A centrifuge uses centrifugal forces, generated at high RPMs to separate solids and liquids. At Greenfield Ethanol, they use centrifuges in their manufacturing processes. They are critical to their operations.

This centrifuge in question rotates at 5250RPM, and it has a suspected bad bearing. The following Figure 1 & 2 depicts the bearing & the asset.

Figure 1 - Centrifuge - Greenfield Ethanol

Figure 2 - Centrifuge Diagram - Bad Bearing in Question

Jonathan Dion, of Greenfield Ethanol previously reported monitoring a critical fan with a bad bearing up until his plants next scheduled shutdown. 

He successfully managed to extend that fans lifespan for a full calendar year by keeping it under a watchful eye with his Vigilant System; An 8-Channel permanent condition monitoring solution, capable of both ultrasound & vibration analysis. 

A similar situation arose at his plant. He discovered a bad bearing on a centrifuge using his SDT Ultrasound Data Collector. The fault was not yet visible with his vibration analysis tools. No cause for concern yet, the bearing had a lot of life left, but it was in the early stages of failure. Still, no reason to use unplanned downtime to replace the bearing. The plan is to replace the bearing during the next scheduled shutdown. Please see the DIPF curve in Figure 3.

Figure 3 - DIPF Curve

Vigilant Permanent Monitoring System

So, Jonathan did what any savvy reliability engineer would; used his Vigilant System to establish permanent monitoring on this critical bearing, as operations & production continued. Jonathan used both ultrasound & vibration to monitor its condition.

For the next few months, the bearings condition continued to slowly deteriorate in the ultrasound spectra. It was eventually visible & well defined in the vibration spectra and demodulated spectrum, as seen in the data in Figure 4 & 5. 

Figure 4 - Vigilant Dashboard - Ultrasound & Vibration Spectra

Figure 5 - Vigilant Dashboard - Ultrasound & Vibration Spectra Demodulated

The severity of the problem has clearly increased since it was first discovered with ultrasound. It is now visible in the vibration spectra, showing a ball pass frequency outer race defect with 1x rpm sidebands.