Determination of the safety valve
Thread Content
Article 147 of the regulations states that the opening pressure of the safety valve on mobile pressure vessels should be 1.05–1.10 times the design pressure of the vessel, while the discharge pressure of the safety valve shall not exceed 1.2 times the design pressure of the vessel; furthermore, the reset pressure must be at least 0.8 times the opening pressure!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~What I don’t understand is that the design pressure is already higher than the maximum operating pressure, and yet the opening pressure of the safety valve is even higher than this design pressure. Is this reasonable? What is the purpose of such regulations? What does the reset pressure refer to, and under what conditions does it occur for a safety valve?
The opening pressure of the safety valve should be 1.05–1.1 times the operating pressure, while the seating pressure refers to the pressure to which the valve disc returns after pressure is released.
You can refer to page 252, Chapter 14 of the training manual for the definitions of these pressures. Once these definitions are clear, it will be obvious which one is lower and which one is higher
I need to figure out whether this 1.2 is related to the test pressure of the container. There’s no concrete evidence; it’s just a guess. But standards and regulations must be followed, and in this case, they need to be adhered to strictly.
When formulating industry standards, our country has largely referred to established foreign standards; 1.2 is based on the ASME standards.
This issue is specifically explained in Article 147 on page 176 of the regulations; for mobile pressure vessels, such provisions are made to prevent frequent activation of the relief devices, which could lead to leaks, and this is different from the case with fixed vessels.