The flow rate controlled by the control valve is unstable; even when the valve position remains unchanged, the flow rate keeps dropping
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Why is the flow rate not stable when controlled by the flow control valve? Once the valve position reaches a certain level, it stays there, yet the flow rate indicated by the flow meter keeps decreasing. The valve has to be adjusted continuously, and the flow rate keeps falling; however, when the manual bypass is used, the decrease in flow rate is less severe. Could someone please give some advice?
Are there any photos of the on-site control valve? “When the valve position is adjusted to a fixed value, the flow rate indicated by the flow meter keeps decreasing. Has the actual valve position indeed been reduced?
What is the control loop like? Are the valve and flow meter located on the same pipeline? Is the valve of type FC or FO? Is the controlling effect a positive or negative effect? First, rule out valve failures – the valve position remains unchanged but the flow rate decreases; is there an issue with the valve position feedback?
The bypass flow increases; there is a problem with valve 1, or the upstream and downstream shut-off valves, or the pipelines are blocked. 2 There is some blockage somewhere in the entire pipeline; since the bypass pressure drop is lower, the flow rate is higher when it is in use. The three valves at the control valve cause a larger pressure drop, resulting in a lower flow rate.
I don’t quite understand. Could you explain it more clearly?
A problem has been identified; mainly, the replacement of the pump has disrupted the pressure difference of the original valve.
Thank you all for your help; it seems that replacing the pump caused interference with the valve pressure.
Thank you all for your participation. The issue with replacing the pump is likely that the pressure difference is different from before.
Check your control valve; it seems that the valve position needs to be adjusted. It’s fine to use a bypass, which indicates that material is flowing through. The decrease in flow rate may be due to an issue with the valve’s feedback mechanism.
1. The accurate adjustment range for the control valve’s opening is 30%-80%; at other openings, the adjustment is not precise. 2. When the pressure drop across the control valve falls below 30% of the total pressure drop in the pipeline, its accuracy in regulation also decreases. Based on your description, it seems that the pressure drop across the control valve is too low, resulting in the flow rate in the pipeline being little affected by the valve’s opening degree.