Question: Can the valve disc that has fallen off be restored (without removing the valve)?
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Dear experts: A manual valve at the outlet of the shell side of a tower top cooler in my unit has had its valve disc fall off due to repeated opening and closing. Unfortunately, the valve closed itself after the disc fell off, and it can no longer be opened; as a result, the pressure in the propylene purification tower is extremely high. I would like to ask if there are any alternative methods that could be used to restore this valve to normal operation. Since it is not yet time for maintenance work, we cannot stop operations to carry out repairs. I hope you can help me find a good solution. Thank you very much!
The only option is to hire a professional team to use pressure-driven drilling technology to install a cross-line; the main materials required are two gate valves, 4 flanges, and a few other components. This technology is quite mature – we have used it to drill and install cross-lines on liquefied gas pipelines as well as on re-refining pipelines. Unexpected situations can arise from time to time.
We have considered this option; since the material in the pipeline is 19-kilogram batches of propylene, the risk of making openings under pressure is too high, and the consequences of a leak would be catastrophic, which is why no action has been taken yet. Is there no other way?
Go back upstairs; with a professional team carrying out the work and using relatively advanced drilling tools, we are confident it can be done. I wonder if your company belongs to one of those two major companies, as they have the capability to do this. Before implementation, develop a detailed plan to reduce system pressure if necessary. Without this method, it’s hard to find a good alternative.
This idea can be tried; generally, once the valve disc comes off, the valve operates more smoothly. One can try using pipe wrenches to turn the valve stem while gently turning the handle, and sometimes this will help get it to function again.
Drilling under pressure is possible, but it may not be cost-effective for me personally. First of all, the risk is very high. Secondly, the cost of drilling under pressure is also high. Rather than taking such high risks, it’s better to stop and deal with it.
We are preparing to use this method for recovery, but it still hasn’t been connected yet!
After reducing the pressure, the valve cover was removed to replace the valve stem
It’s not your fault; it’s only by turning it off and then on again that you can find out if there is a problem with the valve. If temporary measures really need to be taken, it is recommended to: 1. Reduce the capacity: keep it within the range that allows N-2 sets of coolers to operate (N is the number of sets of coolers at the top of your tower) ； 2. Stop the cooler with a faulty valve and one good cooler, clean them thoroughly, and install blind flanges ； 3. Connect the pipeline valves in front of the outlet valves of the two sets of decommissioned coolers together ； 4. Resume work.
Great idea, thank you! How did you come up with this idea? What is your profession?
It’s a very practical and good method; I’ve learned it!