Interview questions for Piping Engineer

Piping is a system of pipes used to convey fluids from one location to another. The advantage of piping is that they are easily transported as a compact pile of parts on a wagon and then assembled as a hollow structure at the jobsite. The role of a piping engineer is to design and build piping systems that carry out water, oil and waste. So, trace out your career as piping designer, structural designer, piping engineer, junior mechanical engineer, steam fitter and so on by seeing through the below offered piping job interview questions and answers.

1. 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.

2. What is the scope of ASME B31.3? What does it cover and what does not?

 The Process Piping Code, ASME B31.3 is usually applicable for the piping systems in petroleum refineries; chemical, petrochemical, pharmaceutical, paper, textile, ore processing, onshore and offshore petroleum and natural gas production facilities; semiconductor, cryogenic plants; food and beverage processing facilities; and related processing plants and terminals. ASME B31.3 provides design, fabrication, erection, test, inspection, assembly and material requirements for piping systems that carries following fluids:
• Petroleum products
• Raw, intermediate, and finished chemicals.
• Refrigerants
• Gas, steam, air, water
• Fluidized soilds
• Cryogenic fluids
Packaged equipment piping design is also covered by the B31.3 code.
The process piping code ASME B31.3 typically does not cover the following:
• The piping systems designed for internal gage pressures at or above zero but less than 105 kPa (15 psi), provided the fluid handled is non-flammable, nontoxic, and not damaging to human tissues as defined in 300.2, and its design temperature is from −29°C (−20°F) through 186°C (366°F).
• Power boiler and power system piping following ASME B31.1
• Fired heater internal piping.
• Pressure vessels, heat exchangers, pumps, compressors, and other fluid handling or processing equipment, including internal piping and connections for external piping.

3. How to calculate the allowable stress for a carbon steel pipe?

The material allowable stress for any material other than bolting material, cast iron, and malleable iron is the minimum of the following:
1. one-third of tensile strength at maximum temperature.
2. two-thirds of yield strength at maximum temperature.
3. for austenitic stainless steels and nickel alloys having similar stress-strain behavior, the lower of two-thirds of yield strength, and 90% of yield strength at temperature.
4. 100% of the average stress for a creep rate of 0.01% per 1000 h
5. 67% of the average stress for rupture at the end of 100000 h for temperatures up to and including 815°C.
6. For temperatures higher than 815°C (1,500°F), (100 × Favg)% times the average stress for rupture at the end of 100000 h. Favg is determined from the slope, n, of the log time-to-rupture versus log stress plot at 100 000 h such that log Favg = 1/n. Favg shall not exceed 0.67.
7. 80% of the minimum stress for rupture at the end of 100000 h

4. What Is Straight Through Valve?

Valve in which the closing operation of valve is achieved by 90 degrees turn of the closing element.

5. What Pressure Tests Are Carried Out On Valves?

Shell-hydrostatic, seat-hydrostatic, seat-pneumatic

6. How To Calculate The Basic Allowable Stress For A Material?

The basic allowable stress is defined in respective code. For example as per B 31.3 the basic allowable stress for a material is the minimum of the following:
o 1/3rd of tensile strength at design temperature.
o 2/3rd of yield strength at design temperature.
o 100% of average stress for a creep rate of 0.01% per 1000 hours.
o 67% of average stress for rupture at the end of 100000 hours.
o 80% of minimum stress for ruptures at the end of 100000 hours.
o For austenitic stainless steel or nickel alloys the lower of yield strength and 90% of yield strength at temperature.
o For structural grade materials 0.92 times of the lowest value of point (a) to (f)

7.  What Is The Main Difference Between Constant And Variable Spring Hanger? When To Use These Hangers?

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:
o When thermal displacement exceeds 50 mm
o When variability exceeds 25%
o 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.

8. what is the most difficult situation you have had to face and how did you tackle it?

The reason why you are asked this question is to hear what you consider difficult and how you approached the situation. Select a difficult work situation, which was not caused by you and can be explained in a few sentences. You can then show yourself in a positive light by explaining how you handled the situation.

9. What is your greatest strength?

This could be a very simple question if you are prepared for it. You just have to talk about the strengths that you know would be of value to the company.
DO:
a. Make the most of this question. This question gives you the control to guide the interview to where you want it so take advantage.
b. Emphasize the strengths you have that are crucial to the position
c. Find out from the job description and from company research, the kind of strengths the company invests in.
DO NOT:
a. Do not be too modest or claim to be what you are not
b. Do not try to mention things you cannot illustrate with a brief example
c. Do not mention the strengths that are not relevant to the job at hand.