Valve positioner
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I have a question for everyone: how long can the correspondence between the signal and the valve position be guaranteed after one self-tuning of the valve positioner? Is it still the case that as long as the connection is reliable, the signal is permanently corresponding to the valve position? Why does it happen that, at the site, the valves that were self-tuned initially no longer have a matching signal and valve position after being in use for some time?
This is Siemens’ positioner. There is indeed such a phenomenon: after being used for a while, the valve position display shows deviations. I think it’s caused by a change in the actual position of the valve.
Self-tuning of the intelligent locator and the correspondence between the valve position and the signal are two different things; even without self-tuning, the valve position should still correspond to the signal, although over time the opening/closing position of the valve may drift, or the feedback from the locator may become distorted. The quality of Siemens’ positioners is quite good.
Check the connection of the feedback mechanism for any gaps or abnormalities in the connections.
Check the feedback mechanism; I have encountered this problem as well.
In my opinion, the locator of any manufacturer will develop deviations after being used for a certain period of time; it depends on how long that period is.
It seems that Siemens positioners have this issue, but it’s only a case-by-case situation; most of them work fine. Moreover, Siemens positioners have high requirements regarding the quality of the instrument air; some of these positioners keep losing air and then having it replenished again, and this process can be heard as a hissing sound when walking by!
Yes, in some cases it is indeed loose connections that cause positioning errors, but there are also cases where the connections are reliable yet errors still occur on site. So I’m a bit unsure whether this is due to the passage of time, or whether the valves were not self-tuned from the moment they were installed on site!
Has the switch position drifted over time? Why does it drift? My connection is reliable; if there is drift, it’s not possible to stop the system and perform self-tuning, so the impact isn’t that great. Also, how long is this period of time? A month? One year? Three years?
Thank you. This issue can occur when the connections are loose; I can understand it if such a phenomenon happens due to loose connections. However, some of the connections at our site are quite reliable, yet their positioning is still inaccurate – there’s an error of about 2%!
“There is a 2% error.” At what valve position does this valve generally operate? What kind of valve is this? Butterfly valve?