21-07-2012, 02:50 PM
Control Valve Terminology
ISA_75.05.01_Control_Valve_Terminology.pdf (Size: 727.28 KB / Downloads: 41)
Definitions
Accuracy:
the degree of conformity of an indicated value to a recognized accepted standard value or ideal value.
Accessories:
devices usually attached to the actuator for various control functions such as positioners, relays, solenoid
valves, airsets, handwheel, and limit switches.
Actuator:
a pneumatic, hydraulic, or electrically powered device which supplies force and motion to position a valve’s
closure member at or between the open or closed position.
Calibration cycle:
the application of known values of the measured variable and the recording of corresponding values of the
output readings, over the range of the valve in both ascending and descending directions. See ANSI/ISAS51.1-
1979 (R1993), Process Instrumentation Terminology.
Fail-safe:
a characteristic of a particular 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. Fail-safe action may involve the use of
auxiliary controls connected to the actuator.
Flangeless control valve:
a valve without integral line flanges, which is installed by bolting between companion flanges, with a set of
bolts, or studs, generally extending through the companion flanges.