Keeping an “EYE” on Your Motor: Part 4 Machine Train

With the release of the PdMAEYE® permanently installed electric motor test system we look forward to sharing success stories from the field as our customers add this new technology to the MCEMAX for an optimal electric motor reliability program. This week the 4th success story comes again from the Cement Industry.

While reviewing demodulation spectral data on a critical raw mill from the comfort of an air-conditioned office the motor analyst noticed two unidentified and elevated peaks. Unidentified means that no band alarms had been established around the peaks. Band alarms include the name/source of the peak and appropriate warning levels to alert the analyst if the amplitude increases beyond a specified threshold. Identifying the source of the peak often requires some homework. In this case a 1200 rpm synchronous motor output went through a reduction gear with a 35:1 ratio resulting in a secondary shaft speed of 33.39 rpm, which turned the mills grinding plate. In the spectrum a significant peak at 4 x (33.39 rpm) and a harmonic peak at 8 x (33.39 rpm) were the peaks of interest. Comparing these suspicious frequencies to an identical raw mills demodulation spectrum showed no similar peaks related to the 33.39 rpm. This further elevated the concern about these peaks of interest and warranted a phone call. After contacting the facility, it was confirmed that four grinding rollers are used to press the material on the grinding plate. The conclusion was that the grinding plate surface was either damaged or contaminated resulting in a heavy load modulation as the suspect area moves under each grinding roller.

To see details and the conclusion of this case study visit the PdMA YouTube Channel at