Piping interview Question and Answers For Mechanical Students

Piping related interview questions for Mechanical Students 

PUMPS

1 What is NPSH ?
Ans : It is measure of the pressure drop of the liquid as it moves form moves form the inlet of the pump to the eye of the impeller, determined by testing and expressed in feet of water by pump manufacturer.

2 What is cavitation ?
Ans : Cavitation is a rapid collapse of vapor pressure that can produce noise, result in loss of head and capacity and create a severe erosion of the impeller and casing surface in the adjacent inlet areas.

3 What is velocity head?
Ans : The head loss caused by the consumed power to accelerate stationary fluid to suction line velocity during pump startup. Its about 1 ft.

4 What is standard for petroleum pumps?
Ans : API 610 is the standard for centrifugal pumps in petroleum industry.

5 Where positive displacement pumps are used ?
Ans : Used to move viscous liquids, injects chemicals or additives into a system, or pump quantities too small for centrifugal pumps.

6 What are types of rotary pumps ?
Ans : External Gear, Cam and piston, two lobe, three lobw, single screw, Two screw.

7 Where rotary pumps are used ?
An s : For viscous liquids that are free of hard and abrasive fluids.

8 Where should boiler feed water pumps be located ?
An s : They take water from a deaerator and generally operate close to the vapor pressure of the liquid, hence they must be located as close to the deaerator as possible.

piping interview question and answers
piping interview question and answers

9 Tell something about vertical pumps ?
An s : Used where low available NPSH is not sufficient, for surface condenser, for waste material in concrete pit, screen at the bottom.

10 Where centrifugal pumps in vacuum service be located ?
An s : directly below tower, may be on spring supports.

11 How to support discharge line of centrifugal pump ?
An s : Discharge line should be supported as close to the top elbow as possible and should be within five diameters of that elbow, using spring support.

1 How suction line is supported?
An s : Commonly supported under the elbow adjacent to the pump nozzle.

2 How the suction line reducer should be placed ?
An s : It should be placed top flat.

3 What are suction line requirements?
An s : To flat reducer, strainer, block valve, no pockets, as short as possible with consideration to stress, min straight length of 3D.

4 What are the requirements of discharge piping?
An s : Reducer, Pressure indicator, check valve, block valve, min. stress, support at top elbow.

5 What is accepted distance between pumps?
An s : 1200 MM / 4 feet.

6 What is special requirement for discharge line of positive displacement pump?
An s : Relief valve whose discharge is connected in suction line between the isolating valve and the pump.

REACTOR

1. Tell about reactor?
An s : Heart, mixing, chemical reaction, heat generated-absorbed, agitation, jacket, heating coils, cooling.

FURNACES
1 Where furnaces shall be located ?
An s : Furnaces shall be located upwind or side wind of process units to blow any combustible leaks away from the open flame, Min 90 M away from tanks and 30 M away from control room.

2 What should be stack height?
An s : Stack height shall be minimum 6 M above working platform in the vicinity of 25 m radius.

SPIRAL HEAT EXCHANGERS

1 Where spiral heat exchangers are used?

An s : Generally in chemical plants

2 How piping is positioned for spiral heat exchanger ?

An s : Piping positioned to allow opening of covers and the removal plates.

SHELL AND TUBE HEAT EXCHANGERS

1 What are the types of tube arrangements?
An s : U-tube, Fixed tube, kettle arrangement.

2 What is full form of TEMA?
An s : Tubular exchangers manufacturers Association.

3 Which fluids to be sent through tubes?
An s : Fouling and/or corrosive fluids (Easy cleaning and cheaper to replace tubes than shell), hotter fluid : To reduce heat loss to the heat loss to the surroundings except steam., refrigerant, cooling fluid.

4 What should be clearance between flanges of exchangers?
An s : 1000 MM.

PLATE EXCHANGERS

27. Where plate exchangers are used ?
An s : Low pressure, low temperature applications.

DOUBLE PIPE OR FIN TUBE EXCHANGERS

28. Where used ?
An s : Used when liquid has a greater resistance to heat flow than another or when the surface area is small.

AIR COOLER EXCHANGERS

29. Where used ?
An s : To cool tower overhead vapors.

LPG STORAGE
1 How to group LPG Vessels ?
An s : Max 6 Vessels, total capacity 15,000 cum, curb wall, distance between vessels of different groups 30M, separate dedicated manifold for each group.

2 Where to located LPG Storage ?
An s : Downwind of process units, important buildings and facilities, not in same dyke where other flammable liquid HC’s stored, single row in case of spheres and bullets, not one above the other, bullet head not toward other vessel, no dip ditch to avoid LPG Settling.

3 How to operate LPG Cylinders ?
An s : Separate area for empty and filled cylinders, Cylinders vertical, not near other gase cylinders, never below grade, smooth trucking traffic.

Subject wise Technical Mechanical Interview Questions By S k Mondal
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