Siemens positioner issues
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The control valve used to regulate the reactor outlet pressure is equipped with a Siemens actuator. At present, the reactor pressure fluctuates significantly; observations on site show that the valve position varies somewhat when operated manually. I’m not sure what the cause is
First, check whether there is any air leakage from the valve and whether the feedback rod is loose; finally, the dead zone can be adjusted appropriately
What is a suitable value for the dead zone? It is 0.0 now.
It depends; start by setting it to 0.5 and see. If the value is greater than 3, then there’s no need to make any further adjustments – find another cause instead
1. First, address the cause of valve fluctuation. If the valve fluctuates when operated manually, it is definitely due to an issue with the instruments. If the output pressure from the actuator remains unstable even when in manual mode, there may be leaks in the air supply to the actuator, especially at the connections, or it could be a problem inside the actuator itself. Leak testing can be performed; if no leaks are found externally, then replacing the actuator might be necessary； 2. Backlash at the connection of the feedback rod can also cause fluctuations in the valve ； 3. It is best not to set a dead zone for the positioner, especially in applications where precise control is required ； 4. If the valve fluctuation problem is resolved, a 3–5 second filter can be added to the pressure indication, the PID parameters can be adjusted, and then automatic mode can be activated to stabilize the pressure ； If the reactor outlet pressure still fluctuates, investigate the causes within the process system as well as the mutual influences between upstream and downstream components.