Oxygen flow regulation
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Oxygen enters the reactor for reaction through analyzed proportions. The normal capacity is 2,600 cubic meters per hour. The control valve regulates the flow rate. Are two control valves needed in parallel here to regulate the flow rate? Whether a control valve can meet the required control accuracy
I’ve never seen piping with parallel adjustment – one large pipe for coarse adjustment and a thin pipe for fine adjustment? If the precision requirement is not very high
I agree with you; they are generally installed in series.
I’ve never seen regulating valves connected in series. What is the purpose of connecting regulating valves in series? I think the purpose of using parallel connection is that the adjustment range may be very large, while the adjustment range of a single control valve is limited.
Use segmented control to increase the adjustable ratio
Can’t a control valve meet the requirement for adjustability ratio? What is the actual adjustable ratio of a general control valve?
It’s usually 30:1, but there are also versions with a higher ratio! By the way, with those two valves connected in parallel, it’s possible to use one of them during abnormal operating conditions such as startup or shutdown, and switch to the other one once normal operation is resumed! One large valve and one small valve – that’s the configuration.
Our process pipelines have similar piping systems for nitrogen; a valve is opened at a low flow rate. If the set amount cannot be achieved with one valve fully open, then another valve comes into play to assist in control.
Use segmented control to increase the adjustable ratio
In large-scale chemical industries with a high degree of automation, all automatic control valves are equipped with bypasses; these bypasses are manual valves. I have never seen two automatic valves connected in parallel. Two automatic valves are connected in series: one can take a bypass route in case it loses its regulating capability due to a fault, while the other performs automatic regulation. When the main valve does not open under certain conditions, the small bypass tube is used to allow flow
Use them in parallel for precise flow control; generally, control valves become less sensitive or lose their accuracy when the flow rate is below 10%. Therefore, using one valve of larger size and one of smaller size in parallel ensures appropriate accuracy