Valve flow and flow resistance testing
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This post was last edited by Chemical industry, hehe, machinery on 2017-8-5 at 11:00. For a valve with a DN50 size, using a DN50 pipe, the flow coefficient when the valve is fully open is 80 m3/h. According to national standards, it is necessary to measure the KV value of the valve in this fully open condition; at that time, the flow velocity in the pipe reaches 11.32 m/s, with a Re value of around 563,184. The pipe resistance is 0.8 MPa, which is an unacceptably high value. If DN80 pipes are used, the flow resistance is around 0.08 MPa, which is acceptable. However, the national standards GB/T 17213.9-2005, JB/T 5296-1991, and the 2006 edition of the Practical Valve Design Manual (by Fang Ruzhou from Tsinghua University) all specify that the nominal sizes of pipes and valves must be identical. On the other hand, the other two national standards, GB/T 30832-2014 and GB/T 4213-2008, do not require that the sizes of pipes and valves match. How should this issue be handled? The image shows the process of calculating pipeline flow resistance:
The flow rate is too high. Why is the flow rate so high?
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First of all, thank you for your question! Since the KV value of the valve is 71, a pump with a capacity of 80 m3/h was chosen to meet the measurement requirements. If DN50 pipes are required according to certain national standards, the flow rate would indeed be very high. If DN80 pipes are used, the flow velocity will be around 4 m/s, but a pipe diameter larger than that of the valve opening does not meet certain national standard requirements
Hello, it’s not about selecting a valve, but rather measuring the KV value of the valve
This post was last edited by Iceberg Corner on 2017-8-6 at 13:06. Reducing sections are added before and after the valve; the pipes are of size 100, with straight DN50 sections left before and after the valve (in the test section)
Different valve types naturally result in different flow capacities.
Different valve types naturally result in different flow capacities.
Different valve types naturally result in different flow capacities.