Can the return valve of a cryogenic liquid pump reduce pressure, and by how much?
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Recently, I have been testing an liquid oxygen pump with a flow rate of 50,000 and an outlet pressure of 5.1. However, once it was started, the safety valve located behind the return valve activated immediately (with an outlet pressure of 0.64). After tightening the screw at the top of the safety valve as much as possible, I tried to restart the pump, but the safety valve still activated (with an outlet pressure of 1.1). It’s the first time I’ve seen a safety valve installed after a check valve following a pump; I’m wondering whether this is a problem with the safety valve or with the piping design Which of these two possibilities is more likely? The check valve should have a pressure-reducing function; where can I find information regarding the pressure after reduction? PS: The liquid oxygen for this pump comes from the storage tank, and the return flow also goes back to the storage tank. Moreover, with the return valve of another liquid nitrogen pump tested a few days ago, the safety valve did not activate. Liquid nitrogen pump outlet 5.1, flow rate 30,000.
Forgot to mention it – the set pressure of the safety valve located after the check valve is 0.68
Check what the pressure rating is for this return pipeline; at the beginning of the return flow, vaporization occurs as well, and the pressure is not low.
Check if there is a problem with the safety valve by performing a pressure test. Another point to consider is whether the equipment and pipelines have been thoroughly pre-cooled, but the issue with safety valves might be more significant.