Structure of a self actuated pressure control valve

Structure of a self actuated pressure control valve

Figure 1 – structure of a self actuated pressure control valve

As figure-1 indicates, a self actuated pressure control valve uses a pitot tube which gives access for

process fluid to pressurize the diaphragm which then acts to open the valve so process fluid from process

line can pass through.

For a pressure regulator valve, pitot tube connects the diaphragm casing to a point downstream of control

valve. When the pressure downstream to control valve increases beyond setpoint, process fluid exerts

increased pressure on the diaphragm thus closing the valve. Closing of the valve stops process flow thus

reducing the valve downstream pressure back to setpoint level. When the pressure downstream of control

valve drops below the setpoint level, process fluid from diaphragm casing recedes back to process line.

This relieves pressure on diaphragm and opens the valve to allow increased process flow. Increased

process flow leads to increase in pressure back to its setpoint.

For a back-pressure regulator valve, the pitot tube connects diaphragm casing to a point upstream of the

pressure control valve and the process fluid from upstream point acts on the valve diaphragm to open or

close the valve in case of high or low pressure respectively.