Step control, control valve and shut-off valve
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I work at a small pharmaceutical factory, where I am involved in technical upgrades. On the nitrogen pipeline connected to the receiving tank, control valves are used, while cut-off valves are used on the vent pipeline. The instrumentation engineer said that this is a form of segmented control; in many other continuous processes, cut-off valves are used as well. He said that control valves are too expensive, so they were all replaced with cut-off valves. I see that in books, proportional control involves two control valves being interlocked; could it be that what’s described in the books is purely theoretical and not applicable in practice? I hope everyone can tell me whether this is reasonable or not.
This post was last edited by Dariga on 2020-11-6 at 12:56 to save money. As long as the small factory can keep operating, it’s fine; automatic control would be useful. As long as it is practical and saves money, it is perfectly reasonable.
Base it on your own knowledge and understanding; ask plenty of questions – no one is an absolute authority
Control valves are indeed expensive. Communicate more with the manufacturer regarding the processes and instruments. What is suitable for them to use is the best.
It can no longer be called stepwise regulation; it can only be shut off. This cannot be regarded as regulation, although a shut-off valve can still be used to control parameters such as temperature and pressure as required by the process.
To save money, a DN25 control valve costs around 10,000
Theory is ultimately just theory; in reality, it’s sufficient as long as it can be used and works well
The price doesn’t have to be this high; it depends mainly on the process requirements and the brand. If the requirements aren’t too high, a locator with good cost-performance can be obtained for around three to four thousand yuan. I’m from a control valve manufacturer; those who need it can send me a private message to discuss further.
Surely no two control valves are identical in performance, but there’s no rule stating that they can’t be used this way; as long as they can serve to regulate pressure, that’s sufficient, although the fluctuations will definitely be significant
Theory is good, but small factories need to cut costs; as long as it meets their requirements, that’s sufficient