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In a steam turbine I have a rare, aleatory and intermittent failure of GAP in two proximity sensors, measuring HP diff.expansion.
Normal measure of every sensor is -8,5v. When fail measure falls to -12v.
The two sensors are measuring distance to both sides of a disc. This disc is part of the turbine rotor near the first bearing.
Both sensors (BentlyNevada 25mm) fail aleatory one each other with a peak of 50us. We replaced proximitor, cables and rack bently 3500 card without success.
This fail can appear for days and disappear for days. When appears you can see the signals failing 4 o 5 times every hour or more but not always at the same time. Now we have one sensor inside the turbine and one sensor at 1m measuring a fixed distance: The interference only appears at sensor inside the machine. This test discards EMI.
There were a little correlation with the last hours of the day (22h, 23h) and the beginning of the failure. Sensors are well grounded, (we have a low pressure diff.expansion in the same card and it's no affected). Now, I'm thinking in rotor ESD discharges, but I don't know how can I test the grounding rotor brushes.
Any idea? Thanks in advance
Normal measure of every sensor is -8,5v. When fail measure falls to -12v.
The two sensors are measuring distance to both sides of a disc. This disc is part of the turbine rotor near the first bearing.
Both sensors (BentlyNevada 25mm) fail aleatory one each other with a peak of 50us. We replaced proximitor, cables and rack bently 3500 card without success.
This fail can appear for days and disappear for days. When appears you can see the signals failing 4 o 5 times every hour or more but not always at the same time. Now we have one sensor inside the turbine and one sensor at 1m measuring a fixed distance: The interference only appears at sensor inside the machine. This test discards EMI.
There were a little correlation with the last hours of the day (22h, 23h) and the beginning of the failure. Sensors are well grounded, (we have a low pressure diff.expansion in the same card and it's no affected). Now, I'm thinking in rotor ESD discharges, but I don't know how can I test the grounding rotor brushes.
Any idea? Thanks in advance
