QUESTIONS RELATED TO CODES & STANDARD:
1. What is the ASME code followed for design of piping systems in Process piping
(Refineries & Chemical Industries)?
Answer :B 31.3
2. Which American institute standard does piping engineer refer?
Answer:
A. The American Petroleum institute (API).
B. The American Iron & Steel institute (AISI).
C. The American Society for Testing and materials (ASTM).
D. The American National standard institute (ANSI).
E. The American welding society (AWS).
F. The American Water Works Association (AWWA).
G. The American Society for Mechanical Engineers (ASME).
3. What is the different ASME 31 code for pressure piping?
Answer:
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.
4. What are the different sections of ASME code? Where these sections are
reffereAnswer:
d?
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 of heating
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.
5. Which American standard is reffered for selection of following piping
element? A. Flanges B. Butt Welded fittings C. Gasket D. Socket & Threaded fittings E. Valves F. Pipes.
Answer:
A. Flanges :
I. ASME B16.1 : Cast iron pipes flanges & flanged fittings.
II. ASME B16.5 : Carbon steel pipes flanges & flanged fittings.(Up to 24”)
III.ASME B16.47 :Large Diameter steel flanges. (Above 24”)
B. Butt welded fittings :
I. ASME B16.9 : Steel butt welding fittings.
II. ASME B16.28 : Butt-welded short radius elbows & returns bends.
C. Gasket :
I. ASMEB16.20/API-601:-Metallicgasketsforpipeflanges-Spiralwound,
Octagonal ring Joint & Jacketed flanges.
II. ASME B16.21 : Non metallic gasket.
D. Socket & Threaded fittings :
I. ASME B16.11 :Forged steel socket welding & threaded fittings.
E. Valves :
I. ASME B16.10 : Face to face & end to end dimension of valves.
II.ASME B16.34 :-Flanged & butt-welded ends steel valves (Pressure &
Temperature ratings) except Ball, Plug & Butter fly Valves.
F. Pipes :
I.ASME B36.10 : Welded & Seamless wrought iron pipes.
II. ASME B36.19 : Stainless steel pipes.
QUESTIONS RELATED TO MATERIALS:
1. What is the ASTM code for the following?
Answer:
A. Pipes :
I. Carbon Steel :ASTM A53 Gr. A/B, ASTM A106 Gr. A/B/C, ASTM A333Gr.1/Gr.6
II. Alloy Steel : ASTM A335 Gr.P1/P2/P5/P7/P9/P11/P12/P22.
III. Stainless Steel :ASTM A312TP304/TP304L/TP304H/TP308/ P310/TP316/TP316L/TP316H/TP317/TP321/TP321H/TP347/TP347H/TP348/TP348H.
IV. Nickel Steel : ASTM A333Gr.3/ Gr.8.
B. Tubes:
I.Carbon Steel : ASTM A178/179/192, ASTM A334 Gr.1/6.
II. Alloy Steel :ASTM A161T1, ASTM A213T1/T2/T5/T7/T9/T11/T12/T22.
III.Stainless Steel :ASTM A213 TP304/TP304L/TP304H/TP310/TP316/TP316L/
TP316H/TP317/TP321/TP321H/TP347/TP347H/TP348/TP348H,ASTM A608 HK40.
IV. Nickel Steel :ASTM A334Gr.3/Gr.8
C. Wrought Iron fittings :
I. Carbon Steel :ASTM A234Gr.WPA/B, ASTM A420 Gr.WPL6.
II. Alloy Steel :ASTM A234 WP1/WP5/WP7/WP9/WP11/WP12/WP22.
III. Stainless Steel :-ASTM A403 WP304/WP304L/WP304H/WP309/WP310/WP316/
WP316L/WP316H/ WP317/WP321/WP321H/WP347/WP347H/ WP348.
IV. Nickel Steel :ASTM A420WPL6/WPL8.
D. Forged Fittings :
I. Carbon Steel :ASTM A181. ASTM A105, ASTM A350 LF1/2.
II. Alloy Steel :ASTM A182F1/F2/F5/F7/F9/F11/F12/F22.
III. Stainless Steel :-ASTM A182F6/F304/F304L/F304H/F310/F316/F316L/
F316H/F321/F321H/F347/F347H/F348.
IV. Nickel Steel :ASTM A350 LF3, ASTM A522.
E. Cast Fittings:
I. Carbon Steel :ASTM A216, ASTM A352 LCB/C.
II. Alloy Steel :M A217 WC1/WC6/WC9/C5/C12.
ASTIII. Stainless Steel :-ASTM A217 CA15, ASTM A296 CA15, ASTM A351 CF8/
CF3/CH20/CK20/CF 8M/CF 3M/CF 8C/HK40.
Nickel Steel :ASTM A352LC3.
IV. F. Plates:
I. Carbon Steel :ASTM A285, ASTM A515, ASTM A516.
II. Alloy Steel :ASTM A387 Gr.2/Gr.5/Gr.7/Gr.9/Gr.11/Gr.12/Gr.22.
III. Stainless Steel :ASTM A240TP410/TP405/TP430/TP304/TP304L/TP309/
TP310S/TP316/TP316L/TP317/TP321/TP347/TP348
IV. Nickel Steel :ASTM A203 Gr.D/Gr.E, ASTM A353.
2. 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 %
III. ASTM A106 Gr. C – 0.35 %
3. What is the difference between pipe specification ASTM A312 TP 304 & ASTM
A312 TP304L, ASTM A312 TP 316 & ASTM A312 TP 316L?
Answer:
Difference is due to the Carbon content. The Letter “L” denotes lower percentage of carbon.
% of carbon content in :
I. ASTM A312 TP 304 -0.08 %
II. ASTM A312 TP 304L-0.035%
III. ASTM A312 TP 316 -0.08 %
IV. ASTM A312 TP 316L-0.035%
QUESTIONS RELATED TO PIPE FITTINGS:
1. How can flanges be classified based on Pipe Attachment?
Answer:
Flanges can be classified based on pipe attachment as: -
A.Slip – on. : The Slip-on type flanges are attached by welding inside as e. These flanges are of forged construction.
well as outside
B.Socket Weld. :The Socket Weld flanges are welded on one side only. These are used for small bore lines only.
C.Screwed. :The Screwed-on flanges are used on pipe lines where welding cannot be carried out.
D.Lap Joint. : The Lap Joint flanges are used with stub ends. The stub with pipes & flanges are kept loose over the same.
E.Welding Neck. :The Welding neck flanges are attached by butt welding to the pipe. These are used mainly for critical services where the weld joints need radiographic inspection.
F.Blind :The Blind flanges are used to close the ends which need to be reopened.
G.Reducing :The reducing flanges are used to connect between larger and smaller sizes without using a reducer. In case of reducing flanges, the thickness of flange should be that of the higher diameter.
H.Integral: Integral flanges are those, which are cast along with the piping component or equipment.
2. How can flanges be classified based on Pressure- temperature ratings?
Flanges are classified based on pressure temperature ratings as: -
A. 150 .
B. 300 .
C. 400 .
D. 600 .
E. 900 .
F. 1500 .
G. 2500.
Pressure temperature rating carts in the standard ASME16.5 specify the non-shock working gauge pressure to which the flange can be subjected to at a particular temperature.
3. How can flanges be classified based on facing?
Answer:
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)
4. How can flanges be classified based on face finish?
Answer:
Flanges are classified based on face finish as: -
A. Smooth finish.
B. Serrated finish.
5. Where the smooth finish flange & serrated finish flange finds its use?
Answer:
The smooth finish flange is provided when metallic gasket is provided and serrated finish flange is
provided when non-metallic gasket is provided.
6. What are the types of serrated finish provided on flange face?
Answer:
A. Concentric or
B. Spiral (Phonographic)
7. How the serration on flanges is specified?
The serration on flanges is specified by the number, which is the Arithmetic Average Rough Height (AARH).
8. Where the concentric serration is insisted for face finish?
Concentric serration are insisted for face finish where the fluid being
carried has very low density and can find leakage path through cavity.
9. How the Gaskets are classified based on the type of construction?
Answer:
Based on the type of construction, gaskets are classified as:
A. Full face.
B. Spiral wound metallic.
C. Ring type.
D. Metal jacketed.
E. Inside bolt circle.
10. What is the most commonly used material for Gasket?
Answer:
Compressed Asbestos Fibre.
11. Which type of gasket is recommended for high temperature & high-pressure application?
Answer:
Spiral Wound Metallic Gasket.
11. What are the criteria for selection of MOC of Spiral Wound metallic Gasket
winding material?
The selection of material of construction for Gasket winding depends upon:
A. The corrosive nature and concentration of fluid being carried.
B. The operating temperature of the fluid.
C. The relative cost of alternate winding material.
12. What are the most common materials used for spiral wound metallic gasket
winding?
Answer:
The most commonly used material for spiral wound metallic gasket winding is:
A. Austenitic stainless steel 304 with asbestos filler.
B. Austenitic stainless steel 316 with asbestos filler.
C. Austenitic stainless steel 321 with asbestos filler.
13. Which material is used as filler material for spiral wound gasket in case of
high temperature services?
Answer:
For very high temperature services, graphite filler is used.
14. What is centering ring in connection to spiral wound gasket?
Answer:
Spiral wound gaskets are provided with carbon steel external ring called centering ring.
15. What will be the AARH finish on flange face for using spiral wound gasket?
Answer:
125-250 AARH finish.
16. On which type of flanges the use of spiral wound gasket are restricted?
Answer:
ASME B16.5 does not recommend the use of 150 .rating spiral wound gasket on flanges other than welding neck and lapped joint type.
17. Up to what temperature limits the low strength carbon steel bolts should not be used for flanged joints?
Answer:
Flanged joints using low strength carbon steel shall not be used above 200.C or below - 28.C.
17. How the pipe fittings are classified based on end connections?
Answer:
Pipe fittings are classified based on end connection as: -
A. Socket weld fittings.
B. Screwed end fittings.
C. Beveled end or Butt weld fittings.
D. Spigot socket fittings.
E. Buttress end fittings.
18. Up to what temperature the carbon steel materials shall be used?
Answer:
Carbon steel materials shall be used for temperature up to 425.C.
19. Which material is used for temperature above 426.C?
Alloy steel materials shall be used for temperature above 426.C.
20. Which type of material is used for corrosive fluid?
Stainless steel materials shall be used for corrosive fluid.
21. Which type of piping materials are used for drinking water, instrument air etc?
Answer:
Galvanized steel materials shall be used for drinking water, instrument air and NI lines (LP).
22. What is the difference between Pipe and Tube?
Answer:
Pipe is identified by NB and thickness is defined by Schedule whereas Tube is identified by OD & its thickness as BWG (Brimingham wire gauge or 1/100 inch).
23. From which size onwards NB of pipe is equal to OD of Pipe?
Answer:
From the size 14” and onwards NB = OD of pipe.
24. What should be the radius of long radius elbow?
Answer:
1.5D (Where “D” is the diameter of the pipe.)
25. What should be the radius of short radius elbow?
1D(Where “D” is the diameter of the pipe.)
26. What is the basis of using of short radius & long radius elbow?
Answer:
Long radius elbow are used for small pressure drop whereas short radius elbow are used for high
pressure drops. For catalyst flows vary long radius elbows are used.
27. Normally where do we use the following?
Answer:
A. Eccentric reducers = Pump suction to avoid Cavitation, To maintain elevation (BOP) in rack.
B. Concentric reducers = Pump discharge, vertical pipeline etc.
28. Concentric reducer is used in pump suction. (Yes / No). Explain.
Answer:
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 with flat side up(FSU) isused in Pump Suction.
29. Where the ERW spiral & longitudinal pipes are used?
Answer:
Use depends upon the availability of pipes. Nothing functional difference.
30. Where the ERW & Seamless pipes are used?
Above 18” ERW pipes are used. Below 18” seamless pipes are used. Seamless pipes can sustain higher temperature & pressure.
31. What is the main use of ASTM A53 & A106 Gr.B pipes?
Answer:
ASTM A53 pipes are mainly used for utility services whereas A106 Gr. B pipes are used for high Pressure & high temperature services.
32. 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.
33. Why don’t we take a branch for Cryogenic Service from bottom side though the fluid is in liquid state?
Answer:
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.
33.Why 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 conducting Hydro-test.
34. What do you mean by Jacketed Piping?
Answer:
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 fluid constant. Usually used for molten sulphur, Polymers service.
35. What is the minimum distance to be maintained between two welds in a pipe?
Answer:
The thumb rule is that the minimum distance between adjacent butt welds is 1D. If not, it is never closer than 1-1/2". This is supposedly to prevent the overlap of HAZs. Minimum spacing of circumferential welds between centerlines shall not be less than 4 times the pipe wall thickness or
25 mm whichever is greater.
36. What do you mean by IBR and which lines comes under IBR purview?
IBR: Indian Boiler Regulation Act.
Steam lines with conditions listed bellow 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 flash drum.
37. 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 sizerestrictions and the piping is of critical / high-pressure service. Sockolet is used for socket welding branch connection, which require reinforcing pad.
38. What is the MOC for Superheated high pressure Steam Lines?
A 335 Gr. P I / P 11, Composition: Cr. – ½ Mo (P1) / 1¼ Cr. – ½ Mo (P11)
39. What is the normal upstream and downstream straight length of orifice flow
meter?
Answer:
Upstream -15D Downstream -5D
QUESTIONS RELATED TO VALVES:
1. What is the function of valves?
Answer:
A. Isolation.
B. Regulation.
C. Non-Return.
D. Special purpose.
2. How the valves are classified based on their function?
A. Isolation.
1. Gate valve. 2. Ball valve 3. Plug valve. 4. Piston valve. 5. Diaphragm Valve. 6. Butterfly valve. 7. Pinch valve.
B. Regulation
1.Globe valve.2. Needle valve. 3. Butterfly valve. 4. Diaphragm valve.
5. Piston valve. 6. Pinch valve.
C. Non-Return
1. Check valve. D. Special purpose
1. Multi-Port valve. 2. Flush Bottom valve. 3. Float valve. 4. Foot valve.
5. Line blind valve. 6. Knife Gate valve.
3. How the valves are classified based on its method of operation?
Answer:
Valves are classified based on its method of operation as:
A. Self-operated valves.
B. Operated valves.
4. Name the Self – operated & operated valves?
Mainly the check valves are self-operated and all other valve types comes under operated valves.
5. How the valves are classified based on end connection?
Answer:
Valves are classified based on end connection as:
A. Screwed ends.
B. Socket ends.
C. Flanged ends.
D. Butt weld ends.
E. Wafer type ends.
F. Buttress ends.
End connection means arrangement of attachment of the valve with the equipment or the piping.
6. What are the types of check valves?
Answer:
Check valves are divided into two types based on check mechanism as:
A. Lift check valve.
B. Swing check valve.
7. What do you mean by special purpose valves?
Answer:
Valves that perform duties other than the two-way isolation, control and
check are called special purpose valves.
8. What are Glandless piston valves? Where these are used?
Glandless piston valves are regulating valves used in steam services.
QUESTIONS RELATED TO WELDING/ WELD DEFECTS/POST HEATING/POST WELD HEAT TREATMENT/ ELECTRODE/FILLER WIRE.
1. What do you mean by following type of welding?
A. SMAW : - Shielded Metal Arc Welding.
B. TIG : - Tungsten Inert Gas Welding.
2. Mention the contents of TIG welding set?
Answer:
A. Torch : Consist of hose for argon gas / welding lead / ceramic nozzle/ collet / tungsten rod as cathode to create arc.
B. Regulator with Pressure Gauge (HP & LP) & flow meter.
C. Argon cylinder – Gr.2 / Gr.1 depending upon requirements of the job.
D. Transformer / Rectifier.
E. Filler wire
3. While welding of pipe trunion to pipe/reinforcement pad you have to put a hole or leave some portion of welding why?
Answer:
For venting of hot gas which may get generated due to welding.
4. What is the thumb rule to calculate Current required for Welding?
Answer:
Current (Amp) = [Diameter of Electrode (mm) X 40] .20
5. What is the minimum thickness of cs pipe that requires stress relieving to be done as per B31.3?
Answer:
19.05 mm thk.
6. Which is the Electrode & filler wire used for welding of following materials?
Covered
Electrode Bare
A.Alloy Steel electrode
I. ASTM A335PI E7018 E70 S-1B
II. ASTM A335P2 E8018-B1
III. ASTM A335P11 E8018-B2 ER515
IV. ASTM A335P5 E502 ER502
V. ASTM A335P9 E505 ER505
B.Stainless Steel
I. ASTM A312TP304 E308 ER308
II. ASTM A312TP304L E308L ER308L
III. ASTM A312TP304H E16-6-2 ER16-8-2
IV. ASTM A312TP308 E309 ER309
V. ASTM A312TP310 E310 ER310
VI. ASTM A312TP316 E316 ER316
VII. ASTM A312TP316L E316L ER316L
VIII. ASTM A312TP316H E16-8-2 ER16-18-2
IX. ASTM A312TP321 E347 ER347
X. ASTM A312TP321H E16-6-2 ER16-8-2
7. What are the common welding defects?
A. Lack of penetration.
This defect occurs at the root of the joint when the weld metal fails to reach it or weld metal fails
to fuse completely the root faces of the joint. As a result, a void remains at the root zone, which
may contain slag inclusions.
Cause:
1.Use of incorrect size of electrode in relation to the form of joint.
2.Low welding current.
3.Faultyfit-up and inaccurate joint preparation.
B.Lack of fusion.
Lack of fusion is defined as a condition where boundaries of unfused metal exist between the
Weld metal & base metal or between the adjacent layers of weld –metals.
1.Presence of scale, dirt, oxide, slag and other non-metallic substance which prevents
the weld metal to reach melting temperature.
2.Improper deslagging between the weld pass.
Precaution:
1.Keep the weld joint free from scale, dirt, oxide, slag and other non-
metallic substance.
2.Use adequate welding current.
3.Deslag each weld pass thoroughly.
4.Place weld passes correctly next to each other.
C.Undercut
This defect appears as a continuous or discontinuous groove at the toes of a weld pass and islocated on the base metal or in the fusion face of a multipass weld. It occurs prominently on the edge of a fillet weld deposited in the horizontal position.
Cause:
1.Excessive welding current.
2.Too high speed of arc travel.
3.Wrong electrode
Rectification:
The defect is rectified by filling the undercut groove with a weld pass. If undercut is deep &
contains slag, it should be chipped away before rewedding.
D.Slag Inclusion
Non–metallic particles of comparatively large size entrapped in the weld metal are termed
as slag inclusion.
Cause:
1.Improper cleaning of slag between the deposition of successive passes.
2.Presence of heavy mill scale, loose rust, dirt, grit & other substances
present on the surface of base metal.
precaution:
1.Clean the slag thoroughly between the weld pass.
2.Keep the joint surface (especially gas cut surface) and bare filler wire
perfectly clean.
3.Avoid undercut & gaps between weld pass.
4.Use proper welding consumables.
E.Porosity
The presence of gas pores in a weld caused by entrapment of gas during solidification is termed as porosity. The pores are in the form of small spherical cavities either clustered locallyor scattered throughout the weld deposit. Sometimes entrapped gas give rise to a single large
cavity called Blow holes.
Cause:
1.Chemically imperfect welding consumables, for example, deficient in
deoxidiser.
2.Faulty composition of base material or electrode, for example, high
sulphur content.
3.Presence of oil, grease, moisture and mill scale on the weld surface.
4.Excessive moisturein the electrode coating or submerged-arc flux.
5.Inadequate gas shielding or impure gas in a gas –shielded process.
6.Low welding current or too long an arc.
7.Quick-freezing of weld deposit.
F.Crack
Fracture of the metal is called crack. Two types of cracks: -Cold crack & Hot crack. Cold crack usually occur in HAZ of the base metal when this zone becomes hard and brittle due to rapid cooling after the weld metal has been deposited & sufficient hydrogen has been absorbed by the weld metal from the arc atmosphere Precaution:
1.Use of low carbon equivalent materials.
2.Higher heat input during welding.
3.preheating.
4.Use of low hydrogen electrode.
5.Faulty weld size and profile
A weld is considered faulty if it has lack of reinforcement, excessive reinforcement or irregular Profile.
H. Distortion
Because a weldment is locally heated (by most welding processes), the temperature distribution in the weldment is not uniform and changes take place as welding processes.Typically, the weld metal and the base metal heat-affected zone immediately adjacent to it are at a temperature substantially above that of the unaffected base metal. As the molten pool solidifies and shrinks, it begins to exert shrinkage stresses on the surrounding weld metal and heat-affected zone area. When it first solidifies, this weld metal is hot, relatively weak, and can exert little stress. As it cools to ambient temperature, however, the shrinkage of the weld metal exerts increasing stress on the weld area and eventually reaches the yield point of the base metal and the heat-affected zone. Residual stresses in weld ments have two major effects. First,they produce distortion, and second, they may be the cause of premature failure in weld ments.
Cause :
when the heated weld region contracts nonuniformly, causing shrinkage in one part of the weld to exert eccentric forces on the weld cross section.
The distortion may appear in butt joints as both longitudinal and transverse shrinkage or contraction, and as angular change (rotation) when the face of the weld shrinks more than the
root. Distortion in fillet welds is similar to that in butt welds: transverse and longitudinal shrinkage as
well as angular distortion results from the unbalanced nature of the stresses in these welds.
8. What is mean by ‘PWHT’? Why it is required?
Answer:
“POST WELD HEAT TREATMENT” This is done to remove residual stress left in the joint which may
cause :
Brittle fracture.
9. Why pre-heating is done on some pipe before starting welding?
To slow down the cooling rate.
10. Why post-heating is done on some pipe after the welding is over?
Answer:
To maintain uniform homogeneous structure.
11. What is the pre-heat temperature for carbon steel above 19.05MM thk.
Answer:
Pre –heat temperature for carbon steel above 19.05 mm is 80.C.
12. Is post heating required for carbon steel material above 19.05MM thk.
No. Post heating is not required for carbon steel material of any thickness.
13. What is the soaking temperature during stress reliving for carbon steel material?
Answer:
Soaking temperature for carbon steel material during stress reliving is 620.C. (.20.C)
14. What is the soaking period during stress reliving for carbon steel material?
Soaking period for carbon steel material during stress reliving is 1hr.
15. What is the rate of heating & cooling during stress reliving for carbon steel material?
Answer:
The rate of heating & cooling for carbon steel material during stress reliving is 150.c/hr.
16. What is the pre-heat temperature during stress reliving for alloy steel materials?
Answer:
Pre-heat temperature for AS materials is 180.C.
17. What is the soaking temperature during stress reliving for alloy steel material?
Answer:
Soaking temperature for alloy steel material is 720.C(.20.C).
18. What is the soaking period during stress reliving for alloy steel material?
Answer:
Soaking period for alloy steel material is 2hrs.
19. What is the rate of heating & cooling during stress reliving for alloy steel material?
Answer:
The rate of heating & cooling for alloy steel material is 100.C/hr.
20. What is the post heat temperature for alloy steel material?
Answer:
Post heat temperature for alloy steel material is 300.C.
21. What is a four or five digit coding for electrode as per AWS classification SFA 5.1?
Answer:
EX X X X X XXXX
The minimum UTS of Welding position. Type of coating the undiluted weld metal and current condition.in psi. ( UTS – Ultimate tensile strength)
22. Where the use of electrode E7018 is recommended?
Answer:
The use of electrode E7018 is recommended for welding the following:
A. For high strength steel.
B. For high thickness carbon steel plates.
C. Higher carbon equivalent material.
23. Why the electrode E7018 is called low hydrogen electrode?
Answer:
The low hydrogen electrodes have in their coating ingredient, which produces carbon di-oxide during melting. This CO2 gives a gaseous shielding for the metal and prevents atmospheric hydrogen from
entering in arc atmosphere. By this way the weld metal has low level of hydrogen.
24. What should be the content of chlorine in water while conducting hydrotest for CS & SS pipes?
Answer:
For CS – 250 PPM.
For SS – 30 PPM.
25. Draw the stress-reliving diagram for carbon steel & Alloy steel material?
Soaking period ( 1hr. for C.S & 2hrs. for AS)
(Note: -The stress reliving diagram remain same
for both AS & CS. The difference is only
in soaking temperature.) Time Temperature
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