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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
Static friction Valve plug
Q2. An example of final control element
Control valve Transmitter
Q3. A part of valve assembly which is used to seal against leakage around the stem
Q4. Color of a fail closed valve in Saudi kayan
Q5. In a globe valve, the line of flow
changes does not change
Q6. The material put in the stuffing box is called ______PACKING________
Q7. If possible a gate valve _____________ be used for throttling
Q8. __________ valve offers much more resistance to flow than __________ valve
globe / gate gate / globe
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.
Q10. _____________ valve is used to allow precise flow control.
Q11. The wear due to the contact friction is _____________ on the disc of a globe valve.
Q12. Identify the valves
Q13. An example of a packing material:
Q14. Name any two types of valve end connections.
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 _____________
3._______ equal percentage ______________
Q18. For this valve, at a valve position of 50% open, flow rate is 50% of maximum
Linear 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 % ?
20.8 gpm 21 gpm
Q20. This valve is used for On/Off applications
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.
Equal percentage Linear
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.
Loading pressure connection
Q24. In a direct acting actuator, increasing air pushes up the diaphragm and the actuator stem retracts. Is this statement True or False.
Q25. Give the names of four control valve accessories
Q26. A positioner acts as if it is a
Control loop on the actual valve position Pneumatic transmitter
Q27. A valve positioner can
Change the valve set point
Change the controllers output signal
Increase the signal to the valve positioned
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
Q29. For flanged valve bodies, finish tightening them in which order?
1-7 ; 4-6; 2-8; 3-5
1-5; 3-8; 2-6; 4-7
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.