How to calculate the pressure before and after a control valve?
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During the selection of a control valve, how are the pressure before the valve and the pressure after the valve calculated?
The pressure before the valve and the pressure after the valve are not calculated; they are determined by the actual process conditions.
Reply to 2# masanhong: The process is provided by the supplier; I want to know how this process is calculated. Also, do we generally calculate the closing pressure difference of the control valve based on a zero pressure after the valve? Is that correct? Thank you.
I understand: the process is determined by the actual operating pressure of the equipment； The pressure behind the valve should be the operating pressure of the devices downstream after the valve is closed; “zero” is just a special case, right?
Reply to 4# masanhong: Thank you.
Reply to 5# Xinglin Yu: Hello from the 2nd floor. The pressure difference when the valve is closed is used to calculate the unbalanced force. To prevent it from failing to close or open, the maximum pressure difference must be taken into account. However, when the valve is closed, the pressure difference is still needed to determine the valve’s leakage rate; therefore, it is not appropriate to use a zero pressure after the valve for the calculations. How should this be solved?
Domestic manufacturers of control valves generally assume a pressure of 0 behind the valve. As far as I know, several well-known domestic manufacturers of control valves use this value; they probably do so out of concern that the force required from the actuator might be too low
Is there any information on this? I want it too
Is there any information on this? I want it too
If the pressure behind the valve is to be determined, I use the height of the pipeline from behind the valve to the equipment as a reference; for example, if the height is 10 meters, I use 0.1 Mpa. If there are 8–10 bends after the valve as well, it’s still 0.1 Mpa. In this way, the pressure behind the valve is around 0.2 Mpa.