Control Valve multiple choice questions

 Control Valve

1. The definition of split range control valves implies that they are
a) calibrated with complementary ranges.
b) easily re-ranged for different characteristics.
c) equipped with quick-acting positioners.
d) only used in sets of three.
Answer: calibrated with complementary ranges.
2. The proper “fail safe” status of a valve should always be dictated by
a) economic savings
b) the nature of the process
c) the controller’s tuning
d) the controller’s action (direct or reverse)
Answer: the nature of the process
3. Calculate the necessary Cv rating for a liquid service valve, given a pressure drop of 24 PSID, a specific gravity of 1.3, and a maximum flow rate of 140 GPM. Assume there will be no flashing or choked flow through the valve.
a) 0.1319
b) 32.58
c) 7.583
d) 2585
Answer: 32.58
4. When a valve is installed in a process with where the differential pressure (drop) across the valve decreases with increasing flow, the best trim characteristic to choose for the valve would be
a) Ported
b) Quick-opening
c) Equal percentage
d) Linear
Answer: Equal percentage
5. The main purpose of a control valve positioner is to
a) Alter the fail-safe status of the valve
b) Improve the precision of the valve
c) Alter the characterization of the valve
d) Increase transmitter accuracy
Answer: Improve the precision of the valve
6. The purpose of valve packing is to
a) Help reduce cavitation in the valve trim
b) Increase stiction
c) Cushion the valve against harm during shipment
d) Seal process fluid from escaping past the stem
Answer: Seal process fluid from escaping past the stem
7. An air-to-open valve assembly may be formed with which of these actuator/valve body combinations?
a) Reverse-acting actuator, direct-acting valve body
b) Direct-acting actuator, direct-acting valve body
c) Direct-acting actuator, reverse-acting valve body
d) A or C
Answer: a or c
8. Cavitation in a control valve is caused by
a)process noise
b) vibration in the piping
c) pressure recovery
d) a laminar flow regime
Answer: pressure recovery
9. Dual-ported globe valves typically enjoy the following advantage over single-ported globe valves
a) Less actuating force required
b) Longer service life
c) Easier disassembly and maintenance
d) Tighter shut-off
Answer: Less actuating force required