Question and Answers on Piping related topics

Top 10 Interview Questions Related To Pipes Supports

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Interview Questions Related To pipes Supports:-

1. What are the Criteria for Pipe Supporting?

Answer: –

Following are the points, which should be taken into account for proper supporting: –

A. Load of bare pipe + fluid + insulation (if any).
B. Load of bare pipe + water fill.
C. Load of valves and online equipment and instrument.
D. Thermal loads during operation.
E. Steam out condition, if applicable.
F. Wind loads for piping at higher elevation, if required.
G. Forced vibration due to pulsating flow.
H. Bare pipe with size above 12” shall be supported with Pad or Shoe.

2. What is the basic span of supports for 2”/6”/10”/24” pipe?

Answer: –

Basic Span is 5.5m / 9m / 11.5m / 15m respectively.

3. What is the function of providing the anchor, cross guide and guide for piping?

Answer: –

Anchor is provided to restrict all the axial and rotational movements of pipe, whereas cross guide is
provided to restrict displacements of pipe along with the axis perpendicular to its centerline and Guide is provided to restrict the longitudinal movements of pipes along with its axis.

4. How is piping to Tank inlet nozzle is supported and why?

Answer: –

Piping to Tank Nozzle is supported with spring type support (first support from Nozzle) in order to
make the nozzle safe from the loads which occurs due to the displacement of pipe ( Displacement
may be due to thermal expansion of pipe, tank material, tank settlement etc).

5. What are the types of flexible spring hangers?

Answer: –

1. Constant Spring Hanger 2. Variable Spring Hanger.

6. What is the purpose of providing Graphite Pads in supports below shoes?

Answer: –

To reduce the friction factor. The coefficient of friction for Graphite Pads is 0.1

7. Where do you provide Anchor and Slotted Support of Heat Exchanger?

Answer: –

Anchor support of Heat exchanger is provided on the side from which Tube bundle will be pulled out for the purpose of maintenance work also it is based on the growth of the connecting piping as
exchanger should grow with the piping.

8. What should be the material of shoes for supporting AS pipes & why?

Answer: –

If CS shoes are used then pad in contact with the pipe shall be of Alloy steel to avoid dissimilar
welding at pipe. To avoid alloy steel welding and dissimilar welding, fabricated clamps either of CS or SS can be used.

9. What are sway braces?

Answer: –

Sway braces are essentially a double acting spring housed in a canister. Their purpose is to limit the
undesirable movement. Undesirable movement means movement caused by wind loading, rapid
valve closure, relief valve opening, two phase flow or earthquake.

10. What is the difference between variable spring hanger and constant spring hanger?

Answer: –

Variable spring Hanger: –
As the name itself indicates the resistance of the coil to a load changes during compression.
Constant spring Hanger: –
Constant spring hanger provides constant support force for pipes and equipment subjected to vertical movement due to thermal expansion.


Questions related to Pipe Fittings: –

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1. How can flanges be classified based on Pipe Attachment?

 Answer: –

Flanges can be classified based on pipe attachment as: –

Slip – on. : – The Slip-on type flanges are attached by welding inside as well as outside. These flanges are of forged construction.

Socket Weld. : – The Socket Weld flanges are welded on one side only. These are used for small bore lines only.

Screwed. : – The Screwed-on flanges are used on pipelines where welding cannot be carried out.

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.

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.

Blind. : – The Blind flanges are used to close the ends which need to be reopened.

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.

Integral. : – Integral flanges are those, which are cast along with the piping

component or equipment.

  1. 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

Pressure temperature rating carts in the standard ASME16.5 specify the non-shock working

gauge pressure to which the flange can be subjected to at a particular temperature.

  1. How can flanges be classified based on facing?

Answer: –

Flanges are classified based on facing as: –

  1. Flat face. (FF)
  2. Raised face. (R/F)
  3. Tongue and groove. (T/G)
  4. Male and female. (M/F)
  5. Ring type joint. (RTJ)
  1. How can flanges be classified based on face finish?

Answer: –

Flanges are classified based on face finish as: –

  1. Smooth finish.
  2. Serrated finish.
  1. Where the smooth finish flange & serrated finish flange finds its use?

Answer: –

The smooth finish flange is provided when metallic gasket is provided and serrated finish flange is provided when non-metallic gasket is provided.

  1. What are the types of serrated finish provided on flange face?

Answer: –

  1. Concentric or
  2. Spiral (Phonographic)


  1. How the serration on flanges is specified?


The serration on flanges is specified by the number, which is the Arithmetic Average Rough

Height (AARH).

  1. Where the concentric serration is insisted for face finish?

Answer: –

Concentric serration are insisted for face finish where the fluid being carried has very low

density and can find leakage path through cavity.

  1. How the Gaskets are classified based on the type of construction?

Answer: –

Based on the type of construction, gaskets are classified as: –

  1. Full face.
  2. Spiral wound metallic.
  3. Ring type.
  4. Metal jacketed.
  5. Inside bolt circle.

  1. What is the most commonly used material for Gasket?

Answer: –

Compressed Asbestos Fibre.

  1. Which type of gasket is recommended for high temperature & high-pressure application?

Answer: –

Spiral Wound Metallic Gasket.

  1. What are the criteria for selection of MOC of Spiral Wound metallic Gasket winding material?

Answer: –

The selection of material of construction for Gasket winding depends upon: –

  1. The corrosive nature and concentration of fluid being carried.
  2. The operating temperature of the fluid.
  3. The relative cost of alternate winding material.


  1. 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: –

  1. Austenitic stainless steel 304 with asbestos filler.
  2. Austenitic stainless steel 316 with asbestos filler.
  3. Austenitic stainless steel 321 with asbestos filler.

  1. 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.

  1. What is centering ring in connection to spiral wound gasket?

Answer: –

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

  1. What will be the AARH finish on flange face for using spiral wound gasket?

Answer: –

125-250 AARH finish.


  1. On which type of flanges the use of spiral wound gasket are restricted?

Answer: –

rating spiral wound gasket on flanges other#ASME B16.5 does not recommend the use of 150 than welding neck and lapped joint type.

  1. Up to what temperature limits the low strength carbon steel bolts should not be used for flanged joints?

Answer: –

C.°C or below – 28°Flanged joints using low strength carbon steel shall not be used above 200

  1. How the pipe fittings are classified based on end connections?

Answer: –

Pipe fittings are classified based on end connection as: –

  1. Socket weld fittings.
  2. Screwed end fittings.
  3. Beveled end or Butt weld fittings.
  4. Spigot socket fittings.
  5. Buttress end fittings.

  1. Up to what temperature the carbon steel materials shall be used?

Answer: –

Carbon steel materials shall be used for temperature up to 425C°


  1. Which material is used for temperature above 426C°?

Answer: –

Alloy steel materials shall be used for temperature above 426 C°

  1. Which type of material is used for corrosive fluid?

Answer: –

Stainless steel materials shall be used for corrosive fluid.

  1. Which type of piping materials are used for drinking water, instrument air etc?

Answer: –

Galvanized steel materials shall be used for drinking water, instrument air and NI lines (LP).

  1. What is the difference between Pipe and Tube?

Answer: –

Pipe is identified by NB and thickness is defined by Schedule whereas Tube is identified by OD & its thickness as BWG (Brimingham wire gauge or 1/100 inch).

  1. From which size onwards NB of pipe is equal to OD of Pipe?

Answer: –

From the size 14” and onwards NB = OD of pipe.

  1. What should be the radius of long radius elbow?


1.5D (Where “D” is the diameter of the pipe.)

  1. What should be the radius of short radius elbow?


1D(Where “D” is the diameter of the pipe.)

  1. What is the basis of using of short radius & long radius elbow?


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.

  1. Normally where do we use the following?

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


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

  1. Concentric reducer is used in pump suction. (Yes / No). Explain.


No. Air pockets may form if concentric reducer is used at pump suction, which results in cavitation

and cause damage to Pump. To avoid this problem, Eccentric Reducer with flat side up (FSU) is

used in Pump Suction.

  1. Where the ERW spiral & longitudinal pipes are used?


Use depends upon the availability of pipes. Nothing functional difference.


  1. Where the ERW & Seamless pipes are used?


Above 18” ERW pipes are used. Below 18” seamless pipes are used. Seamless pipes can sustain

higher temperature & pressure.


  1. What is the main use of ASTM A53 & A106 Gr.B pipes?


ASTM A53 pipes are mainly used for utility services whereas A106 Gr. B pipes are used for high

Pressure & high temperature services.

  1. From which side of pipe will you take a branch connection?


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

When Fluid is Liquid – Bottom Side.

  1. 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.

  1. Why do we provide High Point Vent (HPV) and Low Point Drain (LPD) in piping?


HPV – For removing Air during Hydro-test.

LPD – For draining water after conducting Hydro-test.

  1. 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.

  1. What is the minimum distance to be maintained between two welds in a pipe?

Answer: –

The thumb rule is that the minimum distance between adjacent butt welds is 1D. If not, it is never

closer than 1-1/2″. This is supposedly to prevent the overlap of HAZs. Minimum spacing of

circumferential welds between centerlines shall not be less than 4 times the pipe wall thickness or

25 mm whichever is greater.

  1. What do you mean by IBR and which lines comes under IBR purview?

Answer: –

IBR: Indian Boiler Regulation Act.

Steam lines with conditions listed bellow comes under IBR purview : –

  • 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.

  1. What are Weldolet and Sockolet? And where they are used?


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.

  1. What is the MOC for Superheated high pressure Steam Lines?


A 335 Gr. P I / P 11, Composition: Cr. – ½ Mo (P1) / 1¼ Cr. – ½ Mo (P11)

  1. What is the normal upstream and downstream straight length of orifice flow meter?

Answer: –

Upstream – 15D Downstream – 5D