Questions about work stress and design pressure
Thread Content
The pressure at the steam inlet at the top is 0.7–0.8 MPa; the operating pressure of the container is 0.8 MPa, while the design pressure is greater than 1 MPa. There is a safety valve at the top. What I would like to know is what the operating pressure and design pressure are respectively. I need an answer right away – I’m confused. I hope the expert can give me some guidance
Operating pressure is the pressure under normal usage conditions of the equipment. However, the equipment cannot be designed for normal operating conditions; a large margin is built in, which means the design pressure is higher than the operating pressure. For short periods of time, it’s fine if the equipment experiences pressure levels that reach the design pressure – after all, there’s a safety valve, right? Once the design pressure is reached, it must start to release pressure. In your case, the operating pressure is 0.8 MPa, while the design pressure is higher than 1 MPa; therefore, the activation pressure of your safety valve should be 1 MPa
Thank you, teacher. I understand now; I wasn’t sure at first
Just like a person who sells clothes, the size of the clothes should be slightly larger than the size of the body. If it’s fitted precisely to the body size, it will make movement impossible; any attempt to bend down will result in everything being exposed. Design pressure is like the size of clothing, while work pressure is akin to one’s body size.
If a device is equipped with a safety valve, then the design pressure is not determined arbitrarily. It should be determined following these steps: if your steam inlet pressure is 0.7–0.8 MPa and the operating pressure for the container is 0.8 MPa, then the working pressure is also 0.8 MPa. The setting pressure for the safety valve is generally taken as (1.05–1.1) times the working pressure. The design pressure should be set slightly higher than the set pressure; as for exactly how much higher, it should be greater than the set pressure of 1.03. Because the set pressure deviation of the safety valve is plus or minus 3%. This ensures that the safety valve opens at the design pressure of the pressure vessel, without opening at a pressure lower than the operating pressure. This way it can work properly without overpressure!
The pressure at the steam inlet at the top is 0.7–0.8 MPa; the operating pressure should be such that the design pressure is higher than the maximum operating pressure