Selection issues for pneumatic control valves
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In the process of selecting pneumatic control valves, a key parameter is the pressure levels before and after the valve. I would like to ask everyone: based on what should these pressures before and after the valve be determined or calculated?
This parameter can be set according to the process requirements, that is, the control pressures before and after as specified by the process
We have the same question; it’s the same here for us as well – we don’t know how to determine the pressure difference before and after the valve. I’ve seen the formulas for calculating pipe resistance and valve resistance; it’s too complicated. Some say it’s based on experience, but no one passes on that experience; it’s really difficult! Urgently need an expert’s answer! !
This is calculated by the process design specialty based on principles such as material balance and pressure loss
This is determined by the process engineering field, through engineering calculations, and is basically based on a certain pipe resistance ratio.
The selection of control valves is carried out in accordance with the various requirements put forward by the process and automation teams. When selecting a valve, the following aspects are primarily taken into consideration: the properties of the fluid, static pressure, temperature, pressure difference, corrosivity, leakage requirements for the valve, the operating mechanism of the valve, pipeline layout, as well as flow capacity and adjustable range.
The process design field is based on calculations such as the pressure drop across the entire pipeline and the allowable pressure loss
The process specifications determine the pressure behind the valve… For example, in a furnace, there is a certain inlet pressure; the valve is located at the inlet, and by adding the pressure drop along the pipes, one can determine what the pressure behind the valve is. Similarly, there is also something in front of this valve that specifies the outlet pressure; by adding the pressure drop along the pipes to this value, the inlet pressure can be determined. That’s how I understand it; I’m not sure if it’s correct though.
There is software for calculating the pressure before the valve; it’s small and very useful. I used it before, but after my computer crashed, I couldn’t find it anymore! ! You can search for it online~~
The key factors considered in selection include: the properties of the fluid, static pressure, temperature, pressure difference, corrosiveness, leakage requirements for the valve, the operating mode of the valve, pipe diameter, flow capacity, adjustable range, and whether it should operate in fail-open or fail-closed mode.
Thank you to everyone above for their help and advice
You have the wrong understanding; go and check this standard. HG-T_20570.5-95_ Calculation of the system characteristics of pumps and determination of the relative installation height of equipment