QC Welding Inspector Interview Questions & Answers

Question 1. What Are The Main Duties Of The Piping Inspector?

Answer :

• Material receiving inspection
• Storage & preservation 
• Cutting, assembly & fit-up 
• Pre-welding inspection 
• Visual inspection of socket & threaded joints 
• Pneumatic test for reinforcing pad 
• Pickling & passivation 
• Database reporting 
• Visual inspection of completed spools 
• Piping pre-inspection & spool erection 
• orifice flange inspection 
• Pipe support inspection 
• Verification of slope 
• Internal cleanliness 
• Valve installation 
• Piping flange joint inspection 
• Pre-test punch listing 
• Hydro testing 
• pre-commissioning

Question 2. How Many Types Of Gaskets Do You Know?

Answer :

• Full face (Asbestos)
• Spiral wound metallic
• Ring type
• Metal jacketed
• Inside bolt circle

Question 3. What Are The Different Types Of Mating Flanges? Name The 4 Most Common?

Answer :

Flat face

Raised face

RTJ (Ring type Joint)

Tongue & groove

Male & female

Question 4. What Type Of Information Do You Get From Isometric Drawings?

Answer :

• Line routing
• Line orientation
• Northing
• Easting & elevation
• Bill of mat’l
• Insulation type
• NDT requirement
• Revision status
• Material class’n
• Design
• Operating & testing temp/pressure
• Paint system
• P&ID
• Slope
• Service details
• Flow direction
• Support details
• Notes

Question 5. What Type Of Codes And Standards Do You Use As A Piping Inspector?

Answer :

• ASME B31.3
• ASME B31.1
• ASME B31.5
• ASME B31.9
• JERES-A-004
• JERES-A-007
• JERES-A-206
• JERES-A-301
• JERES-L-105
• JERES-L-108
• JERES-L-110
• JERES-L-150
• JERES-L-130
• JERES-L-310
• JERES-L-350
• JERES-L-351
• JERES-W-011
• JERES-W-016

Question 6. What Are The Types Of Valves?

Answer :

• Gate valve
• Globe valve
• Butterfly valve
• Needle valve
• Check valve
• Control valve
• Knife gate valve

Based on function:-

• non-return valve
• isolation valve
• regulation valve
• special purpose valve

Question 7. What Are The Main Things You Will Check Before Bolt Torquing?

Answer :

• Size of bolt
• Calibration of torque wrench
• Manual /hydraulic require
• Lubricant
• Friction factor for threaded lubricant
• Torque value
• JERES-L-109 / 351

Question 8. Write 3 Saudi Aramco Piping Standards (l-series)?

Answer :

• SAES-L-105
• SAES-L-108
• SAES-L-110
• SAES-L-150
• SAES-L-130
• SAES-L-310
• SAES-L-350
• SAES-L-351

Question 9. Write Minimum Ten Hydro Static Test Punch List Items Prior To Commence Hydro Test At Site? Indicate Which Is Yes Item & No Item?

Answer :

1. All hot work shall be completed
2. Strainers shall be removed
3. All NDT & DT completion
4. PWHT completion
5. Adequate attachment
6. Coating on weld joint shall be removed.
7. Calibration of equipments used. Test blind MTC.
8. Test certificates of testing fluid
9. Components in new piping systems which interfere with filling, venting, draining or flushing shall not be installed.(orifice plates, flow nozzles, sight glasses)
10. All joints (flange, threaded, welded or mechanical seals) are left exposed for visual leak detection during the strength test. 
11. All permanent flange joints were inspected, gasket mat'l verified & properly torque.
12. Drains shall be provided at all low points of the piping system.     
13. Vents and drain valves, both temporary and permanent, conforms with the piping class or rating.
14. Supports are installed. Additional temporary support may be installed as required.
15. Expansion joints and spring hangers or spring supports are provided with temporary restraints. 
16. Arc strikes, gouges, and other indications of careless workmanship (such as surface porosity, uneven weld profiles, and undercut) shall be removed by grinding and inspected by magnetic particle or liquid penetrant method.
17. Drains are provided immediately above check valves (vertical lines)
18. All threaded joints up to the first block valve of hydrocarbon pipeline are seal welded. Thread engagement has been verified & accepted.
19. 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.

Line compliance with Isometrics:                                                       

• Correct Materials utilized grade/schedule (Bill of Mat'ls)                             
• Correct flange and fittings rating                                             
• Construction tolerances per SAES-L-350

Question 10. Weep Hole Size Shall Be Drilled For Dummy Pipe Support Will Be ________mm?

Answer :

Weep hole shall be located near base plate for all vertical dummy pipe support & near run pipe at 6’O clock position for horizontal dummy.(SAES-L-350 13.2.3 & L-310 14.7.2)

Question 11. What Is Dead Leg And Explain?

Answer :

Dead Legs:  Piping sections that are potential for internal corrosion due to flow stagnation. 

• Dead legs are created mainly by flow stagnation enhanced with presence of settled water and solid deposits.
• When the length of the section or branch , for 2 inch pipes and larger, is longer than three times its pipe diameter, or 1.22 m (4 ft) in length, the length of the dead leg is the distance measured from the outside diameter of the header (or run) to the near end of the branch valve.
• For branch connections of 1-½ inch NPS and smaller, the length of the dead leg is the distance measured from the end of the boss to the near end of the valve.

Question 12. Write Any 2 Types Of Piping Supports?

Answer :

• Shoe
• spring loaded
• resting
• wear pad

Question 13. What Type Of Connection Is Acceptable For A 24” Header, 12” Branch?

Answer :

Weldolet or welded branch with reinforcement pad as per JERES-L-110 app: A.

Question 14. How Many Minimum Pressure Gauges To Be Installed During Hydro Test?

Answer :

Two (JERES-A-004, Para 7.1.5)

Question 15. What Is A Pip?

Answer :

Process industry practices.

Question 16. Name The Different Types Of Service Conditions?

Answer :

NFS:- Normal services, Category M, Category D, High pressure fluid services (ASME-B31.3).

Question 17. How Do You Verify (name Several Items To Check) That The Correct Piping Material Is Used?

Answer :

• Material specification
• Pipe size
• Schedule
• Length
• Flange face rating
• Olet size rating
• Threaded/socket weld type
• MTC
• PMI report

Question 18. How Do You Identify Fittings And Flanges?

Answer :

• By material classification
• Size
• Rating
• Joint type (lap, socket, threaded, butt), face;

Question 19. How Do You Check Piping For The Correct Schedule?

Answer :

Verify pipe material thickness by Vernier at the end or UT on surface or stenciling done by the manufacturer (visual) or heat number, traceability by MTC of product.

Question 20. What Is The Standard Mill Tolerance For Piping 2’’ & Less?

Answer :

12% of nominal wall thickness.

Question 21. What Is The Tolerance For Ovality Of Piping?

Answer :

5% of nominal diameter at any cross section other than weld end & 3% at weld end (JERES-L-350 Para 9.2).

Question 22. What Is The Difference Between Torquing Cs And Ss Bolting?

Answer :

CS:- Yield strength High; Torque value High.

SS:- Yield strength low; Torque value low.

Question 23. What Are Jackscrews And When Are They Required?

Answer :

Used in flange joint assemblies which often require frequent separation includes orifice plate, spectacle plates, spacers, screens, and drop out spools shall be provided with jack screw to facility separation and opening for the maintenance. When flange separations are used, jackscrews are not required. Jackscrews shall be installed to be accessible from both sides of the pipe. For orifice flanges, jack screws shall be installed at 3 & 9 o’ clock positions.(JERES-L-310 Para 17.7).

Question 24. What Is Often Overlooked During Orifice Flange Fabrication?

Answer :

• Inside surface of welded joints at @ orifice flanges shall be ground & machined smooth (JERES-L-350 Para 10.4.2).
• Orientation of taps is as per JERES-J-0001.
• All parallel pipe lines with adjacent orifice fittings shall have a min spacing of 300 mm (12 in) between flanges outside diameters if horizontal taps are required. Where this spacing is not practical follow JERSEY-J-0001.

Orifice flanges in adjacent lines shal be staggered so that no two pairs of orifice flanges are less than 1 m (3ft) apart.

Question 25. What Is The Maximum Diameter Piping Allowed In Hazardous Service?

Answer :

Socket weld: - 2” for maintenance & minor modification & 1-½” for new construction.

Threaded:- 1-½” for standard fitting & valve, and 2” maximum when required for maintenance, minor field minor modification of existing piping system(JERES-L-110 Para 7.2).

Question 26. Can Teflon Tape Be Used Prior To Seal Welding?

Answer :

No, (JERES-L-110 Para 8.5).

Question 27. How Many Threads Can Be Visible After Seal Welding Threaded Joints?

Answer :

No, should cover all exposed threads (JEREZ-W-011 Para 12.15.3).

Question 28. What Is The Gap Requirement For Socket Welds For New Construction?

Answer :

1.5mm-3mm (ASME B31.3 fig 328.5.2C).

Question 29. Give Examples Of Unique Support Details That Allow Piping Freedom Of Movement For Thermal Expansion?

Answer :

• Guide support
• Moving saddle support
• Expansion balloons
• Shoe support
• Spring loaded

Question 30. When You Will Apply 24 Hours Recorded Hydro Test?

Answer :

If for justifiable safety reasons the UG line must be backfilled, then the joints shall remain exposed during testing, otherwise the test shall be a 24 hour recorded test.(JERES-L-150 Para 7.4.2).

Question 31. Difference Between Carbon Steel And Stainless Steel?

Answer :

CS:- Low cost, no chromium content, suitable for non-corrosive service upto 350 degree C, max carbon 0.3%.

SS:- Contains more than 12% Cr, 0.08% C, Suitable for corrosive, cryogenic, High temp services, costly.

Question 32. Difference Between Rt & Ut?

Answer :

RT:- Uses X-ray or Gamma ray to detect discontinuities, reveals mostly volumetric. Planar defects & subsurface defects not detectable easily.

UT:- Uses ultrasonic beam to detect discontinuities reveals both planar & volumetric defects, but size & exact location of defects are not easily identifiable. Possible only on materials that do not refract AT waves.

Question 33. Difference Between Pt & Mt?

Answer :

MT:- Only Applicable for ferromagnetic materials & able to detect both surface & sub surface discontinuities, compare to PT examination it takes less time for testing & inspection; Applicable for large temp range.

PT:- Applicable for both ferromagnetic & non ferromagnetic materials & able t detect only surface discontinuities, It requires more time; Applicable for small temp range.

Question 34. How Do You Control Material In Fabrication Shop?

Answer :

1. All materials shall have material spec and grade stamped or stenciled & clearly marked with permanent marker.
2. All materials, heat no. will be made traceable to MTC from approved vendor & no material substitution will be done without proper approval from the company.
3. All materials shall be stored & stacked separately as per material grade.
4. Heat no. shall be transferred before cutting into pipes that have to be cut.
5. All materials shall be color coded as per traceability procedure.

Question 35. Write Inspection Items During Valve Installation?

Answer :

1. Valve type corrects at the location
2. Valve test certificate
3. Valve tag as per P&ID
4. Valve direction of flow as per P&ID
5. Gasket bolts as per isometric & type
6. Handle direction
7. Chain wheel installed
8. Valve flange face condition