Interview questions for Piping Engineering

The following list will provide a few interview questions asked in the different interviews for a Piping Engineering (Stress) position. Answers to most of the questions are added here for reference. I hope you will be able to find remaining answers from ASME B 31.3 and any piping engineering textbooks or from the piping handbook. In case you could not find out a specific answer reply in the comments section.

1. Which code and standard are used in Oil and Gas?

If you are working in Oil and Gas, then the most commonly used code and standard are developed by various American institutes. Some of them that you can include in your answer are;
1. ASME Codes – ASME is the American Society of Mechanical Engineer. ASME Published various designed codes and dimension standards that are used in refinery, petrochemical plants, and power plants.
2. ASTM Standard – ASTM is the American Society for Testing and materials. ASTM published various material standard used in almost all industries. ASTM has published a total of 15 sections out of these only section 1, section 2, and section 3 is used very frequently process industry. Within these sections, there are different volumes that cover various materials. For example, Section 1 has eight volumes, section 2 has five volumes, and section 3 has six volumes.
3. API Standard and Recommended Practice – API is American Petroleum Institute that published Standard and Recommended Practices that are used in the petroleum This is an industry-specific institute whereas ASME and ASTM published standards and codes that are used in general application also. Recommended practices are used in the operation and maintenance of the process facilities.
4. AWS – AWS is an American welding society. As the name suggests, AWS published various codes and standards that use for welding. ASME Section IX is also used to developed different welding procedures used in a process What I have seen is AWS codes used in the structural applications more than the process application. As most process piping and equipment are designed using ASME Code and Standard so they follow ASME Section IX for the welding.
5. AWWA – AWWA is the American Water Works Association. The standard published by AWWA is used in a process plant for water treatment facilities and water transport pipelines.

2. What Are The Main Differences Between Asme B 31.1 And Asme B 31.3?

The main differences are listed below:

  • Material allowable stresses are different in both codes.
  • Stress increases due to occasional loads are different in each code.
  • B 31.3 neglects torsion while calculating sustained stresses, but B 31.1 includes it.
  • Sustained stress calculation is specific in B 31.1 but undefined for B 31.3.
  • B 31.1 intensifies torsion but B31.3 does not intensify it.

In Constant Spring hanger the load remains constant throughout its travel range. But In variable spring hanger the load varies with displacement.
Spring hangers are used when thermal displacements are upwards and piping system is lifted off from the support position. Variable spring hanger is preferable as this is less costly.
Constant springs are used:
1. When thermal displacement exceeds 50 mm
2. When variability exceeds 25%
3. Sometimes when piping is connected to strain sensitive equipment like steam turbines, centrifugal compressors etc and it becomes very difficult to qualify nozzle loads by variable spring hangers, constant spring hangers can be used

4. How To Calculate The Height Of A Variable Spring Hanger?

1. Select the height from vendor catalog based on spring size and stiffness class.
2. For base mounted variable spring hanger the height is mentioned directly. It is the spring height.
3. For top mounted variable spring hanger’s ass spring height with turnbuckle length, clamp/lug length and rod length.

5. Can You Select A Proper Spring Hanger If You Do Not Make It Program Defined In Your Software? What Is The Procedure?

In your system first decide the location where you want to install the spring. Then remove all nearby supports which are not taking load in thermal operating case. Now run the program and the sustained load on that support node is your hot load. The thermal movement in that location is your thermal movement for your spring. Now assume variability for your spring. So calculate
Spring constant = (Hot load × variability)/displacement. Now with spring constant and hot load enter any vendor catalog to select spring inside the travel range.

6. What are the steps in selection of valve?

What to handle, liquid, gas or powder, fluid nature, function, construction material, disc type, stem type, how to operate, bonnet type, body ends, delivery time, cost, warranty.

7. What are functions of valves?

Isolation, regulation, non-return and special purposes.

8. What are isolating valves?

Gate, ball, plug, piston, diaphragm, butterfly, pinch.

9. What is covered in power piping and process piping?

So, there may be an additional question like what is covered in the Power Piping and Process Piping. Let’s see the scope of Power Piping and Process Piping.

10. What are regulation valves?

Globe, needle, butterfly, diaphragm, piston, pinch

11. What Is Blow Down Valve?

Refers to a plug type disc globe valve used for removing sludge and sediment matter from the bottom of boiler drums, vessels, drip legs etc.

12. What Is Breather Valve?

A special self acting valve installed on storage tanks etc. to release vapor or gas on slight increase of internal pressure ( in the region of ½ to 3 ounces per square inch).

13. Can You Explain In Detail Three Or More Major Differences Between Code Ansi B31.1 And Code Ansi B31.3?

There is only one major difference between the two, B31.1 is for Power Piping and B31.3 is for Refinery/Chemical Plant Piping.

14. What are non-return valves?

check valve,

15. What Is Quick Acting Valve?

Any on/off valve rapidly operable, either by manual lever, spring or by piston, solenoid or lever with heat-fusible link releasing a weight which in falling operates the valve. Quick acting valves are desirable in lines conveying flammable liquids. Unsuitable for water or for liquid service in general with out a cushioning device to protect piping from shock.

16. What are special valves?

Multi-port, flush bottom, float, foot, pressure relief, breather.

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