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GLOSSARY
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YOUR COMPLETE GUIDE TO VALVE TERMINOLOGY
Our comprehensive guide to valve industry terminology is a valuable resource, whether you’re learning about the industry for the first time or refreshing your knowledge.
DELTA-P
Differential Pressure. The inlet pressure (Pl) minus the outlet pressure (P2).
DIAPHRAGM
A flexible pressure-responsive element that transmits force to the diaphragm plate and actuator stem.
DIAPHRAGM ACTUATOR
Is a fluid (usually pneumatic) pressure-operated, spring-opposed diaphragm assembly which positions the valve stem in response to an input signal.
DIAPHRAGM PRESSURE
See bench set.
DIFFERENTIAL PRESSURE
The maximum difference in pressure measured between the valve inlet and outlet, against which the valve is required to operate.
DIRECT ACTING
This term has several different meanings depending upon the device it is describing. A direct-acting actuator is one in which the actuator stem extends with an increase in diaphragm pressure. A direct-acting valve is one with a push-down-to-close plug and seat orientation. A direct-acting positioner or a direct-acting controller outputs an increase in signal in response to an increase in set point.
DIRECT ACTUATOR
Is one in which the actuator stem extends with an increase in diaphragm pressure.
DYNAMIC UNBALANCE
The total force produced on the valve plug in any stated open position by the fluid pressure acting upon it. The particular style of valve, i.e. single-ported, double-ported, flow-to-open, flow-to-close, has an effect on the amount of dynamic unbalance.
