Issues regarding the operation of self-acting pressure control valves
Thread Content
Does the self-acting pressure control valve operate by fully opening only when the set pressure is exceeded? Does it still open slowly even when the set pressure has not been reached, and open fully once the set pressure is exceeded?
It will not open or close completely instantly; instead, the degree of opening is determined automatically based on the set pressure.
If the set pressure is not reached, will the valve still be open to a certain extent?
Under normal conditions, the valve maintains an opening that ensures proper flow rate; when the controlled pressure changes, the valve opens or closes to stabilize the pressure.
This post was last edited by efei_74 on 2017-12-22 08:52. Self-acting pressure regulators come in two types, depending on their initial state and failure conditions (when there is no gas flow or when the main diaphragm fails). One type is the Fall Close type; in this case, the valve opening is closed by the force exerted by the main spring. This type has a parameter known as the opening pressure difference (usually between 0.1–0.5 bar). When there is no gas flow, the main spring keeps the valve closed. When the pressure of the gas coming from upstream (P1) is lower than this opening pressure difference, the valve remains closed. However, when P1 exceeds this value, the force of the main spring is overcome and the valve opens； When the outlet pressure (P2) is lower than the outlet pressure setpoint (P2set), the regulator continues to open the valve; if P2 remains below P2set even when the regulator is fully open, it will stay in this fully open state ； When P2 is higher than P2set, the voltage regulator comes into action by reducing the opening of the valve, thereby ensuring that P2 equals P2set ； Put simply, it means that P2 is adjusted when it exceeds the set value P2set; when it is below P2set, it allows direct passage ； The other type is of the FO type; contrary to the previous type, it remains open in the case of no ventilation or a failure in the main membrane, and there is no parameter for the opening pressure difference ； But it still complies with the principle that \"P2 is used for adjustment when it exceeds the set value P2set, and the signal passes through directly when it is below P2set.\" ；