Regarding safety valves for pressure vessels
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A pressure vessel has a design pressure of 2.0 MPa, a safety valve setting pressure of 2.0 MPa, and an approved operating pressure of 2.0 MPa as well. So, a bug occurs when the pressure reaches 2.0 MPa. The question of whether to jump or not. The safety valve is supposed to activate at 2.0 MPa; in that case, the user will blame the testing agency for inaccurate calibration. The approved pressure is below 2.0 MPa, yet the operating unit claims to have reduced the parameters on its own. Another scenario is where the design pressure is 0.50 MPa and the medium is steam, but an actual operating pressure of 0.55 MPa is required. The safety valve is set at 0.60 MPa, but the inspection agency refuses to approve this; setting it at 0.50 MPa causes it to activate prematurely. I tried to ask the design firm to make changes to the design, but they refused, saying that this is the standard practice everywhere in the country. Another scenario: the reaction vessels in the entire workshop are controlled by safety valves located on the steam main; the set pressure of these safety valves is 0.60 MPa, and the pressure is reduced to 0.60 MPa by pressure regulators. The design pressure of the reaction vessels is also 0.60 MPa. When there are few gas-using devices, the safety valve will activate and the pressure relief valve will fail, causing the pressure to exceed 0.70 MPa. Problem with the safety valve of the refrigeration unit: The design requires a safety valve with a DN25 size, but what was delivered from the manufacturer was one with a DN20 size. There is a shut-off valve that changes the size from 25mm to 20mm; should this issue be addressed with the design team or the manufacturing company? How did those who encountered such a situation solve it?
This post was last edited by zjq1962 on 2018-3-23 at 16:29. 1. The design is flawed from the start: work pressure, design pressure, and setting pressure are all given the same value. Leaving safety aside, is it even possible to operate it properly? It must comply with the requirements of B.4.7 in GB150.1. 2. How can the set pressure exceed the design pressure? With changes to the operating conditions, it’s necessary to communicate with the design team; the design pressure has increased, so the strength calculations must first be approved, and there are also issues related to the final pressure resistance test. 3. The safety valve installed in the system shall comply with the provisions of Clause B3.3 in GB150.1.
In the first case, the pressure actually used should be less than the set pressure of the safety valve. In the second case, the set pressure can exceed the design pressure, but there must be a maximum allowable operating pressure, which cannot exceed either of these values. In fact, this situation represents overpressure operation; the solutions are design changes or equipment replacement. The last one isn’t really a problem either; the main issue is that the pressure relief valve tends to break, which causes a lot of trouble in actual use.