Question: How to design a system to reduce compressed air pressure from 0.7 MPa to 0.05 MPa?
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This post was last edited by GMFPJ on 2017-2-22 at 14:13. A compressed air pressure of 0.05 MPa is required, with a flow rate of 9 m3/min; the air supply comes from compressed air at 0.7 MPa pressure. Dear experts, is it possible to use an air storage tank and a pressure regulator? What capacity should the air storage tank have? What specification should the pressure relief valve use? What is the consumption of 0.7MPa compressed air? I don’t know how to calculate and select the right options; I hope experts can give me some guidance! Thank you!
Storage tanks are useless; they merely serve as a buffer or for storage, and in the end the pressure remains the same as that upstream. To reduce pressure, valves are still necessary. Pressure regulators for air are quite common; for example, the filter-regulator valves used in our instrument air systems. Imported versions of such valves cost only a few hundred dollars each, and the outlet pressure can be adjusted as needed. They are very mature products. Fearing it might be considered advertising, I searched on Baidu for manufacturers, and there are many.
Appropriate expansion of the pipeline after the pressure relief valve is sufficient
The backpressure is too low; when selecting a pressure reducing valve, it’s essential to consider the flow curve. Be careful – not much gas will come out after pressure reduction, and also pay attention to the diameter
The simplest one is the self-acting control valve, which is used here where the back pressure is slightly high. Or fully automatically controlled by a control valve
It is recommended to use two pressure regulators; the pressure range from 0.7 to 0.05 is quite large, so using two regulators should work well.
It’s a conventional design; an automatic pneumatic pressure relief valve can be used for this purpose. A manual approach is also possible, and installing a orifice plate after the shut-off valve can also be used to regulate the flow rate. It depends on your process requirements
Generally, for such a large pressure difference, two pressure regulators are required: one is used to reduce the pressure from 0.7 MPa to 0.2–0.3 MPa, and another is used to further reduce it from 0.2 MPa to 0.05 MPa. A buffer tank is only used when the gas source is located at a considerable distance.
This post was last edited by henjuese on 2017-2-23 at 14:30. A minor modification was previously made, reducing the amount of nitrogen from 7 kilograms to 1.2 kilograms； Since purchasing a pressure relief valve is too expensive, it must cost around 20,000 ； Since the operational requirements were not too stringent, it was decided to use a throttle orifice plate ； The calculation standard is HG20570.15; a total of 4 orifice plates are required to reduce the pressure from 7 kilograms to 1.2 kilograms ； We processed the orifice plates ourselves, which saved us money. You can use throttle orifice plates as well; your operating conditions are similar to mine.
In favor of two-stage pressure reduction. I’m not familiar with throttle orifice plates; it seems that throttling requires a basically constant flow rate. If there is no constant flow rate, especially no flow at all, the pressure at the target point will reach 0.7 MPa, which is the pressure at the source
A 1-inch pipe will suffice. A pressure relief valve + pneumatic two-piece unit can meet the requirements.