Steam mains are large size line spanning considerable distance. They have to deliver steam of required quantity •to various steam using devices.Branch lines are much shorter in length. Thus, the pressure drop is not of substantial magnitude.•Steam should be distributed at high pressure because it occupies less space and this in turn means that smaller, •less costly mains can be used. The smaller mains have less heat-losing surface and better quality steam is likely to result.The relativeperformanceofdifferentpipe insulationonanygivenapplicationcanbe influencedbymany•factors.

ReferencesImportant Characteristics in formation of Steam• [Online]. Available at: <http://mechanicalguru.blogspot.com/2009/06/important-characteristics-in-formation.html>. [Accessed 7 April 2011].Piping for Steam Distribution• [Online]. Available at: <http://www.pipingguide.net/2010/01/piping-for-steam-distribution.html>. [Accessed 7 April 2011].Pipes and Pipe Sizing • [Online]. Available at: <http://www.spiraxsarco.com/resources/steam-engineering-tutorials/steam-distribution/pipes-and-pipe-sizing.asp >. [Accessed 8 April 2011].Steam Pipe Sizing and Design • [Online]. Available at: <http://www.productivity.in/knowledgebase/Energy%20Management/c.%20Thermal%20Energy%20systems/4.11%20Steam%20System/4.11.4%20Steam%20Pipe%20Sizing%20and%20Design.pdf>. [Accessed 8 April 2011].

Recommended ReadingBel• l, A. A., 2007. HVAC equations, data, and rules of thumb, 2nd ed., McGraw-Hill Professional, ISBN0071482423, 9780071482424.Sing• h, O., 2007. Engineering Thermodynamics, New Age International, ISBN8122417507, 9788122417500.Sawhney, 2009. • Fundamentals of Mechanical Engineering: Thermodynamics Mechanics Theory of Machines and Strength of Materials, 2nd ed., PHI Learning Pvt. Ltd.

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Self AssessmentThe vapour is said to be ________when the process of vaporization takes place at constant pressure and 1. temperature or when the liquid is completely evaporated.

dry saturateda. supersaturatedb. wet steamc. dry steamd.

Critical temperature is _________.2. 374.14a. °C227.14b. °C273c. °C100d. °C

The freezing point of water is _________.3. 100a. °C 273b. °K213c. °K4d. °C

TheSIunitofspecificenthalpyofsteamis_______.4. J/kga. kJ/kgb. kJ/gc. kJ/mgd.

Specificentropyofsteamisexpressedin________.5. kJ/kg Ka. mb. 3/kgkJ/kgc. bard.

Which of these statements is TRUE?6. Steam tables are tables of thermodynamic data for steam.a. Specificenthalpyofsteamisdegreeofdisorderofthesystem.b. Thespecificentropyofsteamincreaseswithanincreaseintemperatureandpressure.c. Thespecificenthalpyofsteamdecreaseswiththeincreaseintemperatureandpressure.d.

Which of these statements is FALSE?7. The Mollier diagram is a graphic representation of the relationship between air temperature, moisture content a. and enthalpy.The Mollier diagram is a basic design tool for building engineers and designers.b. The Mollier diagram is sometimes known as the h-s diagram.c. The Mollier diagram is divided into two portions by a somewhat vertical line termed as saturation curve.d.

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________ lines are drawn in the wet steam region. i.e., only below the saturation curve.8. Constantspecificvolumea. Dryness fraction b. Constant pressure c. Constant temperature d.

In Urwin equation, pressure drop is measured in _________.9. Kg / hra. mmb. bar∕100mc. Kg /md. 3

Theequivalentlengthoffittingofgatevalve-fullopenis________.10. 0.01a. 0.35b. 0.03c. 0.07d.

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Chapter V

Slurry Piping Systems

Aim


definepressuredrop•

describe slurry characteristics in system design •

explain the method to calculate critical velocity•

Objectives


describe the pumps used in slurry piping system•

explain the restrictions on instrumentation use in slurry piping system•

illustrate the concept of design velocity•

Learning outcome


examine various considerations determining the behaviour slurry•

discuss the parameters in slurry piping system •

highlight the special considerations in slurry piping system•

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5.1 IntroductionLiquid-solid suspensions, called slurries, are produced and handled in many processes throughout the chemical process industries. Layout and mechanical design considerations are as important as hydrodynamic aspects, such as line sizing, pressure drop and critical deposition velocity, when designing piping systems to handle slurries. Because of the nature of slurries, proper layout and mechanical design are critical to prevent operational problems, such as pipeline plugging and erosion. The different slurry piping systems are found in chemical, petrochemical and pharmaceutical plants.

Slurry pipelines are widely used in industrial and mining operations. However, slurry pipeline systems are frequently characterised by operational problems and high running and maintenance costs. This is often due to inadequate design associatedwithalackofunderstandingoftheflowbehaviouroftwophasesolidliquidmixtures.Theimplementationof a reliable slurry pipeline system requires that all parties involved have a sound understanding of the underlying flowmechanismsoftheslurries.

5.2 Slurry Piping SystemsA suspension of solid particles in a liquid, as in a mixture of cement, clay, coal dust, manure, meat, etc. with •water is often called slurry. Slurry can be described as liquid with solids suspended therein.•Slurry piping system, like any other system, consists of slurry pumps, pipelines and valves. •Special considerations relevant to these systems are introduced by the fact that slurry is not a homogeneous •phase (unlike gas or liquid).Typical industrial instances of slurry handling are as follows:•

coal practices suspended in water (in coal washeries) �crystals suspended in solvent in crystallization (wax manufacturing process) fed to any filtration �equipmentpulp suspension encountered in papermaking �sludgeencounteredineffluenttreatmentetc. �

Various considerations determine behaviour of slurry such as:•solid concentration (usually expressed in weight % of solid) �practical size of solids �nature of solids (soft, hard, abrasive) �properties of liquid (density, viscosity, chemical nature) etc. �

The design of the system (including selection of proper materials) is governed by following general •considerations:

no solid deposition in system �no change in slurry composition from inlet to outlet of the system �minimum wear and tear or erosion �

The design and engineering of the system components is discussed in the following order:•line sizing and pressure drop �special consideration �pumps for slurry �instrumentation �

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5.3 Line Sizing and Pressure DropThe basic steps in design are as follows:

Identify slurry characteristic 1. Select slurry concentration2. Select trial pipe size3. Calculate critical velocity4. Compare design velocity with critical velocity5. Calculate design friction loss6. Calculate system pressure gradient and pump discharge pressure 7.

Explanationsand/orclarificationsrelevanttoeachofabovestepsarediscussedbelow.

Step 1: Slurry characteristicsThe type of slurry (whether homogeneous or heterogeneous) dictates rheological (the study of the deformation andflowofmatter)propertiesandthereforeitscharacterisationisimportant.Slurriescanbeclassifiedintobroadcategories as homogenous or heterogeneous.Homogeneous slurryIn this type of slurry, solid particles are uniformly distributed in liquid medium. Such slurries are characterised by highconcentrationofsolidshavingsmall(fine)particlesize.Typicalexamplesincludesewagesludgeandclayslurry.

Cement kiln feed slurrySuchslurriesusuallyexhibitnon-Newtonianflowbehaviour(effectiveviscositychangingwithshearrate).Majorityof them show behaviour like Bingham plastic (no shear rate up to yield stress and Newtonian behaviour for stress beyond yield stress).

Heterogeneous slurryThe solids are not uniformly distributed in liquid in such slurries. In a horizontal pipe the concentration of solids is higher at lower levels and lower at upper levels. Such slurry is characterised by low concentration of large size particles. Phosphate rock slurry is typical example of this type.

Mixed behaviour of slurry Many types of slurry encountered in industry may show behaviour in between homogeneous and heterogeneous states, especially when particles of different sizes constitute the slurry. In such a situation dominant characteristics havetobeidentifiedandproperdesignprocedureshouldbeadoptedtoarriveatsaferdesign.Atypicalexampleofthis type is slurry of coal particles in water.

Step 2: Slurry concentrations (Solid content of slurry)Solid concentration of slurry becomes an important factor for following reasons:

Solidsconcentrationgovernstheslurryspecificgravity(andhencepumpingcost)andsometimes,therheology•of the slurry.At certain solid concentration, slurrymay be difficult to transport or unstable. In such situation, solids•concentration would have to be selected for proper transportation. Solids concentration in static settled slurry would be a useful guidance in this respect. Generally solid concentration of 10-15 % below static settled slurry concentration would prove stable and convenient for handling.Solid concentrations in settled slurries depending on nature of solid, vary over a wide range (10-50%). Generally •solids with particle size of 0.4-0.5 micron may form stable slurry for solid concentration up to 40%.

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Solid

vol

ume

fr

actio

n

Slur

ry sp

ecia

l gra

vity

0.70

0.130 Solid weight %

2.0

1.8

1.6

1.4

1.2

80

Fig. 5.1 A typical graph for slurry specific gravity

Step 3: Trial pipe size selectionSelection of pipe size (particularly pipe inner diameter) will determine the velocity of slurry through the pipe. The velocity calculated is referred to as design velocity.

Volume flow rate = velocity × area of cross section

Example: Given,

Flow rate of slurry 3000 litres/min•Trial pipe size 200 mm ID•

= 1.60 m/s

Thedesignvelocityissignificantwithreferencetothecriticalvelocity.Criticalvelocityisanimportantparameterforslurry.Whenslurryflowsatvelocitybelowthecriticalvelocity,solidsinslurrymaystartseparatingoutandsettinginahorizontalpipe.Thecriticalvelocityisanalogoustotransitionvelocityinflowofhomogeneousfluids,thevelocityatwhichlaminarflowceasestoexist.Tendencyofsolidsinslurrytosettleorseparateoutwillbereducedin pressure of turbulence .The critical velocity for given slurry will be determined by different parameters such as sizeandspecificgravityofsolids,solidsconcentrationviscosityofliquidanddegreeofturbulence.

Step 4: Calculation of critical velocityCalculations of critical velocity for homogeneous slurry are described as below:For heterogeneous slurries the procedure is little complex. For homogeneous slurry, the procedure for calculating critical velocity is as follows:

A. If the slurry shows the Newtonian behaviour, then critical Reynolds No. NRec is considered to be 2100 and critical velocity is calculated.

Example:Given,

Slurryflowrate=3000litres/min,V=1.60m/s �Apparentviscosityofslurryorcoefficientofrigidity(μ)=60 �NRec = 2100 �Pipe ID = 200 mm, D=0.2 m �Slurryspecificgravity(e)=1.61 �

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B. If the slurry is non-Newtonian type and exhibits Bingham plastics type behaviour, then the procedure adopted for calculating critical velocity is as follow:

Referring to example above,Calculate design Reynolds No. NRe

Calculate plasticity no. PL

To= 50dynes/ sq.cm. = 5 N/sq.cm.V for NRe = 1.60 m/sD = 0.2 m

Calculate Hedstom No. NHeNHe = NRe × PL

= 8586 × 10.417 = 89440

UsechartasshowninthefigurebelowtocalculateNRec.EnterthechartwithvalueofNHe,tofindthevalueofcritical Reynolds No. NRec.

Crit

ical

Rey

nold

s N

umbe

r (LO

G) N

Re

(log)NHe Headstorm Number

Fig. 5.2 A typical graph to calculate NRec

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Calculate critical velocity (Vc)If, say NRec = 6400, critical velocity can be calculated by using one of the following relationships:

Since, NRec = 6400 •NRe= 8586•V= 1.60 for NRe•

Step 5: Compare design velocity with critical velocityVc = 1.193 m/sV = 1.60 m/sV-Vc = 1.6 – 1.193 = 0.417 m/sThe trial pipe size selected, should be such that(V-Ve) should be 0.3 m/s or more. In the calculations above, (V-Vc) = 0.417 m/s, therefore selected pipe size is satisfactory.

Step 6: Calculate design friction loss Once the selected trial pipe size is satisfactory, the pressure loss can be calculated by usual equation i.e.

For this calculation, the numerical value off is to be selected from “f vs NRe” charts. Since f depends on roughness of pipe, as considered (Hazen William factor =100). Secondly, it is a common practice to express the friction loss persay10mofpiping.Forthispurpose,equivalentlengthsoffittingsetc.havetobetakenintoaccount.Example,Considering, f = 0.008,Friction loss per 10 m equivalent pipe length

= 3297.3 N/m = 3.297 kN/m2

Since, slurryspecificgravity=1.61•6.4 m of slurry column = 1 atm (101.3 kN/m• 2)

Friction loss per10 m of equivalent piping =

= 0.208 m of slurry column

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Step 7: Calculate pump dish charge pressureFor transport of such slurry, consider

elevation change = 10m•total equivalent length =200m•

Total head to be developed by pump,

=10 + × 0.208 = 10.416 m (of slurry)

Since 1 atm =6.4 m slurryPumpdischargepressurerequired(forfloodedsuctioncondition)

=

=1.63 atm

Slope of line

Fig. 5.3 Slope of line

5.4 Special ConsiderationsSlope of pipe lines: Slopes of horizontal lines should not exceed angle of repose for slurry. •Provisionsforflushinganddrainingofpipelinesandmanualcleaning.•Selection of wear resistance materials or higher thickness. •Identificationofwearpronepoints•

downstream of weld �joints for easy replacement of worn out positions �

Fig. 5.4 Wear Prone Zone

Use of long radius bends •No dead spaces•General observation: Wear /erosion is higher for velocities more than 2.1 m/s whereas critical velocity may •dictate minimum velocity as 1.2 m/s. Use valves with maximum port size•

Use full part ball valves. �Avoid use of globe value (seat may be plugged by solid deposition) �Provideflushingconnectionsforvalves �

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5.5 Pump for SlurryDifferent types of pumps used for slurry are as given below:

CentrifugalFor very dilute slurries with solids concentration up to 10 litres, sump type pumps could be used. •Impeller may have to be replaced frequently due to erosion; therefore split casing type design is preferred. •Lowefficienciesaretobeexpected.•Rubber lining may prove useful in many situations. •Special wear resistant materials should be used. •Flushing connection for shaft sealing arrangement is to be provided. •

Fig. 5.5 Centrifugal pump

(Source: http://www.savinobarbera.com/english/pump-basics.html)

Positive displacement (Plunger/piston type) Used for high discharge pressure (about 40 bar)•Plunger type design is preferred for abrasive slurries. •Flushing arrangement for plunger packing is desirable. •Liners of wear resistant materials inside the cylinder can yield longer trouble free services. •

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Piston Pump Plunger Pump

Fig. 5.6 Piston and plunger pump(Source: http://en.wikipedia.org/wiki/File:Piston_VS_Plunger_Pump.png)

Lock-hopper systemIt is a useful system for slurry of coarse particles.

Surge pumpSurge pump is the lock-hopper system concept used in conjunction with a positive displacement pump. A chamber filledwithclearliquidisinterposedbetweenpistonandpumpvalves.Movementofpistoncreatespressuresludgeinclear liquid chamber which is utilised to discharge the slurry. Such designs have been used for abrasive slurries.

Diaphragm pumpsThese types of pumps are common choice when lower through puts are to be handled for low delivery pressure (Typically up to 3 bar).

Moyno pumpItisaproprietarytypedesignincorporating“advancingcavity”concept.Itisusedformoderateflowsandpressure,the discharge in obtained at a steady pressure, well suited for thick slurries.

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5.6 InstrumentationPressure of solids and possibilities of erosion put many restrictions on instruments to be used. Some relevant observations are as below:

For measuring slurry concentration, use of radiation density meters is convenient. However, periodic calibration •may be necessary.Whenasidestreamisdrawnandthenreturnedconveniently,measuredbymagneticflowmeters(whichare•rather expensive).Flowrateofslurrycanbeconvenientlymeasuredbymagneticflowmeters(whichareratherexpensive).•When positive displacement pump is used for slurry transfer pump speed and displacement can be used to •calculateslurryflowrate.Pressure gauges and other instruments mounted on pipe line are susceptible to damage due to vibrations.•For measurement of pressure, diaphragm type gauges are recommended which should be provided with back •flushingarrangements,connectedtopipelinewithcapillary.Moreoverthegaugesshouldbeseparatelysupportedand not mounted directly on pipe line.

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SummaryLiquid-solid suspensions, called slurries, are produced and handled in many processes throughout the chemical •process industries. Because of the nature of slurries, proper layout and mechanical design are critical to prevent operational problems, •such as pipeline plugging and erosion. The different slurry piping systems are found in chemical, petrochemical and pharmaceutical plants.•The implementation of a reliable slurry pipeline system requires that all parties involved have a sound •understandingoftheunderlyingflowmechanismsoftheslurries.A suspension of solid particles in a liquid, as in a mixture of cement, clay, coal dust, manure, meat, etc. with •water is often called slurry. Slurry piping system, like any other system, consists of slurry pumps, pipelines and valves. Special considerations relevant to these systems are introduced by the fact that slurry in not homogeneous phase •(unlike gas or liquid).Thedesignvelocityissignificantwithreferencetothecriticalvelocity.Criticalvelocityisanimportantparameter•for slurry. Thecriticalvelocityforgivenslurrywillbedeterminedbydifferentparameterssuchassizeandspecificgravity•of solids, solids concentration viscosity of liquid and degree of turbulence.Solid concentrations in settled slurries depending on nature of solid vary over a wide range (10-50%). •For measuring slurry concentration, use of radiation density meters is convenient. However, periodic calibration •may be necessary.

ReferencesGrossel. S., • Improved Design Practices for Slurry Piping Systems [Online]. Available at: <http://www.globalspec.com/reference/9775/349867/improved-design-practices-for-slurry-piping-systems>. [Accessed 8 April 2011].Pump basics • [Online]. Available at: <http://www.savinobarbera.com/english/pump-basics.html>. [Accessed 9 April 2011].Slurry characteristics• [Online]. Available at: <http://www.scribd.com/doc/50809286/10/Slurry-characteristics>. [Accessed 9 April 2011].

Recommended ReadingAude, T.C., Cowper N.T., Thompson, T.L., & Wasp, E.J., 1971. • Slurry Piping System: Trends, chemical Engineering.Abulnaga, B. E., 2002. • Slurry systems handbook, McGraw-Hill Professional, ISBN0071375082, 9780071375085Brown, N. P. & Heywood, N. I., 1991. • Slurry handling: design of solid-liquid systems, Springer, ISBN 1851666451, 9781851666454.

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Self AssessmentWhich of these is not a hydrodynamic aspect?1.

Line sizinga. Pressure dropb. Critical deposition velocityc. Lightd.

Slurry piping system, like any other system, does not consist of __________.2. slurry pumpsa. pipelinesb. valvesc. hazardous materialsd.

Crystallisation occurs in _________.3. wax manufacturing processa. coal washeriesb. papermakingc. effluenttreatmentd.

Which of these is not a property of liquid?4. Densitya. Rigidityb. Viscosityc. Chemical natured.

Sewage sludge is an example of ___________.5. homogeneous slurrya. cement kiln feed slurryb. heterogeneous slurryc. mixed behaviour of slurry d.

Phosphate rock slurry is typical example of _________.6. heterogeneous slurrya. homogeneous slurryb. cement kiln feed slurryc. mixed behaviour of slurry d.

Generally solid concentration of _____ below static settled slurry concentration would prove stable and 7. convenient for handling.

0-5 %a. 10-15 %b. 1-1.5 %c. 50-75 %d.

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Generally solids with particle size of 0.4-0.5 micron may form stable slurry for solid concentration up 8. to_______.

40%a. 0%b. 10%c. 20%d.

Volumeflowrate=__________×areaofcrosssection.9. flowvolumea. specificgravityb. πc. velocityd.

NHe = NRe × _________10. PLa. Db. ηc. μd.

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Chapter VI

Pumps

Aim


definecentrifugalpump•

describe components of centrifugal pump •

explain the applications of centrifugal pump•

Objectives


describe the pump head and net positive suction head concept•

explainthespecificspeedanditscalculation•

discuss the concept of suction head•

Learning outcome


examine various considerations determining the behaviour slurry•

state the importance of low NPSH•

discussthecalculationofflowrequired•

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6.1 IntroductionPump is important rotating equipment used in industries. Pump installation and performance is very important for pipingengineers.Theclassification,workingandstandardengineers’practiceofpumpshouldbeknown.

Selection procedure for the pumpThere are several things we must know before we attempt to select a proper pump:

How many litres per min. are it is going to be pumped?•How high is the pump above water?•How high must the water be pushed after it leaves the pump?•What is the total length of pipe to be used?•Is water merely to be dumped at the end of the discharge run, or will it to be used?•

6.2 Centrifugal PumpsA centrifugal pump is one of the simplest pieces of equipment in any process plant. •Itspurposeistoconvertenergyofaprimemover(electricmotororturbine)firstintovelocityorkineticenergy•andthenintopressureenergyofafluidthatisbeingpumped.The energy changes occur by virtue of two main parts of the pump, the impeller and the volute or diffuser. •The impeller is the rotating part that converts driver energy into the kinetic energy. •The volute or diffuser is the stationary part that converts the kinetic energy into pressure energy.•

Volute Casing

Discharge

Vanes

Impeller Suction Eye

Fig. 6.1 Liquid flow path inside a centrifugal pump(Source: http://www.maintenanceworld.com/Articles/engresource/centrifugalpumps.pdf)

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Components of centrifugal pumpThecentrifugalislikethe‘WORKHORSE’inaprocessindustry.Thefollowingfigureshowsmajorcomponents•in a centrifugal pump.

SUCTION .

DISCHARGE .

SHAFT .

COUPLING TO MOTOR .

BEARINGS . SEAL .

IMPELLER .

PUMP CASING .

Fig. 6.2 Components of centrifugal pump

Liquidispressuredintothesuctionpumpwheretheimpellerimpartsacentrifugalvelocitytothefluid.Asthe•liquid discharges from the pump its velocity head converts to pressure head because of typical shape of the casing. Pumpsareusuallyspecifiedearlyintheprocessschedule,whenlinesarelocatedandsizedinsketches,when•control valves have not been sized and when pump performances must be estimated rather than established.A complex relationship exists between the system head, pump head and valve drop characteristics. •Methods of selecting control valve drop and impeller performance are not readily systematised. •API 610 is a standard that covers the minimum requirements for centrifugal pumps for use in petroleum, heavy •duty chemical and gas industry services. It includes pumps running in reverse as hydraulic power recovery turbines.A system design engineer must consider two characteristics of a centrifugal pump, the discharge pressure and •volumetricflowrate.Thedesigner’sheatandmaterialbalancewillgivetherequiredflowratehydraulic.Alloftheformsofenergyinvolvedinaliquidflowsystemareexpressedintermsoffeetofliquidi.e.,head.•

6.3 Applications of Centrifugal PumpPumps can be used in various settings and to pump different types of liquids. Pumps can be used in the following applications:

Residential • - Small pumps serve many purposes in home. Potable water may enter house after being pumped fromthewellorthroughthemunicipalsystem.Theheatingand/orcoolingunitsusepumpstomovefluidsand air through those systems. High rise apartment buildings must maintain constant water pressure to ensure residentsonthetopfloorsreceivethesamepressureasthoseatstreetlevel.Industrial• - Fire pumps protect buildings and people during the work day. These systems stand primed and readyincaseoffire.Pumpsgeneratehighwaterpressuresforde-scalingandboilerfeedapplications.Somefoodanddrinkpreparationrequirespumpstoinsertthefinishedproductintopackaging.Agricultural• - Pumps support food production and agriculture by irrigating arid lands and areas with little rainfall. Wells and vertical pumps offer life supporting water to live stock as well as people.

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Scientific and medical• -Pumpsareusedinscientificarenasinthemanufacturingofpharmaceuticals,toothpasteand medicine. Chemicals require special pumps, called process pumps that seal the processed liquids from the outsideenvironmentpreventingcontamination.Bloodandbodilyfluidsaremovedwithpumpsandpumpingsystems when in surgical or medical settings.Marine• - Naval ships and other marine going vessels use pumps to de-water bilges, provide boiler feed, stabilize ballast systems, support weaponry and to turn sea water into potable water. Pumps are a very important component of a marine vessel’s safety and security system.

6.4 Calculation of Flow RequiredTheflowrateinkg/hrofliquidtobepumpediscalculatedfromheatandmaterialbalance.Case-1

Suppose we have a simple equationHCL+ NaOH = = > NaCL + H2O= = => (1 mole + 1 mole = = => 1 mole + 1 mole) Molecular weight= = => 36.5 kg + 40 kg = = => 58.5 kg+18 kgHence, for manufacturing 100 kg of NaCL, 62.40 kg of HCL &68.37 kg of NaOH have to be pumped.

Case -2Sometimes, to take away the reaction heat, excess reactant is added. It may be as high as 5 to 6 times the actual requirement.

Case – 3For some reactions, to ensure completion of (100 %) reaction, some excess reactant is added.

Case – 4Asadesignengineer,about20%flowasre-circulationisconsideredtoavoidcavitationsproblemsinthepump.

Hencedesignedflowrateshallbe20%morethantheactualflowrate.•Referringtothediscussionabove,pumpflowratioiscalculatedbyfollowingequation:•

where,Q=pumpflowratio(m3/hr)Forexample,ifonehastopump1000kg/hrofH2SO4(whichhasspecificgravity1.8(98%H2SO4),therequired m3/hr is m /hr.

= 0.56 m /hr

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6.5 Calculation of Pump HeadThebasiccalculationconsistsoffivesteps:

Differential pressure between two vessels•Head to lift the liquid•Friction head loss in the piping•Pressuredropallowedtocontrolflow•Net Positive Suction head (NPSH) for the pump•

Differential pressure between two vesselsTocalculatethedifferentialpressure,thefollowingformulashouldbeused:usingspecificgravityoftheliquid•pumped at the process temperature.

Pump head to lift the liquidThisissimplythedifferencebetweentheliquidlevelinthefirst&secondvessels.•

Friction head loss Actually a design engineer does not lay the piping. Considering that 0.3kg/cm• 2 pressure drop for each 100 m of piping is allowed and the approximate distance run by the piping is estimated. Thecalculatedpressuredropisdoubledtoallowforelbows,bends,valvesandotherpipefittings.•The friction pressure drop into head is converted by same formula given above.•

Control valves / instrumentsAs a thumb rule, the loss across a control valve is equivalent to half the friction loss of pipe line or 1.50 kg/cm •(whichever is greater).

Net Positive Suction head (NPSH) required by pumpNet Positive Suction head (NPSH) required by a pump is normally given in the manufacture’s pump curve •which is normally 0.5-4 m.

Example:

100 m

5 m

Lc

20 m

5 Kg/cm 2

21.5 Kg/cm

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H = 88 m

6.6 Classification of Centrifugal PumpApumpcanbeclassifieddependingwheretheimpellerdischargestheliquidas:

axialflow �mixedflow �radialflow �

Anaxialflowpumpdischargestheliquidintheaxialdirectioncomparedtothepumpshaftcentreline•Aradialflowpumpdischargestheliquidintheradialdirection.•Amixedflowpumpisonethatisacombinationbetweenaradialandanaxialflowpumpdesign.•

6.7 Specific SpeedSpecificspeedisdefinedasthespeedinrevolutionsperminute(rpm)atwhichanimpellerwouldoperateif•reduced proportionately in size so as to deliver a unit of capacity against a unit of total head. The performance of a pump can be determined by stating its speed, the head it generates and the rate of •discharge. Differenttypesofimpellersandflowpatternscanbestbecomparedbymeansofthespecificspeed.•Pumpshavetobeselectedwiththerightspecificspeedimpellersinordertooperatesatisfactorilyinthedesired•application. Highspecificspeedimpellers(asfittedinaxialflowandmixedflowpumps)areforhighflowandlowerhead•applications(suchasditchdrainage,watersupplyoperations,liftstations,floodcontroletc.)wherehugeamountsof water need to be moved quickly. Lowspecificspeedimpellers(suchasthoseinstalledinradialflowpumps)producehigherheads(pressures)at•moderateflowrates,typicallythistypeofpumpisusedtomoveliquidstomuchhigherelevationlevels(e.g.water well pumps, process pumps, boiler feed pumps etc).Specific speed is one of thefirst parameters that a centrifugal pumpdesigner looks atwhen evaluating a•pumpapplication.Specificspeedmaybeusedtorapidlydeterminethemostfeasibledesignsfortheserviceconditions. SpecificSpeed(Ns)isoftentreatedasadimensionlessnumberthatrepresentsthephysicaldesignofanimpeller•regardlessofpumpsize.Theequationforspecificspeedis:

where,N � s = rotative speed in revolutions per minute (rpm)Q=pumpfloworquantityofflowinm � 3/s(atthebestefficiencypoint)H=pumpdifferentialheadatthebestefficiencypoint �

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Type of Impeller Ns D2 (outlet diameter)/D1 (inlet diameters)

Slowspeedradialflow 10-30 3.5-2Normalspeedradialflow 30-50 2.0-1.5Highspeedradialflow 50-80 1.5-1.3Mixedflowimpeller(screw) 80-160 1.2-1.1Axialflow(propeller) 110-500 1.0

Table 6.1 Different types of impellers and their rotative speed

Pumpshavingaspecificspeedlessthan12aregenerallynotrecommended.Infact,thepumpefficiencyfalls•drasticallyifthespecificspeedislessthan20.Thisisbecauseimpellerbecomesdisproportionate,thediameterbeing too large relative to width.Itresultsinleakageandhigherdiscfrictionandfluidfrictionlossesowingtonarrowpassageoffluid.•Itisthereforeadvisabletouseimpellersofsmalldiametersconsequentlyhighspecificspeed.Thiswillreduce•thediscfrictionlosseswhichvarywiththeradius,increaseefficiencyanddecreasecost.Thus, using higher stage pumps came in to picture. If we select higher stages, H will be divided for that many •stages and single impeller head reduce and Ns increases. Dependingonthebladeshape,theefficiencychangesanditcanhaveoneofthefollowingdifferentshapes.•

A B C D

90ᴼ

>90ᴼ

Shape Approx. efficiency (η) %

Blades bent backward 85-90

Straight blades ~80

Blades ending radially 80-85

Blades bent forward N 75

Fig. 6.3 Efficiency relative to different blade shapes

Inordertohavehighefficiency,thebladesbentbackwardshallbeselected.Straightbladescanbeusedforsmall•pumpswhereeconomyisimportant.Bladesbentforwardyieldverylowefficiencyandhencerarelyused.

6.8 Power and Efficiency The work performed by a pump is a function of the total head and the weight of the liquid pumped in a given •time period.Pump input or brake horsepower (BHP) is the actual horsepower delivered to the pump shaft. Pump output or •hydraulic or water horsepower (WHP) is the liquid horsepower delivered by the pump.

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Selecting a pump’s impeller Designofthepumpimpeller(themaininternalmovingpartinacentrifugalpump)determinesthepressure-flow•operating characteristics of the centrifugal pump.Impellersofpumpsareclassifiedbasedonthenumberofpointsthattheliquidcanentertheimpellerandalso•on the amount of webbing between the impeller blades.Impellers can be open, semi-open, or enclosed. •The open impeller consists only of blades attached to a hub. •The semi-open impeller is constructed with a circular plate (the web) attached to one side of the blades. •The enclosed impeller has circular plates attached to both sides of the blades. Enclosed impellers are also •referred to as shrouded impellers.

Open impeller Closed impellerSemi-open impeller

Fig. 6.4 Types of impeller

Selecting a pump motorAn experienced design engineer shall usually select a motor for centrifugal pumps based not on the size of •impellerusedbutonthemaximumimpellerdiameterthatwillfitintothepumps.The reasons for selecting higher Kilowatt (KW) rating motors are :•

it doesn’t trip for higher initial torque �to expand the pump capacity �

Otherwise the motor shall be selected at the end of the curve power OR with the following correlations as per •normal practice depend on the absorbed power.

Absorbed Power (KW) Multiplication Factor

upto 3.7 1.5

5.5 to 18.5 1.25

22 to 55 1.15

75 or above 1.10

Table 6.2 Multiplication factor and absorbed power for pump motor

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6.9 Shut in PressureShutinpressureisthepressurethepumpwillputupatzeroflow.Thelargertheimpellersize,thelargerthe•shut in pressure. The maximum shut in pressure which is allowed is the critical variable when selecting the size of an impeller.•The design engineer shall be assured that eventually the operator will block in a pump down stream. •Theimportanceofshutinpressureisgiveninthefigurebelow.Ifoperatoraccidentallyclosesthisvalve,the•shell of heat exchanger is subjected to shut in pressure of the pump. In case, heat exchanger shell is not designed for shut in pressure, there can be following options:•

use small impeller �install relief valve on shell �eliminate valve �

HEATEXCHANGERPUMP .

TANK .

OPEARTOR ACCIDENTLY CLOSES THE VALVE.

Fig. 6.5 Shut in pressure

Often, a design engineer ignores the consequences to downstream equipment when expanding the capacity of •pump. The need to design all process equipment between pump and a block valve for the pump shut in pressure is a •legal requirement.

6.10 Expanding the Pump CapacityThere are two inexpensive methods to expand pumping capacity:

reduce down stream pressure drop•increase size of impeller•

Reducing downstream pressure drop Thetypicalcausesofexcessivepressuredropandsuggestedremediesidentifiedbymanypracticalexperimentsarelisted below:

High tube side pressure drop through a shell & tube heat exchanger.•reduce no. of tube side passes �if the side passes are decreased in number from 4 to 2, 7/8 of drop is cut-off �

High shell side pressure drop in a shell• ‐and‐tube heat exchangerAnewtubebundlewithlargerspacesbetweenbaffles(expensivechoice) �

High pressure drop through a wide open control valve•change control valve port size or trim to the maximum size permitted in the control valve body, e.g. 3” �control valve can accommodate 2 port size

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Excessive piping losses •increase diameter of piping or parallel piping runs �

Large impellerThe trick to select a larger impeller when expanding a pump capacity is to match the impeller size to the capacity •existing motor drive. The changing of impeller is easy and cheaper when compared to changing the motor and its associate •compounds.The changing of the diameter of impeller is done through following empirical relations.•

Q2 = Q1 (D2/D1)h2 = h1 (D2/D1)

2

P2 = P1 (D2/D1)3

where,Q � 2=flowratewithlargerimpellerQ � 1=flowratewithexistingimpellerD � 2 = Diameter of larger impellerD � 1 = Diameter of existing impellerh � 2 = Head delivered by larger impellerh � 1 = Head delivered by existing impellerP � 2 = Power drawn by motor with larger impellerP � 1 = Power drawn by motor with existing impeller

To decide on the maximum size impeller that can be used existing motor, it is best to observe following in •field.

The control valve position should be placed “wide open.” �The amperage drawn by motor should be measured. �

The rated capacity of the motor (in amps) is multiplied by its service factor (typically 10-15 %) to calculate •maximum size of impeller that can be used with existing motor.

6.11 Importance of Low Discharge FlowWhen discharge of pump is closed, pump will overheat.•The motor’s electric power is converted to heat as the pump churns the trapped liquid. The pump’s case and •bearings become hotter and hotter and eventually the bearings will burn out also damage the pump seal.In addition, many large head pumps are subjected to a phenomenon called internal recirculation, which damages •pumps internal parts when the pump is operated at reduced rate. Asimplemodificationin theprocessasshownbelowwillautomaticallypreventpumpdamagedueto low•flow.Thedesignershouldconsiderwhethertheminimumflowbypassisnecessary,consideringtheprocessvariables•oftheplantdesigned.Nevertietheminimumflowdisclineintothesuctionofpump.Thisdefeatsthepurposeof line; it must be routed back to a point in the process where the pumping heat is dissipated .

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RE - CIRCULATION.

TO PROCESS.

Ro

Fig. 6.6 Low discharge flow

6.12 NPSH (Net Positive Suction Head)The margin of pressure over vapour pressure, at the pump suction nozzle, is Net Positive Suction Head •(NPSH). NPSH is the difference between suction pressure (stagnation) and vapor pressure. In equation form:•

NPSH = Ps - Pvap

where,NPSH = NPSH available from the system, at the pump inlet, with the pump running �P � s = Stagnation suction pressure, at the pump inlet, with the pump runningP � vap = Vapor pressure of the pumpage at inlet temperature

Lowpressureatthesuctionsideofapumpcanencounterthefluidtostartboilingwith•reducedefficiency �cavitations �damage �

To characterise the potential for boiling and cavitation, the difference between the total head on the suction side •of the pump, close to the impeller, and the liquid vapour pressure at the actual temperature, can be used.

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ps

ps

pd

pd

vapor pressure

vapor pressure

NO bubble formation

Bubble Formation

Suction

Suction

Eye

Eye

Discharge

Discharge

Suction

Discharge

Fig. 6.7 Effect of NPSH on pump(Source: http://www.techpedia.in/uploads/8dcbccda736a01969106b71b90a4c49b.pdf?

PHPSESSID=28646d66d12ea7c61dd41478a181830b)

Suction headBasedontheenergyequation,thesuctionheadinthefluidclosetotheimpellercanbeexpressedasthesumofthestatic and the velocity head:

hs = ps/γ+vs2 / 2 g ................(1)

where,hs = � suction head close to the impellerps=staticpressureinthefluidclosetotheimpeller �γ=specificweightofthefluid �vs=velocityoffluid �g = acceleratio � n of gravity

Liquids vapour headThe liquids vapour head at the actual temperature can be expressed as:hv = pv/γ.......(2)

where,hv � = vapor headpv = vapo � r pressure

Thevapourpressureinafluiddependsontemperature.Water,themostcommonfluid,startsboilingat20°C if the absolutepressureinthefluidis2.3KN/m2. For an absolute pressure of 47.5 N/m2, the water starts boiling at 80°C. At an absolute pressure of 101.3 KN/m2 (normal atmosphere), the boiling starts at 100°C.

The net positive suction head can be also be expressed as the difference between the suction head and the liquids vapor head and expressed like

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NPSH = hs - hv......... (3a)

Or, by combining (1) and (2)

NPSH = ps / γ + vs2 / 2 g - pv / γ.......... (3b)

Available NPSH (NPSHa)

The Net Positive Suction Head made available the suction system for the pump is often named NPSHa. The NPSHa can be determined during design and construction, or determined experimentally from the actual physical system.

he

he

ho

Fig. 6.8 NPSH(Source: http://www.techpedia.in/uploads/8dcbccda736a01969106b71b90a4c49b.pdf?PHPSESSID=28646d66d1

2ea7c61dd41478a181830b)

The available NPSHa can be calculated with the energy equation. For a common application where the pump lifts afluidfromanopentankatoneleveltoanother,theenergyorheadatthesurfaceofthetankisthesameastheenergy or head before the pump impeller and can be expressed as:

h0 = hs + hl............. (4a)

where, h � 0 = head at surfaceh � s = head before the impellerh � l = head loss from the surface to impeller - major and minor loss in the suction pipe

In an open tank the head at surface can be expressed as:h0=p0/γ=patm/γ..........(4b)

For a closed pressurized tank the absolute static pressure inside the tank must be used.The head before the impeller can be expressed as:hs=ps/γ+vs

2 / 2 g + he.......... (4c)

he = elevation from surface to pump - positive if pump is above the tank, negative if the pump is below the tank

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Transforming (4a) with (4b) and (4c)patm/γ=ps/γ+vs

2 / 2 g + he + h1.......... (4d)

The head available before the impeller can be expressed as:ps/γ+vs

2/2g=patm/γ-he-h1..............(4e)

or as the available NPSHa:

NPSHa=patm/γ-he-hl-pv/γ............(4f)

6.13 Importance of Low NPSHWhenacentrifugalpumplosessuctionduetolowNPSH,thepumpedfluidbeginstoflashattheeyeofimpeller•.This results bubbles of vapours which when carried towards discharge are compressed and collapse. This phenomenon is called cavitations, which is a common cause for failure of pump.A designer can prevent damage to many pumps by applying a few simple ideas.•

Location of the coolers on suction side of pumps. The decreased pump suction pressure will be usually �morethanoffsetbythereductioninthefluid’sbubblepoint.Providing vortex breakers in bottom of all vessels regardless of the anticipated liquid level in vessel. �Provide adequate liquid hold in process vessels acting as surge drums. As a thumb rule 5-15 min. hold up �is a typical range.

4D

0.5

D

VORTEXBRAKER

D

Fig. 6.9 Design of vortex braker

6.14 Pump Safety TipsMaintenance personnel should be aware of potential hazards to reduce the risk of accidents. The following are the safety tips for pumps operation:

Safety apparel•Insulated work gloves when handling hot bearings or using bearing heater. �Heavy work gloves when handling parts with sharp edges, especially impellers. �Safety glasses (with side shields) for eye protection, especially in machine shop areas. �Steel-toed shoes for foot protection when handling pants, heavy tools, etc. �Otherpersonalprotectiveequipmenttoprotectagainsthazardous/toxicfluids. �

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Couplings guards•Never operate pump without a coupling guard properly installed. �Flanged Connections: �Never force piping to make a connection with a pump. �Use only fasteners of the proper size and material. �Ensure there are no missing fasteners. �Beware of corroded or loose fasteners. �

Operation•Donotoperatebelowminimumratedflow,orwithsuction/dischargevalvesclosed. �Do not open vent or drain valves, or remove plugs while system is pressurized. �

Maintenance safety•Always lockout power. �Ensure pump is isolated from system and pressure is relieved before disassembling pump, removing plugs, �or disconnecting piping.Use proper lifting and supporting equipment to prevent serious injury. �Observe proper decontamination procedures. �Know and follow company safety regulations. �Never apply heat to remove impeller. �

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SummaryPump is an important rotating equipment used in industries. Pump installation and performance is very important •for piping engineers. A centrifugal pump is one of the simplest pieces of equipment in any process plant. •Itspurposeistoconvertenergyofaprimemover(electricmotororturbine)firstintovelocityorkineticenergy•andthenintopressureenergyofafluidthatisbeingpumped.The energy changes occur by virtue of two main parts of the pump, the impeller and the volute or diffuser. •The impeller is the rotating part that converts driver energy into the kinetic energy. •The volute or diffuser is the stationary part that converts the kinetic energy into pressure energy.•API 610 is a standard that covers the minimum requirements for centrifugal pumps for use in petroleum, heavy •duty chemical and gas industry services. It includes pumps running in reverse as hydraulic power recovery turbines.A system design engineer must consider two characteristics of a centrifugal pump, the discharge pressure and •volumetricflowrate.Thedesigner’sheatandmaterialbalancewillgivetherequiredflowratehydraulic.Alloftheformsofenergyinvolvedinaliquidflowsystemareexpressedintermsoffeetofliquidi.e.,head.•Fire pumps protect buildings and people during the work day. Pumps generate high water pressures for de-•scaling and boiler feed applications.Wells and vertical pumps offer life supporting water to live stock as well as people.•Pumpsareusedinscientificarenasinthemanufacturingofpharmaceuticals,toothpasteandmedicine.Pumps•are a very important component of a marine vessel’s safety and security system.The maximum shut in pressure which is allowed is the critical variable when selecting the size of an impeller. •The design engineer shall be assured that eventually the operator will block in a pump down stream. Maintenance personnel should be aware of potential hazards to reduce the risk of accidents.•

ReferencesCentrifugal Pumps• [Online]. Available at: <http://www.engineeringtoolbox.com/centrifugal-pumps-d_54.html>. [Accessed 9 April 2011].Fluid mechanics pumped pipe systems• [Online].Availableat:<http://www.freestudy.co.uk/fluid%20mechanics/t8c203.pdf>. [Accessed 9 April 2011].Centrifugal Pumps• [Online]. Available at: <http://www.techpedia.in/uploads/8dcbccda736a01969106b71b90a4c49b.pdf?PHPSESSID=28646d66d12ea7c61dd41478a181830b >. [Accessed 10 April 2011].

Recommended ReadingLobanoff,V. S., & Ross, R. R., 1992. • Centrifugal pumps: design & application, 2nd ed., Gulf Professional.Bachus, L., & Custodio, A., 2003. • Know and Understand Centrifugal Pumps, Elsevier.Munson, 2007. • Fundamentals of Fluid Mechanics, Wiley-India.

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Self Assessment______ is important rotating equipment used in industries.1.

Valvesa. Boltsb. Pumpsc. Gaugesd.

Centrifugalpumpconvertsenergyofaprimemover(electricmotororturbine)firstinto_______.2. kinetic energya. electricityb. light energyc. heat energyd.

Which is the rotating part that converts driver energy into the kinetic energy?3. Impellera. Suction eyeb. Vanesc. Volute castingd.

Flow rate is measured in _________ S.I unit.4. kg/hra. kg/secb. g/secc. kg/mind.

TheSIUnitofpumpflowratiois_____________.5. kg/hra. mb. 3/hrmc. 3/minkg/mind.

Pumpshavingaspecificspeedlessthan______aregenerallynotrecommended.6. 20a. 12b. 40c. 55d.

Bladesbentbackwardhaveapproximatrefficiencyof________.7. 85-90 %a. 90-95 %b. 10-20 %c. 13-18 %d.

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In the equation, Q8. 2 = Q1 (D2/D1), Q2 is ______________.flowratewithlargerimpellera. flowratewithexistingimpellerb. head delivered by larger impellerc. head delivered by existing impellerd.

The _______impeller consists only of blades attached to a hub. 9. semi-opena. openb. closedc. semi-closedd.

Specificspeedisthespeedin____________.10. km/seca. m/secb. revolutions per minutec. revolutions per secd.

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Chapter VII

Pneumatic Conveying Terms CEMA Standard No. 805

Aim


describe pneumatic conveying terms•

explainthebasictermsanddefinitions•

state the material characterisation•

Objectives


describe the individual particle shape descriptions •

explain the general compositions found in bulk material•

discuss the importance of pneumatic terms •

Learning outcome


examine various bulk density terms•

describe the different gas velocity terms•

get an overview of CEMA•

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7.1 IntroductionOne of the most popular methods of moving solids in the chemical industry is pneumatic conveying. Pneumatic conveying refers to the moving of solids suspended in or forced by a gas stream through horizontal and/or vertical pipes.Pneumaticconveyingcanbeusedforparticlesrangingfromfinepowderstopelletsandbulkdensitiesof16 to 3200 kg/m3 (1 to 200 lb/ft3).

The Conveyor Equipment Manufacturers Association (CEMA) has developed industry standard safety labels for use on the conveying equipment of its member companies. The purpose of the labels is to identify common and uncommon hazards, conditions and unsafe practices which can injure, or cause the death of, the unwary or inattentive person who is working at or around conveying equipment.

The labels are available for sale to member companies and non-member companies. A full description of the labels, their purpose, and guidelines on where to place the labels on typical equipment has been published in CEMA’s Safety Label Brochure No. 201. The Brochure is available for purchase by members and non-members of the association. Safety labels and safety label placement guidelines, originally published in the Brochure, are also available free on the CEMA web site at http://www.cemanet.org/CEMA_Safety_Pg.htm

**Should any of the safety labels supplied by the equipment manufacturer become unreadable for any reason, the equipment user is then responsible for replacement and location of these safety labels. Replacement labels and placement guidelines can be obtained by contacting equipment supplier or CEMA.

7.2 List of Pneumatic Conveying TermsThe list of pneumatic conveying terms is given below:

Abrasiveness �Actual gas velocity �Adhesiveness �Aeration �Air retention �Angle of repose �Average gas velocity �Bulk material composition �Choking velocity �Cohesiveness �Conveying pressure �Corrosiveness �Dense phase conveying �Dilute phase conveying �Explosiveness �Flotation velocity �Flowability �Fluidised �Fluidised bulk density �Friability �Hardness �Hygroscopicity �Loose bulk density �Materialmassflowrate �

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Material temperature �Material temperature sensitivity �Material to air ratio �Material velocity �Maximum particle size �Median particle size �Minimum conveying velocity �Packed bulk density �Particle density �Particle shape �Particle size distribution �Permeability �Saltation velocity �Terminal gas velocity �Two-phaseflow �Volumetricgasflow �

The terms have been grouped into two sections:Material Characterisation �BasicTermsandDefinitions �

7.3 Material CharacterisationThe terms are described below:Loose bulk density

The loose bulk density (sometimes called the poured bulk density) of a bulk material is the weight per unit of •volume (usually pounds per cubic foot) that has been measured when the sample is in a loose, non-compacted or poured condition. The loose bulk density may be close to the “as conveyed” bulk density and is preferred for the purposes of •pneumatic conveying system design.

Packed bulk densityThe packed bulk density of a bulk material is the weight per unit volume (usually pounds per cubic foot) •that has been measured when the sample has been packed or compacted in, for instance, a silo or bin or after containerised transportation. The packed bulk density does not compare to the conditions that would be found in a pneumatic conveying •system. It is for this reason that the loose bulk density is preferred for the purposes of conveying system design.•

Fluidised bulk densityFluidisedbulkdensityistheapparentbulkdensityofamaterialinitsfluidisedstate.•It is generally lower than either the packed or loose bulk density due to the air absorbed into the voids.•

Particle densityParticle density is the mass of a particle divided by its volume. •For a bulk material, average particle density is used, found by dividing the mass of the material by its volume, •excluding the voids.

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Particle size distributionThe particle size distribution of a bulk material is a tabulation of the percentage of particles by mass in each •particle size range. Thepercentagedescribediseitherthatpassingorbeingretainedonaspecificscreensize.IntheUnitedStates,•the screens used are “U.S. Standard Screens” or “Tyler Test Screens”.Othermethodsofsizeanalysismaybeused,particularlyinthecaseofveryfineand/orcohesivepowders.•These methods include photo sedimentation, optical microscopy, electrical sensing zone techniques (such as •the Coulter counter), and laser diffraction spectrometry.

Maximum particle sizeMaximum particle size is the maximum dimension in inches (in the case of lumpy materials) or the maximum •sieve size (in the case of powders and granules) of the largest lump or particle in the bulk material. Maximum particle size can be critical in the design of pneumatic conveying systems.•

Median particle sizeThe median size is the mid-point of the particle distribution.•

Particle shapeThe shape and form of the particles of a bulk material can vary considerably. •Thefollowing tablespecificallydescribes the individualparticleshapeonlyandnot thebulkmaterialasa•whole.

Term Definition

Needle-like Long, thin, rigid, straight and pointed

Angular Sharp edged or having a multi-faced, irregular shape

Crystalline Of geometric shape or multi-faced regular shape

Dendritic Having a branched, crystalline shape with the branches extending from the faces of the body

Fibrous Regularlyorirregularlythreadlikewithaflexiblestructure

Flaky Plate-like

Spherical Globe-like

Out-of-Round Similar to Spherical but being somewhat deformed or elongated

Cylindrical Cylinder-shaped

Agglomerated Several individual particles bended together

Table 7.1 The individual particle shape descriptions

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Bulk material compositionThe following table describes the general compositions and the shapes that may be found.

Term Definition

Uniform A single bulk material whose particles possess the same size and shape.

Non-uniform A single bulk material whose particle size : and shape may vary

Granular A bulk material comprised of individual particles which can be visibly discerned.

Powder A bulk material comprised of individual particles which cannot be visibly discerned.

Mixed Two or more different bulk materials which have been combined.

Table 7.2 The general compositions found in a bulk material

Flow abilityFlowabilityisthecasewhereabulkmaterialflowsundertheinfluenceofgravityonly.•

CohesivenessCohesiveness is described as the tendency of a material to adhere to itself. •The cohesiveness of a bulk solid material can be caused by any and sometimes by all of several factors. •These include electrostatic charging, surface tension effects, and interlocking of certain particle shapes, •particularlyfibroustypesofmaterials.Cohesivenessinbulksolidscauseserraticflowfrombins,pipelinefeedingproblemsandadverseeffectsin•certain kinds of valves.

AdhesivenessAdhesiveness can be described as “external cohesiveness” i.e., the ability of a material to adhere to other •surfaces.

FluidisedFluidised describes the state some bulk materials achieve when a gas has been entrained into the void spaces •between the particles of the material. Material inahighlyfluidisedstateendstobehavemorelikeafluid(asthetermimplies) thanasolidbulk•material.

AerationAeration is the action of introducing air (or gas) to a bulk material by any means.•Aerationmaycausethematerialtobecomefluidisedoragitated.•

Angle of reposeThe angle of repose of a bulk material is the angle between the horizontal and the sloping surface of a heap of •thematerialwhichhasbeenallowedtoformnaturallywithoutanyconditioning,usuallybygravityflowfroma funnel or other similar device.

HardnessHardness is a property of a solid material which contributes to its overall abrasiveness. •The harder a material is, generally, the greater the erosion for a given velocity on a pipeline. •Hardnessisdifficulttoquantityandissomewhatsubjectivewhendescribed.Moh’sscaleofhardnessisused•to describe the materials when designing pneumatic conveying systems.

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AbrasivenessThe abrasiveness of a material is determined by its hardness factor and the shape of its particles. •A material which has, for instance, a high Moh’s hardness factor and its sharp, angular-shaped particles will be •considered highly abrasive.

Material TemperatureGenerally, most bulk materials are handled at ambient temperature conditions.•However, in some cases, the material may be at an elevated temperature.•Elevated temperature can affect both the condition of the material it sell and its surroundings, particularly, the •equipment that is being used to convey it. Care should be taken, when considering high temperature.•Elevated temperature range is clearly and accurately stated, and any effects on the material (particularly its •handling characteristics) should be noted.The temperature of the bulk material, measured in • °F or °C, for purposes of pneumatic conveying design, is the material temperature taken at the point of entry to the system.

Material temperature sensitivityMaterial temperature sensitivity is the temperature at which a bulk material changes its characteristics.•

HygroscopicityHygroscopicity is the ability of a material to absorb moisture from its surroundings. •Moisture may be absorbed from either the ambient air (especially during high humidity conditions) or the •conveying air of the pneumatic system.

ExplosivenessIn certain conditions, some bulk materials can form potentially explosive mixtures when combined with air. •These conditions depend on (a) the nature of the material itself, which would include its ignition temperature, •its chemical reaction with oxygen, its particle size distribution, and so on; and (b) the nature of the operation involving the material.Detailsofexplosionrisk,reactivity,andfirehazardarenowrequiredbylawinmoststatesintheU.S.tobe•listed on the Material Safety Data Sheet (MSDS).The MSDS must accompany any material which is transported stored or tested.In all cases involving explosive materials, reference should be made to National Fire Protection Association •(NFPA)classifications.

CorrosivenessSome materials have chemical properties which will, when combined with other materials such as moisture and •air, cause chemical deterioration to materials of construction.

FriabilityFriability describes a bulk material where particles are crumbled or pulverised.•

PermeabilityThe permeability of a bulk material is the degree to which air (or other gas) may be passed through the void •spaces between the particles of the material.

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Air retentionAir retention is the ability of a material to retain air (or other gas) in the void spaces of the material after the air •(for gas) supply to it has been terminated. Air retention capability can vary between almost zero and several days, depending upon the material’s other •physical characteristics.

7.4 Basic Terms and DefinitionsThe terms are described below:Material mass flow rate

Themassofmaterialconveyedoveraspecifiedperiodoftime,usuallyexpressedintons/hourorlbs./minute.•Materialmassflowrateisalsocalledconveyingrateorsystemcapacity.

Actual gas velocityActualgasvelocityisthevolumeflowrateatpressureandtemperatureconditionsperunitcross-sectionalarea•of the empty pipe, normally expressed in distance/time. Actual gas velocity varies throughout the entire length of the pipeline.•

Saltation velocityThe saltation velocity of a material is the actual gas velocity in a horizontal pipeline at which particles in a •homogeneous mixture with the conveying gas will begin to fall out of the gas stream.

Chocking velocityThe chocking velocity of a material is the actual gas velocity in a vertical pipeline at which particles in a •homogeneous mixture with the conveying gas settle out of the gas stream.

Minimum conveying velocityThe minimum conveying velocity is the lowest gas velocity that can be used to insure stable conveying •conditions. Since the minimum conveying velocity occurs at the material feed point in the system, it is also known as the •“pick-up” velocity. These terms are generally applied to dilute phase systems.•

Terminal gas velocityThe terminal gas velocity in a pneumatic conveying system is the velocity of the gas as it exits the system. •It is also known as the ending gas velocity and conveying line exit velocity.•

Average gas velocityTheaverage(alsocalledmean)gasvelocityofasystemisusuallydefinedasthemeanofthebeginning(or•pick-up) gas velocity and the terminal gas velocity.

Material velocityThe material velocity is the velocity of the material itself, which is somewhat lower than the gas velocity. •Materialvelocityisusuallyspecifiedaseitheraverage(ormean)velocityorterminalvelocity.•There are no reliable means, at the present time, for measuring the actual material velocity, and only an estimate •can be made.

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Volumetric gas flowTheusershouldbeawarethatthereareseveraldifferenttermsusedwhenconsideringvolumetricgasflow.•The volumetric gas rate during conveying is expressed as free air delivered (FAD). •Mostairmovers,suchasblowersandcompressors,arespecifiedintermsofFAD,measuredinstandardcubic•feet per minute (SCFM).FADisthevolumetricgasflowatthesuctionportofapositivepressureblowerorcompressororatthedischarge•port of a vacuum blower or vacuum pump. SCFMisthegasflowrateatstandardatmosphericconditions(i.e.,barometricpressureatsealevel,680• °F, and 36% relative humidity).Actualcubicfeetperminute(ACFM)orinletcubicfeetperminute(ICFM)isthevolumetricgasflowatthe•actual conditions that will be experienced where compressor or blower is located. The ACFM or ICFM must be calculated from the SCFM, taking into account elevation of the location and •maximum summertime ambient conditions.In the case of vacuum systems, the pressure drop of the system must also be taken into account when calculating •the gas at the inlet of the blower.

Conveying pressureThe conveying pressure for any system is required to overcome resistances in the system caused by interactions •between the conveying gas, the material being conveyed, the pipeline, and other system components. It is also referred to as “pressure drop”. •The conveying pressure is the difference measured between the beginning and the end of the pneumatic system •and is applicable to both positive pressure and vacuum (negative pressure) systems.

Two phase flowAllbulksolidmaterialspneumaticconveyingsystemsoperateonatwo-phaseflowprinciple,i.e.,asolidphase•(the materials being conveyed) and the gaseous phase (the conveying gas).

Dilute phase conveyingA dilute phase system is any pneumatic conveying system for which the conveying gas velocity is generally •equal to or above the saltation velocity of the material being conveyed.

Dense phase conveyingA dense phase system is any pneumatic conveying system for which the conveying gas velocity is generally •below the saltation velocity of the material conveyed.

Material to air ratioA parameter used by pneumatic system designers. •It is the ratio of the mass of material conveyed to mass of conveying gas used. •Itisalsoreferredtoas“phasedensity”,“solidsloadingratio”,and“massflowratio”.•

Flotation velocityTheflotationvelocityisthevelocityatwhichmaterialwillbesuspendedinair.•Knowingflotationvelocityiscriticaltodetermining“enclosurevelocity”,whichistheupwardvelocityofgas•inafilterreceiverorbinvent.This term is typically used in the design of bag-houses and dust collection systems.•

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SummaryPneumatic conveying refers to the moving of solids suspended in or forced by a gas stream through horizontal •and/or vertical pipes. The Conveyor Equipment Manufacturers Association (CEMA) has developed industry standard safety labels •for use on the conveying equipment of its member companies. The purpose of the labels is to identify common and uncommon hazards, conditions and unsafe practices which •can injure, or cause the death of, the unwary or inattentive person who is working at or around conveying equipment. Thetermshavebeengroupedintotwosections:materialcharacterisationandbasictermsanddefinitions.•

ReferencesGlossary of Pneumatic Conveying Terms• [Online]. Available at: >http://www.cemanet.org/publications/previews/CEMA%20Standard%20805pv.pdf>. [Accessed 10 April 2011].Conveyor Equipment Manufacturer’s Association Publications• [Online]. Available at: <http://infostore.saiglobal.com/store/Portal.aspx?publisher=CEMA>. [Accessed 10 April 2011].Tekchandaney, J. • Material Properties Affecting Solids Blending and Blender Selection: Bulk Density [Online]. Available at: <http://www.brighthub.com/engineering/mechanical/articles/53444.aspx#ixzz1JZX8j06Y>. [Accessed 10 April 2011].

Recommended ReadingCEMA Standard No. 805, “• Glossary of Pneumatic Conveying Terms - 2005”.Yang, 2003. Handbook of • Fluidization and Fluid-Particle Systems, 2nd ed., CRC Press.Tekchandaney R. Jayesh,• Material Properties Affecting Solids Blending & Blender Selection.

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Self AssessmentA _________is any pneumatic conveying system for which the conveying gas velocity is generally below the 1. saltation velocity of the material conveyed.

dense phase conveyinga. dilute phase conveyingb. conveying pressurec. twophaseflowd.

Pneumatic conveying terms are described as CEMA standard no. ________.2. 805a. 806b. 808c. 803d.

What is sometimes called the poured bulk density?3. Fluidised bulk densitya. Loose bulk densityb. Packed bulk densityc. Particle densityd.

Whichistheapparentbulkdensityofamaterialinitsfluidisedstate?4. Fluidised bulk densitya. Loose bulk densityb. Packed bulk densityc. Particle densityd.

What can be critical in the design of pneumatic conveying systems?5. Material Velocitya. Maximum Particle Sizeb. Median Particle Sizec. Minimum Conveying Velocityd.

Which of these is a method for particle size distribution?6. photo sedimentationa. optical microscopyb. electrical sensing zone techniques c. Nuclear magnetic resonance spectrometryd.

What is similar to spherical but being somewhat deformed or elongated?7. Fibrousa. Flakyb. Sphericalc. Out-of-roundd.

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Which is a bulk material comprised of individual particles which cannot be visibly discerned?8. Powdera. Granularb. Uniformc. Non-uniformd.

__________ is a single bulk material whose particles possess the same size and shape.9. Uniforma. Mixedb. Powderc. Non-uniformd.

___________ is the ability of a material to absorb moisture from its surroundings.10. Abrasivenessa. Explosivenessb. Hygroscopicityc. Corrosivenessd.

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Chapter VIII

Cross – Country Pipe – Line

Aim


highlight the main features of the detailed engineering •

explain construction of cross- country pipe-lines•

analyse the advantages of cross- country pipe-lines•

Objectives


describe the route survey and analysis •

enlist the data on the product to be carried out•

state the limitations of transport modes •

Learning outcome


examine the implementation and planning in detail engineering•

explain the project schedule concept•

state the disadvantages of cross- country pipe-lines•

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8.1 IntroductionInthemodernageofindustrialword,theoilrefineries,petroleumproductsandpetrochemicalsformthemajorpartofthe industrial set-up all over the world. It is often economical and practical to carry the liquid and gaseous products throughpipe-linesratherthanbytankersoverlongdistance.Apipe-linehastocarryproductslikecrudeoil,refinedoil, chemicals like naphthalene, ethylene, propylene etc. over long distance ranging from 10 km to even 1000 km. Passing through land, rivers, sea, mountains, marshy areas, private and public land rivers, sea, mountains, marshy areas, private and public land and crossing other services like roads, railways, transmission lines, underground pipes or cables etc, such a pipeline is called “cross-country pipe-line”. As the name suggests it transfers the liquid or gas products from one place to another at far distance.

Engineering and installation of cross-country pipe-lines form a special branch of piping design and engineering, as it involves many aspects and parameter which are normally faced in plant piping system within the boundaries of refineryorachemicalorpetrochemicalplant.

Special techniques have to be adopted for design, laying, welding or joining, corrosion protection, testing, commissioning etc. The most common line familiar to all is, water-line from reservoirs to different consumption points like, water-main from dams to city of Mumbai. Unlike water line, the hazardous chemical conveying pipelines, involvesmanymorestringentprecautionsintheirdesignandinstallation.Thisismainlyduetofireandexplosionhazards associated with the oils and chemicals.

8.2 Pipeline SystemPipeline systems are the safest and the most environment friendly mode of transportation of crude petroleum, •refinedproductsandnaturalgas.Being a closed system, there is minimal handling and transit losses as compared to other means of transportation, •henceitisconsideredtobemostefficient.The safety and reliability ensure minimum disruptions.•High grade steel pipes (API 5L international code) are used for constructing cross country pipelines.•The typical sizes of pipes are:•

diameter: 4 - 56 inch �pipe thickness: 0.219 – 1 inch �

These pipelines are designed to handle pressures upto 120 kg/cm• 2 to achieve throughput.

3%4%

68%

25%

Rail30%

Pipelines

USA**Road/

Coastal31%

Coastal Rail Road

Pipelines39%

INDIA*

Fig. 8.1 Typical mode-wise transportation of petroleum products(Source: http://petrofed.winwinhosting.net/upload/26-28July10/BDYadav.pdf)

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8.3 Limitations of Modes of TransportThe most common modes of transport known to all includes trucks running over roads, railway goods train and •ships, launches, boats, barges on waterways. The transport by airway or by cargo air-crafts is also another way of bulk-transport. •These modes of transport have the following limitations:•

availabilityofsufficientroads,rail-tracksandport-harbourfacilitiestotakeupthetrafficload. �condition of tracks �hurdles and conditions of the vehicles �maintenance and conditions of the vehicles �procedures and control involved in the transport operation (permits/ licenses/octroi/toll/RTO etc) �manpower to run and maintain the transport system �availability of fuel and power required to run the system �effect of nature on the system like rains, storms, earthquakes, thundering, mist etc. �pollution generated by the transporting vehicles �safety, insurance and security of the transported goods and materials �time taken for transportation and delays �overallefficiencyofthesystem �

While transportation by roads, railways, water and air-ways is widely used all over the world, it has its own •limitations due to the features used all over the world. These limitations especially restrict or forbid their use when large quantities of oil, petroleum, water, chemicals •are to be continuously supplied from the source to the consumption point at user’s end. Hence,themostreliableandefficientsystemcanbeprovidedonlybecross-countrypipe-lines.•

Head Road Rail PipelineEnergy cost Very High High LowOperating cost Very High High LowPollution High Low NilMovement congestion High Low NilHandling loss High Low NegligibleSafety Hazards High Low NegligibleReliability Low Low 100%

Fig. 8.2 Modes of transportation of petroleum-A comparison(Source: http://petrofed.winwinhosting.net/upload/26-28July10/BDYadav.pdf)

8.4 Advantages and Disadvantages of Cross-Country Pipe-LinesThe advantages of cross-country pipelines are given below:•

Continuous un-interrupted transport is ensured. �No dependence on availability of roads, railways, bridges etc. �Least manpower requirement to operate the transport system except for inspection and maintenance of �minimum required level.No hindrances on way due to any reasons for surface transport, air or water ways. �Possibility of crossing any odd areas like seas, oceans, rivers, mountains and underground space. �

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Safety and purity of the product is ensured. The product reaches exactly in the same condition from source �to the supply point, with minimal loss of quality or quantity.Once laid down, the system works automatically especially with the help of modern instrumentation, safety �devices, interlocks, communication system and remote control devices.Minimum or no tampering on the way. �Cost of transport per unit of the product conveyed is far less than the transport by trucks, railways, water �or airways.Fastest mode of transport even between two countries or continents. �Comparatively much less hazardous than surface transport and minimum dependence on human factors. �

There are of course certain disadvantages but they are offset by the advantages to a large extent, so as to make •them ignorable as far as safety and techno-economic aspects are concerned. These disadvantages are listed below:•

Right of way acquisition to run the pipeline, especially through private and agricultural land and habitat �areas.Highfireandexplosionhazardspotential. �Problem of corrosion and leakages and repair work involved �Dailyon-routeinspection,testingandquickarrangementsforattendingtorepairsandrectificationwork �Possibility of laying other services in future (like other pipelines due to ignorance of its existence, among �other agencies) causing damageSpecial techniques and agencies are required to design, engineer, install and operate the pipeline system. �Expensive cathodic protection required for the protection of underground lines running in close proximity �of overhead high tension electrical transmission lines which induce the currents in the metallic pipelines, causing the corrosion by stray-currents.

The modern techniques are well developed to offset the effects of the above disadvantages. Even if a line has •to shut-off for a day or two, the storage facilities at the users end take care of such stoppages even for 15 days to 1 month.

8.5 Preliminary Work for a Cross-Country Pipe-Line ProjectThe following necessary work on planning and collection of information or data is required to be for pre-project activities, once it is decided to install a cross-country pipe-line.Data on the product to be carried

name, quantity per day, properties of the product•source of supply and location details•names and location of consumers•quantity per day to be supplied to each consumer•storage facilities at supplier’s end and consumer end•pumping facilities at supplier’s end•unloading facilities at receiver’s end•safety requirements for the product•risk and hazards associated with product•interruptions in supply at supplier’s end and at receiving end•

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REFINED PRODUCT FROM UNIT OF REFINERIES

IMPORTED/ OTHER PRODUCT IN SHIP/OIL JETTY

REFINERY’S PRODUCT TANKAGE TANKAGES

PUMPING STATION

CROSS COUNTRY PIPELINE

PUMPING CUM DELIVERY STATIONS

DELIVERY TERMINAL

Fig. 8.3 Product transportation(Source: http://petrofed.winwinhosting.net/upload/26-28July10/BDYadav.pdf)

Route survey and analysisThere may be many alternatives for routing the pipeline from supplier to the consumer. It is necessary to study the techno-economic comparison of the alternative routes. This survey includes the following activities:

Spot-level survey• at every 50 to 100 metres and atleast over 10 m on either side of the probable route.Soil conditions• in the form of bore-logs, trial pits, chemical tests on subsoil and ground water etc.Alignment map• with lengths, bearings, angles etc. to know the exact route and the total length of the pipe-line.Details on the route• and their location dimensions etc sea, roads (crossing and along side the route) rivers, Nallas, pipe-lines, bridges, rail-tracks, transmission lines, underground services including cables or pipes etc, hills and mountains, buildings, plantation, forests, agricultural land etc.Cadestral survey• –The route may be passing through so many lands belonging to private owners, farmers, govt. authorities, defence wings etc. En-route information and data has to be collected for such land pieces. Such data will include:

Type of land and the owner’s name �Length of the route through the land �Problems in acquiring Right of Way (ROW) �Authority which will permit or grant ROW �Survey maps for the land available from the local land authorities (such as collector, Tahasildar, Gram- �Panchayat etc.)Land records regarding the title and ownership of the land �Approximate compensation required for acquiring the ROW �Status of habitation on the land �Similar information of the adjacent plots on 50 to 100 m on either side of the route. �Plans for future installations by others on the proposed route and/ or in the vicinity such as roads, rail-tracks, �buildings or pipe-lines etc.

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Availability of construction materials, labour and facilities•Since the pipe-line has to pass through different areas and over a long distance, it is essential to know the �availability of construction labour and materials on the way. Such as excavation labour, transport facilities, access roads, construction material like stones, aggregates, �sand, cement, steel, structurals, etc., workshop facilities. This information will be useful in working out project schedule and cost estimates and assessing the problems �in construction.

Soil resistivity survey •It is required for design of cathodic protection system. �Names and addresses of the statutory and public bodies required to be contacted for acquiring ROW, �construction permission, blasting licences, excavating the public facilities (Roads, rivers, rail-tracks etc.) and cathodic protection work, power supply/water supply etc. Such authorities include the following but not limited to the listed ones. �

Local land authorities – distr. Collector, Municipal Corporation, Tahsildars, etc. i. Owners of the respective landii. PWDauthorities–localofficeiii. Irrigation departmentiv. Electricity supply agencies, bodies or boardsv. Water-supply and public health departmentvi. Controller of explosives and use of hazardous chemicalsvii. Industrial development corporationsviii. Railway authoritiesix. Marine and port authoritiesx. Salt-commissioner and controllerxi. Competent authorities for land and row acquisition.xii. State and central government for necessary permissions, licences, clearances etc.xiii. Import, export rules or regulations authoritiesxiv. Controller of quarrying and miningxv. Navy, army or air force (defence authorities)xvi. Plants for future installations.xvii. Forest authoritiesxviii.

Project scheduleBased on various data collected and the cost estimates, over all project schedules has to be prepared based on •pastexperienceandspecificproblemsuniquetotheprojectunderconsideration.This schedule should cover only broad activities to serve as a guideline for preparation of detail activity •schedule.This will establish the overall completion time for the entire project work.•This should generally include:•

preliminary survey or data collection �finalisingtheroute �cost estimates / budget sanctions �acquisition of ROW and land �basic engineering package �

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detail engineering work �construction work (Civil, mechanical, piping, electrical or marine crossing, river crossing etc or cathodic �protection)testing,flushingorpigging �commissioning and hand over �

Finalising the most optimum routeThis involves the comparison of alternative router surveyed. •The analysis should include various parameters which are tabulated in the following format:•

Sr. No. Parameter Values for Alt-routes Remarks

Alt. 1 Alt. 2 Alt. 31.2.3.4

Under parameter columns, following minimum items should be included:Estimated cost1.

row acquisition•land acquisition•statutory permission•basic engineering•detail engineering•material procurement (pipes/valves/equipments)•construction cost•civil•piping•mechanical•electrical•cathodic protection•on line buildings•marine or river crossings•testing commissioning•cathodic protection•

Overall completion - Time2. Total length3. Cost per km4. Other features5.

rock area �marine zone �no. of road crossings �no. of railway crossings �no. of nallas crossings �underground portion lengths �

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above ground portion lengths �no. of isolation valves �pipe-line diameter �no.ofrectifierstations �no. of diode stations �

cost of operation or year6. cost of maintenance or year7. hazard classifications8. risk-factor9. disaster management category10. stoppages or shut down due to external factors11. threat to security and safety etc.12.

Value analysis should be done for each alternative routes considering appropriate weightage assigned to these parametersandcostsofthesame.Thusfinalandmostoptimumroutecanbeselected.

8.6 Salient Steps in Detail EngineeringAfterdecidingthefinalroute,costestimates,broadprojectscheduleandengineering,thedetailengineeringinvolvesthe following main steps:

Detail design of each systemCivilworksincludingtrenching,sandfilling,backfilling,buildings,concreting,riverweights,valve-chambers,•testpoints,markersandconstructioninfrastructurelikesiteoffice,constructionwater,power,sitegodown/openyards etc.Construction equipment required for transport, laying, welding, erection testing etc.•Piping: stringing, welding, laying or testing pipe support system•Cathodicprotectionsystemdesign,diode stations, sacrificial anodes,UPS installations,on-line test-points,•insulationflangesSpecificdesignsforsubmarineportionsandriver-crossings•Designs of all crossings, pipe-bridges, supports•Preparing detail design and fabrication drawings for all systems•Quantity calculation for materials and work items.•

Implementation, planning and organisingselection and appointing agencies/contractors/suppliers for various activities and materials•division of work among the staff on the project•progress monitoring and reporting system•mobilising planning (manpower deployment planning), resource-planning•implementation work packages•payment to subcontractor system•inventory-control-planning•safety/security guidelines•organising revisions/change/alternatives/improvements in system design/drawing during the project-process•preparationofas-builtconstructiondrawingsandfinalcosting•databank for the executed project, useful for future project•

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SummaryApipe-linehastocarryproductslikecrudeoil,refinedoil,chemicalslikenaphthalene,ethylene,propylene•etc. over long distance. Passing through land, rivers, sea, mountains, marshy areas, private and public land, and crossing other services •like roads, railways, transmission lines, underground pipes or cables etc, such a pipeline is called “cross-country pipe-line.”Engineering and installation of cross-country pipelines form a special branch of piping design and engineering, •as it involves many aspects and parameter which are normally faced with in plant piping system within the boundariesofrefineryorachemicalorpetrochemicalplant.Special techniques have to be adopted for design, laying, welding or joining, corrosion protection, testing, •commissioning etc. The most common modes of transport known to all includse trucks running over roads, railway goods train and •ships, launches, boats, barges on waterways. The transport by airway by cargo air-crafts is also another way of bulk-transport. •Based on various data collected and the cost estimates, over all project schedules has to be prepared based on •pastexperienceandspecificproblemsuniquetotheprojectunderconsideration.Value analysis should be done for each alternative routes considering appropriate weightage assigned to these •parametersandcostsofthesame.Thusfinalandmostoptimumroutecanbeselected.

ReferencesCross-Country Pipeline: A National Asset• [Online]. Available at: <http://www.projectsmonitor.com/detailnews.asp?newsid=7973>. [Accessed 18 April 2011].Yadav, B. D.• Cross-Country Pipelines: An Overview [Online]. Available at: <http://petrofed.winwinhosting.net/upload/26-28July10/BDYadav.pdf>. [Accessed 18 April 2011].Transportation of Flammable and or Toxic Solvents• [Online]. Available at: <http://www.hrdp-idrm.in/live/hrdpmp/hrdpmaster/idrm/content/e7388/e7721/e11065/infoboxContent12091/TransportationofFlammable-ToxicSolvents-if.doc>. [Accessed 18 April 2011].

Recommended ReadingDay, N. B., 1998. • Pipeline Route Selection for Rural and Cross-Country Pipelines: Issue 46 of ASCE Manuals and Reports on Engineering Practice, ASCE Publications.Orszulik, S. T., 2008. • Environmental technology in the oil industry, 2nd ed., Springer.Jacques V. G., 1984. • Fundamentals of Pipeline Engineering, TECHNIP.

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Self AssessmentWhat should be the typical diameter of pipes in cross-country pipelines?1.

4 - 56 incha. 51 - 56 inchb. 25 - 56 inchc. 56 - 96 inchd.

Spot-level survey should be done at every 50 to 100 metres and atleast over ___________ on either sides of 2. the probable route.

20 ma. 10 mb. 30 mc. 40 md.

Pipelines cover___________ of modes of transport in India.3. 39 %a. 75 %b. 50 %c. 89 %d.

Being a ________ system, there is minimal handling and transit losses in pipelines as compared to other means 4. oftransportation,henceitisconsideredtobemostefficient.

closeda. openb. partially-openc. cruded.

Which survey includes the type of land and the owner’s name?5. Spot-level surveya. Cadestral surveyb. Soil Resistivity Survey c. Routes detaild.

Which of the following is an advantage of cross-country pipelines?6. Right of way acquisition to run the pipeline, especially through private and agricultural land and habitat areas.a. Highfireandexplosionhazardspotential.b. Problem of corrosion and leakages and repair work involved.c. Fastest mode of transport between two countries or continents.d.

Pipelines have ________.7. low energy costa. high energy costb. high operating costc. nil pollutiond.

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Pipelines have _________ reliability.8. 100 %a. 30 %b. 86 %c. 70 %d.

Railways have ________.9. low energy costa. high energy costb. low operating costc. high pollutiond.

Estimated cost in pipelines is stated as ______________.10. cost per kma. cost per mb. cost per inchesc. cost per mmd.

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Case Study I

Check Valve Failures

The piping system is normally considered to be the safest part of the plant. However reviews of catastrophic accidents show that piping system failures represent that largest percentage of equipment failures.

Check valves are important safety devices in piping. Check valves have been utilized in the process industry for manyyearstokeepmaterialfromflowingthewrongwayandcausingoperationalorsafetyconcerns.Onecommonmistakeisinstallingthecheckvalvebackwardsandblockingtheprocessflow.Anarrowonthecheckvalvedesignatestheproperflowdirection,indicatingtheproperinstallationposition.

In December 1991, a chemical plant in Saudi Arabia experienced a release of propane gas due to a check valve shaft blowout. The incident followed a process upset in the facility’s ethylene plant, where the unintentional shutdown of acrackedgascompressorresultedindownstreamflowinstabilitiesandsurgingintheunit’spropanerefrigerationcompressor.

During this period, the check valves installed in the propane refrigeration compression system slammed closed repeatedly. The shaft of the compressor’s third stage discharge valve eventually separated from its disk and was partially ejected from the valve. Propane gas began to leak out of the valve around the gap between the shaft and itsstuffingboxuntiloperatorsdiscoveredtheleakandshutdownthecompressor.Thefacilitywasfortunatethatanadjacent steam line kept the shaft from being fully ejected from the valve, thus limiting the leak rate and preventing an accident of potentially greater severity.

A subsequent investigation and analysis of the check valve’s internal components revealed that the dowel pin, whichsecuredthedriveshafttothevalveflapper,hadsheared,andtheshaftkeyhadfallenoutofitskey-way.The investigation report also revealed that facility maintenance records indicated a long history of problems with the check valves installed there. The valves were installed in 1982, and due to continuing valve malfunctions, underwentrepairormodificationsinsubsequentyears.Theserepairsandmodificationsincludedreplacementofdamaged counterweight arms, replacement of seals and gaskets, replacement of dowel pins and internal keys, and installation of external shaft “keepers”.

Questions:How check valves in the piping system is an important safety concern?1. Explain the accidental case at the chemical plant in Saudi Arabia?2. Give the details of the report of the investigation carried out.3.

Answers:Check valves are important safety devices in piping. Check valves in the process industry is used to prevent 1. materialfromflowingthewrongwayandcausingoperationalorsafetyconcerns.Installationofthecheckvalvebackwardsandblockingtheprocessflowisacommonmistakedonebytheprocessdesigners.Anarrowonthecheckvalvedesignatestheproperflowdirection,indicatingtheproperinstallationposition.

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In December 1991, a chemical plant in Saudi Arabia experienced a release of propane gas due to a check valve 2. shaftblowout.Anunintentionalshutdownofacrackedgascompressorresultedindownstreamflowinstabilitiesand surging in the unit’s propane refrigeration compressor. The check valves installed in the propane refrigeration compression system slammed closed repeatedly. Propane gas began to leak out of the valve around the gap betweentheshaftanditsstuffingboxuntiloperatorsdiscoveredtheleakandshutdownthecompressor.

A subsequent investigation and analysis of the check valve’s internal components revealed that the dowel pin, 3. whichsecuredthedriveshafttothevalveflapper,hadsheared,andtheshaftkeyhadfallenoutofitskey-way.The investigation report also revealed that facility maintenance records indicated a long history of problems with thecheckvalvesinstalledthere.Thevalveshadcontinuedmalfunctions,repairormodifications.Theserepairsandmodificationsincludedreplacementofdamagedcounterweightarms,replacementofsealsandgaskets,replacement of dowel pins and internal keys, and installation of external shaft “keepers”.

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Case Study II

Bulk Storage and Piping Case Study

OhioisamajorsteelmanufacturerwhichestablishedthefirstR&Ddepartmentinthesteelindustryin1910.Itgrewthrough the development of specialty steels and new technology. This company holds more U.S. patents than any otherspecialtysteelcompany.Thedevelopmentofcontinuousrollingtechnologywasamongthefirst.Asmeasuredby production and shipped tons, the company is the largest specialty steel company in the US.

However, the environmental and safety concerns grow with the company. As part of its efforts to reduce its environmental expenses and maintain a high level of safety in its manufacturing facilities, it had Mech-Chem inspect to test and certify its waste acid storage tanks. Four bulk storage systems ranging in size from 10,000 gallons to 40,000gallonswereinspectedandcertified.Mech-Chemthenwentontodesignanewwasteacidbulkstoragefacility and related piping system to handle their waste acid production.

The testing and inspection of the waste acid storage tanks included visual internal and external inspection, spark testing of the tank liners and non-destructive ultrasonic thickness survey tests of the tank shell and heads.

An engineering report was prepared to submit to the Ohio EPA, including a CAD drawing for each tank showing resultsofthenon-destructiveultrasonicthicknesssurveyandtests.Theinspection,structuralanalysisandcertificationof the secondary containment systems also included materials of construction and structural-mechanical review of the design for compliance with Ohio EPA waste management regulations.

Mech-Chem was contracted to engineer and design a waste acid bulk storage facility and related piping systems. The waste acid bulk storage facility consists of eight process and storage tanks varying in size from 5,000 gallons to 40,000 gallons.

ThewasteacidspipedandstoredinthissystemincludeHydrofluoricAcid(HF),NitricAcid(HNO3), Hydrochloric Acid (HCl), and Sulfuric Acid (H2SO4). The handling of these various acid mixtures presented unique material of construction requirements.

The bulk storage facility and piping systems are designed to handle 20,000 gallons per day of various hot (160 °F) waste acid mixtures. The facility design provides for secondary containment for the process tanks, storage tanks, pumps, piping, and loading-unloading of tank wagons.

The company not only ensured that its existing tanks met all the necessary OSHA codes and EPA regulations, but it also acquired a new, fully automated bulk storage and piping system designed by Mech-Chem.

Questions:Why Ohio needed Mech-Chem support for its bulk storage tanks?1. What were the activities included in testing and inspection of the bulk storage tanks?2. What was the contract given to3. Mech-Chem?

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Case Study III

Pipeline Asset Management System (PAMS)

Pipeline is the heart-line of oil and gas transportation. There is an increasing demand for sophisticated and advanced tools to cater to the pipeline project implementation, asset management, operation and maintenance. There was a greatchallengetoefficientlymanage850kmofexistingpipelinenetworkand840kmofproposedpipelinenetworkacross India. With limited resource availability, it was an uphill task for Gujarat State Petronet Limited (GSPL) to manage.

Secon,anISO9001:2000certifiedfirm,providesend-to-endservicesongeospatial&engineeringincludingdatacapture, processing, design & drafting, GIS based customization and application development. It used Pipeline Asset Management System (PAMS) for day-to- day easy management of pipelines from inception to commissioning. Pipeline Asset Management System (PAMS) was a one-stop solution for the cross-country pipelines. PAMS database was designed to handle complete data corresponding to the pipeline, and also a powerful tool for disaster management.

PAMS included pre-engineering, engineering, construction, health, safety & environment and operation & maintenance.Itprovidedthegeneralbenefitsofmanagingthemasterdatabaseofentirepipelineinformationforeaseofuse,accessibilitythroughLAN/WAN/WEB,customizedreportgenerationandfaster&efficientdataaccesswithbetterdecisionmakingplatform.Thepipelineprojectexecutiongavestagewisebenefits.Priortoconstruction,survey and land acquisition processes were monitored.

Inter-connectingof all zonal offices using applications for projectmonitoring&acquisitionmanagementwasimplemented.ThePAMSdatabasewascentralizedtoconnectallstationofficesforoperationsandmanagementpurpose. Disaster management tools & web enabled maintenance system were also installed.

Overall, this resulted in manpower reduction requirement for land acquisition process by 55% and time was saved by48%.Efficientandaccuratedatamanagementwasachieved.Webenabledsystemprovidedefficientprocessingand management details.

Questions:What was the challenging task given to Gujarat State Petronet Limited?1. What are the features of PAMS?2. WhatwasthefinaloutcomeoftheeffortsbySecon?3.

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Bibliography

ReferencesBasic and Detailed Engineering • [Online]. Available at: <http://www.technip.com/en/about-us/range-services/basic-and-detailed-engineering>. [Accessed 6 April 2011].

Centrifugal Pumps• [Online]. Available at: <http://www.engineeringtoolbox.com/centrifugal-pumps-d_54.html>. [Accessed 9 April 2011].Centrifugal Pumps• [Online]. Available at: <http://www.techpedia.in/uploads/8dcbccda736a01969106b71b90a4c49b.pdf?PHPSESSID=28646d66d12ea7c61dd41478a181830b >. [Accessed 10 April 2011].Conveyor Equipment Manufacturer’s Association Publications• [Online]. Available at: <http://infostore.saiglobal.com/store/Portal.aspx?publisher=CEMA>. [Accessed 10 April 201].

Cross-Country Pipeline: A National Asset• [Online]. Available at: <http://www.projectsmonitor.com/detailnews.asp?newsid=7973>. [Accessed 18 April 2011].

Design Guide for Layout and Plot Plan • [Online]. Available at: <http://www.chagalesh.com/snportal/Uploads/chagalesh/karafarinan%20farda/jozveh/piping/6.pdf>. [Accessed 6 April 2011].

Design guide for Layout and Plot Plan • [Online]. Available at: <http://webtools.delmarlearning.com/sample_chapters/1418030678_ch12.pdf>. [Accessed 6 April, 2011].

Fluid mechanics pumped pipe systems • [Online].Availableat:<http://www.freestudy.co.uk/fluid%20mechanics/t8c203.pdf>. [Accessed 9 April 2011].Fundamentals of Pipe Stress Analysis with Introduction to CAESAR II• [Online]. Available at: < http://www.idc-online.com/pdf/training/mechanical/SA.pdf>. [Accessed 5 April 2011].

Glossary of Pneumatic Conveying Terms• [Online]. Available at: <http://www.cemanet.org/publications/previews/CEMA%20Standard%20805pv.pdf>. [Accessed 10 April].

Grossel. S., • Improved Design Practices for Slurry Piping Systems [Online]. Available at: <http://www.globalspec.com/reference/9775/349867/improved-design-practices-for-slurry-piping-systems>. [Accessed 8 April 2011].

Important • Characteristics in formation of Steam [Online]. Available at: <http://mechanicalguru.blogspot.com/2009/06/important-characteristics-in-formation.html>. [Accessed 7 April 2011].

Interpreting Piping and Instrumentation Diagrams • [Online]. Available at: < http://chenected.aiche.org/plant-operations/interpreting-piping-and-instrumentation-diagrams-part-2-of-5/>. [Accessed 7 April, 2011].

P&ID - Piping and Instrumentation Diagram • [Online]. Available at: <http://www.engineeringtoolbox.com/p&id-piping-instrumentation-diagram-d_466.html >. [Accessed 7 April, 2011].

Pipes and Pipe Sizing • [Online]. Available at: <http://www.spiraxsarco.com/resources/steam-engineering-tutorials/steam-distribution/pipes-and-pipe-sizing.asp >. [Accessed 8 April 2011].

Piping for Steam Distribution• [Online]. Available at: <http://www.pipingguide.net/2010/01/piping-for-steam-distribution.html>. [Accessed 7 April 2011].

Preparation of Plot Plan• [Online]. Available at: < http://www.epcpj.com/preparation-of-plot-plan/>. [Accessed 6 April 2011].

Process diagrams • [Online]. Available at: <http://www.lle.rochester.edu/media/omega_facility//documents/P&ID.pdf >. [Accessed 6 April, 2011].

Pump basics • [Online]. Available at: <http://www.savinobarbera.com/english/pump-basics.html>. [Accessed 9 April 2011].

Slurry characteristics• [Online]. Available at: <http://www.scribd.com/doc/50809286/10/Slurry-characteristics>. [Accessed 9 April 2011].

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Steam Pipe Sizing and Design • [Online]. Available at: <http://www.productivity.in/knowledgebase/Energy%20Management/c.%20Thermal%20Energy%20systems/4.11%20Steam%20System/4.11.4%20Steam%20Pipe%20Sizing%20and%20Design.pdf>. [Accessed 8 April 2011].

Stress analysis for process piping• [Online]. Available at: <http://www.pipingdesign.com/stressanalysis.pdf>. [Accessed 5 April 2011].

Symbols for Process Flow Diagrams and Engineering Line Diagrams • [Online]. Available at: <http://www.roymech.co.uk/Useful_Tables/Drawing/Flow_sheets.html>. [Accessed 7 April, 2011].

Tekchandaney, J. • Material Properties Affecting Solids Blending and Blender Selection: Bulk Density [Online]. Available at: <http://www.brighthub.com/engineering/mechanical/articles/53444.aspx#ixzz1JZX8j06Y>. [Accessed 10 April 2011].

Transportation of Flammable and or Toxic Solvents • [Online]. Available at: <http://www.hrdp-idrm.in/live/hrdpmp/hrdpmaster/idrm/content/e7388/e7721/e11065/infoboxContent12091/TransportationofFlammable-ToxicSolvents-if.doc>. [Accessed 18 April 2011.]

Wormer, R. V., • Plot plan design [Online]. Available at: <http://www.spedweb.com/index.php/sped-technical/plot-plans.html>. [Accessed 6 April 2011].

Yadav, B. D. • Cross-Country Pipelines: An Overview [Online]. Available at: <http://petrofed.winwinhosting.net/upload/26-28July10/BDYadav.pdf>. [Accessed 18 April 2011].

Recommended ReadingAbulnaga, B. E., 2002. • Slurry systems handbook, McGraw-Hill Professional, ISBN0071375082, 9780071375085.

Aude, T.C., Cowper N.T., Thompson, T.L., & Wasp, E.J., 1971. • Slurry Piping System: Trends, chemical Engineering.

Bachus, L., & Custodio, A., 2003. • Know and Understand Centrifugal Pumps, Elsevier.

Bausbacher, E., & Hunt R. W., 1993. • Process plant layout and piping design, PTR Prentice Hall.

Bel• l, A. A., 2007. HVAC equations, data, and rules of thumb, 2nd ed., McGraw-Hill Professional, ISBN0071482423, 9780071482424.

Blevins, T. L., 2010. • Mark Nixon Control Loop Foundation: Batch and Continuous Processes, 2nd ed., ISA.

Brown, N. P. & Heywood, N. I., 1991. • Slurry handling: design of solid-liquid systems, Springer, ISBN 1851666451, 9781851666454.

CEMA Standard No. 805, “Glossary of Pneumatic Conveying Terms - 2005”•

Day, N. B., 1998. • Pipeline Route Selection for Rural and Cross-Country Pipelines: Issue 46 of ASCE Manuals and Reports on Engineering Practice, ASCE Publications.

Goettsche, L. D., 2005. • Maintenance of instruments & systems: Practical guides for measurement and control, 2nd ed., ISA.

Jacques V. G., 1984. • Fundamentals of Pipeline Engineering, TECHNIP.

Kellogg, 1964. • Design of Piping Systems, 2nd ed., John Wiley & Sons Inc.

Lobanoff,V. S., & Ross, R. R., 1992. • Centrifugal pumps: design & application, 2nd ed., Gulf Professional.

Munson, 2007. • Fundamentals of Fluid Mechanics, Wiley-India.

Nayyar, M. L., 2000. • Piping Handbook, 7th ed., McGraw-Hill.

Orszulik, S. T., 2008. • Environmental technology in the oil industry, 2nd ed., Springer.

Parisher R. A., Rhea, R. A., 2001. • Pipe Drafting and Design, 2nd ed., Gulf Professional Publishing.

Sawhney, 2009. • Fundamentals of Mechanical Engineering: Thermodynamics Mechanics Theory of Machines and Strength of Materials, 2nd ed., PHI Learning Pvt. Ltd.

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Sing• h, O., 2007. Engineering Thermodynamics, New Age International, ISBN8122417507, 9788122417500.

Tekchandaney R. Jayesh,• Material Properties Affecting Solids Blending & Blender Selection.Thakore, 2008. • Introduction to Process Engineering and Design, Tata McGraw-Hill Education.

Towler, G. P., & Sinnott R. K., 2008. • Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design, Butterworth-Heinemann.

Weaver, R., 1986. • Process piping drafting, 3rd ed., Gulf Pub Co.

Yang, 2003. • Handbook of Fluidization and Fluid-Particle Systems, 2nd ed., CRC Press.

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Self Assessment Answers

Chapter Id1. a2. c3. d4. b5. c6. d7. c8. a9. a10.

Chapter IId1. a2. a3. c4. d5. a6. b7. a8. c9. c10.

Chapter IIIa1. b2. a3. b4. a5. d6. d7. b8. d9. d10.

Chapter IVa1. a2. b3. b4. a5. a6. d7. b8. c9. a10.

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Chapter Vd1. d2. a3. b4. a5. a6. b7. a8. d9. a10.

Chapter VIc1. a2. a3. a4. b5. b6. a7. a8. b9. c10.

Chapter VIIa1. a2. b3. a4. b5. d6. d7. a8. a9. c10.

Chapter VIIIa1. b2. a3. a4. b5. d6. a7. a8. b9. a10.