Sizing, Selecting and Applying Process Control Valves (EI30)

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Knowledge Check

1. An improperly sized or selected control valve can cause:
*

a. Process inefficiency

b. Poor product quality

c. Increased maintenance costs

d. All of the above

2. A control valve actuator must overcome:
*

a. Fluid forces acting on the valve plug

b. Frictional forces

c. Fluid forces on the valve stem

d. All of the above

3. Which of the following valves will have the best leakage rating?
*

a. Ball valve

b. Diaphragm valve

c. Sliding gate valve

d. Globe valve

4. Which valve type offers the highest flow capacity? *

a. Butterfly valve

b. Globe valve

c. Ball valve

d. Diaphragm valve

5. Which statement is true?
*

a. Air springs cannot be used with piston actuators.

b. Increasing the air pressure on a direct acting diaphragm actuator causes the stem to move upward

c. The lower chamber of a reverse acting diaphragm actuator is vented.

d. Piston actuators can operate at higher air pressures than diaphragm actuators.

6. Volumetric Flow through a concentric orifice plate is:
*

a. Inversely proportional to differential pressure.

b. Inversely proportional to orifice size.

c. Proportional to the square root of differential pressure.

d. Directly proportional to orifice size.

7. Secondary control valve trim consists of:
*

a. Stuffing box parts, such as the packing follower, springs and lantern ring.

b. Removable parts of the valve that come in contact with the process fluid.

c. Components designed to contain pressure, such as the valve body, bonnet and flanges.

d. An actuator and positioner

8. A butterfly valve with a symmetrically aligned disk becomes disconnected from its actuator. Flow will tend to make the valve:
*

a. Close

b. Open

c. Remain in position

9. The difference between cavitation and flashing is that:
*

a. Cavitation can cause damage, while flashing cannot.

b. Flashing can cause damage, while cavitation cannot.

c. When flashing occurs, the vapor bubbles do not collapse, while during cavitation they do collapse.

d. Cavitation increases flow rate, while flashing does not.

10. Throttling the high-pressure flow of a fluid at high temperature through a control valve will: *

a. Increase fluid temperature downstream.

b. Decrease fluid temperature downstream.

c. Increase fluid temperature upstream.

d. Increase fluid temperature upstream.

11. Which of the following auxiliary devices can provide for "split ranging"?
*

a. Lock-up relay

b. Positioner

c. Limit switch

d. Trip relay

12. Which of the following manual valves is not related to control valve maintenance? *

a. Upstream and downstream isolation valves

b. Bypass valve

c. Inlet drain valve

d. Outlet drain valve

e. All of the above

f. None of the above

13. Which of the following valve types would be suitable for controlling the flow of a slurry? *

a. Double-seated globe

b. Butterfly

c. Knife edge gate

d. Diaphragm

14. Which of the following is not a consideration when sizing valves for incompressible fluids? *

a. Fluid density

b. Size of valve, piping, inlet and outlet fittings.

c. Viscosity of the fluid at the operating temperature.

d. Pressure, temperature and metallurgical characteristics of the valve.

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