Diagnostics to Detect Rotating Machinery Misalignment

Drew Mackley Product Line Manager

Drew Mackley
Product Line Manager

Let’s continue our route-based maintenance video series with a look at diagnostics to detect misalignment issues on rotating machinery.

In this 5:53 YouTube video, Misalignment Detection: Cross Channel Phase and Fault Frequencies, Emerson’s Drew Mackley demonstrates the analysis provided to data collected by portable vibration analyzers in route-based maintenance applications.

He emphasizes the CSI 2140 machinery health analyzer, beyond collecting route data and it spectrum waveforms, is its ability to do additional advanced troubleshooting tests while your maintenance folks are still in the field. Decisions can be made on the spot whether additional data collection and analysis is required.

Coupling-ProblemAfter collecting some data, Drew shows a CSI 2140 screen indicating high vibration at two times the turning speed of the rotating equipment. This reading typically indicates of a misalignment condition.

The frequency spectrum plot shows a really large peak in the lower frequencies. Zooming in on the spectrum in this low frequency area confirms a peak at two times the turning speed.

To confirm that misalignment across the coupling is in fact the problem, Drew showed how measuring the cross-channel phase across the coupling can do this. If misalignment is the issue then a 180-degree phase shift should be detected.

Cross-Channel-PhaseFour vibration sensors come into the 4-channel CSI 2140 portable analyzer to perform this cross-channel amplitude & phase test. First Drew set the frequency to match the turning frequency and then enabled data collection from the four accelerometers.

The cross channel phase and amplitude test showed nearly a 180-degree phase shift confirming the diagnosis of a misalignment problem.

You can connect and interact with other reliability professionals in the Asset Optimization, Maintenance and Reliability track of the Emerson Exchange 365 community.

5 comments

  1. Hakan Ersoy says:

    Thanks for the interesting post. I have a question: In order to make a “cross channel phase test”, do we have to have all 4 probes mounted on the machine at the same time? In other words, can this analysis still be made if we only have one sensor available ? Thanks.

    • Drew Mackley says:

      Hakan, Cross channel phase is a comparison between two or more signals
      and thus at least two sensors are needed. However phase can also be obtained
      with just a single sensor and a tachometer signal.

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