The relationship between the design pressure and the discharge pressure of a safety valve
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I would like to ask about the relationship between the design pressure and the discharge pressure. The standards specify the design pressure of the container, not that of the safety valve; in this case, it is sufficient for the design pressure to be greater than or equal to the discharge pressure. But how is the design pressure of the safety valve itself determined?
The safety valve itself does not have a concept of design pressure
I hope this document will be helpful to the original poster
The discharge pressure of the Pd safety valve is given by PS, which represents the opening pressure of the safety valve. In the calculations related to safety valves, Pd = 1.1PS + 0.1. The opening pressure of a safety valve is the pressure at which its valve disc begins to rise, allowing the material to flow out continuously. The value is the same as the specified pressure. Relief pressure of the safety valve: the pressure at the inlet of the valve opening once the pilot disc of the safety valve reaches its maximum height. The discharge pressure equals the set pressure plus the overpressure. The overpressure in a safety valve system: during the discharge process, it refers to the amount by which the pressure at the inlet of the safety valve exceeds the set pressure, and is usually expressed as a percentage. This principle is similar to that of a spring: different displacements result in different forces. When opening a pressure vessel, it happens when the valve just moves away from the inlet seal surface; whereas pressure release occurs when the valve moves away from the outlet seal surface
But the safety valve itself also needs to have a designed pressure
Thank you for your reply, but the relationship between design pressure and relief pressure is not mentioned
The design pressure of a safety valve is unrelated to its discharge pressure
The pressure release value is determined according to standards based on the design pressure of the corresponding container. But how is the design pressure determined? The standards don’t provide any details on this. I would appreciate it if someone with expertise could help me out. Thank you
The safety valve pressure specifies the pressure at the inlet pipe flange and the pressure at the outlet pipe flange; for example: 1.5D2-900-300, which means 1.5” at 900 pounds at the inlet, and 2” at 300 pounds at the outlet
It is similar to the selection of process valves: based on the operating temperature and pressure, as well as the material and medium used, a pressure rating (PN) is determined; of course, it must comply with various relevant standards and specifications, and design engineers have the capability to do this.