Instrument valves and hand valves
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Must hand valves be installed before and after the instrument valves on the process main line?
Not all of them are included; depending on the importance of the valve rating, a bypass is added to facilitate online replacement and reduce operation time
Generally, the instrument comes with valves, and the connection wires are supplied as part of the set. Gauge valves are welded manual valves, and different organizations have different management practices~~~
Personally, I think it’s better to include a hand valve.
Most control valves in the refining and chemical plants built last century were equipped with bypass valves, whereas most control valves today no longer have such valves.
I’m still very grateful to the original poster for sharing it~
If you are referring to control valves, in terms of design costs, valves are generally not installed at the beginning or end of pipelines that are larger than 8 inches in diameter, that is, DN200 pipelines； Those below this size generally have them. Furthermore, from a process perspective, dry-process systems all require such valves for safety reasons.
You must be referring to a control valve; if such a valve were to fail, it should not affect the shutdown process or normal production, and therefore a bypass is necessary. It’s just three more valves that might not be needed in a lifetime, which only increases the investment cost slightly.