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Calculation of Pressure Regulators for Liquids |
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Calculating the Kv-value
To design or select a valve you should first calculate the KV-value from the operating data at which the valve is to operate.
| Kv |
Flow Coefficient |
m³/h |
| Q |
Volume Flow |
m³/h |
| p |
Density |
kg/m³ |
| p1 |
Inlet Pressure ( abs. ) |
bar |
| p2 |
Outlet Pressure ( abs. ) |
bar |
 p |
Differential Pressure ( p1-p2 ) |
bar |
Example:
We are looking for a pressure reducing valve for 2-7 m³/h of methanol having a density of 790 kg/m³; the
inlet pressure varies between 9 and 12 bar and the outlet pressure is to be maintained at 4 bar.
In our calculation we use the maximum flow rate and the minimum pressure drop
 |
m³/h |
To the Kv-value calculated from the operating data we add an allowance of 30 %
and thus obtain the minimum Kvs-value which the valve should have.
Kvs-value = 1,3 x Kv-value = 3,61 m³/h
Additional allowances are required if evaporation occurs as the pressure drops,
which is the case especially where the pressure drops are large and the temperatures
high. The value of p to be used
in the formula can be calculated. Frequently the data required for this calculation
are, however, difficult to obtain. For the sake of simplicity we therefore recommend
that a pressure difference should be used in the formula which does not exceed
0.6 times the absolute inlet pressure, i.e.
also p £
0,6 x p1 [bara]
If this is not feasible we suggest that you contact us for advice; the same applies to
other extreme operating conditions such as high-viscosity liquids, abrasive media as well
as high pressures and temperatures.
Continue
download the PDF-file:  Calculation of pressure regulators / PDF (156 kb)
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