Piping Interview Questions and Answers with Expert Answers

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45 Mastering Piping Interview Questions: Expert Answers to Help You Succeed

 

Piping Interview Questions and Answers: Preparing for a piping interview can be stressful, especially if you’re not sure what questions might come your way. That’s why I’ve put together this list of **45 important piping interview questions and answers**. These questions are carefully selected based on real interviews and industry experience. No matter if you are a fresher, experienced employee, or an experienced individual in piping, this guide will equip you with confidence. These questions are from the basic to expert levels, which are frequently asked in piping engineer, supervisor, foreman, and other related job interviews.

Each question is followed by a simple, clear answer so that anyone – even if English is not your first language – can understand and learn from it. I’ve kept the language straightforward, avoiding complicated technical terms unless necessary, and when they appear, they’re explained in an easy way. So, take your time to read through each question and answer carefully. Use this as a study guide prior to your interview. Being familiar with these 45 questions won’t only enable you to pass the interview — it will make you feel more confident on a daily basis in your job as well. Let’s get started and set you up for success.

  1. Write the weld layers?
  2. Root
  3. hot pass
  4. fill
  5. cap

2. Accepted misalignment in piping?

1.5mm as per ASME 31.3
1.6mm as per ASME sec IX

  1. What is meant by ITP?

An Inspection and Test Plan (ITP) or test plan is a document detailing a systematic approach to testing a system or product (e.g. material, component, machine, etc), such as a visual inspection, dimension inspection, welding inspection, function test, factory acceptance test, etc. and participation of all parties.

  1. What are the four types of inspection stages? Explain.
  2. Hold 2. Witness 3. Surveillance 4. Review

Hold: QA/QC Organisation shall be notified of the timing of the inspection or test in advance. Inspection Or the test shall not be carried out, with a QA/QC Organisation representative in attendance

Witness: QA/QC Organisation shall be notified of the timing of the inspection or test in advance.

Inspection or test shall be performed as scheduled if the QA/QC Organisation representation is not present

Surveillance: QA/QC Organisation monitoring the work in process without notice from the construction Organization

Review: Review and approve all documents

  1. Explain about ‘specifications’?

Specifications are guidelines for the construction requirements, and minimum quality standards are listed.

  1. What is P&ID?

A piping and instrumentation diagram, or P&ID, shows the piping and related components of

a physical process flow. (Branches, reducers, valves, equipment, instrumentation and control interlock)

  1. What is WPS?

A Welding Procedure Specification (WPS) is the formal written document describing welding procedures, which provides direction to the welder or welding operators for making sound and quality production welds as per the code requirements

  1. What is PQR?

A PQR is a record of a test weld performed and tested (more rigorously) to ensure that the procedure will produce a good weld. A WPS is supported by a Procedure Qualification Record (PQR)

  1. What is WPQ?

A Welder Performance Qualification (WPQ) is a test certificate that shows whether a welder possesses the necessary experience and knowledge to perform the specifications of a particular weld procedure

  1. What is the difference between a Pipe and a Tube?

PIPE: It is identified by NB(Nominal Bore), and its thickness is identified by schedule

TUBE: It is identified by OD (Outside Diameter), and its thickness is identified by BWG

(Birmingham Wire Gauge)

  1. What are the main duties of the piping inspector?

Material receiving inspection, Storage & preservation Cutting, assembly & fitup

Prewelding 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 and pre-commissioning.

  1. How many types of gaskets do you know?

Full face (Asbestos)

Spiral wound metallic

Ring type

Metal jacketed

Inside bolt circle

  1. What are the different types of mating flanges? Name the 4 most common

Flat face

Raised face

RTJ(Ring type Joint)

Tonge & groove

Male & female

  1. What type of information do you get from Isometric drawings?

Line routing, Line orientation, Northing, easting & elevation, Bill of mat’l, Insulation type, NDT requirement, Revision status, Material class, Design, operating & testing temp/pressure, paint system, P&ID, slope, Service details, flow direction, support details, notes;

  1. What type of codes and standards do you use as a piping inspector?

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

  1. What are the types of Valves?

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,

  1. What are the main things you will check before Bolt torquing?

Size of bolt, Calibration of torque wrench, Manual /hydraulic required, Lubricant, Friction

factor for threaded lubricant, torque value, JERES-L-109 / 351

  1. Write 3 Saudi Aramco piping standards (L-Series)?

SAESL105

SAESL108

SAESL110

SAESL150

SAESL130

SAESL310

SAESL350

SAESL351

  1. Write a minimum of ten hydrostatic test punch list items prior

to commencing hydrotest at the site. Indicate which is the YES item & NO item

  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 the weld joint shall be removed.
  7. Calibration of equipment 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)
  1. All joints (flange, threaded, welded or mechanical seals) are left exposed for visual leak detection during the strength test.
  1. All permanent flange joints were inspected, gasket material verified & properly torqued.
  1. Drains shall be provided at all low points of the piping system.
  2. Vents and drain valves, both temporary and permanent, conform to the piping class or rating.
  1. Supports are installed. Additional temporary support may be installed as required.
  1. Expansion joints and spring hangers or spring supports are provided with temporary restraints.
  1. 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.  Drains are provided immediately above check valves (vertical lines)
  1. All threaded joints up to the first block valve of the hydrocarbon pipeline are seal-welded.
  2. Thread engagement has been verified & accepted.
  1. The pressure testing manifold is separately pressure tested to at At least 1.2 times the system test pressure but not less than the discharge pressure of the pump used for the pressure testing.
  1. Line compliance with Isometrics:
  1. Correct Materials utilised grade/schedule (Bill of Mat’ls)
  2. Correct flange and fittings rating

iii. Construction tolerances per SAESL350

  1. Which type of documents/reports are attached to the hydrostatic test package?

Refer Attached

  1. Weep hole size shall be drilled for dummy pipe support will be ________mm

Weep hole shall be located near the base plate for all vertical dummy pipe

support & near the run pipe at 6 o’clock position for horizontal dummy.

(SAESL350

13.2.3 & L310

14.7.2)

  1. What is a dead leg, and explain?

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

Dead legs are created mainly by flow stagnation, enhanced by the 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 1-1⁄2 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.

  1. Write any 2 types of piping supports?

Shoe, spring-loaded, resting, weir pad,

  1. Line class 103CS3C is listed on the Isometric Drawing. Explain each 1 03 CS 3 C

Raised face Flange rating 300 Carbon steel C.A. 4.5 mm Caustic

As per JERESL105 page 375377

  1. What type of connection is acceptable for a 24” header, 12” branch?

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

  1. How many minimum Pressure gauges are to be installed during the hydro test?

Two(JERES-A-004, para 7.1.5)

  1. Relief valve calibration period would be___________

One week, per JERES-A-004 para 5.5.1

  1. What is a PIP?

Process industry practices

  1. Name the different types of Service Conditions?

NFS:- Normal services, Category M, Category D, High-pressure fluid services(ASMEB31.3)

  1. How do you verify (name several items to check) that the correct piping material is

used?

Material specification, Pipe size, schedule, length, flange face rating, oletsize rating, threaded/socket weld type, MTC, PMI report.

  1. How do you identify fittings and flanges?

By material classification, size, rating, joint type (lap, socket, threaded, butt), face;

  1. How do you check piping for the correct schedule?

Verify pipe material thickness by Vernier at the end, or UT on the surface or stencilling done

by the manufacturer (visual) or heat number, traceability by MTC of the product.

  1. What is the standard mill tolerance for piping 2’’ & less?

12% of nominal wall thickness

  1. What is the tolerance for ovality of piping?

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

  1. What is the difference between torqueing CS and SS bolting?

CS:- Yield strength High; Torque value High

SS:- Yield strength low; Torque value low

  1. What are jackscrews, and when are they required?

Used in flange joint assemblies, which often require frequent separation, include orifice plate, spectacle plates, spacers, screens, and drop-out spools shall be provided with a jack screw to facilitate separation and opening for 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)

  1. What is often overlooked during orifice flange fabrication?

Inside surface of welded joints at @ orifice flanges shall be ground & machined smooth (JERESL350

para 10.4.2) Orientation of taps is as per JERSDJ0001. All parallel pipe lines with adjacent orifice fittings shall have a minimum spacing of 300 mm (12 in) between flanges outside diameters if horizontal taps are required. Where this spacing is not practical, follow JERSDJ0001. Orifice flanges in adjacent lines shall be staggered so that no two pairs of orifice flanges are less than 1 m(3ft) apart.

  1. What is the maximum diameter piping allowed in hazardous service?

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

Threaded:- 1-1⁄2” 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)

  1. What is the minimum-sized piping that can be installed on pipe racks?

Ø1”

  1. Can Teflon tape be used before seal welding?

No, (JERES-L-110 para 8.5)

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

No, should cover all exposed threads(JERES-W-011 para 12.15.3)

  1. What is the gap requirement for socket welds for new construction?

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

  1. Give examples of unique support details that allow piping freedom of movement for thermal expansion.

Guide support, Moving saddle support, Expansion balloons, shoe support, Spring loaded

  1. When will you apply the 24-hour recorded hydro test?

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)

  1. Difference between carbon steel and stainless steel?

CS:- Low cost, no chromium content, suitable for non-corrosive service up to 350 degrees

C, max carbon 0.3%.

SS:- Contains more than 12% Cr, 0.08% C, Suitable for corrosive, cryogenic, and high-temperature services, which are costly.

  1. Difference between RT & UT?

RT:- Uses X-ray or Gamma ray to detect discontinuities, reveals

mostly volumetric. planar defects & subsurface defects are not easily detectable

UT:-Uses an ultrasonic beam to detect discontinuities, revealing both planar & volumetric defects, but the size & exact location of defects are not easily identifiable.

Possible only on materials that do not defract UT waves.

  1. Difference between PT & MT?

MT:- Only Applicable for ferromagnetic materials & able to detect both surface & subsurface discontinuities, compared to the PT examination, it takes less time for testing & inspection;

Applicable for a large temperature range.

PT:- Applicable for both ferromagnetic & non-ferromagnetic materials & able to detect only surface discontinuities. It requires more time; it is Applicable for a small temperature range.

  1. How do you control material in the fabrication shop?

1) All materials shall have the material spec and grade stamped or stencilled & clearly marked with a permanent marker.

2) All materials heat numbers. Will be made traceable to MTC from the 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 shall not be transferred before cutting into pipes that have to be cut.

5) All materials shall be colour-coded as per the traceability procedure

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

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