Knowledge Module

Valve Terminology

Engineering glossary of industrial valve terminology including pressure classes, Cv values, sealing standards, face-to-face dimensions, torque, flow coefficients, and performance classifications.

TermDefinition (simplified)TurndownRatio of max tomin controllable flowRangeabilityMax Cv ÷minimum controllable CvFail-safeValve positionon loss of actuating energyDeadbandMinimum signalchange to cause movement
Operational terminology defines how a valve performs in a control loop. Qualitative. Illustrative cross-section; not to scale.
Core valve terminology (schematic)MAWPMax allowableworking pressureCv / KvFlow coefficient(US/SI)P-T ratingPressure vstemperature limitLeakage classANSI/FCI 70-2shutoff tightness
Understanding MAWP, Cv, P-T rating, and leakage class underpins valve specification. Illustrative cross-section; not to scale.

What Is Pressure Drop Across a Valve?

What Is Pressure Drop Across a Valve? Direct Answer Pressure drop across a valve is the difference in fluid pressure measured between the upstream and downstream sides of the valve during flow. It …

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What Is Valve Torque?

What Is Valve Torque? Direct Answer Valve torque is the rotational force required to open, close, or modulate a valve under specified operating conditions. It is typically expressed in Newton-meter…

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What Is a Valve Actuator?

What Is a Valve Actuator? Direct Answer A valve actuator is a mechanical device that converts energy — such as pneumatic, electric, or hydraulic power — into motion to open, close, or modulate a va…

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What Is Control Valve Rangeability?

What Is Control Valve Rangeability? Direct Answer Control valve rangeability is the ratio between the maximum controllable flow and the minimum controllable flow a valve can regulate while maintain…

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What Is Flow Coefficient in Valve Engineering?

What Is Flow Coefficient in Valve Engineering? Direct Answer Flow coefficient is a quantitative parameter that expresses the flow capacity of a valve or flow-restricting device under specified cond…

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What Is Cv Value in Valve Engineering?

What Is Cv Value in Valve Engineering? Direct Answer Cv value (flow coefficient) is a numerical parameter that quantifies a valve’s flow capacity. It is defined as the number of U.S. gallons …

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What Is Double Block and Bleed (DBB) in Valve Systems?

What Is Double Block and Bleed (DBB) in Valve Systems? Direct Answer Double block and bleed (DBB) is a valve arrangement or valve design that provides two independent sealing surfaces (blocks) in s…

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What Is a Trunnion Mounted Ball Valve?

What Is a Trunnion Mounted Ball Valve? Direct Answer A trunnion mounted ball valve is a quarter-turn valve in which the ball is mechanically anchored by upper and lower trunnions, allowing it to ro…

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What Is the Difference Between Full Port and Reduced Port Valves?

What Is the Difference Between Full Port and Reduced Port Valves? Direct Answer Full port valves have an internal bore diameter equal to the nominal pipe size, allowing unrestricted flow through th…

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What Is the Difference Between NPT and BSP Threads?

What Is the Difference Between NPT and BSP Threads? Direct Answer NPT (National Pipe Taper) and BSP (British Standard Pipe) are two distinct pipe thread standards used for threaded pipe and valve c…

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