Flow Coefficient Cv and Flow Factor Kv

Comparing flow coefficient Cv with flow factor Kv

The flow coefficient - Cv - and the flow factor - Kv - are commonly used to specify the capacity of control valves.

Flow Coefficient - Cv

It is often convenient to express the capacities and flow characteristics of control valves in terms of the

  • Flow Coefficient - Cv

The flow coefficient - Cv - is based on the imperial units system and is defined as:

  • the flow of water through a valve at 60 oF in US gallon/minute at a pressure drop of 1 lb/in2

The flow coefficient is commonly used in the U.S.

Flow Factor - Kv

The metric equivalent of the flow coefficient - Cv - is based on the SI-system and is called the

  • Flow Factor - Kv

The flow factor - Kv - is defined as

  • the flow of water with temperature ranging 5 - 30 oC through a valve in cubic meters per hour (m3/h) with a pressure drop of 1 bar

The flow factor is commonly used outside U.S.

Converting between Flow Coefficient Cv and Flow Factor Kv

The relationship between Cv and Kv can be expressed as:

  • Cv = 1.16 Kv         (1)
  • Kv = 0.862 Cv         (2)

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