Safety valve set pressure value

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The set pressure is the predetermined pressure at which the safety valve disc begins to open under operating conditions; it is the gauge pressure measured at the valve inlet. At this pressure, under the specified operating conditions, the force generated by the medium pressure to open the valve is balanced by the force that keeps the valve disc in place on the valve. At this pressure, a measurable opening height begins to appear, and the medium is discharged in a continuous manner that can be perceived visually or audibly. 1) Safety valves for steam boilers
a. The set pressures of safety valves on the boiler drum (shell) and superheater shall be in accordance with Table 1. b. The set pressure of the safety valves for the economizer, reheater, and direct-flow boiler start-up separator is 1.1 times the operating pressure at the installation location. c. Set pressure deviation: It is ±0.015 MPa when the set pressure is less than or equal to 0.5 MPa; it is ±3% of the set pressure when the set pressure is between 0.5 and 2.3 MPa; it is ±0.07 MPa when the set pressure is between 2.3 and 7.0 MPa; and it is ±1% of the set pressure when the set pressure is greater than 7.0 MPa. Table 1: Setting pressures of safety valves on the boiler shell and superheaters. Rated operating pressure (MPa): Setting pressure of the safety valve (MPa) – For P ≤ 0.8: Operating pressure + 0.03; Operating pressure + 0.05. For 0.8 < P ≤ 5.9: 1.04 times the operating pressure; 1.06 times the operating pressure. For P > 5.6: 1.05 times the operating pressure; 1.08 times the operating pressure. Note: A safety valve must be installed on the boiler, and its setting pressure should be adjusted according to the lower value specified in the table. For boilers equipped with superheaters, the safety valves adjusted for a lower pressure must be those located on the superheater, to ensure that they open first. The working pressure in the table refers, for pulse-type safety valves, to the working pressure at the point where the impulse is discharged, and for other types of safety valves, to the working pressure at the location where the safety valve is installed. (2) Safety valves for hot water boilers a. The set pressure of the safety valves shall be in accordance with Table 2. b. Set pressure deviation: It is ±0.015 MPa when the set pressure is less than or equal to 0.5 MPa, and it is ±3% of the set pressure when the set pressure is greater than 0.5 MPa. Table 2 Set pressures of safety valves for hot water boilers (MPa): 1.12 times the operating pressure, but not less than the operating pressure + 0.07 MPa; 1.14 times the operating pressure, but not less than the operating pressure + 0.10 MPa. Note: One safety valve on the boiler must be adjusted to the lower set pressure specified in the table. The working pressure here refers to the working pressure of the components directly connected to the safety valve. (3) Safety valves for stationary pressure vessels. a. When only one safety valve is installed on a stationary pressure vessel, the set pressure of the safety valve shall not exceed the design pressure of the pressure vessel ； When multiple safety valves are installed on a stationary pressure vessel, the set pressure of one of the safety valves shall not exceed the design pressure of the pressure vessel. The set pressures of the remaining safety valves may be appropriately increased, but they must not exceed 1.05 times the design pressure. b. Set pressure deviation: It is ±0.015 MPa when the set pressure is less than or equal to 0.5 MPa, and it is ±3% of the set pressure when the set pressure is greater than 0.5 MPa. (4) Safety valves for mobile pressure vessels
a. The set pressure of the safety valve should be 1.05 to 1.10 times the design pressure of the tank; the reseating pressure must not be less than 0.8 times the opening pressure. For safety valves used in cryogenic tankers, the set pressure must not exceed the design pressure of the tank. b. Set pressure deviation: It is ±0.015 MPa when the set pressure is less than or equal to 0.5 MPa, and it is ±3% of the set pressure when the set pressure is greater than 0.5 MPa. (5) Safety valves for pressure pipelines a. The setting pressure of safety valves for industrial metal pipelines is 1.05 to 1.1 times the maximum operating pressure ； The set pressure of the safety valves used in pipelines at oil and gas stations is 1.05 to 1.15 times the maximum operating pressure. b. Set pressure deviation: It is ±0.015 MPa when the set pressure is less than or equal to 0.5 MPa, and it is ±3% of the set pressure when the set pressure is greater than 0.5 MPa. (6) Safety valve for medical hyperbaric oxygen chambers a. The set pressure of the safety valve is the maximum operating pressure + 0.02 MPa. b. The set pressure deviation is ±0.015 MPa. (7) Safety valve for compressor a. The set pressure of the safety valve is the maximum operating pressure + 0.02 MPa. b. Set pressure deviation: It is ±0.015 MPa when the set pressure is less than or equal to 0.5 MPa, and it is ±3% of the set pressure when the set pressure is greater than 0.5 MPa.