Control valves Question answers for Interview

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Control valves Question answers for Interview

Q1. __________ is one of the major causes of  dead band in a control valve assembly
  1. Linearity
  2. Resolution
  3. Static friction
  4. Valve plug
Q2. An example of final control element
  1. Control valve
  2. Transmitter
  3. I/P transducer
  4. Thermocouple
Q3.   A part of valve assembly which is used to seal against leakage around the stem
  1. Seat
  2. Limit switches
  3. Valve plug
  4. Packing
Q4. Color of a fail closed valve in Saudi kayan
  1. Grey
  2. Yellow
  3. Red
  4. Green
Q5.  In a globe valve, the line of flow
  1. changes
  2. does not change
Q6. The material put in the stuffing box is called ______PACKING________
Q7. If possible a gate valve _____________ be used for throttling
  1. should
  2. should not
Q8. __________ valve offers much more resistance to flow than __________ valve
  1. globe / gate
  2. gate / globe
  3. butterfly / globe
Q9. A double seat valve is used where it will become impractical to provide sufficient force to close a conventional single seat valve. State true or false.
  1. True
  2. False
Q10. _____________ valve is used to allow precise flow control.
  1. gate
  2. globe
  3. butterfly
  4. needle
Q11. The wear due to the contact friction is _____________ on the disc of a globe valve.
  1. uneven
  2. more even
Q12.  Identify the valves
                                           ______PLUG________CHECK________BUTTERFLY_____  NEEDLE___________

 

Q13.   An example of a packing material:
 Ans:    _______PTFE____________
Q14.  Name any two types of valve end connections.

1.______THREADED________________

2.__________BOLTED FLANGES____________

Q15. What is the purpose of using extension bonnets ?

 

Q16. Show the packing material in the figure.

 

      

 

Q17.  Identify the flow characteristics (equal percentage, quick opening, linear)
    1.________ quick opening _____________
    2._______L inear______________
    3._______ equal percentage ______________
Q18.  For this valve, at a valve position of 50% open, flow rate is 50% of maximum

  1. Equal percentage
  2. Linear
  3. Quick opening
Q19. For an equal percentage control valve, the flow increases 4% for every 1% of valve movement. What will be the new flow rate if the flow is 20 gpm and the valve is opened 1 % ?
  1. 24 gpm
  2. 20 gpm
  3. 20.8 gpm
  4. 21 gpm
Q20.  This valve is used for On/Off applications
  1. Equal percentage
  2. Linear
  3. Quick opening
Q21.  For this valve, the change in flow rate observed  will be relatively small when the valve plug is near its seat and relatively high when the valve plug is nearly wide open.
  1. Equal percentage
  2. Linear
  3. Quick opening
Q22.  What is the purpose of actuator in a  control valve ?
TO ACTUATE THE VALVE STEM
Q23.  Identify the following parts of the actuator by putting the numbers corresponding to the arrows.



  1. Actuator tem
  2. Loading pressure connection
  3. Diaphragm plate
  4. Actuator spring
Q24.  In a direct acting actuator, increasing air pushes up the diaphragm and the actuator stem retracts. Is this statement True or False.
  1. True
  2. False
Q25.  Give the names of four control valve accessories
         1.______LIMIT SWITCH________________
         2._______SOLENOID_______________
         3.___________POSITINER___________
         4.___________I/P___________
Q26. A positioner acts as if it is a
  1. Control loop on the actual valve position
  2. Pneumatic transmitter
  3. PLC
  4. Sensor
Q27. A valve positioner can
  1. Change the valve set point
  2. Change the controllers output signal
  3. Increase the signal to the valve positioned
  4. Adjust valve position to match controller output
Q28. When a liquid enters the valve and the static pressure at the vena contracta drops to
less than  the fluid vapor pressure (PV), and the valve outlet pressure is also less than the fluid vapor pressure, the condition is called


  1. Cavitation
  2. Flashing
  3. Saturation
  4. Hunting
Q29.  For flanged valve bodies, finish tightening them in which order?
  1. 1-7 ; 4-6; 2-8; 3-5
  2. 1-5; 3-8; 2-6; 4-7
  3. 1-3;2-4;5-8; 6-7
  4. 1-2; 5-6 ; 3-4 ; 8-7
Q30. Water flows through a 2 inch control valve with a pressure drop of  4 psi. Find the volumetric flow rate if the control valve has a Cv of 55.
Q=Cv√ΔP/G
Q=55√4/1
Q=110 gpm
Please read also:  All Fluid Control Valves Types
Please read also: Basic Control Valve Principles

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