【Safety Management and Standardization of Special Equipment】The two “setting pressures” of safety valves”

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Ensure proper safety management of special equipment – Standardization ensures safety! [Special Equipment Safety Management and Standardization] – Comprehensive summary post! Constantly being updated – feel free to communicate! ! ! https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=5718553 (Source: Haichuan Chemical Industry Forum (Hua Haichuan Liu hcbbs)). Everyone is welcome to participate in the discussions. --------------------------------------------------------- A safety valve is a type of automatic valve that uses the force of the fluid itself, without any external assistance, to discharge a specified amount of fluid, thereby preventing pressure from exceeding the designated safe level. Once the pressure returns to normal, the valve closes again to prevent further flow of the medium. The setting pressure is a key operating parameter of a safety valve; it determines at what pressure the valve will open to release pressure. It is a crucial indicator for ensuring the safe operation of equipment such as pressure vessels and pipelines, and its setting must strictly comply with regulatory requirements. Why do I say that a safety valve has two “set pressures”? One is the \"set pressure\" indicated on the safety valve calibration plate; it refers to the pressure at the inlet of the safety valve when it is detected that the valve disc has opened, and when a continuous discharge of the test medium can be seen or heard. This is a specific pressure value. It is the predetermined pressure at which the safety valve begins to open under operating conditions, measured as gauge pressure at the valve inlet. Another is the \"set pressure\" indicated on the safety valve’s nameplate; this actually refers to the range of operating pressures allowed for the safety valve’s spring, and it is a value representing a range. Within this pressure range, the opening pressure of the safety valve (i.e., the set pressure) can be adjusted by changing the pre-compression amount of the spring. Safety valves with the same nominal pressure can be divided into various operating pressure range categories depending on the spring design requirements. When selecting a safety valve, the operating range of its set pressure should be determined based on the required opening pressure value. In other words, the set pressure value on the test plate must be within the range of the set pressure value indicated on the nameplate. If the actual set pressure value is not within the range, the safety valve must be selected again. How is the set pressure on the test plate determined? First, one needs to examine the equipment design documents, drawings, calculations regarding the strength of the equipment, the certification for pressure vessel products, as well as the design specifications for boilers and pipelines; these documents will explicitly state the setting pressure of the safety valve: ×.×× MPa. Secondly, when no design values are available or cannot be found, the relevant standards are applied. The common rule (most applicable to pressure vessels) is that the setting pressure of the safety valve should be ≤ the design pressure; generally, this setting pressure is taken to be 1.05 to 1.1 times the working pressure.