Leak in the safety valve at the outlet of the liquid argon pump
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Since the calibration facility for safety valves in this area does not have the necessary conditions for calibrating low-temperature safety valves, the safety valve at the outlet of the liquid argon pump was calibrated at normal temperature, with a setting pressure of 1.2 MPa； It turns out that the outlet pressure under normal operation is around 0.85 MPa. Now the safety valve has activated after operating at 0.6 MPa for a few hours. Could everyone analyze the reasons? What is the impact of calibration at room temperature?
I don’t think it has much of an impact; our unit verifies things in the same way. Some safety valves did not experience this issue; it has happened with other safety valves as well, and then the setting pressure at which the valve activates was manually adjusted (in a less critical position). Is the safety valve currently in a cold state? If it is in a cold state, there will definitely be a difference compared to when it is at normal temperature. Because the spring inside is made of metal. The position of the point of action also changes with temperature.
Safety valves are all calibrated at normal temperatures; calibration agencies cannot perform such calibration in low-temperature conditions. Is the pipe connecting your main pipeline to the safety valve too short? Do not insulate it, so that the inlet part of the safety valve remains in a gaseous state at room temperature. If it is detected from the start that there is cold flow, it must be addressed immediately; otherwise, as the low-temperature area rises and the spring cools down, it will start to jump very quickly.
I’m not sure if it was the person in charge of calibration who made a mistake and didn’t adjust it properly.
Upon on-site inspection, it was found that these safety valves had minor leaks; the flow of cold gas caused the springs to shorten, resulting in the valves opening. But during the process of returning it to its original position, the aluminum shavings inside the pipe got stuck on the valve core of the safety valve, causing the valve to leak continuously
Personally, I think normal-temperature calibration is sufficient, and it has always been done this way. Under normal conditions, the safety valve does not come into contact with low-temperature shut-offs, as the fluid in the pipeline ahead of the valve is at normal temperature.
Is the pipe leading to the safety valve too short? Do not insulate it, so that the inlet part of the safety valve remains in a gaseous state at room temperature. ------Support
The analysis is excellent. In the past, our liquid safety valves also tripped frequently; it was later found that the short connection pipes were causing the low-temperature liquid to come into contact with the safety valves and trigger their tripping. Finally, it was sufficient to use a slightly longer connector for installation; now it runs perfectly normally.
If you’re worried, lift the safety valve a bit higher.