Problem of fluctuating feedback in Siemens positioners
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Dear sea friends, the anti-surge valve for the unit in our setup uses a Siemens positioner with feedback indication, and the signal is fed into the TRICON system. As it is an anti-surge valve for the engine unit, this valve remains in a closed state at 0% throughout most of the time; in fact, its position is always at 0%. However, there are times when fluctuations occur in the feedback from the actuator, with these fluctuations reaching up to around 40%. Such fluctuations are irregular and follow no pattern – sometimes there are no fluctuations for several months, while at other times they occur several times a month, each time lasting for a few days. We checked the installation and configuration of the locator, and everything seemed fine. Considering factors such as signal interference and shielding, we replaced the cables, and even replaced TRICON’s terminal boards and connectors, but the problem still persisted. I would like to ask fellow sailors whether anyone has encountered similar fluctuations in the feedback from the anti-surge valve. Are there any methods to address such fluctuations? It would be great if someone could analyze the reasons behind this issue. Thank you!
I think you should replace the locator! There shouldn’t be any other factors.
Consult the manufacturer’s experts; P; P; P; P; P; P
In the unit anti-surge valve, we used the Akka 827A-X2-AB0….. intelligent positioner; the feedback fluctuations were very large and irregular. Things returned to normal after replacing the feedback safety barrier. Recently, another Akka 827A-X2 intelligent locator also experienced fluctuations in its feedback; at that time, the valve itself was vibrating, and the pressure gauge connected to the locator’s air supply also fluctuated from time to time, which caused these feedback issues. To this day, this new problem has not been resolved fundamentally. I have checked that the air supply pressure is normal and the locator has no error codes; however, based on the trends, fluctuations of up to 30% can occur. Do any of you have any suggestions? ?
If there are no issues with the hardware installation, then there may be interference in the circuit processing part of the locator or in the signal transmission. If the shielding and grounding for such transmission interference are not effective, signal isolators or safety gates can be used. If there are problems with the electronic circuits of the locator, it’s difficult to address them, as these issues are random and can only be detected on-site when a fault occurs. If strict control requirements are imposed based on feedback, a separate signal feedback instrument can be installed; for example, an angular displacement sensor can be used. Alternatively, a conventional float-type level transmitter can be modified to function as a feedback rod for indicating the valve’s travel distance.
Generally, this situation is caused by unstable signals from the locator; pipe oscillation (mild, not reaching 30% levels) and electromagnetic interference can also lead to such issues. You can try using a different locator. If there are accessories related to the speed regulator, its sensitivity can be adjusted to mitigate this phenomenon
I encountered the exact same situation as you; the difference is that my feedback level peaked at 70%. The feedback signal seems to not be interlocked, so there’s no need to worry. You can simply replace the feedback module when you have the opportunity to stop the machine for maintenance.