3.5 set pressure predetermined pres

3.5 set pressure predetermined pressure at which a safety valve under operating conditions commences to open Note 1 to entry: It is the gauge pressure measured at the valve inlet at which the pressure forces tending to open the valve for the specific service conditions are in equilibrium with the forces retaining the valve disc on its seat. 3.6 maximum allowable pressure PS maximum pressure for which the protected equipment is designed 3.7 overpressure pressure increase over the set pressure Note 1 to entry: Overpressure is usually expressed as a percentage of the set pressure. 3.8 reseating pressure value of the inlet static pressure at which the disc re-establishes contact with the seat or at which the lift becomes zero 3.9 cold differential test pressure inlet static pressure at which a safety valve is set to commence to open on the test bench Note 1 to entry: This test pressure includes corrections for service conditions, e.g. back pressure and/or temperature. 3.10 relieving pressure pressure used for the sizing of a safety valve which is greater than or equal to the set pressure plus overpressure 3.11 back pressure pressure that exists at the outlet of a safety valve as a result of the pressure in the discharge system Note 1 to entry: The back pressure is the sum of the superimposed and built-up back pressures. 3.12 built-up back pressure pressure existing at the outlet of a safety valve caused by flow through the valve and the discharge system 3.13 superimposed back pressure pressure existing at the outlet of a safety valve at the time when the device is required to operate Note 1 to entry: It is the result of pressure in the discharge system from other sources.