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Design of Steam Piping including
Stress Analysis
Muhammad Sardar
Thesis submitted in partial fulfillment of requirements for the MS
Degree in Mechanical Engineering
Department of Mechanical Engineering,
Pakistan Institute of Engineering & Applied Sciences,
Nilore, Islamabad, Pakistan.
October, 2008.
Note. This is not a handbook, it is MS Thesis of a student in PakistanInstitute of Engineering & Applied Sciences, Pakistan (PIEAS).
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Department of Mechanical Engineering,
Pakistan Institute of Engineering and Applied Sciences (PIEAS)
Nilore, Islamabad, Pakistan
Declaration of Originality
I hereby declare that the work contained in this thesis and the intellectual content of
this thesis are the product of my own work. This thesis has not been previously
published in any form nor does it contain any verbatim of the published resources
which could be treated as infringement of the international copyright law.
I also declare that I do understand the terms copyright and plagiarism and
that in case of any copyright violation or plagiarism found in this work, I will be held
fully responsible of the consequences of any such violation.
Signature:
Name: Muhammad Sardar
Date:____________________
Place: PIEAS, Nilore Islamabad
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Certificate of Approval
This is to certify that the work contained in this thesis entitled
Design of Steam Piping including Stress Analysis
was carried out by
Muhammad Sardar
Under my supervision and that in my opinion, it is fully adequate, in
scope and quality, for the degree of M.S. Mechanical Engineering from
Pakistan Institute of Engineering and Applied Sciences (PIEAS).
Approved By:
Signature:________________________
Supervisor:Mr. Basil Mehmood Shams,P.E. (DTD, Islamabad)
Signature:_______________________
Co-Supervisor:Muhammad Younas, S.E. (DTD, Islamabad)
Signature:________________________
Co-Supervisor:Hafiz Laiq-ur-Rehman, J.E. (PIEAS, Islamabad)
Verified By:
Signature:________________________
Head, Department of Mechanical Engineering
Stamp:
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Dedication
Dedicated to my parents, brothers, sisters and my teachers
who always supported me and whose
prayers enabled me to
do my best in every
matter of my life
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Acknowledgement
First of all I am humbly thankful to Allah Almighty, giving me the power to think and
enabling me to strengthen my ideas. I glorify ALMIGHTY ALLAH for HIS
unlimited blessings and capabilities that HE has bestowed upon me, without HIS
blessings, I would not be able to complete my work. I offer my thanks to Holy
Prophet(Peace Be Upon Him), The mercy for all the worlds and whose name hasgiven me special honor and identity in life.
I am very grateful to my project supervisor Mr. Basil Mehmood Sham, P.E. for his
guidance for the completion of this work. I am also grateful to my co-supervisors
Mr. Muhammad Younas, S.E. and Mr. Hafiz Laiq-ur-Rehman, J.E. for their
inspiring guidance, constant encouragement and fruitful suggestions. At the end I am
also thankful to Engr. Dr. Mohammad Javed Hyder for his keen interest in the
project and constructive criticism, which enabled me to complete my report.
Muhammad Sardar
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Table of Contents
1 INTRODUCTION................................................................................................1
1.1 Thesis Introduction ........................................................................................1
1.2 Basic aim of the thesis ...................................................................................1
1.3 Steam Piping Network ...................................................................................2
1.4 Thesis Organization .......................................................................................2
2 THEORETICAL BACKGROUND OF PIPING SYSTEM ............................5
2.1 Historical background of the piping system ..................................................5
2.2 Piping Terminologies.....................................................................................6
2.2.1 Pipe.......................................................................................................................6
2.2.2 Types of pipes and its uses...................................................................................6
2.2.3 Pipe Size...............................................................................................................6
2.2.4 Nominal Pipe Size (NPS).....................................................................................6
2.2.5 Piping ...................................................................................................................6
2.2.6 Piping System ......................................................................................................7
2.2.7 Process Piping......................................................................................................7
2.2.8 Service Piping ......................................................................................................72.3 Pipe Fittings ...................................................................................................7
2.3.1 Valves...................................................................................................................7
2.3.2 Expansion Fittings................................................................................................8
2.4 Supports .........................................................................................................9
3 PIPING CODES AND STANDARDS..............................................................12
3.1 Piping Code Development ...........................................................................12
3.2 B31.1 Power Piping .....................................................................................13
3.3 ASME Code Requirements..........................................................................14
3.3.1 Stresses due to sustained loadings......................................................................14
3.3.2 Stress due to occasional loadings.......................................................................14
3.3.3 Stresses due to thermal loadings ........................................................................15
3.4 Stress analysis of piping system ..................................................................15
3.4.1 Stress and Strain.................................................................................................15
3.4.2 Failure Theories .................................................................................................15
3.4.3 Piping Design Criteria........................................................................................16
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4 PIPING DESIGN PROCEDURES...................................................................19
4.1 Process Design.............................................................................................19
4.2 Piping Structural Design..............................................................................19
4.2.1 Pipe Thickness Calculations ..............................................................................204.2.2 Allowable Working Pressure .............................................................................20
4.2.3 Sustained Load Calculations ..............................................................................21
4.2.4 Wind Load Calculations.....................................................................................21
4.2.5 Thermal Loads Calculations ..............................................................................22
4.2.6 Occasional Loads ...............................................................................................22
4.2.7 Seismic Loads ....................................................................................................22
4.3 Pipe Span Calculations ................................................................................23
4.3.1 Span Limitations ................................................................................................23
4.3.2 Expansion Loop Calculations ............................................................................24
5 SUPPORT DESIGN...........................................................................................25
5.1 Beam Design................................................................................................25
5.1.1 Bending Stress....................................................................................................26
5.1.2 Shear Stress ........................................................................................................26
5.1.3 Deflection...........................................................................................................27
5.2 Column.........................................................................................................27
5.3 Base Plate.....................................................................................................29
5.4 Base Plate Bolts ...........................................................................................29
6 PIPE DESIGN CALCULATIONS...................................................................30
6.1 Design Parameters .......................................................................................30
6.2 Physical Properties.......................................................................................32
6.3 Design Calculations .....................................................................................32
6.3.1 Pipe Thickness Calculations ..............................................................................32
6.3.2 Allowable Working Pressure .............................................................................36
6.3.3 Wind load Calculations ......................................................................................38
6.3.4 Dead Loads Calculation .....................................................................................40
6.3.5 Pipe Span Calculations (based on limitation stress)...........................................42
6.3.6 Calculation for Supports based on Standard Spacing ........................................45
6.3.7 Thermal Expansion (deflection).........................................................................47
6.3.8 Expansion Loops Calculations...........................................................................496.3.9 Impact Loading on Bends ..................................................................................53
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6.3.10 Normal Impact Load on elbow ..........................................................................54
7 THERMAL CALCULATIONS........................................................................56
7.1 Thermal Analysis .........................................................................................56
7.2 Verification from Code................................................................................67
7.3 Static Loads Calculations.............................................................................68
7.3.1 Manual Calculations...........................................................................................68
7.3.2 Verification from Code ......................................................................................71
7.4 Piping Analysis on ANSYS.........................................................................72
7.4.1 Comparison of Analysis.....................................................................................74
7.5 Seismic Loads Calculations .........................................................................74
7.5.1 Seismic stress .....................................................................................................747.5.2 Seismic Lateral load...........................................................................................74
7.5.3 Verification from Code ......................................................................................75
8 SUPPORT DESIGN CALCULATION............................................................77
8.1 Design Parameters .......................................................................................77
8.2 Beam Design................................................................................................77
8.3 Beam Analysis .............................................................................................79
8.3.1 Manual Analysis.................................................................................................798.3.2 ANSYS Analysis................................................................................................80
8.4 Column Design ............................................................................................82
8.4.1 Verification for critical load...............................................................................84
8.4.2 Verification for stresses......................................................................................84
8.4.3 Manual Analysis.................................................................................................85
8.4.4 ANSYS Analysis................................................................................................87
8.4.5 Comparison of analysis......................................................................................89
8.5 Base Plate Design ........................................................................................89
8.5.1 Base Plate Design Calculations..........................................................................90
8.5.2 Thickness of the plate due to concentric load ....................................................91
8.5.3 Thickness due to bending moment.....................................................................91
8.5.4 Specifications of base plate................................................................................93
8.5.5 Bolt specifications..............................................................................................93
9 COMPLETE SYSTEM MODELING..............................................................94
9.1 Pro-E Modeling............................................................................................94
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9.2 ANSYS 3-D Modeling and Analysis...........................................................95
9.2.1 Results and Discussion.......................................................................................98
10 CONCLUSIONS................................................................................................99
11 FUTURE RECOMMENDATIONS ...............................................................100
REFERENCES.........................................................................................................101
APPENDIXE ............................................................................................................101
VITA..........................................................................................................................113
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List of Figures
Figure 1-1 PFD of the complete piping net work ........................................................4
Figure 2-1 Full loop ....................................................................................................8
Figure 2-2 Z, L and U shaped loop .............................................................................9
Figure 2-3 Anchor support ........................................................................................10
Figure 2-4 Hanger support ........................................................................................10
Figure 2-5 Sliding support ........................................................................................10
Figure 2-6 Spring support .........................................................................................11
Figure 2-7 Snubber support .......................................................................................11
Figure 2-8 Roller support ..........................................................................................11
Figure 5-1 Effective length constants table ..............................................................28
Figure 6-1 Forces on the bend by the fluid ................................................................53
Figure 7-1 Header Pipe including an expansion loop................................................56
Figure 7-2 Header Pipe Sections................................................................................57
Figure 7-3 Symmetry of header pipe considering as a beam.....................................68
Figure 7-4 Segment A-B............................................................................................69
Figure 7-5 Segment A-B-C........................................................................................69
Figure 7-6 Shear Force Diagram................................................................................70
Figure 7-7 Bending Moment Diagram.......................................................................71
Figure 7-8 Loaded view of the meshed beam............................................................72
Figure 7-9 Deflection in Pipe....................................................................................73
Figure 7-10 Bending stress in Pipe .............................................................................73
Figure 8-1 Uniformly load distributed Cantilever Beam...........................................77
Figure 8-2 Double Cantilever beam...........................................................................79
Figure 8-3 Deformed Shape of the beam ..................................................................80
Figure 8-4 Bending Moment diagram of the beam ...................................................81
Figure 8-5 Max. Stress distribution Diagram ...........................................................81
Figure 8-6 Loads on column of the support...............................................................82
Figure 8-7 Meshed and loaded column......................................................................88
Figure 8-8 Deformation of the column .....................................................................88
Figure 8-9 Stress distribution in column ...................................................................89
Figure 8-10 Base Plate Dimensions.............................................................................90
Figure 8-11 Pressure diagram ......................................................................................91
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Figure 8-12 Bolt dimensions........................................................................................93
Figure 9-1 Anchor support along with a pipe............................................................94
Figure 9-2 Convergence line b/w no. of elements and Von Mises Stresses..............95
Figure 9-3 Meshed diagram of the support model.....................................................96
Figure 9-4 Deformed shape of the support model .....................................................96
Figure 9-5 First Principle Stress distribution in support...........................................97
Figure 9-6 Von Mises stress distribution in support..................................................97
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List of Tables
Table 3-1 Primary stresses of pipes ...........................................................................17
Table 3-2 Secondary stresses of pipes .......................................................................18
Table 5-1 Limitation of column slenderness ratio .....................................................28
Table 6-1 Characteristics of Fluid at inlet and out let of pipes and its sizing............30
Table 6-2 Material Properties ....................................................................................32
Table 6-3 Input Parameters used in pipe thickness calculation .................................33
Table 6-4 All pipes thickness along with standard thickness ....................................34
Table 6-5 Input data ...................................................................................................36
Table 6-6 Design and working Pressure ....................................................................36
Table 6-7 Wind loads for each pipe...........................................................................38
Table 6-8 Pipe, Fluid and insulation weights.............................................................40
Table 6-9 Pipe Span based on limitation of stress .....................................................43
Table 6-10 Spacing based on standard spacing ...........................................................45
Table 6-11 Thermal deflection for pipes complete segments......................................47
Table 6-12 Sizing of expansion loops..........................................................................50
Table 6-13 Input Data ..................................................................................................53
Table 6-14 Input data ...................................................................................................54
Table 7-1 Input Data ..................................................................................................56
Table 7-2 For main line magnitude of expansion and directions...............................58
Table 7-3 Vertical section magnitude of expansion and direction ............................58
Table 7-4 Summary of all Loads due to Thermal expansion.....................................66
Table 7-5 Input data ...................................................................................................67
Table 7-6 Input data ...................................................................................................71
Table 7-7 Comparison of analysis for beam..............................................................74
Table 7-8 Input data ...................................................................................................76
Table 8-1 Available loads for analysis of anchor support .........................................77
Table 8-2 Properties of the channel beam..................................................................78
Table 8-3 Comparison of analysis for beam..............................................................82
Table 8-4 Specifications of column ...........................................................................83
Table 8-5 Input data ...................................................................................................86
Table 8-6 Input data ...................................................................................................87
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Table 8-7 Comparison of analysis of column.............................................................89
Table 8-8 Base plate specifications.............................................................................93
Table 8-9 Bolts standard dimensions..........................................................................93
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Abstract
This report is about the design of steam piping and its stress analysis of a
given process flow diagram. The prime objective of this project is to design
the piping system and then to analyze its main components. Wall thicknesses
are calculated for all pipes which were found very safe for the operating
pressure. For header pipe the calculated wall thickness is 0.114 inch and the
standard minimum wall thickness is 0.282 inch which is greater than the
calculated one by more than 2.4 times. Different loads such as static loads,
occasional loads and thermal loads of all pipes were also calculated. After
load calculations, spacing of supports and designing of expansion loops were
carried out. Thermal, static and seismic analysis of main system pipe has
been done and results were compared with ASME Power Piping Code B31.1.
After calculation of all applied loads, anchor support components including
half channel beam C5 x 9 and standard circular column of 4 inch nominal size
were designed and analyzed both manually and on ANSYS software. Base
plate of size 15x15x1/4 inch and bolts of inch diameter and of length 20
inch were also designed. The results obtained from both methods were
compared and found safe under available applied loads.
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1 Introduction
1.1 Thesis Introduction
Piping System design and analysis is a very important field in any process and power
industry. Piping system is analogous to blood circulating system in human body and is
necessary for the life of the plant. The steam piping system, mentioned in the thesis
will be used for supplying steam to different locations at designed temperature and
pressure. This piping system is one of the major requirements of the plant to be
installed.
This thesis includes the following tasks:
a) Process design of the complete piping system
b) Structural design of the pipes manually
c) Stress analysis of the pipes using ANSYS
d) Structural and thermal analysis of the expansion Loops
e) Structural design of supports manually
f) Modeling and stress analysis of support
1.2 Basic aim of the thesis
The aim of the thesis was to design and analyze piping system according to standard
piping Codes. The design should prevent failure of piping system against over stresses
due to:
I. Sustained loadings which act on the piping system during its operating time
e.g. static loads including dead loads, thermal expansion loads, effects of
supports and internal and external pressure loading.
II. Occasional loads which act percentages of the systems total operating time
e.g. impact forces, wind loads, seismic loads and discharge loads etc.
While piping stress analysis is used to ensure:
1) Safety of piping and piping components
2) Safety of the supporting structures
3) Safe stress relieving of the expansion loops
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1.3 Steam Piping Network
Basically the sizing of this steam piping has already done and contained nearly on
750x300m2area, including 48 pipes and 52 junctions. The detail of the piping system
e.g. length of each pipe, Nominal Pipe Size (NPS) with pipe no. starting from 208 and
ending on pipe no. 256 are shown from the following Figure 1-1. The rest of the data
e.g. inlet and out let velocities of each pipe, inlet and out let pressure of each pipe and
inlet and out let temperature of each and every pipe are arranged in Table 6-1, which
will be used in further calculations.
1.4 Thesis Organization
Chapter 1
In this chapter introduction to the project, basic aim of the project and process flow
diagram of the complete piping system with information about sizing has been
discussed.
Chapter 2
Literature survey has been done in this chapter. Detail study about the pipes and
piping system along with the code development has been included. This chapter also
consists on some of the basic terminologies relating to pipes, explanation of the piping
components and supports.
Chapter 3
Explanation about piping codes and standards and stress analysis of the piping system
has been included in this chapter.
Chapter 4
In this chapter piping design procedure, pipe span and expansion loop calculations
and support design methodology has been discussed.
Chapter 5
This chapter included all the detail about Anchor support and its components.
Chapter 6
This chapter related to all calculations of pipe design. All loads applied on the pipes
during operation have been calculated.
Chapter 7
This chapter included on thermal, static and seismic loads on pipes and their analysisalong with verification from the code has been done.
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Chapter 8
This chapter consists on the piping support design calculations, in which selection and
analysis of beam, column, base plate and bolts has been done.
Chapter 9
This chapter contained full modeling of anchor support in Pro-E and ANSYS and its
analysis in ANSYS.
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Steam Piping Network
Figure 1-1 PFD of the complete piping network
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2 Theoretical Background of Piping
System
A piping system is generally considered to include the complete interconnection of
pipes, including in line components such as pipe fittings, valves, tanks and flanges
etc. The contributions of the piping systems are essential in industrialized society.
They provide drinking water to cities, irrigation water to farms, cooling water to
buildings and machinery. Piping system are the arteries of our industrial processes;
they transmit the steam to turn the turbines which drive generators, thus providing
electricity that illuminates the world and power machines [1].
2.1 Historical background of the piping system
Initially there were no basic concepts of the piping system engineering when wind,
water and muscle were the prime movers. The advent of the industrial revolution,
especially the practical use of steam in the seventeenth century required the design
and manufacturing of piping to withstand the rejoins of conveying pressurized and
heating fluids. The combination of very high pressures, thermal stresses and thermal
deformations required that fundamental design requirements and analytical technique
be developed. However, piping system design progressed with little or no design
standards or code limitations during the early years of industrial revolution [3].
In the 1920s, the introduction to meet the electrical demand of turbine plants
with super heated steam at temperature up to 600oF and gauge pressure of 300 psi
posed to the next major piping system design challenge. These design conditions
exceeded safe cast iron values, thus requiring the introduction of cast steel for critical
components. By 1924, the steam gauge pressure had increased to 600 psi, doubling in
just a few years. One year later, steam pressure and temperature of 1200 psi and
700oF were achieved, demonstrating the advances made in the development of steam
generator and attached piping. By 1957, some 900oF designs were in service with
1200oF designs projected, using austenitic stainless steel materials in the high
temperature zones, currently, the top gauge pressure is 2400 psi for most fossil fuel
plants. With new materials available, the boiler, turbine and piping have equal
strength capabilities [3].
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2.2 Piping Terminologies
Detail of some of the basic terminologies like pipe, pipe sizes and pipe system are
given below.
2.2.1 Pipe
A pipe is a closed conduit of circular cross section which is used for the
transportation of fluids. If pipe is running full, then the flow is under pressure and if
the pipe is not running full, then the flow is under gravity.
2.2.2 Types of pipes and its uses
Standard Pipe: Mechanical service pipes, low pressure service e.g. refrigeration pipes
Pressure Pipe: It is used for liquid, gas or vapor for high pressure and temperature
application.
Line Pipe: Threaded or Plain ends used for gas, steam and as an oil pipe.
Water Well: Pump pipe, turbine pipe and driven well pipe etc [1].
2.2.3 Pipe Size
Initially a system known as iron pipe size (IPS) was established to designate the pipe
size. The size represented the approximate inside diameter of the pipe in inches e.g.
an IPS 6 pipe is one whose inside diameter is approximately 6 inches (in). With the
development of stronger and corrosion-resistant piping materials, the need for thinner
wall pipe resulted in a new method of specifying pipe size and wall thickness. The
designation known as nominal pipe size (NPS) replaced IPS, and the term schedule
(SCH) was invented to specify the nominal wall thickness of pipe.
2.2.4 Nominal Pipe Size (NPS)
NPS is a dimensionless designator of pipe size. It indicates standard pipe size when
followed by the specific size designation number without an inch symbol.
For example, NPS 2 indicates a pipe whose outside diameter is 2.375 in [2].
2.2.5 Piping
Pipe sections when joined with fittings, valves, and other mechanical equipment and
properly supported by hangers and supports, are called piping.
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2.2.6 Piping System
The piping system means a complete network of pipes, valves, and other parts to do a
specific job in plant. There are two types of piping systems.
2.2.7 Process Piping
It is used to transport fluids b/w storage tanks and processing unites.
2.2.8 Service Piping
It is used to convey steam, air, water etc. for processing.
2.3Pipe Fittings
Fittings permit a change in direction of piping, a change in diameter of pipe or a
branch to be made from the main run of pipe. Some of the fittings are elbows, long
radius and short radius elbow reducing elbow, reducer, bends and mitered bends etc.
2.3.1 Valves
A valve is a mechanical device that controls the flow of fluid and pressure within a
system. There are different types of valves some of them are discussed below [3].
a) ON/OFF Valves
These are the kind of valves which are used to stop of start the fluid flow e.g. Gate
valve, Globe valve, rotary ball valve, Plug valve and diaphragm valve etc.
b) Regulating Valve
These are the kind of valves which are used to start, stop and also to regulate the fluid
flow e.g. Needle valve, butterfly valve, Diaphragm and Gate valve etc.
c) Safety Valve
This valve reacts to excessive pressure in piping system. They provide a rapid means
of getting rid of that pressure before a serious accident occur. Safety valve is used
normally for gasses and steams. In safety valve the steam is discharge to the air
through a large pipe.
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d) Pressure Regulating Valve
These valves regulate pressure in a fluid line keeping it very close to a pre-set level.
The valve is set to monitor the line, and make needed adjustments on signal from a
sensitive device.
2.3.2 Expansion Fittings
Expansion loops are used to release the stresses which produced due to thermal
gradients. All pipes will be installed at ambient temperature. Pipes carrying hot fluids
such as water or steam operate at higher temperatures. It follows that they expand,
especially in length, with an increase from ambient to working temperatures. This will
create stress upon certain areas within the distribution system, such as pipe joints,
which, in the extreme, could fracture. Therefore the piping system must be
sufficiently flexible to accommodate the movements of the components as they
expand [1].
The expansion fitting is one of method of accommodating expansion. These
fittings are placed with in a line, and are designed to accommodate the expansion,
with out the total length of the line changing. They are commonly called expansion
bellows, due to the bellows construction of the expansion sleeve. Different kinds of
expansion loops are used, some of which are given below.
2.3.2.1 Full loop
This is simply one complete turn of the pipe and, on steam pipe work, should
preferably be fitted in a horizontal rather than a vertical position to prevent
condensate accumulating on the upstream side as shown in Figure 2-1 below. When
space is available, it is best fitted horizontally so that the loop and the main are on the
same plane.
Figure 2-1 Full Loop [6]
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2.3.2.2 Z, L, and U shaped loops
In majority of these loops guided cantilever method is used to find the deflection in
the loop. These loops are shown in the Figure 2-2 below.
Figure 2-2 Z, L and U shaped Loop [2]
2.4 Supports
Pipe support specifications for individual projects must be written in such a way as to
ensure proper support under all operating and environmental conditions and to
provide for slope, expansion, anchorage, and insulation protection. Familiarity with
standard practices, customs of the trade, and types and functions of commercial
component standard supports and an understanding of their individual advantages and
limitations, together with knowledge of existing standards, can be of great help in
achieving the desired results [1]. Good pipe support design begins with good piping
design and layout. For example, other considerations being equal, piping should be
routed to use the surrounding structure to provide logical and convenient points of
support, anchorage, guidance, or restraint, with space available at such points for use
of the proper component. Parallel lines, both vertical and horizontal, should be spaced
sufficiently apart to allow room for independent pipe attachments for each line. There
are different types of supports used in the piping system; some of them are discussed
below [2].
a) Anchor support
A rigid support providing substantially full fixity for three translations and
rotations about three reference axes. Figure 2-3 shows the model along with
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the pipe and welding positions. Detail of this support will be discussed in
chapter 8.
Figure 2-3 Anchor Support [3]
b) Hanger support
A support for which piping is suspended from a structure, and so on, and
which functions by carrying the piping load in tension as shown below in
figure.
Figure 2-4 Hanger Support [3]
c) Sliding support
A device that providing support from beneath the piping but offering no
resisting other than frictional to horizontal motion as shown in Figure 2-5
below..
Figure 2-5 Sliding Support [3]
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d) Spring support
Spring support is used when there is an appreciable difference b/w operating
and non operating conditions of the pipes. Constant load support is used when
loading condition change up to 6%.
Figure 2-6 Spring support [1]
e) Snubber support
These supports are used to restrain the dynamic load such as seismic loads,
water hammer and steam hammer etc. These supports are not capable of
supporting gravity loads. A simplified snubber support view is shown in
Figure 2-7 below.
Figure 2-7 Snubber support [3]
f) Roller support
A means of allowing a pipe to move along its length but not side ways. Roller
support is shown in Figure 2-8 below.
Figure 2-8 Roller support [3]
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3 Piping Codes and Standards
Before the selection of codes for the steam piping, a little detail about codes,
standards and its historical background is given below.
3.1Piping Code Development
The increase in operating temperatures and pressures led to the development of the
ASA (now ANSI) B31 Code for pressure piping. During the 1950s, the code was
segmented to meet the individual requirements of the various developing piping
industries, with codes being published for the power, petrochemical and gas
transmission industries among others. The 1960s and 1970s encompassed a period of
development of standard concepts, requirements and methodologies. The
development and use of the computerized mathematical models of piping system have
brought analysis, design and drafting to new levels of sophistication. Codes and
standards were established to provide methods of manufacturing, listing and reporting
design data [3].
A standard is a set of specifications for parts, materials or processes intendedto achieve uniformity, efficiency and a specified quality. Basic purpose of the
standards is to place a limit on the number of items in the specifications, so as to
provide a reasonable inventory of tooling, sizes and shapes and verities [4]. Some of
the important document related to piping are:
I. American Society of Mechanical Engineers (ASME)
II. American National Standards Institute (ANSI)
III. American Society of Testing and Materials (ASTM)
IV. Pipe Fabrication Institute (PFI)
V. American Welding Institute (AWS)
VI. Nuclear Regulatory Commission (NRC)
On the other side A code is a set of specifications for analysis, design,
manufacture and construction of something. The basic purpose of code is to provide
design criterion such as permissible material of construction, allowable working
stresses and loads sets [4]. ASME Boiler and Pressure vessel codeB31, Sectiion-1 is
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used for the design of commercial power and industrial piping system. This section
has the following sub section [1].
B31.1: For Power Piping.
B31.3: For Chemical plant and Petroleum Refinery Piping.
B31.4: Liquid transportation system for Hydrocarbons, liquid petroleum gas, and
Alcohols.
B31.5: Refrigeration Piping.
B31.8: Gas transportation and distribution piping system.
B31.1 Power piping code concerns mononuclear piping such as that found in
the turbine building of a nuclear plant or in a fossil-fueled power plant. Detail of this
code is given below in section 3.2. B31.3 code governs all piping within limits offacilities engaged in the processing or handling of chemical, petroleum, or related
products. Examples are a chemical plant compounding plant, bulk plant, and tank
farm. B31.4 governs piping transporting liquids such as crude oil, condensate, natural
gasoline, natural gas liquids, liquefied petroleum gas, liquid alcohol, and liquid
anhydrous ammonia. These are auxiliary piping with an internal gauge pressure at or
below 15 psi regardless of temperature. B31.5 covers refrigerants and secondary
coolant piping for temperatures as low as 320
o
F. B31.8 governs most of the pipe linesin gas transmission and distribution system up to the outlet of the customers meter set
assembly. Excluded from this code with metal temperature above 450oF or below -
20oF. As for as the steam piping is concerned, B31.1 Power piping is used because of
its temperature and pressure limitations which is discussed below in detail.
3.2B31.1 Power Piping
This code covers the minimum requirements for the design, materials, fabrication,
erection, testing, and inspection of power and auxiliary service piping systems for
electric generation stations, industrial institutional plants, and central and district
heating plants. The code also covers external piping for power boilers and high
temperature, high-pressure water boilers in which steam or vapor is generated at a
pressure of more than 15psig and high-temperature water is generated at pressures
exceeding 160psig or temperatures exceeding 250oF. This code is typically used for
the transportation of steam or water under elevated temperatures and pressure as
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mentioned above, so this is the reason that why this code is selected for the steam
piping system which is external to the boiler [5].
3.3ASME Code Requirements
As it already mentioned in the previous section 3.2, Boiler outlet section of the steam
system comes under the category of ASME Code B31.1 Power. In order to ensure the
safety of the piping system, code requirements should be fully satisfied. For different
loads this code incorporates different relationships for stress level as given below.
3.3.1 Stresses due to sustained loadings
The effects of the pressure, weight, and other sustained loads must meet the
requirements of the following equation [1].
0.751.0
4
o A
L h
PD i MS S
t Z
= + (3.1)
Where
P = Internal Pressure, psi
Do = Out Side diameter of Pipe, in
t = nominal wall thickness, in
Z = Section modulus of pipe, in3
MA = Resultant moment due to loading on cross section due to weight and other
sustained loads, in-lb
Sh = Basic material allowable stress at design pressure, psi
3.3.2 Stress due to occasional loadings
The effects of pressure, weight, and occasional loads (earthquake) must meet therequirements of the following equation [1].
0.75 ( )
4
o A B
h
PD i M MKS
t Z
++ (3.2)
Where
MB = Resultant moment loading on cross section due to occasional loads, psi
K= Constant factor depend on plant operation time
The rest of the terms are same to above equation.
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3.3.3 Stresses due to thermal loadings
The effects of thermal expansion must meet the following equation [1].
( )
C
A h L
iM
S f S S Z + (3.3)
where
f = Stress range reduction factor
Mc =Range of resultant moment due to thermal expansion, in-lb
SA = Allowable stress range for expansion
The rest of the terms are same to above equation.
3.4Stress analysis of piping systemPiping stress analysis is a discipline which is highly interreralated with piping layout
and support design. The layout of the piping should be performed with requirements
of piping stress and pipe support in mind. If necessary, layout solutions should be
iterated until a satisfactory balance b/w stress and layout efficiency is achieved [1].
3.4.1 Stress and Strain
Stress is defined as the reactive force per unit area which is developed when an
external force is being applied on the body. The stress is responsible for the
deformation and deterioration of the material.
There are two types of stresses, normal stress and shear stress. The normal
stresses are perpendicular stress on a body and they are directed normal of the surface
of the body. The tensile stresses are those stress which produces tension in the
material whereas compressive stresses are those stresses which produce the
compression in the material.
On the other side shear stress is the force per unit area of shearing plane. The
shear stresses are those stresses which tend parallel plates of the material to slip past
each other. The strain is the deformation in the dimension a material when it is under
stress. The strain is of two types shear strain and normal strain [3].
3.4.2 Failure Theories
The failure theories most commonly used in describing the strength of the piping
system are the:
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1) Maximum principle stress theory
2) Maximum shear stress theory (Tresca theory)
3.4.3.1 Maximum principle stress theory
This theory states that failure will always occurs, whenever the greatest tensile stress
tends to exceed the uni-axial tensile strength or whenever the largest compressive
stress tends to exceed the uni-axial compressive strength. This theory has been found
to correlate reasonably well with test data for brittle fracture [3]. The maximum
principle stress theory form the basis for piping system governed by ANSI/ASME
B31 and subsection (class2 and class3) of section III of the ASME boiler and pressure
vessel codes [1].
3.4.3.2 Maximum shearing stress theory
Where on the other side the maximum shear stress theory states that failure of a
piping component occurs when the maximum shear stress exceed the shear stress at
the yield point in a tension test. In tensile test, at yield, 1= Sy, where 2= 3 = 0. So
yielding in the component occurs when
1 3max
( )
2 2
yS
= =
(3.4)
This theory correlates reasonably well with the yielding of ductile materials [3]. This
maximum shear stress theory forms the basis for piping of subsection NB (calss1) of
ASME section III [1].
3.4.3 Piping Design Criteria
There are various failure modes which could affect a piping system. The piping
engineer can provide protection against some of these failure modes by performing
stress analysis according to the piping codes. Protection against other failure modes is
provided by methods other than stress analysis. For example, protection against brittle
fracture is provided by material selection. The piping codes address the following
failure modes, excessive plastic deformation, plastic instability or incremental
collapse, and high-strainlow-cycle fatigue. Each of these modes of failure is caused
by a different kind of stress and loading. It is necessary to place these stresses into
different categories and set limits to them. The major stress categories are primary,
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secondary, and peak. The limits of these stresses are related to the various failure
modes as follows [3].
3.4.3.3 Primary Stress
The primary stress limits are intended to prevent plastic deformation and bursting.
Primary stresses which are developed by the imposed loading are necessary to satisfy
the equilibrium between external and internal forces and moments of the piping
system. Primary stresses are not self-limiting. Therefore, if a primary stress exceeds
the yield strength of the material through the entire cross section of the piping, then
failure can be prevented only by strain hardening in the material. Thermal stresses are
never classified as primary stresses. They are placed in both the secondary and peak
stress categories [1].
Primary stresses are the membrane, shear or bending stress resulting from imposed
loadings which satisfy the simple laws of equilibrium of internal and external forces
and moments as arranged in table below;
Table 3-1 Primary stresses of pipes
Type of primary stress Due to type of sustained load
Circumferential membrane stress Pressure
Longitudinal membrane stress Pressure, Dead weight
Primary bending stress Pressure, Dead weight, wind
Primary stresses which considerably exceed the yield strength of the piping material
will result in gross distortion or failure [5].
3.4.3.4 Secondary Stresses
The primary plus secondary stress limits are intended to prevent excessive plastic
deformation leading to incremental collapse. Secondary stresses 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.
Under this loading condition, the piping system must satisfy an imposed strain pattern
rather than be in equilibrium with imposed forces. Local yielding and minor
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distortions of the piping system tend to relieve these stresses. Therefore, secondary
stresses are self-limiting [1].
Secondary stresses are self equilibrium stresses which are necessary to satisfy
the continuity of forces within a structure. As contrasted with stresses from sustained
loads, secondary stresses are not a source of direct failure in ductile with only a single
application of load. If the stresses exceed the material yield strength, they cause local
deformation which result in a redistribution of the loading and upper limit of the stress
in the operating condition. If the applied load is cyclic, however these stresses
constitute a potential source of fatigue failure e.g. the secondary stresses due to
different type of loads are given below in Table 3-2, [5].
Table 3-2 Secondary stresses of pipes
Type of secondary stresses Due to type of load
Bending and Torsional Thermal loading (expansion or contraction)
Bending and TorsionalNon-uniform distribution of temperature
with in a body
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4 Piping Design Procedures
The following are the steps which need to be completed in mechanical design of any
piping system.
Flow chart:Complete stage designing of piping system
4.1Process Design
This process is based on the requirement of the process variables. It defines the
required length & cross sectional area of pipe, the properties of fluid inside the pipe,
nature & rate of flow in it. These variables affect the positioning and placements of
equipments during lay outing and routing. The operating and design working
conditions are clearly defined. The end of Process Plan Design is the creation of a
Process Flow Diagram (PFD) and Process & Instrumental diagram (PID), which are
used in the designing & lay outing of the Pipe. The process design step in this project
is already been done and the data obtained from this step is arranged in Table 6-1.
4.2Piping Structural Design
In piping structural design, according to pressure in pipelines, the design and
minimum allowable thicknesses are calculated; according to the required codes and
standards. ASME codes for various standards are available, for process fluid flow,
ASME B31.1 is used.
ProcessDesign
Lay outing
Analysis
of PipesAnd
ExpansionLoops
Support
Designand
Analysis
Structural Design Loads
Calculations
Piping SystemDesign
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In the structural design of pipes, when all the loads are calculated then the required
span is also calculated for supporting the pipes.
4.2.1 Pipe Thickness Calculations
Piping codes ASME B31.1 Paragraph 104.1.2 require that the minimum thickness tm
including the allowance for mechanical strength, shall not be less than the thickness
calculated using Equation [2].
2 ( )m
P Dot A
S Eq P Y
= +
+ (4.1)
Or
mt t A= + (4.2)where
tm= minimum required wall thickness, inches
t = pressure design thickness, inches
P = internal pressure, psig
Do= outside diameter of pipe, inches
S = allowable stress at design temperature (known as hot stress), psi
A = allowance, additional thickness to provide for material removed in threading,corrosion, or erosion allowance; manufacturing tolerance (MT) should also
be considered.
Y = coefficient that takes material properties and design temperature into account.
For temperature below 900F, 0.4 may be assumed.
E q= quality factor.
4.2.2 Allowable Working Pressure
The allowable working pressure of a pipe can be determined by Equation [2].
2( )
( 2 )
S Eq t P
Do Yt
=
(4.3)
where
t = specified wall thickness or actual wall thickness in inches.
For bends the minimum wall thickness after bending should not be less than the
minimum required for straight pipe.
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4.2.3 Sustained Load Calculations
Sustained loads are those loads which are caused by mechanical forces and these
loads are present through out the normal operation of the piping system. These loads
include both weight and pressure loadings. The support must be capable of holding
the entire weight of the system, including that of that of the pipe, insulation, fluid
components, and the support themselves [2].
Pipe Weight 2 2( )4
steel
c
gDo Di
g
= (4.4)
Fluid Weight 2( )4
fluid
c
gDi
g
= (4.5)
Insulation wt.=Insulation factor x Insulationx g/gc (4.6)Where
D0 = Out side diameter of pipe, in
Di= Inside diameter of pipe, in
t = Insulation Thickness depend on the NPS, in
g = Acceleration due to gravity, ft/sec2
gc= Gravitational constants, lbm-ft/ft-sec2
Steel= Density of steel, lb/in3
fluid =Density of water, lb/in3
insul= Density of Insulation, lb/in3
Insulation factor depends on the thickness of the insulation of the pipe.
4.2.4 Wind Load Calculations
Wind load like dead weight, is a uniformly distributed load which act along the entire
length or portion of the piping system which is exposed to air.
For standard air, the expression for the wind dynamic pressure is given below [1]:
20.00256D
P V C= (4.7)
And to calculate the wind dynamic load (lb/ft), the following expression is used [1]:
20.000213 DF V C D= (4.8)
Where
P = Dynamic pressure, lb/ft2
V = basic wind speed, miles/hr
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CD= Drag co-efficient, dimensionless
CDcan be calculated using table and the following equation;
R = 780xVxD
R = Reynolds number
F = Linear dynamic pressure loading (lb/ft)
D = Pipe Diameter (in)
4.2.5 Thermal Loads Calculations
All pipes will be installed at ambient temperature. If pipes carrying hot fluids such
steam,
then they expand, especially in length, with an increase from ambient to working
temperatures. This will create stress upon certain areas within the distribution system,
such as pipe joints, which, in the extreme, could fracture. The amount of the
expansion is readily calculated using the following expression [6].
( )Expansion mm L T= (4.9)
Where
L = Length of pipe (m)
T = Temperature difference between ambient and operating Temperatures (C)
= Expansion coefficient (mm/m C) x 10-3
4.2.6 Occasional Loads
Occasional load will subject a piping system to horizontal loads as well as vertical
loads, Where as sustained loads are normally only vertical (weight). There are
different types of occasional loads that act over a piping system but for our analysis
we will use wind loads and seismic loads.
4.2.7 Seismic Loads
Earthquake loads are of two major types
Operation Based Earthquake Load
Safe Shutdown Earthquake Load
Piping systems and components are designed to withstand two levels of site
dependent hypothetical earthquakes, the safe shut down earthquake and the
operational basis earthquake. Their magnitudes are expressed in terms of the
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gravitational g. There motions are assumed to occur in three orthogonal directions,
one vertical and two horizontal directions.
Earthquake loads can either be calculated by dynamic Analysis or static
Analysis. In Dynamic analysis frequency response of the system is used to calculate
the Earthquake load whereas in Static Analysis, these loads are taken to be some
factor of the Pipe Dead load [3].
4.3Pipe Span Calculations
The maximum allowable spans for horizontal piping systems are limited by three
main factors that are bending stress, vertical deflection and natural frequency. By
relating natural frequency and deflection limitation, the allowable span can bedetermined as the lower of the calculated support spacing based on bending stress and
deflection [2].
4.3.1 Span Limitations
The formulation and equation obtained depend upon the end conditions assumed.
Assumptions
The pipe is considering to be a straight beam
Simply supported at both ends
So based on limitation of stress [2]
0.33h
s
ZSL
w= (4.10)
Based on limitation of deflection [2]
4
22.5s
EIL
w= (4.11)
Where
Ls= Allowable pipe span, ft
Z = Modulus of pipe section, in3
Sh= Allowable tensile stress at design temperature, psi
w = Total weight of pipe, lb/ft
= Allowable deflection/sag, inI = Area moment of inertia of pipe, in4
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E = Modulus of elasticity of pipe material at design temperature, psi.
4.3.2 Expansion Loop Calculations
Thermal expansion are calculated for all the pipes by using equation
Expansion (mm)
Based on thermal expansion calculated above, size of expansion loops can be
calculated from equation below as [2]
3
144
o
A
EDL
S
= (4.12)
Where
L = Length of expansion Loops, ftE, Do, SA, same as in above calculations
Size of Expansion Loops assuming to be symmetrical U shaped.
L = 2H + W
Where
H = 2W for U shaped loop.
L T=
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5 Support Design
Pipe support specifications for individual projects must be written in such a way as toensure proper support under all operating and environmental conditions and to
provide for slope, expansion, anchorage, and insulation protection. Familiarity with
standard practices, customs of the trade, types and functions of commercial
component standard supports and an understanding of their individual advantages and
limitations, together with knowledge of existing standards, can be of great help in
achieving the desired results [3].
Good pipe support design begins with good piping design and layout. For
example, other considerations being equal, piping should be routed to use the
surrounding structure to provide logical and convenient points of support, anchorage,
guidance, or restraint, with space available at such points for use of the proper
component. Parallel lines, both vertical and horizontal, should be spaced sufficiently
apart to allow room for independent pipe attachments for each line. There are
different types of supports used in the piping system e.g. Anchor support, Guide,
hanger, sliding, snubber support etc. The type of support which we will design in this
project is anchor support. It is a rigid support providing substantially full fixity for
three translations and rotations about three reference axes.
This support mainly includes the beam, column, base plate and anchor bolts. So the
design of all these components will be discussed in this chapter [1].
5.1Beam Design
Beams are the structural members resisting forces acting laterally to its axis. Either
forces or couples that lie in a plane containing the longitudinal axis of the beam may
act upon the member. The forces are understood to act perpendicular to the
longitudinal axis, and the plane containing the forces is assumed to be a plane of
symmetry of the beam. There are some limits states that must be considered when
designing a beam that are bending, shear and deflection [3].
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5.1.1 Bending Stress
Bending stresses which caused by bending moments are internal member moments
which resist externally applied moments in order to maintain the member in
equilibrium. Bending stresses are usually far more significant than normal stresses
due to axial forces, therefore the flexural formula in its many form is one of the most
commonly used equations in structural analysis.
The flexural formula states that the value of the bending stress at any point on the
cross section of a member is [3].
b
c
I = (5.1)
where
M = Bending moment on the cross section, in-lb
c = Distance from neutral axis to point of interest, in
I = Moment of inertia of cross section, in4
The failure mode for bending is material yielding. For this reason the allowable stress
for bending is usually limited to the material stress reduced by a safety factor.
5.1.2 Shear Stress
Theses stresses resist the relative slippage of adjacent cross-sectional planes in the
members and can cause by shear forces. Shearing stress can be find out by using the
following formula [3]:
VAy
Ib= (5.2)
where
V = shear force on cross section, lb
A = Cross sectional area, in2
y = Distance from the neutral axis to the centriod of the area, in
I = Moment of inertia of the beam cross section, in4
b = width of the beam, in
The horizontal shear stress is a maximum at the neutral axis of the beam.
This is opposite of the behavior of the bending stress which is maximum at the outer
edge of the beam and zero at the neutral axis.
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5.1.3 Deflection
The lateral load acting on beam causes the beam to bend, deforming the axis of the
beam into a curve called the deflection of the beam. This deformation of a beam is
most easily expressed in terms of the deflection of the beam from its original
unloaded position. This deflection is measured from the original neutral surface to the
neutral surface of the deformed beam. The deflection in uniformly distributed
cantilever beam can be calculated by using the following equation [3]
4
max8
wly
EI
= (5.3)
Where
y = deflection at point l, in
w = uniformly distributed load, lb/in
l = length at which deflection is to be calculated
E = Modulus of elasticity of the material being used in beam, Mpsi
I = Moment of inertia, in4
5.2Column
A long slender bar subject to axial compression is called a column. The term column
is frequently used to describe a vertical member. Column may be divided into three
general types: Short columns, Intermediate columns and Long Column. The
compressive capacity of a column is dependent on its slenderness ratio, which is
defined as [3]
Slenderness ratio =Kl
r (5.4)
Where
K = a constant dependent on boundary conditions
r = least radius of gyration of the member = IA
, in
I = moment of inertia of cross section, in4
A = area of cross section, in2
Theoretical and recommended values of K for some typical column end conditions are
shown in Figure 5-1 below.
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Figure 5-1 Effective length constants for different columns [7]
Combination of K and L is also called effective length, l eff= Kl. A generally accepted
relationship between the slenderness ratio and type of column is as follows.
Table 5-1 Limitation of column slenderness ratio [7]
Type of Column Limits of slenderness Ratio
Short column 0 60eff
l
r
Intermediate column 60 120eff
l
r
Long column 120 300eff
l
r
Critical load and critical stress can be find out from the following equations [7]
2
2cr
eff
EIP
L
= (5.5)
2
2cr
eff
E
L
r
=
(5.6)
For column subjected to both axial and bending stress, AISC subsection H1
specification requires that the following equations must be satisfied [7].
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10.6
bya bx
y bx by
ff f
F F F+ + (5.7)
Also, when fa/Fa< 0.15, following equation can be used,
1bya bx
a bx by
ff f
F F F+ + (5.8)
Where
fa= axial stress in column = P/A
Fa= allowable axial stress
Fb, x/y = Bending stress in x or y direction = Mc/I
Fb, x/y= allowable bending stresses in x or y direction
5.3Base Plate
Base plate is used to provide ground support to the column concentric and bending
load. Base plate may either be of the anchor bolted type or embedded type. Base
plates with anchor bolts are normally used in cases where the building concrete has
already been poured, while embedded plates are used when they can be specified prior
to pouring the concrete [3].
5.4Base Plate Bolts
The strength of the bolts is a function of the embedment depth, the bolt or stud head
diameter, the concrete strength and the spacing between adjacent bolts. Anchor bolts
are installed by drilling a hole through the concrete into which the bolts are inserted.
Depending on the type of bolt the bolt expands to grip the concrete either by
hammering the bolt or by torquing the nut against the base plate [7].
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6 Pipe Design Calculations
In this chapter piping thickness as well as all the basic loads are calculated and the
characteristics are also given below.
6.1Design Parameters
As already sizing of this piping system has been done and the available
information are;
Number of pipes = 48Number of junctions = 49
Wind Velocity = 100 miles/hr
Pipe Nominal Size, Inlet-Out let velocities, Temperatures and Pressure of steam for
every pipe are given below in the following Table 6-1.
Table 6-1 Characteristics of Fluid at inlet and out let of pipes and its sizing
S.No
Pipe
Line
No.
NPSDo,
(in)TIn,
C
TOut,
C
VIn,
m/sec
Vout
m/sec
Pin
(static)bar
POut
(static)
bar
1 P-208 8.00 8.63 169.59 168.70 35.37 36.21 7.98 7.78
2 P-209 2.00 6.63 168.20 167.04 13.98 14.03 7.77 7.73
3 P-210 8.00 8.63 168.70 167.04 35.27 36.43 7.78 7.52
4 P-211 8.00 8.63 167.04 166.20 36.46 37.58 7.51 7.27
5 P-212 8.00 8.63 165.92 165.04 28.15 28.65 7.29 7.14
6 P-213 4.00 4.50 164.81 158.09 27.77 31.10 7.14 6.30
7 P-214 8.00 8.63 165.04 164.92 21.61 21.62 7.14 7.13
8 P-215 6.00 6.63 166.20 166.09 16.27 16.29 7.27 7.26
9 P-216 2.00 2.38 165.87 162.92 20.79 21.03 7.26 7.13
10 P-217 4.00 4.50 166.04 164.70 31.60 32.27 7.23 7.07
11 P-218 3.00 3.50 164.65 164.31 17.70 17.81 7.08 7.03
12 P-219 4.00 4.50 157.37 157.20 18.15 18.14 4.00 3.99
13 P-220 4.00 4.50 164.59 161.42 22.01 22.29 7.06 6.92
14 P-221 2.00 2.38 161.26 153.81 17.99 18.21 6.92 6.72
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Table 6-1 Characteristics of Fluid at inlet and out let of pipes and its sizing (continued)
S.No
Pipe
Line
No.
NPSDo,
(in)TIn,
C TOut,
C
VIn,
m/sec
Vout
m/sec
Pin
(static)
bar
POut
(static),
bar
15 P-224 4.00 4.50 161.31 157.81 17.56 17.62 6.92 6.83
16 P-225 2.00 2.38 157.76 151.53 18.07 18.28 6.83 6.65
17 P-226 3.00 3.50 157.92 156.42 22.18 22.38 6.82 6.74
18 P-227 2.00 2.38 155.87 132.75 10.95 10.55 6.74 6.59
19 P-228 3.00 3.50 156.37 155.09 17.43 17.46 6.73 6.70
20 P-229 2.00 2.38 154.65 147.09 10.26 10.15 6.70 6.64
21 P-230 2.00 2.38 134.14 123.87 23.95 25.66 2.00 1.89
22 P-231 1.00 1.32 133.92 119.20 37.41 43.79 1.98 1.63
23 P-232 3.00 3.50 154.92 149.98 12.81 12.76 6.69 6.64
24 P-233 2.00 2.38 149.20 140.09 6.93 6.79 6.64 6.61
25 P-236 1.50 1.90 126.81 117.36 23.32 23.84 1.99 1.90
26 P-237 1.00 1.32 126.81 118.70 32.02 34.36 1.99 1.82
27 P-238 2.00 2.38 150.09 145.42 21.20 21.65 6.63 6.42
28 P-239 1.00 1.32 145.09 130.70 21.74 22.91 6.42 5.88
29 p-240 2.00 2.38 145.31 140.48 16.06 16.12 6.42 6.31
30 P-241 1.00 1.32 140.37 125.70 29.15 35.66 6.30 4.99
31 P-242 2.00 2.38 140.03 130.87 8.63 8.45 6.31 6.28
32 P-243 2.00 2.38 130.31 112.98 5.52 5.27 6.28 6.24
33 P-244 1.00 1.32 130.64 95.31 11.43 10.80 6.28 6.00
34 P-250 3.00 3.50 159.15 158.87 12.28 12.32 4.00 3.98
35 P-251 1.00 1.32 158.53 121.48 29.53 36.80 3.97 2.97
36 P-252 2.00 2.38 158.87 152.87 19.58 19.77 3.98 3.89
37 P-253 1.50 1.90 152.48 146.31 16.82 16.84 3.89 3.83
38 P-254 1.00 1.32 152.59 132.53 37.37 48.68 3.86 2.83
39 P-256 2.00 2.38 155.87 150.03 37.39 41.14 4.00 3.59
40 P-257 6.00 6.63 152.70 152.37 21.55 21.59 4.00 3.99
41 P-259 3.00 3.50 142.09 137.09 27.65 28.75 2.00 1.90
42 P-260 3.00 3.50 139.81 138.42 27.50 28.06 2.00 1.95
43 P-261 3.00 3.50 118.25 116.42 20.90 21.16 1.50 1.47
44 P-262 3.00 3.50 134.81 133.98 15.23 15.21 2.00 2.00
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Table 6-1 Characteristics of Fluid at inlet and out let of pipes and its sizing (continued)
6.2Physical Properties
Physical properties of pipe material, insulation and water are arranged in Table 6-2
below;
Table 6-2 Material Properties [Appendix Table A14]
Material Parameter Value
Modulus of Elasticity E 27.5 Mpsi
Allowable stress Sall 14.4 ksiCarbon Steel
Density, steel 0.283 lb/in
3
Insulation Density, Rock wool 0.00343lb/in
3
Water Density, water 0.0361 lb/in3
6.3Design Calculations
Piping design calculation means to find out the pipe thickness for the available
size and operating pressure of the fluid. This thickness is then compared to the
allowable minimum standard thickness defined by the code. After thicknesscalculations all loads applied on this pipe can be calculated, which will form the
basis for spacing of supports and sizing of expansion loops.
6.3.1 Pipe Thickness Calculations
Piping codes require that the minimum thickness tm including the allowance for
mechanical strength, shall not be less than the thickness calculated using Equation
(4.1) as follows.
S.No
Pipe
Line
No.
NPSDo,
(in)TIn,
C TOut,
C
VIn,
m/sec
Vout
m/sec
Pin
(static)
bar
POut
(static),
bar
45 P-263 2.00 2.38 127.87 126.70 22.37 22.36 2.00 1.99
46 P-264 2.00 2.38 119.20 115.70 17.26 17.35 2.00 1.97
47 P-270 3.00 3.50 157.31 152.37 28.44 29.92 3.99 3.75
48 P-271 1.00 1.32 156.48 151.48 24.31 24.67 4.00 3.89
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Design thickness2 ( )
om
q
P Dt A
S E P Y
= +
+ (4.1)
or
= t + ALet take Pipe no. 208 and calculate its minimum thickness by using equation.
Where all the parameters are arranged in Table 6-3 below;
Table 6-3 Input Parameters used in pipe thickness calculation
Parameter Value Reference/Reason
Do 8.625 in Appendix Table A2
Pg 193.3 Psi Table 6.1
E 1 For seamless pipe
Y 0.4 b/c Temperature < 900oF
S 14400 Psi Appendix Table A1
Tolerance limit 12.5% Assuming maximum limit
A 3 mm = 0.03937 in data provided
Putting all these values in above equation of minimum thickness
193.3 8.625 0.039372 (144000 1 193.3 0.4)
mt = +
+
0.09984mt In=
0.0998
0.85
0.12
2.9
m
m
m
t
t in
t mm
=
=
=
Standard tm = 0.282 in
For all 48 pipes the thickness were calculated and arranged in the Table 6-4 below
along with the standard minimum wall thickness. From the table it is cleared that
nearly 2 to 3 times, so our calculated thickness is safe.
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Table 6-4 All pipes thickness along with standard thickness (Continued)
S
.No
PipeL
ine
No.
PipeNominal
S
ize,
Ou
tside
Diameter,D(in)
Design
Pressure
(stat.),
P(lb/In2)
Veloc
ity,Inlet
(m
/sec)
TotalHead,(m)
H=(P/W
+V^2/2*
g)
Pab
s(Psi)=
*g*H
Design
Pressure
(gage.),
P(lb
/In2)=
Psa
t-14.7
Allowable
Stress
s,S(psi)
D.T.Factor
(y)
Min
.Wall
thickness,t(in)=P
*D/2*
(S+.4*P)
Cor
rosion
allowance(in)
thick
t(t)(in)
26 P-237 1 1.315 29.27 32.02 72.901 103.67 88.97 14400 0.4 0.0043 0.0394 0.0
27 P-238 2 2.375 97.40 21.21 91.441 130.04 115.34 14400 0.4 0.0100 0.0394 0.0
28 P-239 1 1.315 94.34 21.74 90.466 128.65 113.95 14400 0.4 0.0055 0.0394 0.0
29 p-240 2 2.375 94.30 16.06 79.478 113.02 98.32 14400 0.4 0.0085 0.0394 0.0
30 P-241 1 1.315 92.67 29.15 108.524 154.33 139.63 14400 0.4 0.0067 0.0394 0.0
31 P-242 2 2.375 92.80 8.63 69.054 98.20 83.50 14400 0.4 0.0072 0.0394 0.0
32 P-243 2 2.375 100.25 5.52 72.050 102.46 87.76 14400 0.4 0.0076 0.0394 0.0
33 P-244 1 1.315 92.27 11.43 71.549 101.75 87.05 14400 0.4 0.0042 0.0394 0.0
34 P-250 3 3.5 58.80 12.28 49.046 69.75 55.05 14400 0.4 0.0070 0.0394 0.035 P-251 1 1.315 58.33 29.53 85.499 121.59 106.89 14400 0.4 0.0051 0.0394 0.0
36 P-252 2 2.375 58.54 19.58 60.724 86.35 71.65 14400 0.4 0.0062 0.0394 0.0
37 P-253 1.5 1.9 57.15 16.82 54.626 77.68 62.98 14400 0.4 0.0044 0.0394 0.0
38 P-254 1 1.315 56.77 37.37 111.180 158.11 143.41 14400 0.4 0.0069 0.0394 0.0
39 P-256 2 2.375 58.80 37.39 112.691 160.25 145.55 14400 0.4 0.0126 0.0394 0.0
40 P-257 6 6.625 58.80 21.55 65.042 92.49 77.79 14400 0.4 0.0188 0.0394 0.0
41 P-259 3 3.5 29.40 27.66 59.703 84.90 70.20 14400 0.4 0.0089 0.0394 0.0
42 P-260 3 3.5 29.40 27.50 59.258 84.27 69.57 14400 0.4 0.0089 0.0394 0.0
43 P-261 3 3.5 22.05 20.90 37.781 53.73 39.03 14400 0.4 0.0050 0.0394 0.0
44 P-262 3 3.5 29.40 15.23 32.510 46.23 31.53 14400 0.4 0.0040 0.0394 0.0
45 P-263 2 2.375 29.40 22.37 46.194 65.69 50.99 14400 0.4 0.0044 0.0394 0.0
46 P-264 2 2.375 29.40 17.26 35.877 51.02 36.32 14400 0.4 0.0031 0.0394 0.0
47 P-270 3 3.5 44.10 28.44 72.267 102.77 88.07 14400 0.4 0.0112 0.0394 0.0
48 P-271 1 1.315 14.70 24.31 40.496 57.59 42.89 14400 0.4 0.0021 0.0394 0.0
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6.3.2 Allowable Working Pressure
After calculating the design thickness, now checking the working pressure by using
the standard thickness to find the maximum pressure that the pipe material can
withstand. The allowable working pressure of a pipe can be determined by Equation
(4.3) given below.
2( )
( 2 )o
S Eq t P
D Yt
=
(4.3)
Let take Pipe no. 208 and calculate its minimum thickness by using Table 6-5.
Table 6-5 Input data
Parameter Value Reference/Reason
Do 8.625 in Appendix Table A2
E 1 For seamless pipe
Y 0.4 b/c Temperature < 900oF
S 14400 Psi Appendix Table A1
t 0.322 in Appendix Table A2
t = specified wall thickness or actual wall thickness in inches, in
So the allowable working pressure comes out to be P = 993.87 psi
Where as the designed working pressure =117.23 psi (From Table 6-1). For all the 48
pipes the working pressures are calculated and arranged in the following table.
Table 6-6 Design and working Pressure
S.NoPipe Line No.
NPS,
inDo(in)
Pressure (gage)
psiAllowable Pressure psi
1 P-208 8 8.625 193.31 993.877
2 P-209 2 6.625 113.69 1955.074
3 P-210 8 8.625 189.93 993.877
4 P-211 8 8.625 192.17 993.877
5 P-212 8 8.625 149.94 993.877
6 P-213 4 4.5 146.28 1479.188
7 P-214 8 8.625 124.09 993.877
8 P-215 6 6.625 111.40 1156.616
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Table 6-6 Design and working Pr