Should a drain valve be a threaded valve or a flanged valve?
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On the PID diagram, there are drain valves at both the inlet and outlet of the pump. If the material is moderately to highly hazardous, or if it is something like gasoline, should threaded valves or flanged valves be used?
Welding or threading, to reduce leakage points.
I’ve always been confused as to whether threaded valves can be used in pipelines for toxic materials
I haven’t come into contact with any toxic or harmful substances, so I think it’s better to use welding as a precaution. Threads still have the potential to leak. It’s not necessary to do it, but I’m not sure if there’s any specific standard definition for it.
It is possible to first connect them with threads and then weld them.
Using threaded valves for the small valves is convenient and also reduces the number of leakage points.
I think you can’t have both fish and bear paws. Welded valves eliminate leakage at the flanges, but repairs are more difficult if the valve fails ； There are basically no issues on the valve side; blind flanges can be used for flanged valves, and plug seals can be used for threaded valves.
The threads should be of better quality; flanges tend to leak over time