Why can’t the valve be closed?
Thread Content
We have a valve in our facility – a DN200, 900LB globe valve. It passed the pressure testing during manufacturing, but once it was installed on-site (in a vertical position), it wouldn’t close properly. Even if the valve was closed first and then the pump started, leakage persisted. The manufacturer’s technicians suspected that the gap between the valve stem and the valve disc was too large; after adjusting it, the problem remained. A new valve was installed, but the issue continued. Could someone with expertise help resolve this issue? Thank you!
Quality issue! It seems that the gap between the valve core and the valve seat is too large; probably insufficient sealing is to blame for the inability to reduce this gap to its minimum
It is likely a quality issue with the valve; it is recommended to remove it and inspect all its components, especially the bending degree of the valve stem as well as its operation when opened and closed, and to also perform a pressure test.
It’s the manufacturer’s problem; let them deal with it
If, after inspection, no quality issues are found with the valve, it is likely that the pressure at the pump outlet exceeds the valve’s rated pressure, or the valve did not pass the pressure testing procedures prior to leaving the factory
Is a pressure test conducted upon leaving the factory? If the pressure test is successful, there are usually no immediate issues on-site. The pipeline pressure is monitored, especially under complex operating conditions at the pump outlet. Be cautious.
This could be due to too large a pressure difference on either side of the valve, as well as an excessive gap
It’s not clear whether it’s an internal leak or an external leak. Based on everyone’s analysis, it’s an internal leak. 1. Those who say the inspection was successful are being irresponsible; it might be qualified only under normal pressure conditions； If internal leakage occurs after pressurization. 2. Another cause of this phenomenon is that the newly installed pipelines are not thoroughly purged, and impurities prevent the valves from closing properly, resulting in internal leakage.
There are three aspects: first, problems with the valve itself. Second, if the valve has not been disassembled for inspection, it may be due to an installation issue with impurities inside the valve. Third, the pressure difference before and after the valve exceeds the rated value
It’s a quality issue on the manufacturer’s end; just ask them to resolve it
I’m not sure what type of valve the original poster is referring to; if replacing it with a new one doesn’t work, then try using a valve from another manufacturer. Perhaps there is a problem with the quality of the valves produced by this manufacturer