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Flow Rate and Valve Sizing |
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For the correct design of process system valves, the valve size is determined by the required flow rate. The Kv-value serves as a calculation basis for the different process conditions. This value is stated in the following table with regard to nominal diameter and standards.
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Kv-Value
The Kv-value is a parameter defining the flow rate of valves. It describes the amount of water at temperatures between 5° and 30°C which flows through the valve at a pressure loss of 1 bar. The Kvs-value describes the Kv-value when the valve is 100% open. |
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For Water 5-30 °C applies:
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General Liquid Flow Formula:
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Conversion:
For correct Kv to Cv conversion calculation, please use the unit formulas stated below, exclusively. The Kv-value must be converted from (cubic meter / hour) by utilizing the following conversion factors. The US flow rate measure of water is expressed by means of the Cv-value in US-gallons per minute (gpm) with a pressure drop of Δp 1 PSI.
Conversion of Kv to Cv
Cv = 1,17 x Kv
Conversion of Cv to Kv
Kv = 0,86 x Cv
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Explanations:
Kv in m³/h = flow rate parameter
Q in m³/h = volume flow rate
ρ in kg/m³ = specific gravity
p1 in bar = pressure before the valve
p2 in bar = pressure after the valve
Δp in bar = pressure drop through the valve Δp = p1 – p2
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| The Kvs-values in the table refer to the specification with two-way valves with EPDM diaphragm (depending on the specification variations are possible). |
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