Using the SDT flexible airborne sensor, sweep the coupling area listening for clicking, crackling, and/or popping sounds.  The sound coming from a good coupling should be a low constant noise without any clicking or popping sounds.

The data shown below was taken from a flexible style coupling in good condition. Notice the low amplitude scaling (+30/-30 uV) on the left side of the data graph. Also, the waveform is relatively flat, indicating that no impacting is occurring.

Flexible grid and amplitude scale

Contrast this with data shown below which was taken from a flexible grid-style coupling that lacked lubrication and as a result had caused damage to the coupling’s flexible grid.

Notice that the amplitude scale is now (+2000/-2000 uV) and impacting is apparent in the waveform data. In the spectrum, you can see an elevated turning speed peak with multiple harmonics indicating looseness and wear.amplitude scale

The images below show the condition of the flexible grid and the inside of the coupling housing after disassembly.

flexible grid after the disassembly


Download our Coupling Faults: Signs and Signals with Airborne Ultrasound infographic for a basic guide to coupling inspection using ultrasound technology.

Related Blog: Ultrasound and Alignment Meet at the Coupling to Reduce Failures

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by Dave Leach CRL CMRT CMRP