Operating flow characteristic of control valves
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In actual production, control valves are equipped with upstream and downstream manual valves as well as bypass valves. At low load levels, the opening degree of the control valve is small, resulting in significant fluctuations in flow rate. In such cases, what adjustments should be made to the upstream and downstream manual valves and the bypass valves associated with the process valve?
There’s not much you can do if the opening degree is too low; you usually keep your secondary line closed, right? In your case, the control valve chosen is too large
Your response time is really fast; the forum is truly powerful. All the auxiliary lines are closed; the valves chosen were a bit too large, but it’s impossible to make any changes now. See if changing the opening degree of the upstream and downstream valves can adjust the pressure drop across the control valve, thereby altering its operating characteristics and making it easier to control.
It seems that adjusting the valves before and after the control valve doesn’t have much effect. If you want to make a change, you can add a return pipeline behind the control valve, install a shut-off valve on that return pipeline, and then adjust the flow rate of the return stream. This way, the flow rate passing through the control valve increases, allowing it to meet your operational requirements. However, due to the return flow, there will definitely be some loss in efficiency
Your method is good, but how do I add this reflux? Is the pressure behind the valve lower than that in front of it?
The backflow does not return to the valve; it goes back to the source of power, that is, back to the pump