Can the valve opening and the diameter of the control valve be larger than the pipe diameter?
Thread Content
Regarding the opening degree of control valves, I asked a well-known domestic manufacturer for data on this topic, and the results showed that for the largest valves, the linear opening degree does not exceed 70%, while the percentage-based opening degree does not exceed 85%. I would like to ask: if the normal opening degree calculated for my valve meets the requirements, but its maximum opening degree is close to 90%, is that acceptable? I would also like to ask whether the diameter of the control valve chosen can be larger than that of the pipeline? For example, if the diameter of the pipe is only 50, can I choose a valve with a bore size of 65? I hope everyone can explain the reasons why it can or cannot be used. Thank you all
Reply to 2# Kawashima Elementary School: Oh, thank you. No, the valve’s opening degree isn’t very small; both the normal opening degree and the minimum opening degree are still quite high
If the valve is chosen to be too large, it will operate at a low opening degree, which causes severe erosion of the valve core. Moreover, a larger valve diameter increases the cost of the valve, so there is no need for this
Please have the engineering team recheck your parameters; once it is confirmed that they are correct, run the calculation again. It’s possible that there is an issue with the maximum flow rate estimated by the engineering team. Under normal circumstances, selecting a valve with the same diameter as the pipe and its maximum CV value will be sufficient to meet the flow requirements; in other words, the maximum CV value corresponding to a DN50 valve will definitely be enough to meet the flow needs of a DN50 pipe. If a low pressure loss after the valve is required, valve types with relatively low flow resistance such as butterfly valves and eccentric rotary valves should be chosen.
Reply to 5# Double Gun General: It’s indeed a problem with the process parameters. The flow rate he mentioned is beyond what the diameter of the pipe he specified can handle, so it’s quite confusing
The process parameters must be incorrect – either the maximum flow rate has been overestimated, or the pipe diameter is too small. If the parameters are accurate, then the flow velocity in this pipe will be extremely high, almost reaching the limit for such pipes; as a result, the pipe won’t last long
Generally, both the pressure and flow rate of pipelines fall within certain ranges, and the same is true for control valves. If these values exceed those limits, it is necessary to select different valves; it’s best to discuss this with the process engineers and recheck the parameters. If you have any questions, feel free to ask me – I work in this area of valve selection as well. QQ: 21069825