Bearing Grease

Q My question involves the proper technique for adding grease to a pillow-block bearing on an air handler. I was taught to wipe the grease off, pump in the grease until you see a bead around, stop and wipe it off again. I have been told by some techs that is not correct. I can handle constructive criticism. So, have I been on the right track?

A This is an excellent question. As with so many tasks expected of those engaged in the maintenance or repair of hvacr equipment, the correct answer can be different, depending on the application and/or situation. For example, on a new bearing, and in a perfect world, the technician would know the volume of grease the gun expels with each stroke.He'd also know the volume of grease required by the bearing as listed in the bearing manufacturer's specifications and he'd add the correct amount of grease. However, we all know the world isn't perfect and as such that information is rarely, if ever, in the hands of the technician. This requires the tech to use good judgment based on his level of experience and the bearing application.

As an example, if you perform maintenance for a facility where down time simply cannot be tolerated, before adding grease to a bearing, you should measure its temperature after having run for a period of time, record that information, then add three or four “squirts” from your grease gun. During your next inspection, if you see a significant rise in the bearing's operating temperature you should replace it, as high temperatures may indicate a bearing is likely to fail. This type of accurate recordkeeping and preventive maintenance will reduce unscheduled down time due to unexpected and unplanned bearing failures. Again, a technician checking up on a building he may not see again does not have historical data to rely on. The best way to serve the customer is by inspecting the entire assembly (bearing, seals, shaft, wheel, belt, motor, housing) for proper alignment and wear. If all looks good, add three or four squirts or pumps from the grease gun. There is no need to completely fill or overfill the bearing with grease, particularly if the bearing and grease are cold. This could actually create a negative effect called bearing churning or ball slippage. And if the seals look good, grease needs to be added no more than twice yearly under all but the most extreme cases.

Question from John West, via e-mail. Answer by Jack Bartell, manager, training services, York/JCI.