In our plant we have this pressure/ flow control station to maintain feed gas pressure and flow at required optimum values. I have a difficult time understanding how both of these controllers work at the same time. For example, if it is desired to increase the flow then the flow controller opens the flow control valve and as a result more flow will be obtained, however, the pressure will also increase the pressure upstream the flow control valve which in turn induces the pressure controller to open the pressure control valve to compensate for pressure decrease but this will lead to flow increase as well so the flow control valve shall close to maintain constant flow. How is the required steady flow and pressure is realized if adjustment in any valve will make the other valve close or open as well?! and what is the point of having such control configuration rather than having one valve?
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