Valve Cv calculation parameters
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I have a question regarding the selection of automatic valves: when calculating the Cv value of a valve, how is the pressure drop of that valve determined? (Is this pressure drop provided by the process engineering team?) Is it related to the physical structure of the valve? ) Is the shutdown pressure difference of the valve equal to the pressure before the valve?
The shut-off pressure is specified in the process specifications; it is generally required only for control valves, as it is necessary to determine the torque of the actuation mechanism. A manual valve works because force creates miracles
The pressure difference before and after the valve is also specified by the process; only the process engineering team knows the process parameters of the fluid flowing before and after the valve during operation.
The maximum pressure difference before and after the valve when it is closed. For a simple calculation, take the design pressure of the nearest equipment before and after the valve, and subtract one from the other. For valves in general, the pressure difference is specified as three values: maximum, normal, and minimum. The normal value is obtained by subtracting the design value from these values. In the case of process fluctuations, the maximum and minimum differences between the upstream and downstream equipment are used accordingly.