Control valve bypass

Either the pipe is too large, making it uneconomical to install inlet and outlet valves as well as bypass valves, or it’s simply not possible to add such valves; the control valve itself already has a handwheel； Either the probability of overpressure is too low, or when the control valve fails and needs repair, it can be manually controlled to prevent overpressure.

How can an overpressure vent be a control valve? It should be a on/off valve

Hand valves are often unreliable

The object for venting is the gas pipeline, which consists of high-pressure and low-pressure gas mainlines; the venting pressure in such cases is negligible compared to the overpressure. Here are my thoughts: First and foremost, from a safety perspective, the presence of bypass lines implies the existence of flanges and valves, and it is necessary to ensure that there are no leaks at those flange connections. High-pressure flanges… you know what I mean； Secondly, the addition of flanges, valves, and bypass lines increases costs ； Finally, the pressure difference is high, making it difficult to operate the switch; moreover, there is a lot of noise. Generally, no one would take such a big risk to operate it – it’s really unbearable. Have you ever tried to operate the steam release valve at 3.5 MPA? Once you do, you’ll understand~ It’s just my personal opinion

It is mainly for safety reasons; manual pressure relief is not practical. If the valve wears out and is unable to maintain pressure, the only option is to install a blind flange, but this approach is even less effective than not installing one at all