Avoid Over-lubricating Bearings

Using too much grease to lubricate bearings can cause serious complications for your machine. During operation, the grease that has accumulated in the bearing cavity will begin to churn. If the grease is sufficiently agitated, it will quickly oxidize (chemically degrade) as it begins to lose its base oil, becoming thicker and less lubricating. This thickened grease can also be pushed out of the cavity all together and distributed across all the windings of the rotor assembly.

With little to no lubrication, operating temperatures can rise, leading to seal damage, bearing failure, and energy loss. The excess heat will eventually “cook” the remaining grease, thickening it into a hard, crusty solid that is difficult to remove, preventing any new grease from reaching the core of the bearing and accelerating wear of the rolling elements. In short, the real danger of over-lubricating a bearing is total machine failure and costly equipment downtime.

Another negative result of over-lubrication is increased pressure. Lip seals tend to fail at around 500psi, so any additional pressure from a grease gun (which can generate up to 15,000psi) can cause the lip seal to rupture, allowing contaminants to enter the bearing housing. The increase in pressure can also cause hard, encrusted grease to break apart, sending it directly into the bearing tracks, causing accelerated wear and ultimately total failure.

Fortunately, over-lubrication is easy to avoid. If you have a maintenance schedule and use calculations to determine the correct amount of grease and frequency of application, you should have no problem. The formula for calculating the volume of grease for the appropriate bearing size is as follows:

G (amount of grease in ounces) = 0.114 x D (bore diameter in inches) x B (bearing width in inches)

1. Stop lubricating when you feel abnormal back pressure.

2. Clean the exhaust port regularly to ensure there is no blockage.

3. Clean the area around the filling and pressure relief fittings.

4. Consider installing a grease gun with a pressure gauge.

5. Pump grease into the bearing slowly and in short strokes.

6. Avoid using quick lever operations, as this can cause seal damage.

7. Run the motor during and after lubrication to drain excess grease.