Section 5 FINAL CONTROL DEVICES Flashcards
- Refer to Figure 75. What is the flow characteristic determined by the cage?
A. Linear.
B. Cavitation.
C. Quick opening.
D. Equal percentage.
- When replacing a control valve. What is done after opening the bypass valve?
A. Close the upstream and downstream block valves.
B. Close the upstream valve and unbolt the existing valve.
C. Close the downstream block valve and open the upstream block valve.
D. Close the upstream block valve and open the downstream block valve.
- The packing on a valve has been adjusted. At 50% rising signal, the valve opens 40%, and at 50% falling signal, it closes to 60%. How is this corrected?
A. By tightening the packing.
B. By loosening the packing.
C. By replacing the actuator.
D. By replacing the plug and the seat.
- Loop tuning has been performed on a control loop. The valve continues to oscillate. What is the cause?
A. The trim is undersized.
B. The packing is too loose.
C. The trim is oversized.
D. The packing is leaking.
- After cleaning out a tank, the level cannot be controlled when the system is brought back online. What is the cause?
A. The drain valve is obstructed.
B. The drain valve is oversized.
C. The fill valve trim is worn.
D. The fill valve packing is worn.
- What is done when a valve stem has build-up, causing a leak?
A. Replace the O-ring and lubricate the stem.
B. Change the packing size.
C. Clean and polish the stem.
D. Grind and lubricate the stem.
- A valve with a Teflon seat is not providing sufficient shut-off. How is this corrected?
A. By lapping the plug.
B. By lapping the seat.
C. By replacing the seat.
D. By replacing the plug.
- Which actuator is installed on a direct acting wave to make the system fail close?
A. Electric gear.
B. Double-acting air piston.
C. Diaphragm air-to-open.
D. Diaphragm air-to-close.
- What is done when a reverse acting spring and diaphragm actuator does not provide the travel expected?
A. Check the air vent.
B. Lubricate the diaphragm.
C. Move the travel indicator.
D. Decrease the air supply.
- What is done when performing scheduled preventative maintenance on a pneumatic piston actuator?
A. Adjust the travel stop.
B. Adjust the feedback linkage.
C. Replace the O-rings.
D. Replace the diaphragm.
- Refer to Figure 38. When removing a direct-acting spring-opposed valve actuator from the valve bonnet. What is the sequence to disassemble?
A. Relieve spring tension, remove stem connector, then remove yoke locknut.
B. Remove yoke locknut, remove stem connector, then relieve spring tension.
C. Remove stem connector, relieve spring tension, then remove yoke locknut.
D. Remove travel indicator, remove yoke locknut, then remove stem connector.
- What is the procedure for adjusting an electric actuated gate valve after the actuator overhaul and before testing the valve operation?
A. Power off, place valve in mid-position, power on, adjust open limit switch, then adjust close limit switch.
B. Power on, open valve, adjust close limit switch, close valve, then adjust open limit switch.
C. Power on, place valve in mid-position, open valve, adjust open limit switch, close valve, then adjust close limit switch.
D. Power off, open valve, adjust open limit switch, close valve, adjust close limit switch, place valve in mid-position, then power on.
- How is a diaphragm actuator disassembled?
A. By removing the spring tension and removing bolts in a clockwise pattern.
B. By removing bolts in a clockwise pattern and removing the spring tension.
C. By removing the spring tension and removing bolts in a cross pattern.
D. By removing bolts in a cross pattern and removing the spring tension.
- A spring and diaphragm actuator has stopped working. The yoke and the dome are corroded with nitric acid. What is done to correct the problem?
A. Repair the yoke.
B. Replace the cylinder housing.
C. Repair the corroded areas.
D. Replace the actuator.
- Refer to Figure 71. What is the characteristic of the positioner?
A. Linear.
B. Quick opening.
C. Equal percentage.
D. On/off.