Repair of control valves
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There is a control valve operating at a pipeline pressure of 3 Mpa; the medium is a liquid oxide. Over time, deposits form on the pipes as a result of continuous flow. The process team states that the flow rate downstream of the valve is the same as before, but that the valve setting is not sufficient. What is going on here?
Weren’t there deposits on the valve? There are backflow valves and control valves on the bypass lines, allowing for easy isolation for maintenance and cleaning at any time.
One can first check whether the upstream shut-off valve is fully open, whether the bypass is activated, whether there are any issues with the filter, and whether there are problems with the DCS output signals and the valve input signals. The poster should determine whether the flow rate is higher or lower compared to before, given the same valve position. The poster can first close the valve completely and see if the leakage amount is the same as before; by comparing it with the previous values, if the current leakage is higher, it could be because the valve wasn’t closed properly and needs to be adjusted again, or it might be due to damage to the valve core from prolonged exposure to flow, as well as possible loosening of the valve seat over time····
If there are no problems, then it means the flow rate of the pipe has decreased
First of all, thank you for your response. The issue has been resolved by taking the valve offline; there is nothing wrong with the valve itself. I just wanted to explain why the current quantity is decreasing. Just because there’s no problem with the valve doesn’t mean that the issue isn’t still present.
It’s normal operational procedure; the valve can be adjusted properly, though there is some delay. After it was sent for repair, no problems were found. Could it be that deposits inside the pipeline are reducing the flow rate? Thank you for the idea.
If the valve is fine, then it’s probably a problem with the pipes or the flow rate. The simplest way is to record the values from the flow meter in front of the valve every day; after some time, by comparing those values, we’ll know what’s going on. Haha… I guess it will take until next year
A few days ago, I encountered a control valve for which the central control system indicated a setting of 0 degrees, while the actual opening degree on site was around 25 degrees. After inspecting the instrument, it was found that the packing was the problem, which prevented the valve stem from closing fully~~
Due to the deposits on the pipes after prolonged flow, the flow coefficient of the control valve has decreased.
I think what was said upstairs is correct; since you mentioned that there are deposits inside the pipes, those deposits will inevitably affect flow regulation. The original poster can think of it this way: if you have a tube with nothing inside, fluid can flow through it without any obstruction. However, when there are some magazines stuck inside the pipe, it will inevitably have an impact as the fluid passes through; as more and more debris accumulates, the pipe will eventually get blocked. . .
Then tighten the screws a bit. Generally speaking, the two issues of leakage due to the packing and hard sealing in domestically produced control valves are quite prominent···