Safety valve setting pressure
Thread Content
Section B3.2.1 of Appendix B to the Standard for Pressure Vessels (GB150.1-2011) stipulates that when only one relief device is installed on a vessel, the operating pressure of this relief device shall not be greater than the design pressure, and the overpressure limit of the vessel shall not be greater than the larger of 10% of the design pressure or 20 kPa. May I ask: how should this be understood? If only one safety valve is installed on the container, must the set pressure of the safety valve be ≤ the design pressure, or can the set pressure of the safety valve exceed 10% of the design pressure or the larger of the two values, 20 kPa?
Let’s put it this way! In any case, there must be a safety valve whose pressure does not exceed the design pressure or the maximum allowable operating pressure.
150 is just a standard; compliance should be achieved in accordance with the higher-level regulation TSG 21-2016.
The overpressure limit and the set pressure are two different concepts.
The set pressure is also known as the operating pressure; the pressure may rise further after the safety valve activates, but it must not exceed the sum of the design pressure and the overpressure limit.
Two conditions must be met: First, the actuation pressure, that is, the set pressure. The setting pressure of the safety valve must be ≤ the design pressure. Second, the discharge pressure of the safety valve ≤ max (1.1 times the design pressure, or design pressure + 20 kPa). For operational stability, the discharge pressure of a safety valve is generally set at max(1.1 times the design pressure, or the design pressure + 20 kPa). The setting pressure is then determined based on the parameters of the safety valve, ensuring that it satisfies the condition that the setting pressure ≤ the design pressure.
The overpressure limit is the incremental value based on the set pressure. The two are not the same concept.
Maximum discharge pressure – Overpressure = Setting pressure of the safety valve
The setting pressure of the safety valve shall not exceed the design pressure.