How to determine the setting pressure of a safety valve
Thread Content
Dear sea friends: What exactly should be used to determine the setting pressure of a safety valve? The operating pressure, the design pressure, or the maximum allowable operating pressure? Everything is confusing. As indicated on the equipment nameplate, the maximum operating pressure is 0.28 MPa, and the design pressure is 0.59 MPa. What is the setting pressure of the safety valve? If a safety valve and a burst disc are connected in series, what should the setting be? Is the maximum allowable operating pressure lower than the design pressure? Seeking advice, thank you!
1. Check the standard set pressure of the safety valve; this pressure represents the rated pressure of the product, and it is generally slightly lower than the design pressure. When purchasing a safety valve, it is necessary to carefully read the product’s instruction manual; if no clear indications are provided, it should not be installed or used. 2. The setting pressure of the safety valve is determined based on the design pressure or the system operating pressure; generally, this setting pressure should be slightly lower than the design pressure or system operating pressure. 3. If a safety valve is used in a low-pressure system, its setting pressure must be set to a value lower than the system’s operating pressure; otherwise, the safety valve will not function properly and may even damage the system. 4. Determine the required setting pressure for the safety valve based on its normal operating conditions and design pressure; generally, this value should be around 0.05MPa to 0.1MPa lower than the design pressure, with exceptions for hydraulic systems. -
(3) Safety valves for fixed pressure vessels a. When only one safety valve is installed on a fixed pressure vessel, the set pressure of the safety valve shall not be greater than the design pressure of the pressure vessel； When multiple safety valves are installed on a fixed pressure vessel, the set pressure of one of these safety valves shall not be greater than the design pressure of the vessel; the set pressures of the remaining safety valves may be increased appropriately, but 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 shall be 1.05 to 1.10 times the design pressure of the tank; the reset pressure shall not be less than 0.8 times the opening pressure. For safety valves on low-temperature cryogenic tank trucks, the set pressure shall 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 set 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: ±0.015 MPa when the set pressure is less than or equal to 0.5 MPa, and ±3% of the set pressure when the set pressure is greater than 0.5 MPa
This post was last edited by AtlantisH on 2023-2-27 at 11:19. The term “maximum allowable operating pressure” on this nameplate should be changed to “operating pressure”; in pressure vessels, “operating pressure” refers to the highest pressure that may occur at the top of the vessel under normal operating conditions. Since the wall thickness of a container is determined by strength calculations and then rounded up, this rounded wall thickness can be used to calculate the maximum allowable operating pressure for the container. The maximum allowable operating pressure is greater than or equal to the design pressure and higher than the actual operating pressure. If the maximum allowable operating pressure is not specified on the drawings or nameplate, it can be assumed that the design pressure is the maximum allowable operating pressure. The setting pressure of the safety valve should be less than or equal to this maximum allowable operating pressure.
The maximum allowable operating pressure should be related to your system and tank; it is slightly higher than the normal operating pressure of the system, serving to protect the system and the reaction tank. However, the design pressure should be the maximum pressure that the safety valve can withstand, as exceeding this pressure will cause the safety valve to be damaged.
It mainly depends on the pressure at which it is used