A problem has arisen in the level control loop for the flash separation unit shown in Figure. The level control loop had functioned in a satisfactory manner for a long period of time. However, the liquid level is gradually increasing with time even though the PI level controller output has saturated. Furthermore, the Liquid flow rate is well above the nominal value, while the feed flow rate is at the nominal value, according to the recorded measurements from the two flow transmitters. The accuracy of the level transmitter measurement has been confirmed by comparison with sight glass readings for the separator. The two flow measurements are obtained via orifice plates and differential pressure transmitters, as described. Suggest possible causes for this problem and describe how you would troubleshoot thissituation.

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Vapor LT LC Feed Liquid