I would like to know which standards specify exactly how much backflow flow a check valve can reduce
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For example, in an existing system, the operating pressure at the upstream equipment is 0.8 MPaG; the designed pressure for the downstream main pipe is 0.6 MPaG, although it is designed to operate at 1.2 MPaG (we will not discuss the design issues here for now). There is a orifice plate and a check valve in the pipeline between these two sections. To prevent backflow in the downstream main pipe from causing overpressure in the upstream equipment, it is planned to install a safety valve on the upstream equipment with a set pressure of 1 MPaG. Based on the pressure difference under backflow conditions and the known parameters of the orifice plate, it is known that the backflow rate without a check valve is, for instance, 3 t/h. The question is: what should be the backflow rate considering the presence of this check valve? I’m not sure whether any standard specifies this explicitly or if there are any established conventions regarding it. Thank you
In my opinion, industry standards for check valves do not address this aspect; there are no manufacturing standards in the industry, so it is difficult to calculate the backflow rate. For safety reasons, it is better to rely on orifice plates.
Check valves can also fail sometimes; it’s better to assume they are not present.
Theoretically, a check valve should prevent backflow, so the amount of liquid returning should be 0. However, in actual operating conditions, some leakage does occur; as a general guide, one can refer to the performance of the control valve, specifically the number of bubbles produced per minute. In the case of the safety valve mentioned earlier, it can be omitted from the calculations.
This is indeed safe; I just want to see if it’s possible to reduce the leakage volume a bit, and make the safety valve smaller as well
I had heard before that UOP has company regulations specifying what percentage the backflow can be considered to be when two different types of check valves are used, but this isn’t entirely reliable either. So I would like to ask if there are any relevant standards in China
The last edit to this post was made by longkui1990 on 2017-7-15 at 14:48; I personally don’t agree with your view, buddy
If I remember correctly, it should be two check valves at 10% of the full flow rate