Rotary-Shaft Control Valve Terminology

Question 1

Actuator
Lever

Answer 1

Arm attached to rotary valve shaft to convert linear actuator stem motion to
rotary force to position disk or ball of rotary-shaft valve

Question 2

Ball Full

Answer 2

The flow-controlling member of rotary-shaft control valves using a complete
sphere with a flow passage through it. The flow passage equals or matches the
pipe diameter

Question 3

Ball Segmented

Answer 3

The flow-controlling member of rotary shaft control valves using a partial
sphere with a flow passage through it.

Question 4

Ball V-notch

Answer 4

a polished or plated partial-sphere surface that rotates against the seal ring
throughout
the travel range with a V notch shape

Question 5

Bench Set

Answer 5

The calibration of the actuator spring range of a control valve to account for
the in-service process forces

Question 6

Double-Acting
Actuator

Answer 6

An actuator in which power is supplied in either direction

Question 7

Fail-Closed

Answer 7

A condition wherein the valve closure member moves to a closed position
when the actuating energy source fails

Question 8

Fail-Open

Answer 8

A condition wherein the valve closure member moves to an open position
when the actuating energy source fails

Question 9

Fail-Safe

Answer 9

A characteristic of a valve and its actuator, which upon loss of actuating energy
supply, will cause a valve closure member to be fully closed, fully open, or
remain in the last position, whichever position is defined as necessary to
protect the process

Question 10

Flow Coefficient

Answer 10

A constant related to the geometry of a valve, for a given travel, that can be
used to establish flow capacity

Question 10

Flow Characteristic

Answer 10

Relationship between flow through the valve and percent rated travel as the
latter is varied from 0 to 100 percent. Designated as either inherent or
installed

Question 11

Hunting

Answer 11

An undesirable oscillation of appreciable magnitude, prolonged after external
stimuli disappear. Sometimes called cycling or limit cycle

Question 12

Operating Medium

Answer 12

This is the fluid ,generally air or gas, used to supply the power for operation of
valve positioner

Question 13

Split Range

Answer 13

Action in which two or more signals are generated or two or more final
controlling elements are actuated by an input signal, each one responding
consecutively, with or without overlap, to the magnitude of that input signal

Question 14

Cavitation

Answer 14

a process in which vapour bubbles in a flowing liquid collapse inside a control
valve as the pressure begins to increase

Question 15

Flashing

Answer 15

a process in which a portion of a liquid converts to a vapour as it passes
through a control valve because the pressure has fallen below the vapour
pressure of the liquid

Question 16

Manipulated Variable

Answer 16

independent variable in a process control system that is used to adjust the
dependent, process variable

Question 17

Pressure Regulator

Answer 17

an adjustable valve that is designed to automatically control the pressure
downstream of the valve

Question 18

Rotary Shaft Valve

Answer 18

a throttling control valve used to change the flow of materials by means of the
movement of a rotating wafer, contoured disc, ball or plug

Question 19

Three-Way Solenoid

Answer 19

an electrical device that shuts off the air supply and vents the air from the
actuator or cylinder when the device is de-energized

Question 20

Valve Body

Answer 20

the main pressure boundary of the valve that also provides the pipe
connecting ends

Question 21

Valve Stem

Answer 21

a valve component that consists of a metal shaft that transmits the force of the
actuator to the valve plug