The valve recloses when the pressure is re-applied.įlowing pilot: A pilot which discharges the fluid throughout the relieving cycle of the pilot operated safety valve whilst it remains closed in normal operating conditions. The valve opens when the fluid pressure that keeps it closed is removed or reduced. The pilot responds to the pressure of the fluid alone without any energy other than that of the fluid itself and controls the operation of the valve. Pilot operated safety valve (POSV): A pilot operated safety valve is a self actuated device comprising a main valve and an attached pilot. It discharges a quantity of the fluid in order to prevent the safe pressure level from being exceeded and recloses after normal operating conditions have been restored.ĭirect loaded safety valve: A safety valve in which the loading due to the fluid pressure underneath the valve disc is opposed only by a direct mechanical loading device such as a weight, lever and weight, or a spring.Īssisted safety valve: A direct loaded safety valve, whose disc may additionally be lifted by means of a powered assistance mechanism, failure of which will not prevent the direct opening of the valve. Safety valve: A valve which, with the sole assistance of the energy generated by the process fluid, opens automatically when a predetermined pressure is reached.
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