Interview Queries

8/18/2019 Interview Queries

http://slidepdf.com/reader/full/interview-queries 1/59

What is the difference between quality assurance & quality control?

Quality Assurance shall be maintained by ensuring the systematic implementation of thisQuality Plan and ensure that necessary quality records are generated as per ITPs.

QA provides the objective needed to give a maximum confidence for quality while QC isinvolved with the monitoring of a process and eliminating the causes of any deficient outputwith any process, which has effect on quality.

What is an essential variables as related to a Weld Procedure Specification ( WPS ) ?Essential variables are those in which a change, is considered to affect the mechanical properties of the weldment and shall require requalification of the WPS.

What is the relationship between Procedure Qualification Record (PQR) and a WPS?PQR is a record of the welding data used to weld a test coupon, it contains the result of thetested specimens, while the WPS is the written form of the welding procedure for making aspecified kind of weld joint using specified base and filler materials.

Heat input (SMAW per ASME IX) is a common of what two electrical characteristics &travel speed?Volts and amperes, heat input = volts x amperes / travel speed.

Excessive heat input is mainly attributed to what poor welding techniques during SMAW process?

Incorrect welding technique

What are 3 potential sources of Hydrogen encountered during SMAW process? Hydrogen induced cold cracking ( usually occurs at HAZ ) Fish eyes ( hydrogen – inclusion ) Weld cracks.

What are several likely causes of porosity in a carbon steel welds using the SMAW process? Excessive moisture in the flux

Arc length too long Use of low welding current Damage electrode flux

What dimension is measured to determine the size of a concave fillet weld?Its height and length

What dimension is measured to determine the size of a convex fillet weld?Its throat

Where would cracking most likely occur from excessive current input in a single pass weld?Liquation cracking



Using GTAW process, describe what happens to a root pass applied without purging/backgauging on SS?It will produce oxidizing, coking to the weld metal

Name 3 of the 5 mechanical test in ASME IX employed for procedure & performance

qualifications? Tension test Guided bend test Filler-weld test Notch-toughness test

Mechanical/NDT, assume SMAW process for all questions.

How is Magnetic Particle inspection of a weld using wet continuous test method performed ?

Measure and record the temperature of examination surface, temperature shall not exceed135*F (57 *C )Clean examination surface and adjacent area within 3 inches ( 76.2 mm ) of the examine areaPerform visual inspection of the examination surface for cleanliness and discontinuitiesCheck for remnant magnetic fields exceeding + 2 gauss.

Indications with Liquid Penetrant Testing are easily seen if the surface has been prepared bygrinding prior to testing? True or False? Why?False, surface discontinuities of the examine area will not be seen or occur

Name an NDT method and techniques that employs a reflected sound beam that can be usedfor the volumetric examination of welds?Ultra-sonic test

List 3 advantages of RT over other NDT Methods?Advantages:

Permanent record Little surface preparation Defect identification very easy No material limitation Not so reliant operator skill

Disadvantages:

Requires bulky and expensive machinery Expensive consumables Cannot detect plate laminations, lack of inter-run fusion or cracks

perpendicular to x-ray beam

If a product is to be stress relieved, why is it important to use exactly the same RT procedure before and after stress relieving?To ensure the weld has no cracks or defects.



A dark narrow area 2-3 mm wide appears on a radiograph all along the edge of the area of therepresenting the weld. The joint has a 60 Degree double vee groove. What is the indicationmost likely to be?Slag inclusion

A localized darker density Radiographic image with fuzzy edges in the center of the with ofthe weld image that may or may not be wider than the width of the root pass images is mostlikely what?Burn through

Name 5 common film artifacts that may be cause for rejection of the Radiographic film? Film marks Low density Poor identification Fog and processing irregularities Unacceptable technique and set-up

When the radiation source is located inside piping with the film located outside, single-wallexposure and single-wall view, name this type of exposure?Panoramic- single wall exposure, single wall viewing

How do gamma rays compare with x-rays when applied to RT of welds?X-rays generally produces better quality radiograph and safe, while gamma sources permanently produces radiation and require shielding when not in used

Per ASME B31.3, name three of the four Categories of Fluid Service? Category “D” Fluid service Category “M” Fluid service High Pressure Fluid service Normal Pressure Fliud service

Per ASME B31.3 who is responsible for classification of service to a given category?

Per ASME B31.3 what are the RT requirements for Socket welds in a severe cycle service?Random RT

Relating to the above question, give 2 reasons why random RT of socket welds is

recommended even though code does not require RT?Gap verification

Briefly describe good QC practice relating to the installation & bolting of flanges ?Bolt holes shall be aligned within 3 mm maximum offsetFlange bolts and studs shall be long enough to penetrate completely through the nuts min. of3 threads protrutionBolts nuts faces and nut bearings surfaces shall be lubricated before installation

What is an often- overlooked inspection/ NDT requirement on the installation of the orifice

flanges?



Welds at orifice flanges shall be ground or machined smooth and flush on the inside of the pipe, and it requires RT

What API documents apply to the replacement of the existing floor for an Aboveground OilStorage tank?API 653Relating to weld fabrication shop evaluation prior to the beginning of pipe welding for amajor project, what are several key items you would look for as the Inspector before youapproved the shop for welding?The inspector must considered the following: material specification, welders qualification,WPS

Hint: 5M + E formula = Manpower, Methods, Materials, Machines, Measurements,Environment

Per SAES – W-011What is the maximum size of low hydrogen (E7018) permitted?

5mm for the 1g/1f position, 4mm other positions

for non-hydrogen; 5mm for all positions

What are the diameter limitations (per pipe size) for the different welding processes?SMAW GTAW GMAW

3”- up ½” to 10 ‘ 3”- upWhat is the requirement (Material, location) for bridges tacks?It should be same materials, electrodes, minimum preheat and should be located above theroot area

For temporary supports and attachments welded to the pipe, what are requirements related toMaterials? NDT?It should be same materials, and PT

What is the minimum amount of time that E-7018 electrodes can be kept out in the field?

Up to 4 hoursWhat is the minimum drying temperature and drying time?260*C-430*C for 2 hours

How many times can electrodes be rebaked?One time only

What is the maximum internal misalignment of butt joints?1.5 mm max.

Piping during preparation before fit-ups shall be cleaned/ground internally/externally forwhat distance from the edge of the prepared joint?



Ground internally/externally for at least 25 mm, and should be clean

Moist surfaces require moisture removal and surface to be preheated must be preheated towhat distance from the joint edge?75mm from the joint edge

ASME B 31.3 - SOME IMPORTANT POINTS

Tack welding can be done only by a qualified welder. Refer: ASME B 31.3 Clause: 328.5.1 (c)

How much can a branch pipe be inserted to the run pipe? Refer: ASME B 31.3 Clause: 328.4.3 (c)(1)

How much should be the preheating area near a weld joint? Refer: ASME B 31.3 Clause: 330.1.4

What are the conditions when PWHT is not required, if the general condition of the jobrequires PWHT? Refer: ASME B 31.3 Clause: 331.1.3 (b)

What is the % of hardness test required after PWHT? Refer: ASME B 31.3 Clause: 331.1.7

How much should be the PWHT area near a weld joint? Refer: ASME B 31.3 Clause: 331.2.6

Preheat temperatures for different materials.Refer: ASME B 31.3 Table 330.1.1

Requirements for heat treatment. Refer: ASME B 31.3 Clause: 331.1.1

Minimum welding dimensions for socket welding components other than flanges. Refer: ASME B 31.3 Fig 328.5.2C

Typical details for double welded slip on and socket welding flange attachment welds. Refer: ASME B 31.3 Clause: 328.5.2BIs WPS, PQR or WPQ/WOPQ need to be amended for using it according to a later edition ofASME BPV Section IX? No. Except as specified in QW:420 (Last Paragraph)

What are the different type of mechanical tests used in procedure or performancequalification as per ASME Section IX?



1. Tension test. 2. Guided bend test. 3. Fillet weld test 4. Notch toughness test

Why the different mechanical tests are conducted for procedure or performance qualificationas over ASME Section IX?

1. Tension test: Used to determine the ultimate strength of grrove-weld joints

2. Guided bend test: Used to determine the degree of soundness and ductility of groove-weld joints.

3. Fillet weld test: Used to determine the size, contour and degree of soundness of filletwelds.

4. Notch toughness test: Used to determine the notch toughness of the weldment

What are the tests done for stud welding procedure and performance qualification? Deflection bend, hammering, torque or tension tests and macro examination.

What is the first test that to be done on a procedure or performance qualification test coupon? Visual Testing.

How many studs are to be welded for procedure qualification of stud weld test? Ten Studs; as per QW 192.1.1

Any requirement for stud welding equipment for procedure qualification as per ASME SecIX? The equipment used for stud welding shall be completely automatic except for manualstarting. What are the test to be done for the procedure qualification of stud welding? 1. Every other welding stud (five joints) shall be tested either by hammering over until onefourth of its length is flat on the test piece, or by bending the stud to an angle of atleast 15degree and returning it to its original position using a test jig and an adapter locationdimension that are in accordance with figure QW-466.4

2. The remaining five welded stud joints shall be tested in torque using a torque testingarrangement that is substantially in accordance with figure QW-466.5. Alternatively wheretorquing is not feasible, tensile strength test may be used.

What the acceptance criteria is for bend and hammer tests? In order to pass the test(s), each of the five stud welds and heat affected zones shall be free of

visible separation or fracture after bending and return bending or after hammering.





sectionV.

Is a written ultrasonic examination procedure is needed for welders/welding operatorqualification using ultrasonic examination?

Yes As per QW-191.2.1 (b), Ultrasonic examination shall be performed using a written procedureverified by the manufacturer to be in compliance with paragraph T-150, Article1, Section Vand the requirements of Article 4, Section V for methods, procedure and qualification.

Is there any base material thickness restriction for ultrasonic examination of test coupons ofwelders and welding operators?YesAs per QW-191.2.1 (a), The ultrasonic examination for welder and welding operators may beconducted on test welds in material 1/2in. (13mm) thick or greater. What is WPS? WPS stands for Welding Procedure Specification. A WPS is a written document that providesdirection to the welder or welding operator for making production welds in accordance withcode requirement.(Refer: ASME Sec IX; QW:100.1)

What is PQR? PQR stands for procedure qualification record. The PQR documents what occurred duringwelding the test coupon and the results of testing of the coupon.

Why a WPS needs qualification? The purpose for qualification of a WPS is to determine that the weldment proposed forconstruction is capable of providing the required properties for its intended application.Welding Procedure Qualification establishes the properties of the weldment not the skill ofthe welder or welding operator.

Why a performance qualification is done for welder? In performance qualification, the basic criteria established for welder qualification is todetermine the welders ability to deposit sound weld metal. The purpose of the performancequalification test for the welding operator is to determine the welding operators mechanicalability to operate the welding equipment.

Is there any expiry date for WPS/PQR/WPQ/WOPQ? NO.WPS, PQR, WPQ/WOPQ made in accordance with the requirements of the 1962 edition or

any later edition of section IX may be used in any construction built to the ASME Boiler andPressure Vessel Code or the ASME B 31 Code for pressure piping.



What do you mean by QMS?

If you work on documentation, how can you work as a piping inspector? Should have knowledge about project applicable standards. Reviewing of hydro test packages. (All documents such as NDE reports, PMI

reports, Orifice flange reports, Joint Summary sheet shall be reviewed.) Reviewing of calibration certificates of valves, manifold and pressure gauges. Reviewing of Mill test certificate. Analysing the ISO drawings, checking whether the design pressure is as per the

line class.

What are the piping inspector responsibilities? Material receiving inspection Ensure that approved procedure and ITP are used by construction. Pipe fit up activities Retention of QC reports and records. Line checking Hydro test activities Reinstatement activities

How can you identify an ISO in a P&ID?

Line number, service, instrument, equipment, and slope.

What 4 types of Inspection Action points are found in the ITP & Explain?

Hold, Witness, Surveillance, Review

Hold- QA/QC organization shall be notified of the timing of inspection or test in advance.Inspection or test shall not be carried out without the QA/QC organization representative in

attendance.Witness- QA/QC organization shall be notified of the timing of Inspection or test in advance.However, the inspection or test shall be performed as scheduled if the QA/QC organizationrepresentative is not present.

Surveillance- QA/QC organization to monitor work in progress without notice fromConstruction Organization.

Review- Review and approval of documents.

What is tack weld?



Tack weld is the temporary weld to maintain joint alignment. All tack welds shall be made byqualified welders. Recommended tack thickness is 3.2 – 4.8mm & length is 12.5 - 25.4 mm.the minimum number of tack welds for 3.5 inch and below are 3 equally spaced tacks. Above3.5 inch 4 equally spaced tacks.

Why water certificate is necessary for hydro test?To know the chloride content and PH value, Water certificate is necessary.

What is NCR, CAR, DR?

NCR: (Non Conformity report): A record reporting the variation from the specifiedrequirements.

CAR: Corrective action report: A record reporting the action taken to eliminate the effect andcauses of an existing non –conformity, defect or other undesirable situation in order to preventrecurrence.

DR: Deviation report: A record of the concessions granted by client or owner to certaindeviation from project specification.

What are specifications?

Specifications (Specs) are guideline details for construction requirements to assure minimumquality standards are listed and met.

What is an Inspection & Test Plan?It is a mandatory item in the Quality Plan to guide and assure quality in a specific type ofwork in a specific sequence of QC activity steps.

What is an isometric drawing?

A detailed piping system/line drawing with reference to construction and materialrequirements.

If we are using valve as a test limit, what are the things to be checked?

The valve certificate of seat test to be attached.

What is an SIS?

Safety Instruction Sheet that gives full design details related to a piping system or line.

What is Schedule ‘Q’?

Schedule Q stands for Owner’s minimum quality requirements for Contractor/Subcontractorquality system.

What is a P&ID?



Piping & instrument Diagram shows piping layouts and detailed notes relating to piping andinstrumentation.

What is WPS?A document providing the required welding variables for a specific application to assurerepeatability by properly trained welders and welding operators.

What is PQR?A record of welding variables used to produce an acceptable test weldment and the results oftests conducted on the weldment to qualify a welding procedure specification.

What is PMI?Verification that the nominal chemical composition of an alloy material is as specified andordered.

What are the gauges used for fit up?Bridge cam, High Low gauge

What material used for drinking water service?Galvanized steel materials

What is color coding?

Marking of piping bulk materials to identify the Material.

What we check in water analysis and its value for CS & SS?In water analysis we check the PH value and chloride content of water. For CS the PH valueis 7.5±.5 & chloride < 250ppm. For SS the PH value is 10.5±0.5 & chloride < 50ppm

What are the documents in hydro test package?

a) Table of contents

b) Safety Instruction sheet for critical services

c) Flow Chart of Test Packages

d) Pre-Test Punch List

Test Procedure & Pressure Test DiagramRelated P&ID and Isometric DrawingsLine ListPre-test Punch List Checklist I Forme) QA/QC Documentation of the system to be tested.



Weld Inspection Summary SheetWeld Map NDE Record/sAs-Built drawingsIsolation valve Test CertificatesFlange Joint Inspection ReportInternal Cleanliness I Flushing Reportf) Pressure Testing

Verification of Temporary gasketsVerification of Test blind rating

Checklist for Verification of system readiness for TestingCalibration certificates for Pressure gauge & PSVCalibration certificates for Pressure & Temperature recordersTest manifold CertificateWater Analysis (test medium)Pressure Test Report FormSystem Lay-Up Certificate

Re-Instatement or Final Assembly Inspection (Final Punch List)What are the difference b/w A punch & B punch?List of unfinished work or unmatched item according to DRWG and specifications beforeHydro test.

A - To be done before Hydro test

B - To be done before Mechanical completion

What are the factors in a mill test certificate?

Chemical compositionMechanical properties (hardness, tensile strength, yield strength, elongation, reduction ofarea)

Heat number

What is material receiving inspection?

Match physical condition in field to service condition shown on Drawings/Hardware lists Specification and marking/color-coding & PMI





Flange face and threads shall be protected from rust by applying suitable rust preventives.

After completion of pre-fabrication, the spool shall be cleaned and free from weldspatters, arc strikes and foreign materials on outside and inside of pipes.

Lined and coated pipes and fittings shall be lifted with wide fabric or rubber-coveredslings and padding shall be used to prevent damage to lining or coating. Wire ropeslings shall not be used.

SS materials shall be covered and protected from water splash and othercontamination during storage

What are the calibration requirements for pressure gauge, min number used and its location? The calibration interval shall not exceed one (1) month. Calibration certificates shall be

made available to Inspection personnel prior to commencement of the pressure test.Stickers shall be applied indicating the latest calibration date.

All gages shall have a range such that the test pressure is within 30 to 80% of the fullrange.

A minimum of two pressure gages are required for the test system. One pressure gage shall be on the test pump and the other(s) on the test system. Their accuracy shall be within 5% ofone another

General requirements to be done after hydro test?

Draining of Test FluidRelease of pressure and draining shall be done on the downstream side of check valves.All vents shall be opened before draining to facilitate drainage and to prevent formation ofa vacuum. No test fluid shall remain in low spots.

Disposal of Test FluidThe test fluid shall be disposed in accordance with SAEP-327 or as directed by the Owner.

Test Vents and Drains

Vents and drains used only for the pressure test shall be plugged, seal welded and penetrant tested.



Removal and Reconnection of Components

All temporary items installed for testing purposes (e.g., manifolds, valves, blinds, spacers,supports) shall be removed.

Items that were removed from testing shall be reinstalled. Items, such as instrument air tubing, check valve discs which were disconnected before

testing shall be reconnected.

Isolation valves closed for the test purposes and that are required to be in the open positionfor process reasons shall be opened. If the valve cavity has a drain, the cavity shall bedrained.

What punch to be closed after hydro test?

B punches to be closed before hydro test.Temporary items shall be removed, bolt torquing, all instruments shall be installed, and itemsremoved for testing shall be reinstalled.

How to cut a SS pipe and what are the things to be ensured before cutting?Stainless steel SS pipes - By grinding or Plasma cutting providing internal protection fromspatter, slag…etc.What are the instruments to be calibrated before bolt tightening?

Torque Wrench What are the difference b/w a pipe and a tube?

Pipe is identified by NPS and thickness is defined by Schedule whereas Tube is identified byOD & thickness identified by Birmingham Wire gauge

What are the different types of fluids in ASME? Explain?Category D fluid Service – non flammable, non toxic and non damaging to human tissues.(temp range -29 ˚C to 186˚ C)

Category M fluid service- toxic and flammable

High pressure fluid service – based on class 2500 rating for specified design temp. andmaterial group.

Normal fluid service – Not subjected to D, M or High pressure fluid service

What are the types of CS & SS pipes?

Carbon Steel: - ASTM A53 Gr. A/B, ASTM A106 Gr. A/B/C, ASTM A333 Gr.1/Gr.6



Stainless Steel: - ASTM A312 TP304/ TP304L/ TP304H/ TP308/ TP310/ TP316/ TP316L/TP316H/ TP317/ TP321/ TP321H/ TP347/ TP347H/ TP348/ TP348H.

What are the different types of 304 & 308?304 – Cr- 18-20%, Ni- 8-10%

308 – Cr 20% , Ni-10%

How do we identify Nace Carbon Steel and Normal Carbon Steel?By color coding

What is a line schedule?A line schedule gives the full details of P&ID No, Line identification, Line routing, fluidservice, phase, density, temperature( operating, design and test), pressure( operating, designand test), insulation type, painting systems, PWHT, Jacketing identification for the entireunit.Where do we attain test pressure and why?We attain test pressure at highest pressure gage because due to gravity, effect every 10 mheight 1 bar pressure reduces

What is the different ASME 31 code for pressure piping?

A. ASME B31.1 - Power piping.B. ASME B31.2 - Fuel Gas Piping.C. ASME B31.3 - Process piping.D. ASME B31.4 - Pipeline Transportation system for liquid

hydrocarbon & other liquid.E. ASME B31.5 - Refrigeration Piping.F. ASME B31.8 - Gas transmission & distribution piping system.G. ASME B31.9 - Building services piping.H. ASME B31.11 - Slurry transportation piping system.

Which is the rope used for lifting the external coated pipe?

Nylon

What is the minimum clearance b/w a pipe and a structure?

50mm

What is the hydro test holding time for A/G piping?



30 minWhat are the important activities to be checked during flange alignment fit up?

Misalignment

Flange faceRotation of flanges (±2.4 mm)Tilt of the flange (shall not exceed 1.6 mm from the square position)Flange face thickness, gasket thickness ± 1.6 mmCombination of vertical, horizontal and rotational offset ± 3.2 mm

What is an insulation kit?To isolate between above ground and underground.

What is insulation gasket?Isolation of dissimilar metal flanged joints (electrical insulation)Insulating joints for cathodic protection.Eg. PIKOTEK GASKETS.

What are PIKOTEK Gaskets and what are their limitations?It is nonmetallic gaskets made of self-energized Teflon seal supported by glass reinforcedepoxy laminated to 316 stainless steel core.

The minimum required gap shall be 3.2 mm.

It shall not be used services with temp. 154’C or higher

It shall not be used in hydrocarbon gas service in which flange rating is 300 or higher.It shall not be used in Chemical incompatibility of nonmetallic component with the servicemedia.

What are the general points to be checked prior to hydro test? (Pre-pressure checklist) Seal weld threaded nipples from headers to 1st block of valve (hydrocarbon

service) p Guides are in direct contact with piping horizontal run at 3 locations (6mm gap

required). Relocate guides per drawing. These are welded to the pressure boundary.

Check valve is oriented in the wrong direction (flow arrow). Reverse check

valve to assure correct flow direction. Reposition valve & restore internalsimmediately after test, COMPANY to witness.



Piping clearance to structural bracing is (50 mm spacing required). Install permanent gaskets at flange sets 1, 4, 5, 6 on ISO dwgs per approved

torque tables and install spectacle blinds oriented as per approved P&ID. Completely remove all water and debris from low point/valve cavity for the in-

line Valves with SS 400 trim, do so immediately after test. Clean with drycompressed air and relubricate sealing surfaces with approved lubricant in preparation for "ambient" lay-up specified in test package.

Indicate “No Punch items. “as applicableQA is reviewed/initialed/dated prior to package certification to verifycompleteness.

What are the ASME codes for Flanges?

ASME B16.5 PIPE FLANGES AND FLANGED FITTINGS (UPTO 24”) ASME B16.47 LARGE DIAMETER FLANGES (ABOVE 24”)

What is the colour code for the material?( standard)

PFI ES 22( PIPING FABRICATION INSTITUTE)

How you inspect the flush grinding?

Any distortion resulting from the butt weld shall be removed and ground flush with theinside diameter of the pipe, PT shall be done. The inside surface of welded joints at orifice flanges shall be ground or machined smooth.

What things are found in a Piping Isometric drawing?

Line conditions, references to drawings, materials of construction(Bill Of Materials),continuations, orientation, piping and drawing details and notes, revision control andapproval status.

What kind of inspection required during gasket installation?

QC Piping Inspector will ensure the cleanliness of the gasket surfaces of theflanges and the condition of the gasket. Care shall be taken during this operationto prevent entering of debris in the pipe or equipment.

QC piping Inspector shall verify on site, prior to installation, each gasket hasthe proper material size and rating according to drawings and line class. Gasketswill have an individual painted mark, which will identify the rating number.

For gaskets 24” and less, colours code on the gaskets shall be applied on the

outside surface, Mark shall be an approximately 1 inch in lengthcircumferentially.



For Gaskets 24” and above, will be market in two locations each. Spiral wound gaskets should have three colours, which identify the particular

material spec, rating and gasket with inner ring respectively. During reinstatement, QC Piping Inspector shall verify that bolting is tightened

according JERES-L-351. QC Inspectors shall inspect, before hydro test and during lines reinstallation thatall permanent gasket are installed accordingly.

What is the difference b/w torquing of CS & SS bolting?

Yield strength of CS is greater than SS.

How many threads can be visible after seal welding threaded joints?Zero

What is the basic difference between Pipe specification A106 Gr.A / Gr.B/ Gr.C.?Difference is due to the Carbon content.% of carbon content in : -I. ASTM A106 Gr. A – 0.25 %II. ASTM A106 Gr. B – 0.30 %II ASTM A106 Gr. C – 0.35 %.

What are the different sections of ASME code? Where these sections are referred?

A. ASME section I : - Rules for construction of power boiler.B. ASME Section II : - Materials.

Part A – Ferrous materials.Part B – Non-Ferrous materials.Part C – Specification for electrodes & filler wire.Part D – Properties.

C. ASME Section IV : - Rules for construction of Heating Boiler.

D. ASME Section V : - Non- destructive Examination.E. ASME Section VI : - Recommended rules for care & operation ofheating boiler.F. ASME Section VII : - Recommended guidelines for care of power boiler.H. ASME Section VIII : - Rules for construction of pressure vessels. (Division I & II)I. ASME Section IX : - Welding & Brazing qualification.

What types of PMI machines are available?X-Ray FluorescenceOptical Emission Spectrography



For sour service and NACE which material is used?

HIC Carbon Resistant Material

Color coding for CS, LTCS, and Alloy?As per PFI ES-22.

What type of cutting used is SS? Types of Grinding wheel and how to identify them?

Plasma arc cutting and grinding wheelTypes for grinding wheel are: Iron oxide, zirconium, Aluminum oxide.Identification by color coding.( blue)

Name the different types of Service Conditions?Temperature, pressure and fluid type

What are the equipment’s excluded from pressure test?

a) Rotating machinery, such as pumps, turbines and compressors; b) Strainers and filter elements;c) Pressure relieving devices, such as rupture disks and pressure relief valves;d) Locally mounted indicating pressure gages, where the test pressure will exceed their

scale range;e) Equipment that cannot be drained;f) Instrument Devices.

What is the difference b/w Hydrostatic pressure test & pneumatic pressure test?

Hydrostatic pressure test is a pressure test conducted using water or other approved liquid asthe test medium.Pneumatic Test: A pressure test conducted using air or other approved gas as the testmedium or in conjunction with liquid.

What is the value of test pressure in each test?Hydrostatic pressure: not more than 1.5 times the design pressure.

Manifold pressure: at least 1.2 times the system pressure but not less than discharge pressure of pump used for pressure testing.

Pneumatic pressure: a set pressure not higher than the test pressure plus the lesser of 345 kPa(50 psi) or 10% of the test pressure.



The instrument impulse lines, whether piping or tubing, between the root isolation valve andthe instrument isolation shall be pneumatically pressure tested (using air or nitrogen) at 1.25times the design pressure of the piping system or process equipment to which it is connected.

Can you use pneumatic test in lieu of hydrostatic test?Pneumatic testing is not permitted without written approval of the company inspector, unlessspecifically allowed by this standard

When pneumatic testing is not practical (e.g., - pressure greater than 1000 psig, physicalconfiguration, etc.) testing with liquid is permitted.

What are the general criteria checked for line-checking?

All joints (flange, threaded, welded or mechanical seals) are left exposed forvisual leak detection during the strength test.

All permanent flange joints were inspected, gasket mat'l verified & properlytorqued.

Drains shall be provided at all low points of the piping system. Vents and drain valves, both temporary and permanent, conforms with the

piping class or rating. Supports are installed. Additional temporary support may be installed as

required. Expansion joints and spring hangers or spring supports are provided with

temporary restraints. Arc strikes, gouges, and other indications of careless workmanship (such as

surface porosity, uneven weld profiles, and undercut) shall be removed bygrinding and inspected by magnetic particle or liquid penetrant method.

Drains are provided immediately above check valves (vertical lines) All threaded joints up to the first block valve of hydrocarbon pipeline are seal

welded. Thread engagement has been verified & accepted. The pressure testing manifold is separately pressure tested to at least 1.2 times

the system test pressure but not less than the discharge pressure of the pump

used for the pressure testing. Pressure gages and pressure recorders are calibrated within one (1) month before the test. Check stickers at the time of the test.

Line compliance with Isometrics:A) Correct Materials utilized grade/schedule (Bill of Mat'ls)B) Correct flange and fittings rating

What are the general requirements for pressure gauges? A minimum of two pressure gages are required for test systems, with accuracy

within 5% of one another.



Pressure gages and pressure recorders are calibrated within (1) month prior totest. Stickers applied indicate latest calibration date.

Test gauge is located at bottom of any equipment/system under test to enable

reading test pressures inclusive of hydrostatic head. All gauges have a range such that the test pressure is within 30% to 80% of thefull range.

What are the types of valves? Based on functionA. Isolation: Gate valve, Ball valve, Plug valve, Piston valve, Diaphragm Valve, Butterflyvalve, Pinch valve. B. Regulation: Globe valve, Needle valve, Butterfly valve, Diaphragm valve, Piston valve,Pinch valve. C. Non- Return: Check valve. D. Special purpose: Multi- Port valve, Flush Bottom valve, Float valve, Foot valve, Line blind valve, Knife Gate valve.

Method of operation: Self- operated valves, Operated valves.

Based on end connection (arrangement of attachment of the valve with the equipment or the piping.): Screwed ends, Socket ends, Flanged ends, Butt weld ends, Wafer type ends,Buttress ends

Where we use temporary gaskets?Used as a test limit during hydro test.

What are the types of gasket?Based on constructionA. Full face.B. Spiral wound metallic.

C. Ring type.D. Metal jacketed.E. Inside bolt circle.

Based on materialA. Synthetic rubberB. Solid TeflonC. Compressed AsbestosD.CS (High pressure fluid)E. SS (High fluid corrosive)F. Spiral Wound a) Teflon b) CS c) SS



Why and how color coding gaskets are done?Color coding of gaskets are done based on material specification and the suitable flangerating. It helps to check correct gaskets are used on flanges, also helps to store and handle

gaskets easily.What is a test limit?Test limit is the boundary up to which the pressure testing is conducted.

What are the types of flanges?Based on pipe attachmentSlip – on. - The Slip-on type flanges are attached by welding inside as well as outside. Theseflanges are of forged construction.

Socket Weld. : - The Socket Weld flanges are welded on one side only. These are used forsmall bore lines only.

Screwed: - The Screwed-on flanges are used on pipe lines where welding cannot be carriedout.

Lap Joint. : - The Lap Joint flanges are used with stub ends. The stub ends are welded with pipes & flanges are kept loose over the same.

Welding Neck. : - The Welding neck flanges are attached by butt welding to the pipe. Theseare used mainly for critical services where the weld joints need radiographic inspection.

Blind. : - The Blind flanges are used to close the ends which need to be reopened.

Reducing. : - The reducing flanges are used to connect between larger and smaller sizeswithout using a reducer. In case of reducing flanges, the thickness of flange should be that ofthe higher diameter.

Integral. : - Integral flanges are those, which are cast along with the piping component orequipment.

Flanges are classified based on pressure temperature ratings as: -A. 150 B. 300 C. 400 D. 600 E. 900 F. 1500 G. 2500



Flanges are classified based on facing as: -A. Flat face. (FF)B. Raised face. (R/F)C. Tongue and groove. (T/G)D. Male and female. (M/F)E. Ring type joint. (RTJ)Based on face finish as: -A. Smooth finish.B. Serrated finish

How to give a gap in socket flange?

Place gap-o-let ring at the inside of socket, gap range is 1.5 to 3 mm. if gap-o- let ring is notavailable measure the socket length, mark it on the pipe and give 1.5 to 3mm gap duringsocket welding.

NACE – MR- 0175? Sulphide stress cracking resistant metallic material for oil field equipment..For the verification/traceability of materials what are the different procedures to be used?

PMI –Positive Material Inspection

Marking& Colour Coding ( - Piping Fabrication institute)

Spools are stamped, stencilled, or clearly marked with a permanent marking method, properlycolour-coded and uniquely identified, labelled & traceable to Isometric Drawings.

Why do we provide Drip Leg in Steam Line?

To remove condensate when there is a rise of same in the pipe along the flow direction. Ifdrip leg is not provided in steam line, the condensate which forms inside the pipe will resultin Water Hammer effect causing damage to piping system.

What do you mean by Jacketed Piping?Piping which is recognized as providing the most uniform application of heat to the process,as well as maintaining the most uniform processing temperatures where steam tracing is notcapable of maintaining the temperature of fluid constant. Usually used for molten sulphur,Polymers service.

What is shot peening?Inducing chemical stress in a material surface layer by bombarding it with a selected mediumunder controlled conditions.

What is cold spring?



Application of mechanical stress (bending twisting pulling) upon a piping segment to achieve bolting and connection to another segment. It is not acceptable.

What is often overlooked during orifice flange fabrication?

Grinding butt welds flush and seal welding orifice.What NDT methods are required during orifice flange installations?Visual and PT/MT

What are the criteria for cold bending?

Cold bends are made below 649°C, (below 315°C for grades of pipe strengthened by coldwork).

Only seamless Grade B pipes are to be used.

For wet sour service, cold bends to a radius of 5D or less, are heat treated at 593°C to 649°Cfor one hour per 25.4 mm of nominal wall thickness, and not less than one hour.

For cold bends with a radius of less than 30D, the nominal diameter (O.D.) divided by thenominal wall thickness does not exceed 35.0.

For wet sour service, each bend has a hardness measurement made at the outer radius of the bend area. Maximum allowable hardness is 237 Brinell (22 HRC).

What are the criteria for hot bending?

Furnace hot bends are only be used for Grade B pipe

Furnace hot bends are made at 871°C to 954°C, but may be finished below 871°C providedthe bend is started above 871°C. The pipe is not heated above 954°C prior to the start of bending. After bending, the bend is cooled in still air.

How do we preserve pipes and pipe fittings?Pipe shall not be stored directly on the ground. Pipe shall be placed on wooden or sleepers.

Stacking of pipes shall be made in a manner to avoid damage to pipes or coatings.Fittings and valves shall be stored in shipping crates or on racks. Stainless pipe and fitting must be separate from carbon steel to avoid contamination.

End bevel protectors shall remain on pipes and fittings while in storage, protectors shall notdamage internal or external coating.

Flange face and threads shall be protected from rust by applying suitable rust preventives.

Before cutting the pipe, the Heat Number will be transferred to the cut pieces by low stress dye

stamping, Paint marking or Tagging.



What are the tolerances to be followed in piping?

The tolerance for axial dimensions, face-to-face, centre-to-face and location of attachmentsshall be ±3 mm maximum.

Flattening of bends, measured as the difference between the largest and the smallest outsidediameter at any cross section, shall not exceed 5% of the nominal diameter of the pipe.Flattening of bends at weld ends shall not exceed 3% of the nominal pipe diameter.

Lateral transition of branches and connections from the centreline of the run shall not exceed±1.5 mm.

Flange bolt holes shall straddle the established centerlines. Rotation of flanges, measured as

the offset between elevations of bolt holes on opposite sides of a flange centreline, shall notexceed ±2.4 mm.

The tilt of a flange measured at the periphery across any diameter shall not exceed 1.6 mmfrom the square position.

For piping over 3-inch NPS connected to machinery/equipment, flange alignment shall bewithin the following limits,

a) Vertical bolt hole offset: ±2.4 mm b) Horizontal bolt hole offset: ±2.4 mm

c) Rotational offset: ±2.4 mm

d) Flange face tilt across diameter: 0.001 inch per inch of flange outside diameter up to amaximum of 0.030 inch, and 0.010 inch for all flanges with an outside diameter less than 10inches.

e) Flange face separation, gasket thickness: ±1.6 mmf) Combination of vertical, horizontal and rotational offset: ±3.2 mm

If a spectacle plate is installed between two flanges, these tolerances can be increased by 30%except for tolerances for flange face tilt across diameter and flange face separation.

A wrinkle (buckle, dent, cracks and mechanical damage) is caused for rejection and isdefined as deviation of the pipe wall from the ideal contour of more than 15% of the normal

surface perpendicular to the surface.Dimension of the flat spot shall not exceed the value given by the formula:



D =√ (2tD)d= largest dimension of the flat spott= nominal wall thicknessD= nominal pipe diameterHow we will represent a slope in P& ID?A slope is represented by(A ratio shall be given)

Why weep hole is provided in pad?Reinforcing pad of welded branch connections shall be pneumatically leak tested with air at1.75 bar through a minimum of one ¼” (6mm) tapped vent hole / weep hole for venting andexamined for leaks using a soap solution at a reduced pressure of 0.2 to 0.35 bar. The 6mmtapped vent shall not be located in the crotch of the branch.

What are jackscrews and when are they required?They are located at flanged connections to facilitate maintenance and removal of spectacleand orifice plates to facilitate maintenance.

For orifice flanges, jack screws shall be installed at 3 and 9’ O Clock position.

What are piping joint limitations?

Socket Welded pipe in hazardous services is 1½-inch maximum

For sour service, socket-welded joints are not allowed.

The axial gap between male and female components a maximum of 3 mm and minimum of1.5 mm. This gap is obtained prior to welding

In hazardous services, the maximum size of threaded connections is 1½-inch for standardfittings and valves

In non-hazardous services, the maximum size of threaded connections is 3-inch for standardfittings and valves

The minimum number of the engaged pipe threads per nominal size is as follows:

For 1/2" & 3/4", 6 threads must be engaged

For 1" through 1-1/2", 7 threads must be engaged

For 2" through 3", 8 threads must be engaged

What are the general requirements for test manifold and fittings?

Pressure testing manifolds were separately pressure tested to at least 1.2 times system test pressure.



Pressure rating or design of test manifold components (isolation valves, pipe nipples, andfittings) exceeds system test pressure by 20%.

A blow down valve of adequate pressure rating is installed to depressurize the system safely.

Test piping, fittings and hoses are designed or have adequate pressure ratings that match orexceed system class/ test pressure.

Paddles or spectacle blinds & other fabricated test items used to isolate test sections are atleast the same code class rating of systems under test.

Define Pressure Test, Service Test

Pressure Test- A test conducted to piping or equipment by subjecting it to an internal pressureusing liquid or gas to ensure strength or tightness of the system at the test pressure.

Service Test- A leak test conducted at operating pressure using the service fluid.What is design? The act of working out the form of something (as by marking a sketch or out line or plan)

What is design interpretation?Design interpretation means to interpret or understand the drawing.

Introduction to pressure vesselSeveral types of equipment, which are used in the chemical, petrochemical fertilizerindustries are described below.

Pressure vessel Storages vessel Distillation columni Heat exchanger Evaporator Reactor, etc.

In all this equipment pressure vessel is a basic and generally used in all above types ofindustries.Pressure vessel are usually spherical or cylindrical with domed ends. They are provide withopenings or nozzles with facilities for marking threaded or flanged joints. Various methodsare used for supporting the vessel.

Which codes used make design of pressure vessel?Various code reference which is used for design and construction of pressure vessel are as below.

ASME sec viii div-1 IS 2825 BIS 5500

Why designing is required for pressure vessel?



The selection of the types of vessel based primarily upon the fictional service of the vessel.The functional service requirements impose certain operating conditions such as temperature, pressure, dimensional limitation and various loads.

If the vessel is not designed properly the vessel may be fail in service. The design of moststructure is based on formulas. Formula may be used form any relative code/standards so thevalue derived form that formula is reliable.

What parameter affect the failure of vessel?Failure may also result from corrosion, wear or fatigue. Design of the vessel to protectagainst such as failures involve the consideration of these factors and the physical propertiesof the materials.

If the vessel is not properly designed then chances of failure is more because we don’t knowwhat is the maximum operating pressure and temperature. We don’t know about maximumload, pressure or temperature carrying capacities of the vessel.

Stresses in pressure vesselPressure vessel are subjected to various loading which exert stresses of different intensities inthe vessel components.

The various stresses, which are generating during working and service time, are tabulated below.Loading on pressure vessel

Internal pressure External pressure Weight of vessel itself. Static reaction form piping other vessels, attached equipment, support such as lugs,

saddles, rings, legs, skirts and internals. Cyclic and dynamic reactions due to wind pressure, seismic forces Impact reactions such as those due to fluid shock. Temperature gradients and differential thermal expansion

What is components of design pressure vessel?The part which is common in any pressure vessel are described below

Shell Head or cover

Nozzle Reinforcement pad Support

The above parts are common parts of the pressure vessel. The all above parts of the vesselrequires designing before fabrication.

Design of shellShell is a major components of vessel. Shells are made form sheet or plate. Seamless orwelded pipe may be also used. There is two types of shell

1. Cylindrical shell2. Spherical shell

Generally a cylindrical shell is mostly used for construction of pressure vessel.



Stresses in cylindrical shellUniform internal or external pressure includes in the longitudinal seam a unit stress two timeslarger than in the circumferential seam because of the geometry of the cylinder.

Design of shell under internal pressureThickness of cylindrical shell in terms of inside dimension or longitudinal joints(Code reference ASME sec. Viii div.1 UG 27) When thickness does not exceed one half or the inside radius, p does not exceed 0.385 se thefollowing formula shall apply.

PrT = +c.a.

Se-0.6p

Design of various type of dish end.Pressure vessel requires closer at ends. Which is attained by using various dish ends. Thereare various aspects for selection of type head like volume inside head & space availableabove vessel at site. The various types of dished ends widely used are describe bellow.

Tori spherical headAs shown, this type of head consists of profile generated by two different circles havingcrown radius & knuckle radius. Generally these types of heads are used for low thick vessel.The required thickness of a tori spherical head for the case in which the knuckle radius is 6%of the inside crown radius, shall be determined by

0.885 plT = + c.a.

Se-0.1 pT = minimum required thickness of head after forming, inchP = internal design pressure Psi

L= inside spherical or crown radius, inch

Ellipsoidal headThese types of head consists of 2:1 ellipse profile as shown in figure. These types of headsare widely used in pressure vessel.



The thickness of the 2:1 ellipsoidal defined will be determined with the help of givenformula.

PdT = +c.a.2se – 0.2p

D= inside diameter of the head / inside length of the major axis.

Hemispherical headAs name implies the profile of this type head is half of sphere. These types of head havethroughout constant radius that allows maximum volume for reaction gases. This is also awidely used head especially for high thick vessel like reactors. Thickness of thehemispherical head shall be determined with the help of following formula.

PlT = + c.a.

2se – 0.2 pConical head and sections (without transition knuckle



The required thickness of conical heads or conical shell sections shall be determined withthe help of given formula.

PdT = + c. A.

2cosa (se – 0.6 p)Tori conical heads

The required thickness of the Tori conical dished end shall be determined by thefollowing formula

A = one half of the included angle of the conePdi

T = + c.a.2cosa (se – 0.6 p)

Where di = 2cos a* at the center line of the head



Design of nozzleAssembly of pipe or forging to flange is called nozzle.

What is design of skirt supports?Tall vertical vessels are usually supported by cylindrical shell or skirts.The skirts are welded to the bottom dished head, or outside of the shell.A bearing plate is attached to the bottom of the skirts. This plate is made to rest on concretefoundation and is securely anchored to the foundation by means of anchor bolts in concrete prevent over turning form the moments induced by wind or seismic loads.The bearing plate is in the form of rolled angle or a single flat ring with or without gussets.

Design of saddle supportsHorizontal cylindrical vessel are supported on saddles. These are placed as two positions.For large thin wall vessel or vessels under vacuum, it is necessary to provides ring supports.The location of the saddle supports should be equal form the centerline of the vessel or equaldistance from the tan line of the both side of vessel

Design of bracket or lug type supportsThese type can be easily fabricated form the plate and attach with the vessel wall withminimum welding length. They are made to rest on short columns or on beams of a structuredepending on the elevation required. They can be easily leveled.

Bracket supports are most suitable for vessel with thick walls.The main loads on the brackets supports are the dead weight of the vessel with its content andthe wind load.

Design of leg supportsStructural sections such as angle, channels can be directly welded to the pressure vessel shellto form vertical legs the legs is attached to the vessel by fillet welds.This type of support is use for small vessels. Several local stresses are produced at theconnection of the support to the vessel wall.

Which symbol indicates seam number?

Which symbol indicates item number?

Which symbol indicates nozzle?

What is full form of BOM?BOM means “bill of material”

Which details indicates in BOM?





Flatness

Circularity

Perpendicularity

Which is drawing projection method?

1. First angle

2. Third angle

1 st angle

Elevation axies

R.h.s.view plan l.h.s.view

3rd angle

R.h.s.view plan l.h.s.view

Axies



Elevation

Describe minimum thickness of shell or head?

The thick ness after forming and without for corrosion of any shell or head subject to pressureshall not less than ¼ (6 mm) for carbon and low alloy steel. Or 1/8 inch (3.2) for stainlesssteel and non-ferrous materials.Describe the selection of material thickness?

The selected thickness of material shell be such that the forming, heat treatment, and otherfabrication processes will not reduce the thickness of the material at any point below theminimum value required by the rules.Describe the corrosion allowance in design formula?

The dimensional symbols used in all design formulas thought out the division representdimensions in the corroded condition.Describe the lodes?

Internal and external pressure including static head. Weight of vessel and normal contentsunder operating or test conditions. Superimposed loads, such as other vessel operatingequipment, insulation, corrosion resistance or erosion resistant lining and piping. Wind loads,snow loads and earthquake loads.Why corrosion allowance is required in shell plates.

Vessel and part there of subject to loss of metal by corrosion , erosion ,mechanical abrasionsor other environmental effect shall have provisions made for such loss during the design orspecified life of the vessel by a suitable increase in or addition tool a thickness of the basemetal over that determined by the design formula or stress analysis.Why corrosion allowance is required in shell plate?

Material added an included for these losses need not be of the same thickness for all parts ofthe vessel. If different rates of attack are excepted for the various parts. No additional

thickness need be provided when previous experience in like service as soon that corrosiondoes not occur or is of only a superficial nature.Why required lining in the shell?

Corrosion resistance or abrasion resistance lining are these not integrally attach to the vesselwall. They are intermittently attach or not attach at all . In either case, such lining shell not begiven any credit when calculating the thickness of the vessel wall.Definition of the design pressure.

Design pressure is the pressure at the top of the vessel and which together with the applicableco incident (metal.) Temperature is stamped on the name plate. The pressure at the top of the



vessel is also the basis for the pressure setting of the pressure relief device protecting thevessel.Definition of the design temperature?

The temperature used in the design shall be based on the actual metal temperature expectedunder operating condition for the part considered at the designated coincident pressure.Definition of the operating pressure?

The operating pressure is the pressure at the top of the vessel at which it normally operators.The operating pressure shall not exceed the design pressure and is usually kept at a suitablelevel bellow it to prevent the frequent opening of the pressure relieving devices.Definition of the test pressure?

The test pressure is the pressure to be applied at the top of the vessel during the test. This pressure +any pressure due to static head at any point under consideration is used in theapplicable formula to check the vessel under test condition.

Which data indicates in design data?Design & construction code, design pressure, design temperature, operating pressure &temperature, hydro test temperature, corrosion allowance, radiography, joint efficiency,seismic code, wind data code is 875 specific gravity, post weld heat treatment etc.

What is the objective of stress analysis?1. To ensure that the in piping components in the system are within allowable limits2. To solves dynamic problems developed due to mechanical vibration, fluid hammer, pulsation, relief valves, etc.

What are the steps involved in stress analysis?1. Identify the potential loads that the piping system would encounter during the life of the

plant2. Relate each of these loads to the stresses and strains developed3. Get the cumulative effect of the potential loads in the system4. Decide the allowable limits the system can withstand with failure as per code

5. After the systems is designed to ensure that the stresses are within safe limitsWhat are the different types of stresses that may get generated within pipe during normaloperation?Axial stresses (tensile / compressive), shear stresses, radial stresses, hoops stresses.

How are the loads classified in stress analysis package?a. Sustained loads, b. Occasion loads, c. Displacement loads

What are the source of sustained loads generated in piping system?a. Pressure b. Dead weight of pipe and attachmentsSustained load is calculated asWeight of pipe with fluid + pressure load + load due to springs W + p1

How do you calculate the operating load?



W + p1 + t1T1- load due to thermal expansion.

Give some example for occasional loads.Wind, wave, earthquake

Mention some of primary loads.Dead weight, pressure, forces due to relief or blow down, force due to water hammer effects.

What is the ASME code followed for design of piping systems in process piping?B 31.3

While welding of pipe trunion to pipe/reinforcement pad you have to put a hole or leave some portion of welding why?For venting of hot gas which may get generated due to welding

What should be the radius of long radius elbow? 1.5 d

Normally where do we use the following?Eccentric reducers & concentric reducers1. Eccentric reducer = pump suction to avoid cavitations, to maintain elevation in rack2. Concentric reducers = pump discharge, vertical pipe line etc.

What do you mean by NPSH? Net positive suction head.

What is the thumb rule to calculate current required for welding?Current (amp) = [diameter of electrode (mm) *40] +20

What is the thumb rule to calculate spanner size for given bolt?1.5 * diameter of the bolt.

Which piping items will you drop down before conducting flushing and hydro test?Item like control valve, orifice plates, rot meters, safety valve, thermo wells are dropped orreplaced with temporary spool hydro test.

Why do we provide a dampner in the piping of reciprocating pump?To take care of pulsation.

Why do we provide full bore valve in connecting pipeline of launcher/ receiver?For pigging.

What is the astm code for the following?1. cs pipe = a106 gr.b2. cs fitting =a 234 gr. Wpb/wpbw3. cs flanges = a105As pipe = a 335 gr. P1/p11

Which parameters will u check during checking piping isometrics?



Bill of material, pipe routing wrt gad, supporting arrangement, details of insulation, hydrotest pressure, painting specs, and provision of vent and drains at appropriate location.

What is the ansi/ASME dimensional standard for steel flange & fitting?B 16.5

How can flanges be classified based on facing?Flat face, raised face, tongue and groove, ring type joint

What do mean by aarh?Arithmetic average roughness height.

Which are the different types of gaskets? Full face, spiral wound, octagonal ring type, metal jacketed and inside bolt circle.

What should be the relative hardness between thertj gasket and flange groove.For an rtj flange, the join ring should have a 30-40 Vickers hardness less than that of themating face of flange.

From which side of pipe will you take a branch connection?When fluid is gas, air or steam and cryogenic service – topside.When fluid is liquid – bottom side.

Why don’t we take a branch for cryogenic service from bottom side though the fluid is inliquid state?There is the chance of ice formation during normal operation and since ice flow from the bottom of the pipe it will block the branch pipe connection.

What is the ASME code followed for design of piping systems in Process Piping’s(Refineries & Chemical Industries)?

B31.3

What do you mean by following items?

I.)ISLB-400 ii) ISMB-600 iii) ISHB-350 IV) ISMC-300 v) ISJB-150 VI) ISLB-200

Vii) ISMB-450 viii) ISWB-400 ix) ISJC-200 x) ISLC-350 xii) ISMC-250Answer:

I. Indian STD light weight beam, Web size – 400

Ii. Indian STD medium weight beam, Web size – 600

Iii. Indian STD ‘H’ beam, Web size – 350

Iv. Indian STD medium weight channel, Web size –300

V. Indian STD junior beam, Web size – 150



Vi. Indian STD light weight beam, Web size – 200

Vii. Indian STD medium weight beam, Web size – 450

Viii. Indian STD wide flange beam, Web size – 400

Ix. Indian STD junior channel, Web size – 200

X. Indian STD light weight channel, Web size – 350

Xi. Indian STD medium weight channel, Web size – 250

What is this item?

I. ISA-100X100X12 ii) ISA-80X50X10 iii) ISLT-100X100

I. Equal angle size 100x12 THK

Ii. Unequal angle size 80x50x10 THK

Iii. Indian STD light weight tee bar size 100x100

What is the difference between stub in and stub on branches? Describe with Sketch. Whichone is preferred?

For branching of one size lesser of run pipe, Stub On is preferred. For other branching

Less than one size of run pipe stub in is preferred. The Design is based on ANSI B 31.3

What is the difference between Pipe and Tube?

Pipe is identified by NB and thickness is defined by Schedule whereas Tube is

Identified by OD.

From which size onwards NB of pipe is equal to OD of Pipe?

From the size 14” and onwards NB = OD of pipe.

Write down the outside diameter of following pipe?

I. 3 inch ii) 6 inch iii) 10 inch IV) 14 inch

I. 3 inch = 88.9mm ii) 6 inch = 168.28mm

Iii) 10 inch = 273.06mm IV) 14 inch = 355 mm (OD= Size X 25.4)

What is the difference between machine bolt and stud bolt?

Machine bolt has a head on one side and nut on other side but stud bolt have nuts on

Both sides.



What is soluble dam?

Soluble dam is a water-soluble material used for restricting the purging gas within the

Pipe.

While welding of pipe trunnion to pipe/reinforcement pad you have to put a hole Or leavesome portion of welding why?

For venting of hot gas which may get generated due to welding

What do you mean by following type of welding?

I. SMAW ii) TIG

Ii. SMAW = SHIELDED METAL ARC WELDING. iii. TIG = TUNGSTEN INTER GAS

WELDINGFind out the elevation of marked point ‘A’

Elevation of marked point ‘A’ is 100.050

What should be the radius of long radius elbow?

1.5D (Where “D” is the diameter of the pipe)

Normally where do we use the following?

I. Eccentric reducer’s ii) Concentric reducersI. Eccentric reducers = Pump suction to avoid Cavitation, to maintain elevation (BOP) inRack.

Ii. Concentric reducers = Pump discharge, vertical pipeline etc.

Concentric reducer is used in pump suction. (Yes / No). Explain.

No. Air pockets may form if concentric reducer is used at pump suction, which results in

Cavitation, and cause damage to Pump. To avoid this problem, Eccentric Reducer withFlat Side up (FSU) is used in Pump Suction.

What do you mean by Cavitation in Pump?

A pump is designed to handle liquid, not vapor. Vapor forms if the pressure in the

Pump falls below the liquid’s vapor pressure. The vapor pressure occurs right at the

Impeller inlet where a sharp pressure drop occurs. The impeller rapidly builds up the

Pressure which collapses vapor bubbles causing cavitation and damage. This is



Avoided by maintaining sufficient NPSH.

(Cavitation implies cavities or holes in the fluid we are pumping. These holes can also

Be described as bubbles, so cavitation is really about the formation of bubbles and their

Collapse. Bubbles form whenever liquid boils. It can be avoided by providing sufficient

NPSH.)

What do you mean by NPSH? How do you calculate it?

W.P EL. “A”

W.P.EL –100.050

3 Æ Pipe

5000

50

Slope 1:100. NPSH: Net Positive Suction Head. NPSH is the pressure available at the pumpsuction

After vapor pressure is subtracted.

It is calculated as : Static head + surface pressure head - the vapor pressure of your

Product - the friction losses in the piping, valves and fittings.

It thus reflects the amount of head loss that the pump can sustain internally before

Vapor pressure is reached.

What is the ASTM code for the following?

I. CS pipe ii) CS fittings iii) CS flanges iv) AS pipe P5/P11 v) Cast CS Valves

I. CS pipe = A106 Gr.B

Ii. CS fittings = A234 Gr.WPB/WPBW

Iii. CS flanges = A105

Iv. AS pipe = A335 Gr P1/P11

V. Cast CS Valves = A216 Gr.WCB

What is the thumb rule to calculate spanner size for given bolt?

1.5 x diameter of Bolt



What is the thumb rule to calculate Current required for Welding?

Current (Amp) = [Diameter of Electrode (mm) X 40] + 20

What is steam tracing? How do we decide the location of SSM & CRM?

Steam Tracing is a process which is used to prevent the fluid passing through a Process linefrom freezing by keeping the temperature high enough for free flow of fluid And thusmaintaining pump ability. SSM and CRM are generally located 38M max for open systemand 24 M max for Closed system when we use LP Steam up to 3.5 kg/sq cm. As a heatingmedia.

Which piping items will you drop down before conducting Flushing and Hydro test?

Items like Control Valve, Orifice plates, Rota meters, safety valves , Thermo wells

Are dropped or replaced with temporary spools before hydro test.Why do we provide a Damper in the Piping of Reciprocating Pump?

To take care of Pulsation.

Why do we provide Full Bore Valve in connecting pipeline of Launcher /Receiver?

For Pigging.

Which parameters will u check during checking Piping Isometrics?

Bill of Material, Pipe Routing wrt GAD, Supporting arrangement, details of

Insulation, hydro test pressure, painting specs and provision of Vent and Drains at

Appropriate locations.

What is the ANSI/ASME dimensional standard for steel flanges & fittings?

B16.5

How can flanges be classified based on facing?

A. Flat Face b. Raised Face c. Tongue and groove d. Ring type joint

What do you mean by AARH (Flange Finish)?

Arithmetic Average Roughness Height.

Which are the different types of Gaskets?

Full Face, Spiral Wound, Octagonal Ring Type, Metal Jacketed and Inside Bolt Circle.

What should be the relative hardness between the RTJ gaskets and flange Groove



For a RTJ flange, the joint ring should have a 30-40 Vickers hardness less than

That of the mating face of flange. (Brinnel hardness for RTJ groove shall be 20-50 BHN

More than the corresponding gasket hardness)

From which side of pipe will you take a branch connection?

When Fluid is Gas, Air or Steam and Cryogenic Service – Topside.

When Fluid is Liquid – Bottom Side.

Why don’t we take a branch for Cryogenic Service from bottom side though the Fluid is inliquid state?

There is the chance of Ice formation during normal operation and since ice flows

From the bottom of the pipe it will block the branch pipe connection.

Why do we provide Drip Leg in Steam Line?

To remove Condensate when there is a rise in the pipe along the flow direction. If

We do not provide the drip leg in steam line, the condensate which forms inside the pipe

Will result in Water Hammer effect causing damage to piping system.

How do you support any small size HDPE/PVC (Plastic) pipe?

It should be supported continuously by using channel or Angle so that line should

Not Sag or fall from the sleeper/rack due to uneven expansion because of Hot Temp.

Why do we provide High Point Vent (HPV) and Low Point Drain (LPD) in piping?

HPV – for removing Air during Hydro-test. LPD – for draining water after conductingHydro-test.

Which standard and codes will you refer while designing the piping?

Following are the codes and standards –

· ASME SEC I: Rules for construction of Power Boilers.

· ASME SEC VIII: Rules for construction of Pressure Vessels.

· ASME B 31.1: Power Piping

· ASME B 31.3: Process Piping

· ASME B 31.4: Pipeline Transportation system for liquid hydrocarbon and

Other liquids.



· API RP 520: Sizing selection and installation of Pressure Relieving

Devices in refineries

· API Std 610: Centrifugal Pumps for Petroleum, Heavy Duty Chemical and

Gas Industry Services.

· ANSI/NEMA SM 23: Steam Turbines for Mechanical Drive Services.

· API Std 617: Centrifugal Compressor for Petroleum, Chemical and Gas

Industry Service.

· EJMA: Expansion Joints Manufacturer’s Association.

· OISD – 118: Layout for Oil and Gas Installations.

· IBR: Indian Boiler Regulations.

· NACE MR – 0175: Sulfide Stress Cracking Resistant Metallic Materials for Oilfield

Equipment.

· NACE MR – 0284: Evaluation of Pipeline and Pressure Vessel Steel for

Resistance to Hydrogen Induced Cracking.

· NACE TM – 0177: Laboratory Testing of Metals for Resistance to Sulfide StressCracking in H2S Environment.

What do you mean by IBR and which lines comes under IBR purview?

IBR: Indian Boiler Regulation Act.

Steam lines with conditions listed below comes under IBR purview –

· Lines for which design pressure is 3.5 kg/sq cm and above.

· Line size above 10” having design pressure 1.0 kg/sq cm and above.· Boiler feed water lines to steam generator, condensate lines to steam generator and Flashdrum.

What are Weldolet and Sockolet? And where they are used?

Weldolet and Sockolet are basically self-reinforced fittings.

Weldolet is used for Butt weld branch connection where standard tee is not

Available due to size restrictions and the piping is of critical / high pressure service.



Sockolet is used for socket welding branch connection, which require reinforcing Pad.

What is the MOC for Superheated high pressure Steam Lines?

A 335 Gr P I / P II

Composition: 0.5 Mo (P1) /1.25 % Cr-.5 Mo (P11)

What is the normal upstream and downstream straight length of orifice flow Meter?

Answer: Upstream - 15D Downstream - 5D

What are the essential data required for the preparation of equipment layout?

1) PFD and P&ID 2. Project Design data 3. Equipment Sizes & Buildings

What are the various statutory requirements to be considered during layout?

State Industrial Development Corporation (SIDC)

Central / State Enviromental Pollution Control Boards (PCBS)

Factory Inspectorate

State Electricity Boards

Chief Controller of Explosives (CCOE)

Static & Pressure Vessel Rules (SMPV)Tariff Advisory Committee

Aviation Laws

Chief Inspector of Boilers (CIB)

Oil Industry Directorate (OISD)

Food and Drug Administration (FDA)

Ministry of Environment and Forest (moef)What do you mean by Composite Flange?

The flange that is made up of more than one MOC is called a Composite flange.

A. Lap Joint Flanges Insert Flanges are a specialty in the arena of pipe size flanges andconsist of two parts - the insert and the flange ring. The flange ring is the outer part of theinsert flange Assembly, containing the bolt holes. The two piece construction of the insertflange also offers the economy of matching the Insert material to the process pipe (usually

some corrosion resistant alloy) while the Outer flange ring may be manufactured from steel.



When the environment requires the Flange ring to be made of some alloy the rotating featureis still maintained.

B. RF flanges with Raised of one MOC and rest of the flange with different MOC

C. RF blind flange with an overlay of 90/10 Cuni for Sea water service.What do you mean by Insulated Joint?

Insulating Joints are a prefabricated, non-Separable union used to isolate specific sections of

Pipelines to prevent corrosion caused by stray Electrical currents or interference from otherPipelines and power transmission cables.

What are Insulating Gasket Kits?

Insulation gasket kits are designed to combat the effects of corrosion often found in flanged pipe systems. Galvanic corrosion between dissimilar metal flanges (flow of Currents), flangeinsulation associated with cathodic protection of underground piping Are also the placeswhere Insulating gasket kits are used. It consists of Gasket Neoprene faced Phenolic /GlassReinforced

Epoxy(G10) Insulation sleeve Reinforced Phenolic/Nylon/Polyethylene/(G10)

Insulation washer Reinforced Phenolic/Nylon/Polyethylene/(G10)

Plated Washer Electro plated steel washer

What is the min. Distance to be maintained between two welds in a pipe?

The rule of thumb is that the minimum distance between adjacent butt welds is 1D. If not, itis never closer than 1-1/2". This is supposedly to prevent the overlap of HAZ s. Minimumspacing of circumferential welds between centerlines shall not be less than 4 Times the pipewall thickness or 25 mm whichever is greater.

What are the different hardness tests carried out?

Brinell hardness Test

Rockwell Hardness test

Vicker Hardness Test

What is the relation between Brinell Hardness No and Rockwell Hardness No?

22 HRC (Rockwell Hardness) = 238 BHN (Brinell hardness No)

Harder



Piping which is recognized as providing the most Uniform application of heat to the process,as well As maintaining the most uniform processing

Temperatures where steam tracing is not capable of maintaining the temperature of fluidconstant. Usually used for molten sulphur, Polymers service..

During fabrication you observed that one small crack has appeared on a freshplate, what typeof measure you will take to obtain desired quality with minimum wastage?

First identify the exact length of crack by DP test. Drill on the end point to resistfurtherCrack. Remove the crack portion by cutting the strip.

Describe different types of destructive and non-destructive tests?

DESTRUCTIVE TEST: Bend test, tensile test, Impact test, and Hardness test.

NON-DESTRUCTIVE TEST: DPT, MPT, Radiography and ultrasonic test What is mean by ‘PWHT’? Why it is required?

“POST WELD HEAT TREATMENT” This is done to remove residual stress left in the Jointwhich may cause brittle fracture.

What is the minimum thickness of pipe that requires stress relieving to be done as per B31.3?

19 mm thk.

What is the difference between Thermostatic and Thermodynamic Steam Trap?

Thermostatic Trap is actuated by Temp differential and is economic at steam Pressure lessthan 6 PSI. It is operated by the movement of liquid filled bellows or by Bimetal elementwhich may get damaged by Water Hammer.

Thermodynamic traps are most suited to applications where the pressure downstream of trapis always less than about ½ the upstream pressure. These are suitable for Pressure higher than8 PSI. Water hammer doesn’t affect it.

What is the Code for Sour Service?

Code for Sour Service is NACE (NACE MR – 0175)

NACE: National Association of Corrosion Engineers.

How much should be the pressure for Hydro-Test?

Hydro test pressure should be calculated as follow except as provided against

Point no-4.

1. 1.5 Times of Design Pressure.

E 3180600



E 3181400 1” line.2. For a design temperature above the test temperature, minimum test pressure can

Be calculated as:

Pt = (1.5 X P X St) / SWhere:-Pt:

Minimum Test Pressure.

P: Internal design pressure.

St: Allowable stress at test temperature.

S: Allowable stress as design temperature.

(see SE in table A-1 or S in table B-1/2/3).

3. If a test pressure as per above would produce a stress in excess of the yield

Strength at test temp. The test pressure may be reduced to maximum pressure that will

Not exceed the yield strength at test temp.

4. If the test pressure of piping exceeds the vessel pressure and it is not consideredPracticable to isolate piping from vessel, the piping and vessel may be tested together At test pressure of the vessel when approved by owner and provided the test pressure For vessel isnot less than 115% of piping design pressure adjusted for temperature as Per point no 2.

How do you calculate the pipe spacing?

Pipe Spacing (mm) = (Do + Dt) / 2 + 25mm + Thickness of Insulation (mm).

Where: D0: OD of Small size Pipe (mm).

Dt: OD of Flange of Large size Pipe (mm).

144. How do you calculate the width of Pipe rack?

Ans: W = (f X n X s ) + A + B.

Where: s=

F: Safety Factor

= 1.5 if pipes are counted from PFD.

= 1.2 if pipes are counted from P&Id.

N: number of lines in the densest area up to size 450



NB

= 300 mm (estimated average spacing)

= 225 mm (if lines are smaller than 250 NB)

A: Additional Width for –

· Lines larger than 450 NB.

· For instrument cable tray / duct.

· For Electrical cable tray.

S: 300 mm (estimated average spacing)

: 225 mm (if lines are smaller than 250 NB)

B: future provision. = 20% of (f X n X s) + A

Which fluid is used in Heat Exchanger in shell side and tube side?

Generally corrosive fluid is used from the tube side (as tube can be easily replaced) andcleaner fluid is used from shell side. Sometimes Hot fluid is also used from the shell side.

What is Reynold’s number and what is the value of Reynolds’s number up to Which the flowis laminar?

It’s a dimensionless number to classify the nature of flow.Re=_YG__

Where: Re: Raynold’s no.

___DVV_'HQVLW\_RI_IOXLG_

D: diameter of Pipe.

V: average velocity of fluid.

__9LVFRFLW\_RI_IOXLG_

Flow is laminar upto Re=2100

What are Glandless Piston Valves? Where these are used?

Glandless piston valves are maintenance free valves used in the steam service.

How do you carry out Estimation?

Input from Bid: -·



P&Id, Line list, Temperature, Pressure.

· Overall Plant Layout and Piping corridor plan.

· Scope of work and the Specifications for the Job.

· Specifications for materials like PMS and VMS.

Value Addition: -·

Items like Valves, Flanges, Speciality items, Reducers can be estimated from P&Id.

· Length of Pipes, Elbows, and Width of Pipe Rack can be estimated by referring P&Id andOverall Plot Plan.

· No of Tires (on rack) can be estimated by referring the spacing required for pipes and also

the space available.· MTO for Steam Traps, Valves (for Vent and drain) can be calculated by using ThumbRules.

Loads: -·

Hydro Test Loads: Can be estimated by assuming all the Pipes (on a grid) empty

Except some bigger size lines filled with Water.

· Actual Operating Loads: Gas lines to be considered as empty and rest of the lines To beconsidered as filled with the Fluid (which they are suppose to carry in Operating condition).

The loads whichever is higher from above two cases should be referred for Structuralloading. Stress

What is the objective of stress analysis?

1. To ensure that the stresses in piping components in the system are within

Allowable limits

2. To solve dynamic problems developed due to mechanical vibration, fluid

Hammer, pulsation, relief valves, etc

3. To solve problems associated due to higher or lower operating temperature such As a)Displacement stress range b) Nozzle loading on connected equipments c) Pipe Displacementsd) Loads & moments on supporting structure

What are the steps involved in stress analysis (or any stress package carries out)?

1. Identify the potential loads that the piping system would encounter during the life

Of the plant



2. Relate each of these loads to the stresses and strains developed

3. Get the cumulative effect of the potential loads in the system

4. Decide the allowable limits the system can withstand without failure as per code

5. After the system is designed to ensure that the stresses are within safe limits

What are the different types of stresses that may get generated within pipe during normaloperation?

Axial Stresses (Tensile / Compressive), Shear Stresses, Radial Stresses, HoopsStresses.

How are the loads classified in stress analysis package?

a. Sustained Loads 2. Occasional Loads 3. Displacement Loads (Self-limiting Stresses due to

thermal effects) what are the Inputs for stress analysis of a piping system I) Pipe Size ii) FluidTemperature iii) Pipe Material

Iv) Design pressure v) Insulation Thickness

Vi) Specific gravity vii) Friction coeff. Viii) Model

What are the sources of sustained loads generated in piping system?

a. Pressure b. Dead weight of Pipe and attachments Sustained load is calculated as Weight ofPipe with Fluid + Pressure load + Load due to springs

W+P1

How do you calculate the operating load?

W+P1+T1

T1 – Load due to thermal expansion

Give some Examples for occasional Loads.

Wind, wave & earthquake

Mention some of Primary Loads (Have their origin in force)

Dead Weight, Pressure, forces due to relief or blow down, force due to water hammerEffects.

Mention some of secondary Loads (Have origin in displacement)

Force on piping due to tank settlement Vessel nozzle moving up due to expansion of vesselPipe expansion or contraction Vibration due to rotational equipment’s

What is the failure theory subscribed under ASME B31.3?



(i) Maximum principal stress theory (Rankines Theory)

What are the types of failures encountered in Piping?

1. Catastrophic Failure 2. Fatigue Failure

Select the failure stress range for fatigue failure due to thermal expansion asPer B31.3

(i) (1.6Sc+1.6Sh)f

(ii) 0.78 Sh

(iii) (1.25 Sc+0.25Sh)f

(iv) Sc+Sh

Answer: (III)

Sc and Sh –Basic Allowable material stress in cold & hot condtions respectively.

F ---- Is the stress range reduction factor (1 for 7000 cycles

What is desired life cycle for Piping in operation?

Desired life cycle for Piping in operation is 20 Years (7000 Cycles).

The normal no. Of cycles for which the displacement or thermal stresses are

Designed is7000 cyclesHow do you calculate the stress developed due to thermal expansion?

Stress developed = E x e/L

E – Young’s Modulus

E- Increase in length due to thermal expansion

L – Original Length of the pipe

How do you calculate the thermal expansion in a pipe?E= __[_/_[_5LVH_LQ_7HPSHUDWXUH __±_&R_HIILFHLQW_RI_H[SDQVLRQ

L- Length of pipe

What do you mean by Stress Intensity Factor (SIF)? Give some examples.

Stress Intensity Factor (SIF) is the ratio of maximum stress intensity to normal stress. It isused as safe factor to account for the effect of localised stress on piping under Respectiveloading. In piping it is applied to welds, fittings, branch connections etc. where stress



concentration and possible fatigue failure may occur. Egg: SIF for Reducer and Weld neckFlange: 1.0 SIF for socket weld flange: 1.3.

Which is the Criteria for Pipe Supporting?

Following are the points which should be taken into account for proper supporting· Load of bare pipe + fluid + insulation (if any).

· Load of bare pipe + waterfill.

· Load of valves and online equipment and instrument.

· Thermal loads during operation.

· Steam out condition, if applicable.

· Wind loads for piping at higher elevation, if required.

· Forced vibration due to pulsating flow.

Bare pipe with size above 12” shall be supported with Pad or Shoe

What is the basic span of supports for 2”/6”/10”/24” pipe?

Basic Span is 5.5m / 9m / 11.5m / 15m respectively.

How do we decide the anchor / cross guide and guide for offsite rack piping

Anchor is provided to restrict all the axial and rotational movements of Pipe, whereas CrossGuide is provided to restrict displacements of Pipe along with the axis Perpendicular to itscenterline and Guide is provided to restrict the longitudinal Movements of pipes along withits axis.

What are the things to be taken care of while doing pump piping?

Pipe strain may distort equipment alignment, so welding should be done in such a way thatthe tension in the equipment flange is minimised

What is the Steam out condition?

Hydrocarbon lines are usually subjected to Steam Out condition and designed and anlysed atlow pressure steam design temperature (should be minimum 180 Degree C) or design temp.Whichever is more. Lines having negative design temp. Is Analysed for both conditionsseperately.

Where do you provide Anchor and Slotted Support of Heat Exchanger?

Anchor support of Heat exchanger is provided on the side from which Tube Bundle will be pulled out for the purpose of Maintenance work also it is based on the Growth of theconnecting piping as exchanger should grow with the piping.



What do you mean by Hoop Stresses and how do you calculate it?

Stresses which are generated circumferentially due to the action of Internal Pressure of pipeare called as Hoop Stress. It is calculated by

Hoop Stress (Sh) = Pdo / 4tWhere P = Force Acting from Inside.

Do = OD of Pipe.

T= Pipe Thickness.

How does Hoop Stress affect the system?

As per membrane theory for pressure design of cylinder, as long as hoop stress is less than

yield stress of Moc, the design is safe. Hoop stress induced by thermal Pressure is twice theaxial stress (SL). This is widely used for pressure thickness

Calculation for pressure vessel.

What is the design standard followed for the calculation of allowable forces /Moments innozzles of centrifugal compressor & Steam turbines nozzle?

For strain sensitive equipment piping to be routed and supported to limit nozzle Loadings andmoments in equipment within allowable limits furnished by respective Vendors or in absenceof vendor data API 560/610/615/621/661 & NEMA SM23.

NEMA – SM 23 (Referred by API 617) is used for compressor & steam turbine nozzle.

What is the mill tolerance to be considered for the thickness of pipe during Stress analysis as per ASME B31?

12.5%

What is the purpose of providing Graphite Pads in supports below shoes?

To reduce the friction factor. The co-efficient of friction for Graphite Pads is 0.1

How is piping to Tank inlet nozzle is supported and why?

Piping to Tank Nozzle is supported with Spring type support (first support from Nozzle) inorder to make the Nozzle safe from the loads which occurs due to the Displacement of pipe(thermal expansion of pipe / tank material, tank settlement etc.

What are the two types of flexible spring hangers?

1. Constant Spring and 2. Variable Spring

What is the difference between Variable Spring Hanger and Constant spring hanger?



Variables use coiled springs to support a load and allow movement. The

Resistance of the coil to a load changes during compression, which is why these devices arecalled "variables". Constant Spring Hanger provides constant support force for Pipes andequipment subjected to vertical movement due to thermal expansion at Locations wheremaintaining a constant stress is critical. This constant resistance is achieved by having twomoment arms pivoted about a common point. The load is suspended from one of these arms,and a spring is attached to the other. With an Appropriate choice of moment arms and spring properties, a resisting force can be provided that is nearly independent of position. Constantsupport hangers are principally used to support pipes and equipment subjected to verticalmovement due to thermal expansion at locations where transfer of Stress to other supports orequipment can be critical. The maximum recommended Variation according to MSS standardfrom the operating load is 25% for variable spring Hangers. If the variation exceeds 25%, aconstant support hanger should be used.

The constant resistance to a load is achieved by combining a spring coil with a cam whichrotates about a main pivot point. The cam is designed such that the distances from the main pivot changes to compensate for the variable resistance during Compression of the coil. TheMSS standard provides for a tolerance of 6% in the Constant load through the travel range.Constant support hangers are designed per MSS, ANSI, and ASME standards.

The sizing of constants primarily depends on the total travel and load.

How much should be the difference between the load which will be taken by variable SpringHanger during Cold and Hot condition of Pipe?

It should be Maximum 25% of Load for which spring is designed.

Differentiate between static load and dynamic load.

A piping system may respond far differently to a dynamic load than it would to a Static Loadof the same magnitude. Static loads are those which are applied slowly enough that thesystem has time to react and internally distribute the loads, thus remaining in Equilibrium. Inequilibrium, all forces and moments are resolved (i.e., the sum of the Forces and moments arezero), and the pipe does not move. With a dynamic load—a load which changes quickly with

time—the piping system may Not have time to internally distribute the loads, so forces andmoments are not always Resolved—resulting in unbalanced loads, and therefore pipemovement. Since the sum Of forces and moments are not necessarily equal to zero, theinternally induced loads Can be different—either higher or lower—than the applied loads.

Give different types of dynamic loads with example

1. Random – Wind, Earthquake.2. Harmonic – Equipment Vibration, Pulsation, AcousticVibration Impulse – Fluid Hammer, relief valve opening, slug flow

What is Dynamic Analysis and why it is used?



Dynamic analysis is performed for all two phase lines in order to ensure that the Linesupported is safe from vibrations loads which may occur during normal operation as Well asin startup or any upset condition.(Diesel mixed with hydrogen in DHDT process)

What is WRC 107 / WRC 297?

Localized stresses at Nozzle to Shell is calculated by WRC 107 / 297 and these Computedstress values shall be limited in accordance with ASME Sec VIII for Pressure Vessels.

How to get the Foundation Loads?

Foundation Loads for pipe rack should include the loads of Pipes, Cable Trays andInstrumentation duct at that location and also the design load for future tier shall be Full loadof the most heavily loaded tier in addition to all other wind/seismic/fraction and Pipingthermal loads for future pipes.

Load of pipes filled with water (Largest of1St Case – During hydrotesting dead Weight(wt/m X piperack spacing) of pipes + 2 –3 maximum size pipes filled with water

2NdCase – Actual commissioned condition except the gas lines ) + Proportionate wt of Extraspace required by client (normal 30%) + Load of 1 heavily loaded tier + Electrical Cables +Instrument duct + Guide load for 50% of lines

Guide Load = 0.3X (Dead wt of pipes at including water)

The maximum induced thermal loads on the Anchor at the battery limit shall be limited To F

in kg <= 150 X NB of pipe in inches (It should be <2 tonnes)M in Kgm <=75 X NB of pipe in inches.

Horizontal Load = 0.3 X (Dead wt of pipes including water)

This load is used for designing of foundation bolts.

Foundation loads for any vessel having agitator mounted on top should contain weightOftank at operating or design condition (whichever is more) plus 20% of it for dynamicLoading.

What is the maximum expansion absorbed in loops in normal design?10 Inches

What is the limiting factor in deciding the length of the spool in Jacketed Piping?

Force exerted by dissimilar expansion of inner pipe = Force exerted by dissimilar Expansionof jacket pipe the stress developed due to this should be within limits as per ANSI B31.3(Also fabrication constraints)

What is the factor to be checked concerning the expansion of header attached To air cooler

piping?



Vendor drawing to be checked to see how much movement is permitted to Compensate lineexpansion. To accommodate the diff. Expansion between inlet and Outlet (The inlettemperature >The outlet temperature) offset can be built in to outlet Piping to compensate fordiff. expansion Since the tubes are of floating design the nozzle flange is of 150# and loads

transferred are to be kept minimum.Since the tubes are of floating design, the nozzle flange is150#. Load of the nozzle Tobe kept minimum.

What is the maximum no. Of cell nozzles connected to a single header of air Cooler pipingheader in normal practice?

Six nos.

What is fluid hammer and how it is generated?

When the flow of fluid through a system is suddenly halted at one point, through Valve

closure or a pump trip, the fluid in the remainder of the system cannot be stoppedinstantaneously as well. As fluid continues to flow into the area of stoppage (upstream of thevalve or pump), the fluid compresses, causing a high pressure situation at that Point.Likewise, on the other side of the restriction, the fluid moves away from the Stoppage point,creating a low pressure (vacuum) situation at that location. Fluid at the Next elbow or closurealong the pipeline is still at the original operating pressure,

Resulting in an unbalanced pressure force acting on the valve seat or the elbow. The fluidcontinues to flow, compressing (or decompressing) fluid further away from the point of flowstoppage, thus causing the leading edge of the pressure pulse to move through the line. As the

pulse moves past the first elbow, the pressure is now equalized at each end of the pipe run,leading to a balanced (i.e., zero) pressure load on the first Pipe leg. However the unbalanced pressure, by passing the elbow, has now shifted to the second leg. The unbalanced pressureload will continue to rise and fall in sequential

Legs as the pressure pulse travels back to the source (or forward to the sink). The ramp Uptime of the profile roughly coincides with the elapsed time from full flow To low flow, suchas the closing time of the valve or trip time of the pump. Since the Leading edge of the pressure pulse is not expected to change as the pulse travels through the system, the rampdown time is the same. The duration of the load from Initiation through the beginning of thedown ramp is equal to the time required for the Pressure pulse to travel the length of the pipeleg.

What is the purpose of expansion bellows?

Expansion bellows are used absorb axial compression or extension, lateral shear Or angulartorsion developed in the pipes (specially near nozzles)

What should be the material of shoes for supporting AS pipes & why?



If CS shoes are used Pad in contact with the pipe to be of Alloy steel to avoid Dissimilarwelding at pipe. To avoid alloy steel welding and dissimilar welding fabricated Clamps eitherof CS or SS can be used.

What is the allowable stress range for CS pipes?

2070 kg/cm

What are sway braces?

Sway Braces are essentially a double-acting spring, housed in a canister. Unlike Variableeffort supports, Sway Braces are not intended to carry the weight of pipework; their purposeis to limit undesirable movement. Sway Braces act like a rigid strut until a Small preload isreached, where after the restraining force increases in proportion to the applied deflection.

Fig. 1. Undesirable movement can occur due to many phenomena, such as wind loading,

Sympathetic vibration, rapid valve closure, relief valves opening, two phase flow orEarthquake. It may be necessary to limit this type of deflection to prevent the Generation ofunacceptable stresses and equipment loadings.

The Sway Brace is a cost-effective means of limiting pipework deflection. It should be notedhowever that it does provide some resistance to the thermal movement of the Pipework andcare should be taken when specifying to ensure that this is acceptable. Installation of SwayBraces will have the effect of raising the fundamental frequency of Vibration of a pipeworksystem; this is likely to reduce undesirable deflections. Sway Braces are often used to solveunforeseen problems of resonant vibration. For Situations where the resistance to thermal

movement provided by Sway Braces is Unacceptable, you are referred to Pipe SupportsLimited’s range of hydraulic snubbers

And dampers.

In an offsite pipe rack change in direction during analysis it is found two adjacent pipes arehaving unequal expansion with the inner pipe having 50cm thermal expansion. What can bedone to eliminate collision during hot condition?

Use Cold Pull technique. Calculate the thermal expansion of the inside pipe, cut an Equallength form the elbow joint and then reweld with a shorter length to take care of Expansion inhot condition.

What are the Insulation material used for piping systems?

1. Fibrous – Rock & Glass Wool

2. Rigid - Calcium silicate, Polyisocyanurate, cellular Glass

Documents

Interview Queries