Can the design pressure of the outlet pipeline of the safety valve at a CNG refueling station be at atmospheric pressure?
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I would like to ask the experts: For the safety valve of a CNG refueling station, with a set value of 25 MPaG, although the outlet pipe is connected to a vent tank, can the design pressure of this outlet pipe be set at atmospheric pressure? I personally think it’s unreasonable, but how much would be appropriate? The regulations don’t specify this either, so I can only seek advice from everyone; thank you.
It is unreasonable to take atmospheric pressure as the design pressure at the outlet of a safety valve, as there is pressure at the point where the safety valve discharges the medium, and it is not atmospheric pressure. Also, although it is released into the atmosphere, it takes some time to do so. There are safety hazards here.
It is possible to calculate the pressure drop in the outlet pipeline when the safety valve discharges, thereby determining the back pressure; the design pressure can then be established based on this back pressure. https://bbs.hcbbs.com/thread-2953230-1-1.html
Hello, may I understand it as follows: the pressure drop in the outlet pipeline of the safety valve (due to the pipeline, fittings, and the sudden expansion at the outlet of the vent tube, etc.) + the static backpressure = the pressure at the outlet after the safety valve activates. The pressure at the outlet is the highest pressure in the outlet pipe, and the design pressure of the pipe is determined by taking this pressure and adding a safety margin – is that what constitutes the design pressure of the outlet pipe?