Piping Interview Question Answers for Oil and Gas Companies

Today we will talk about top 20 piping interview question answers which is asked in interview 

Question 1:- How can flanges be classified on the basis of facing?

Answer: Flanges are classified on the basis of facing as:
a) Flat face. (F/F)
b) Raised face. (R/F)
c) Tongue and groove. (T/G)
d) Male and female. (M/F)
e) Ring type joint. (RTJ)

Question 2:- How Can Flanges Be Classified Based On Pressure- Temperature Ratings?

Answer: Flanges are classified based on pressure temperature ratings as:
a) 150#
b) 300#
c) 400#
d) 600#
e) 900#
f) 1500#
g) 2500#

Note: – # read as class like – 150# read as 150 class 

 Question 3:- 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 well as outside. These flanges are of forged construction.

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 pipelines where welding cannot be carried out.

d) Lap Joint. : – The Lap Joint flanges are used with stub ends. The stub ends are welded 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.

Question 4 :- How the gaskets are classified based on the type of construction?

Answer: On the basis of construction, gaskets are classified as:
a) Full face.
b) Spiral wound metallic.
c) Ring type.
d) Metal jacketed.
e) Inside bolt circle.

Watch Different Types of Flanges

Question 5 :- How do we select the MOC of winding material for spiral wound metallic gasket ?

Answer: The selection for 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.

Question 6 :- 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.

Question 7:- What is the most commonly used material for gasket?

Answer:  Compressed Asbestos Fiber.

Question 8:- Which type of gasket is recommended for high temperature & high-pressure application?

Answer: Spiral Wound Metallic Gasket.

Question 9:- 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.

What is Fitter & Types of Fitter worked in oil and gas refineries and petrochemicals click here

Question 10:- What is centering ring in connection to spiral wound gasket?

Answer: Spiral wound gaskets are provided with carbon steel external ring called centering ring.

Question 11:- How the pipe fittings are classified on the basis of end connections?

Answer: Pipe fittings are classified on the basis of  end connections as:
a) Socket weld fittings.
b) Screwed end fittings.
c) Beveled end or Butt weld fittings.
d) Spigot socket fittings.
e) Buttress end fittings.

Question 12:- Normally where do we use the following?

(1) Eccentric reducers. (2) Concentric reducers.

Answer: Eccentric reducers = Pump suction to avoid Cavitation, to maintain elevation (BOP) in rack.
Concentric reducers = Pump discharge, vertical pipeline etc.

 Question 13:- From which side of pipe will you take a branch connection?

Answer:  Topside – When fluid is Gas, Air or Steam and Cryogenic Service

Bottom Side – When Fluid is Liquid

 Question 14:- 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.

Question 15:- Why Do We Provide High Point Vent (HPV) And Low Point Drain (LPD) In Piping?

Answer: HPV – For removing Air during Hydro test.
LPD – For draining water after conducting Hydro test.

 Question 16:- 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.

Question 17:- 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.

 Question 18:- What do you mean by IBR and which lines comes under IBR preview?

Answer:  IBR: Indian Boiler Regulation Act. Steam lines with conditions listed bellow comes under IBR preview: – 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.

 Question 19:- What are weld let and socket ? And where they are used?

Answer: Weldolet and Sockolet are basically self-reinforced fittings.
Weldolet is used for Butt weld branch connection where standard tee is not available due to size restrictions and the piping is of critical / high-pressure service. Sockolet is used for socket welding branch connection, which require reinforcing pad.

 Question 20:- What is the normal upstream and downstream straight length of orifice flow meter?

Answer: Upstream – 15D
Downstream – 5D

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