Unscheduled downtime, caused by bearing failures on critical equipment, is almost always unacceptable today. Non-intrusive monitoring of bearings, as part of a department-based or company-wide predictive maintenance programme, is becoming standard practice in most forward-looking companies.

Ultrasound is an effective technology for recognising the onset of brinelling on bearings surfaces, fatigue failure, flooding and lack of lubricant. With some instruments, it is possible to set-up 'routes' to monitor many machines, and the technology can even be used to diagnose and trend very linear and slow speed bearings.

Operators are often able to listen to the condition of the bearing in headphones, and the sound quality can provide further insight. It is also easy to isolate each bearing and eliminate competing sources of ultrasound, as we typically contact on to the bearing housing using a stethoscope module.

Vibration is another established technology for monitoring bearings. If you have the technical expertise on-site, then it is possible to identify the exact defect in a bearing. Unfortunately, this approach does take considerably more time, has a very steep learning curve, and isn't at all suitable on slow speed bearings.

Infrared is also often considered for this application, although it has very limited value, as heat is one of the last known effects of a bad bearing. If an infrared camera detects a bearing running hot, then it may already be damaged and in need of replacement.

Bearing lubrication

Traditionally, companies that lubricate bearings have used a time-based lubrication schedule, as many suppliers often recommend that bearings should be lubricated based on hours of operation.

In most cases, suppliers also provide recommendations as to the amount of lubricant that should be applied during this scheduled work.

Unfortunately, some bearings simply don't need to be lubricated when the schedule suggests that they do, and the amount of grease that should be used will often differ to the amount suggested by the supplier.