Control valve and bypass
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Is it still effective to open the bypass valve when the control valve is at its maximum opening? (The pipe diameters before and after the control valve are the same as those of the bypass pipe)
This depends on factors such as the flow rate of the specific fluid in the pipeline and the pressure difference resulting from the maximum flow velocity. If you are interested in this topic and the skills required for this position involve this area, I recommend \"Principles of Chemical Engineering\" – it serves as a reference book for those working in this field. The content of this book isn’t very difficult; you might as well give it a try.
The manual valves and bypass valves before and after the installation of the control valve are mainly intended to facilitate the maintenance of the control valve
It’s useful, after all, there are two exits
Some flow can be increased; the amount depends on the pressure drop across the control valve when it is fully open. Assuming that the flow rate when the control valve is fully open (which is also equal to the flow rate in the pipeline) is 100, with the pipeline accounting for 80% of the pressure drop and the control valve accounting for 20%, then if you want to increase the flow rate by 15%, the pipeline will absorb 0.8*（1.15）2 = 100% of the pressure drop, leaving almost no pressure drop for the control valve. At this point, operating any combination of valves (including bypass hand valves), no matter how large the diameter or how fully they are opened, can only increase the flow rate by 15%.
It is likely to be useful, as the diameter of the control valve pipe is generally smaller than that of the pipeline, and even at 100% opening, the valve element still limits the flow rate to some extent; therefore, it’s very likely that using a bypass will work
Under normal circumstances, it works, as the control valve has its own Cv value, and this value is ultimately lower than the flow rate when the pipe is in a straight configuration; therefore, the bypass system can provide some compensation. However, bypass valves are used when control valves need to be taken out of service, and their primary function is to open and close in order to cut off flow. If they are used to regulate flow, it can cause erosion of the valve’s sealing surfaces, leading to internal leaks when the valve is closed. As a result, when there is a problem with the control valve, it becomes impossible to take it out for repair, which poses a risk to production.
It works; it’s equivalent to increasing the CV