The Siemens positioner experiences up and down fluctuations at the fixed valve position
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Question: The Siemens positioner makes a hissing sound when the valve is at a fixed position, and the valve position keeps fluctuating up and down, with the fluctuation range being around 0.1–0.3 valve positions. What could be the cause of this?
Is there any debris or water accumulation in the air path of the electrical converter?
It’s the same even after replacing the new locator
Vibration of the valve body? Is there a leak in the gas line? Feedback rod fixation issue?
Is the valve opening too small? What is the back pressure? If replacing the positioner doesn’t help, it may be that the torque of the actuator is insufficient; in such cases, adding a spring or similar component could help. If the valve opening is too small or the back pressure is too low, it is recommended to close the manual valve and increase the valve opening of the control valve, which should have an effect
Is the valve position feedback rod loose, and is there any air leakage from the valve body? Are there any issues with the gas circuit and signals?
Siemens often experiences this issue for no apparent reason! I called, and they charged a service fee; so I want to know as well. But it’s definitely not due to air leakage, re-inflation, or vibration. I think the sealant has aged. Because there were no problems in the first 3 years!
Is it because the structural dimensions of the valve seat were not properly designed, which prevents the adjustment from achieving stability?
It is necessary to conduct inspections: replace the locator, check for leaks in the air supply lines, check for leaks in the cylinders, verify that the feedback components are secure, and ensure that the springs in the actuator have sufficient stiffness. We also often encounter such problems. If it’s only 0.2 valve positions, there’s no need to worry about it; it has no impact on usage.