Glossary
Control Valve Terms
Control valve terms: Cv and Kv, characteristics, authority, cavitation, choked flow, leakage class, actuators, positioners and fail action.
30terms
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All Control Valve Terms
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ATOAir to OpenAir to open means air pressure on the actuator opens the valve and the spring closes it, so the…TermBall ValveA ball valve uses a rotating ball with a bore to control or stop flow; segmented V ball designs…TermButterfly ValveA butterfly valve is a quarter turn valve with a disc that rotates in the flow path; it is…FormulaCavitationCavitation is the formation and violent collapse of vapour bubbles when liquid pressure drops…FormulaChoked FlowChoked flow is the condition where flow through a valve stops increasing even though the…TermControl ValveA control valve is a power operated valve that varies flow in response to a signal from a…TermFail Safe PositionFail safe position is the position a valve goes to on loss of air or signal: fail open, fail…TermFlashingFlashing is when liquid partly turns to vapour across a valve because the outlet pressure stays…
CvFlow Coefficient (Cv)Flow coefficient Cv is the flow of water in US gallons per minute through a valve with a…TermGlobe ValveA globe valve is a linear motion valve where a plug moves towards or away from a seat; it is…FormulaI/P ConverterAn I/P converter changes a 4 to 20 mA current signal into a proportional pneumatic signal,…TermInstalled CharacteristicInstalled characteristic is the actual relationship between valve travel and flow once the…KvKv Flow FactorKv flow factor is the flow of water in m³/h through a valve with a pressure drop of 1 bar; it…FLLiquid Pressure Recovery FactorLiquid pressure recovery factor FL describes how much pressure a valve recovers after the vena…PSTPartial Stroke TestingPartial stroke testing moves a shutdown valve a small amount, typically 10 to 20 %, to prove it…FpPiping Geometry FactorPiping geometry factor Fp corrects valve capacity for reducers and other fittings attached…
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xTPressure Differential Ratio FactorPressure differential ratio factor xT is the ratio of pressure drop to inlet pressure at which…TermSeat Leakage ClassSeat leakage class is the maximum allowed flow through a closed valve, defined by ANSI/FCI 70-2…FormulaSplit Range ControlSplit range control uses one controller output to operate two valves, each over part of the…TermSpring RangeSpring range is the air pressure range over which a spring diaphragm actuator moves through…TermStroke TimeStroke time is the time a valve takes to move from fully open to fully closed, or the reverse,…FormulaValve ActuatorA valve actuator is the device that produces the force or torque to move a valve, using air…NValve AuthorityValve authority is the fraction of the total system pressure drop taken by the control valve,…FormulaValve CharacteristicValve characteristic is the relationship between valve travel and flow coefficient, such as…
TermValve PackingValve packing is the seal around the valve stem that stops process fluid leaking out while…TermValve PositionerA valve positioner is a device on the valve that compares the control signal with the actual…FormulaValve RangeabilityValve rangeability is the ratio of the largest to the smallest flow coefficient over which a…TermValve StictionValve stiction is static friction that makes a valve stick, then jump, instead of moving…TermValve TrimValve trim is the set of internal parts in contact with the flow that control it, such as the…TermVolume BoosterA volume booster is a pneumatic relay that copies the positioner output at much higher air…
Frequently Asked Questions
What does the control valve glossary cover?
Control valve terms: Cv and Kv, characteristics, authority, cavitation, choked flow, leakage class, actuators, positioners and fail action.
Are the formulas checked?
Yes. Formulas follow the relevant standards such as ISO 5167, and every worked example is calculated and checked.
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