Purvis Industries

Article by: Dan Whitehouse

Bearing failure due to lubrication is a very common occurrence. About 50% of bearing failure is related to lubrication. Below is a section of an article from www.machinerylubrication.com that details eight failure mechanisms.  (Full article can be read here.)

When in doubt, it does not hurt to ask when lubrication comes into play.

1. Unsuitable Lubricant - First, you must choose the correct lubrication for the application. Fundamental properties, such as the viscosity, additive package and consistency (for grease), should be carefully selected based on the bearing type, speed factor and operating conditions. If these factors are not thoroughly considered and an unsuitable lubricant is applied, the lubricant may become overly stressed or be insufficient for the machine's lubrication needs. In either situation, the bearing will likely undergo premature wear and failure.

2. Lack of Lubricant - For greased bearing applications, the correct regreasing volume and frequency must be established to ensure the bearing load zones are lubricated properly. Too much time between regreasing intervals or applying too little grease will cause excessive boundary and bearing wear.

By: Blake Timmons

With the increased use of Variable Frequency Drives (VFDs) in industrial and commercial electric motors, there becomes a source of current flow through the bearing. Note that inverter-induced bearing currents and premature bearing failures occur in a relatively small percentage of installations and applications. Nevertheless, it's best to understand the topic when you run across the problem.

The damage to the outer or inner race of a motor bearing will look something like the pictures below.

The damage to the outer or inner race of a motor bearing will look something like the pictures below. In these photos. Notice that the “fluting” is seen as symmetrical damage which is a common sign of a bearing current issue. Also notice that damage can also occur that is not symmetrical, shown by individual random spots on metal surfaces. With motors using with an inverter, you need to be aware of the high-frequency current paths from the motor back to the inverter and to ground. This will help in understanding potential bearing current problems and remedies. High frequency motor bearing currents can occur in any motor driven by a drive using Pulse Width Modulation (PWM).