NDE Probe Spurious Spikes for Centrifugal Compressor


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We are facing a spurious spikes from only one radial probe (X) from NDE of Centrifugal compressor driven by a steam turbine. all other 7 probes are normal (y of this radial, x&y of compressor DE, X&Y of steam turbine DE and NDE) and no any abnormal process conditions existing. We made everything (replaced the probe, the extension cable, the SPD (surge Protection Device) and the proximitor). all replaced by new ones but problem still exist. extension cable is in a metallic conduit. we tried swapping the probe and extension cable together between X&Y and found the problem received in the Y channel of the 3500 BN monitor. so the problem now from the probe and extension cable only, but they are new and also in a conduit for noise immune. So any suggestions or ideas? Is there any mechanical issue on the compressor can cause such this scenario?
Dear hany5757

First of all; I'm not familiar with Steam Turbines but I have not too bad experience with Centrifugal Compressors, 3500 BN monitor, probes, ..

You said: "so the problem now from <b>the probe</b> and <b>extension cable only</b>". The third possible problem it could be a <b>true reading!</b> And there is a real vibration problem, Why not?

Sorry if my English is no so well because I didn't understand what do you want to say with "<b>spurious spikes</b>"

Are pic readings too high (above trip value)? Because if "spikes" readings don't exceed the maximum graduation of your BN monitor you can use a vibration analyzer tool to gather data and make an initial diagnostic.

More clarifications are needed:
Is there any increase, even small increase, on the Y probe reading?
One parameter is not enough to build an investigation.. What about oil temperatures and bearing metal RTDs? Is there any change? When did this happen? Did something happened recently to lead this trouble?