An oil flooded rotary screw compressor will typically
require less repair maintenance than a reciprocating
compressors. However, a preventive maintenance program is
essential for maximizing service life and avoiding problems.

If you have a belt driven rotary screw compressor, it is
very important to monitor the drive end bearing. A failure
with this bearing can cause severe damage to the rotor shaft
and other components.

The belt driven style provides design flexibility for the
compressor manufacturers. They can use a common airend for
a variety of horse power and pressure applications by
changing the size of the pulley.

The belt driven design does not cause rotor shaft damage.
There are thousands of belt driven rotary compressors, of
all brands, providing exceptional service. However, the
drive rotor shafts can fail prematurely if belt drives are
not properly installed and maintained.

In addition to the loads caused by the compression process,
the male rotor drive end bearing must operate under the
tension of the belts. Heat and friction can build within
this bearing if the belts are too tight, the lubricant is
contaminated or the bearing is worn.

Heat and friction can cause the rollers to skid in the
bearing. The inner race can heat up and break loose on the
shaft.

The inner race will spin on the shaft wearing a significant
groove and crystallizing the metal of the shaft. This makes
it difficult and less reliable to repair the shaft with a
welding process.

You can prevent this problem by paying attention to the
following:

1. Install and maintain belts at the OEM recommended
   tension. Most belts need to be adjusted a couple of times
   shortly after replacement. Avoid the temptation to over
   tighten belts to prevent slippage. Set them by the book and
   check them as part of a normal maintenance schedule.

2. At least once a year, check the drive end bearing for
   side movement. This should be less than .002 of an inch.
   This inspection must be done after loosening the belts to
   release the tension.

3. Watch for wear metals in your oil analysis.

4. Determine the wear rate of the drive end bearings.
   Then, resolve to stick with a replacement schedule that will
   eliminate these bearings from causing damage to the shaft.

Summary

There are many components of a successful preventive
maintenance program. The objective of this article is to
illustrate the importance of monitoring the drive end
bearings on belt driven rotary screw compressors.