Valve Selection

Question 1

What type of end fitting is best to use for control valves when ease of installation and maintenance is considered?

Answer 1

Flanged

Question 2

Describe Control Valve CV

Answer 2

The number of gallons of water that can flow through a fully open valve at 15 degrees Celsius and 1 psi of differential pressure

Question 3

The condition of excessive sound coming from a control valve in operation is identified as?

Answer 3

Noise

Question 4

The phenomenon of the fluid passing through a control valve causing the pressure of the fluid to go below it’s vapor pressure and then back above the vapor pressure as the fluid exits the valve is called?

Answer 4

Cavitation

Question 5

The phenomenon of the fluid passing through a control valve causing the pressure of the fluid to go below it’s vapor pressure and remain below vapor pressure as the fluid exits the valve is called?

Answer 5

Flashing

Question 6

What options are available to instrument designers to minimize the effects of flashing and cavitation in control valves?

Answer 6

Incorporating a special trim to size the valve so that flashing and cavitation does not occur

Question 7

What will be the effect of noise from a control valve if the pressure drop across the valve increases?

Answer 7

Noise increases

Question 8

What type of flow does flashing and cavitation occur in?

Answer 8

Liquid

Question 9

When specifying an option for a control valve to ensure the valve position is accurate for the given control signal, one would specify a?

Answer 9

Valve positioner and actuator

Question 10

When specifying the size requirements of an actuator for a linear control valve, what key factor must be considered in the sizing of the actuator?

Answer 10

The maximum DP that will occur and force needed to move the valve stem under maximum DP

Question 11

What is the rule of thumb for globe control valve size in relation to pipe size?

Answer 11

Control valve is between 0.5 and 1 times the size of the pipe

Question 12

When sizing an equal percentage globe valve, what percent opening is typically used for normal flow rate?

Answer 12

70%

Question 13

When sizing a control valve what 3 conditions should you size it for?

Answer 13

Minimum, normal, and maximum pressure drop

Question 14

Which issues are related to over-sizing a control valve?

Answer 14

1) More expensive
2) Less control at low flowing conditions

Question 15

What determines the control valve capacity (Cv) for a certain valve type?

Answer 15

Body size and trim

Question 16

Assuming that inlet pressure is constant and the pressure drop is happening due to change in outlet pressure describe choked flow through a valve.

Answer 16

When an increase in pressure drop through the valve does not increase the flow

Question 17

How can you find mass flow rate for a gas service valve?

Answer 17

Multiply with density at standard conditions

Question 18

The _______ the DP across the valve the __________ is the CV of the valve.

Answer 18

higher, higher

Question 19

What parameter would you choose to pick a CV for a ball valve

Answer 19

60 degrees open

Question 20

The sound coming from a control valve in operation shall not typically exceed ___________ dB(A) at 1 m?

Answer 20

85 decibels

Question 21

What is used to move the valve stem?

Answer 21

Actuator