Cv (Flow Coefficient)
The numerical measure of a valve's capacity to pass flow. Defined as the flow in US gal/min of water at 60 degrees F with a 1 psi pressure drop. Higher Cv = larger valve capacity. Formula for liquids: Cv = Q x sqrt(SG / delta-P). European equivalent: Kv (m3/h at 1 bar delta-P). Relationship: Cv = 1.156 x Kv.
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Frequently Asked Questions
What is Cv (Flow Coefficient) in the context of industrial valves?
The numerical measure of a valve's capacity to pass flow. Defined as the flow in US gal/min of water at 60 degrees F with a 1 psi pressure drop. Higher Cv = larger valve capacity. Formula for liquids: Cv = Q x sqrt(SG / delta-P). European equivalent: Kv (m3/h at 1 bar delta-P). Relationship: Cv = 1.156 x Kv.
How does Cv (Flow Coefficient) affect valve selection and sizing?
The numerical measure of a valve's capacity to pass flow. Valve sizing must account for this phenomenon to prevent premature failure, excess noise, and vibration. For control valves, ISA-75.01 and IEC 60534-2-1 cover sizing for incompressible and compressible flow. Vajra Industrial Solutions can assist with valve sizing calculations - contact sales@vajravyuh.com with your process data sheet.
What valve types minimise Cv (Flow Coefficient) problems?
The choice of valve type and trim significantly affects susceptibility to flow-related problems. Anti-cavitation trims, low-noise cages, multi-stage pressure reduction, and proper Cv sizing reduce velocity-related damage. For critical applications, control valve sizing is performed using the ISA/IEC methodology with FL (liquid pressure recovery factor) and Fd (valve style modifier) for the specific valve geometry.
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