Change control valve from automatic to manual mode
Thread Content
Dear experts, the flow rate of the heat carrier flow control valve at the bottom of one of our distillation towers is currently at its upper limit; once automatic mode is activated, it switches to manual mode after a while. Why is this happening? There is another control valve whose flow rate is also at the upper limit, but it doesn’t switch modes! Please those who know it, teach me! Thank you! :handshake
Please have the instrumentation team check what caused the switch on the DCS. If the traffic reaches the upper limit, there should also be a record of an automatic redirect to DCS.
When operating in automatic mode, if the controller reaches around 106% of its upper limit (the maximum limit varies depending on the controller), it loses its control function. Perhaps the two amounts exceeding the limit are different. You can check it out and compare. Another possibility is that the configuration settings of the two controllers are different; if the first approach doesn’t solve the problem, then check the configuration of the instrument.