What are the causes of no flow in the flow meter and an inability to adjust the control valve?
Thread Content
In an oxidation reaction unit flow control circuit, the orifice plate differential pressure flow meter suddenly stopped measuring any flow, and the valve could not be adjusted either. I would like help in analyzing what could be the cause of this
Is it the closed control valve that causes the flow meter to show no flow? It depends on where the control valve is located. When it is in the closed position, it is necessary to determine whether this control valve is normally open or normally closed; then check the control signal for the valve – for electric valves, check the voltage. If possible, turn it on manually to see if the flow meter is damaged. Check them separately. Mutually exclusive.
Can’t even do such a simple check? Are you in automation?
It would be best to include a flowchart. According to what you said, the flow meter and control valve form a simple control loop; therefore, first check the control valve by applying a 4–20mA signal directly to it from the field using a signal generator, to see whether the valve responds. There is nothing wrong with the actuator valve itself; check the connection from the valve to the DCS as well as the DCS configuration. No movement – there is a problem with the valve body; check for sticking or similar issues. 2. Flow meter: Check whether the transmitter is clogged. For waste discharge, it is connected to the circuit via a manual operator to conduct circuit testing and check for any issues in the circuit. 3. If the flow meter and control valve themselves are fine, and there’s no issue with the circuit, then it’s a problem with the DCS configuration
Everyone, read the question carefully! First is the orifice plate differential pressure flow meter: there is no flow suddenly. The reason for this has been identified – whether the actual flow rate has really dropped to 0, or if there is a problem with the transmitter, or if the pressure tapping is blocked, or if the cable connections are loose. The second valve cannot be adjusted, which is strange. It’s a single-loop control system – where is the flow control element and the valve? Is it positive or negative action control? Could there be an issue with the configuration, or with the PID parameter settings?
According to you, if the valve fails to close properly, does that mean the valve is out of control?
A sudden loss of data flow may be caused by interference or a malfunction in the flow meter.