Discussion on the minimum setting pressure of safety valves
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It is a low-pressure storage tank; the tank itself is designed for a relatively high pressure. To control the maximum operating pressure of the tank, it is planned to install a safety valve with a set pressure of 0.05 barg. Can an appropriate safety valve be selected provided that the pressure losses in the inlet and outlet pipelines meet the required standards? If not, what is the lowest set pressure for safety valves that people have used? Is it still a conventional safety valve?
It’s indeed too small, making it difficult to find. I’ve seen safety valves with a pressure rating of 10 PSi before
What medium? If environmental regulations permit, a breathing valve can be used.
Valves designed for pressures equal to or greater than atmospheric pressure are suitable for use as safety valves; your pressure is significantly below this range, so it falls within the category of breather valves, and the calculation formulas used are different.
Above the set pressure valve upper limit = 0.2 barg; below the maximum operating pressure of the pipeline or vessel = -0.1 barg
This fixed pressure should belong to a breathing valve, not to accessories for pressure pipelines
I don’t know how large your tank is, nor what the medium and temperature conditions are. Previously, I designed a one-way valve for a client, which relied on a spring and the weight of the valve core to ensure one-way discharge, and it worked very well. However, your pressure of 0.05 bar is too low – it’s only 0.725 psi – and the breathing valve mentioned above simply cannot provide sufficient protection. The opening deviation of ordinary safety valves usually exceeds this value; the same is true for breather valves, and the deviation of check valves is also 2 psi. Considering the effects of self-weight, friction, and temperature changes, it is very difficult to find a valve that meets your requirements; even valves with small tolerances will have a narrow diameter, failing to meet the exhaust requirements. With a larger diameter, the deviation is too great, and it still doesn’t meet the requirements.