Home / Blog / Piping Design Engineer Interview Questions Part-12 (Valves – VI)

Piping Design Engineer Interview Questions Part-12 (Valves – VI)


1. What are instrument categories?
General, flow, temperature, pressure, level, density etc.
2. Which instruments are handled by piping department?
Flame arrestor, breather valve.
3. What are basic functions of instruments?
To sense, transmit, indicate, read and control
4. Why block valve is used at the root of an instrument like pressure indicator?
They are needed to isolate gauges for maintenance during plant operation and during hydro static testing of piping system. They are called root valve.
5.Where diaphragm assembly is used?
For corrosive, abrasive, viscous fluids. Neutral fluid like glycol is used on instrument side of diaphragm.

6.Where and why bleed valve is used in instruments?
If the conveyed fluid is hazardous or under high pressure, a branch fitted with a bleed valve is inserted between the gage and its isolating valve, to relieve pressure and/or drain the liquid before servicing the gage. It can also be used to sample or for adding a comparison gage.
7.Why control valves are usually flanged?
For ease of installation and removal during maintenance.
8. Where ball contol valve is used?
Suitable where nature of fluid is slurry form or handling two phase flow having particle in suspension, for non-critical and critical fluids having a fluid temperature to suit the soft seat material and where relatively low pressure drop is required across control valve. They have side mounted actuator.
9. Where butterfly control valve is used?
Used for large size piping network handling clean fluid for low pressure drop across control valve and soft seated control valve. Metal seated valves used for higher temperatures.
10. How control valve block valves should be located?
They should be as close to control valve as possible, considering drain requirement and handwheel clearance. At least one of the block valve should be paced in vertical so that spool can be removed allowing the control valve to be removed.

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One comment

  1. Hello sir i am completed with BE mechanical eng after i will interested in value courses in abroad in current suchuvation … So pls help me sir.

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