How are the pressure before and after the control valve determined? Is it when the valve is open or when it is closed?
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How are the pressure before and after the control valve determined? Is it when the valve is open or when it is closed?
For example, when the valve is closed, there may be a pressure of 5 kilograms before the valve, but no pressure at all behind it, i.e., 0. In this case, should it be filled in as 5 before the valve and 0 behind it?
Moreover, a valve may be subject to different operating conditions, with various pressures before and after the valve; how should this be filled in in such cases? ?
What’s there to worry about? The pressures before and after the control valve are set according to the requirements of the process; the values corresponding to the desired pressures before and after are chosen accordingly, and then the size of the valve element in the control valve is determined based on the pressure difference.
The pressure before the valve is the upstream pressure minus the pressure drop along the line, while the pressure behind the valve is calculated by reversing the back pressure
Under normal circumstances, these are the pressures before and after the valve that need to be considered when selecting a control valve. The main purpose is to use the existing conditions of the pipeline network, along with the designed flow rate, to calculate the pressures before and after the valve during operation, so as to select a valve with an appropriate KV value. Therefore, the pressures before and after the valve are the values at normal flow rates.
These are the parameters of the established process operations; they are very important and serve as the basis for selecting and designing control valves. If the parameters fluctuate, the range of those fluctuations can be indicated.
However, after steam enters the heating coil for heat exchange, steam condensate is generated and is discharged through a trap. The pressure inside this coil is not very definite; so how can the pressure downstream of the valve be determined?