Please, experts, help me figure this out! Regarding the pressure issue of safety valves

This issue should have been discussed on this forum; give it a search...

Okay, I’ll go look it up. Thank you so much

This post was last edited by fzujunru on 2015-8-13 at 13:38. 1. Setting pressure, opening pressure, and operating pressure refer to the same thing; 150.1 Appendix B. 2. The discharge pressure is higher than the setting pressure. The setting pressure refers to the predetermined pressure at which the valve disc of a safety valve begins to open under operating conditions ； Discharge pressure, the inlet pressure when the valve disc reaches the specified opening height. What is the difference between the set pressure and the discharge pressure of a safety valve? http://bbs.hcbbs.com/thread-231943-1-1.html What are the differences between the set pressure and the discharge pressure of a safety valve? http://bbs.hcbbs.com/thread-929003-1-1.html 3. The relationship between the set pressure and the design pressure: Appendix B4.7 suggests that once the operating pressure is known, the set pressure can be determined (=1.1x operating pressure); subsequently, the design pressure is determined based on this set pressure, with the design pressure being slightly higher than the set pressure. 4. Clause 3.9.2 of the standards stipulates that if the drawing indicates the maximum allowable operating pressure, then the set pressure shall not be higher than this maximum allowable operating pressure. And the maximum allowable operating pressure may be greater than the design pressure; therefore, the set pressure at this time may also be greater than the design pressure. 5. The overpressure limit is specified in 150.1 Appendix B3.2. The overpressure limit = max{10% of design pressure, 20 kPa}. It’s more or less like that; it might not be entirely accurate, so you should study it further.

Can it be assumed then that: discharge pressure = set pressure + overpressure limit? If the set pressure is equal to the maximum allowable operating pressure, could the discharge pressure exceed the maximum allowable operating pressure? Is this situation reasonable?

Can it be assumed then that: discharge pressure = set pressure + overpressure limit? If the set pressure is equal to the maximum allowable operating pressure, could the discharge pressure exceed the maximum allowable operating pressure? Is this situation reasonable?

Can the rated discharge pressure of a safety valve exceed the equipment’s maximum allowable operating pressure? http://bbs.hcbbs.com/thread-1247376-1-1.html

Personally, I think the discharge pressure is slightly higher than the set pressure; theoretically, when the discharge pressure reaches the set value, a state of equilibrium is achieved, and discharge will occur as long as the pressure is above that value； The set pressure cannot be equal to the maximum allowable operating pressure; it should be higher.

Thank you. After reading it, I indeed gained a deeper understanding; it was very helpful

From HG/T 20570.2-95: Installation and Selection of Safety Valves, 2.0.14 Maximum Operating Pressure refers to the maximum pressure that may be reached at the top of the container under normal operating conditions. Refer to the provisions in \"Determination of Design Pressure and Temperature for Equipment and Piping Systems\" (HG/T20570.1-195). 2.0.15 Design pressure refers to the maximum pressure specified at the top of the container, and it shall be not less than the setting pressure (opening pressure) of the safety valve. 2.0.16 Setting pressure of the safety valve: The safety valve will activate when the static pressure at its inlet reaches this value. The set pressure requirement shall not be greater than the lowest design pressure within the protected system. 2.0.17 Opening pressure (set pressure) of the safety valve: The pressure at which the valve disc of the safety valve begins to rise, allowing the material to flow out continuously. The value is the same as the set pressure. 2.0.18 Back pressure of the safety valve: The pressure acting at the outlet of the safety valve. Back pressure is divided into static back pressure and dynamic back pressure. Static back pressure refers to the pressure at the valve outlet when the safety valve has not activated; dynamic back pressure refers to the frictional pressure drop caused by fluid flow after the safety valve has activated. 2.0.19 Overpressure of the safety valve: The portion of the pressure at the inlet of the safety valve that exceeds the set pressure during discharge. It is usually expressed as a percentage. 2.0.20 Relief pressure of the safety valve: The pressure at the inlet of the safety valve when its valve element reaches its maximum height. The discharge pressure equals the set pressure plus the overpressure. 2.0.21 Reset pressure of the safety valve: The pressure at which the valve disc returns to its seat after the safety valve activates, as the pressure within the system being protected decreases. 2.0.22 Maximum allowable working pressure refers to the maximum gauge pressure that the top of the vessel is permitted to withstand at the design temperature. This pressure is calculated based on the effective thickness of the pressure-bearing elements of the container, and the minimum value is taken.

Very comprehensive. Now I also understand the relationship between them very well; thank you for your help