Preventing Premature Bearing Failure

Category: Bearings

Article Tags:

Bearing

bearing life

bearings

unit handling

Improper installation is the most common cause of bearings failure for unit handling equipment. Issues vary depending on the style of the bearing. Let’s look at several different styles, addressing the primary installation issue of each:

Eccentric cam
Spring locking set screw
Concentric collar mounted
Tapered adapter mounted

Eccentric Cam
While not widely used, the eccentric cam locking collar style shaft mounting presents a unique installation issue. Since the locking collar can be tightened in either a clockwise or counterclockwise direction, it is imperative to always tighten it in the direction of shaft rotation. If you don’t, the bearing may come loose on the shaft, leading to premature failure.

Spring Locking Set Screw/Concentric Collar Mounted
The most common failure of both spring locking set screw mounted bearings and concentric collar mounted bearings occurs when locking screws are improperly tightened. If the mounting screws are under-tightened, the bearing will eventually come loose on the shaft. This will cause the shaft to turn inside the bearing bore, consistently stressing the mechanism over time and resulting in premature bearing failure.

All Rexnord mounting screws should be properly tightened in accordance with the applicable service and installation instructions.

Tapered Adapter Mounted
This bearing style features a tapered sleeve inserted between the shaft and the bearing bore. As the adapter nut is tightened, the bearing is driven up the adapter, resulting in an interference fit between the shaft and the bearing bore. If premature bearing failure occurs, it is likely due to improper adapter tightening (either too much or too little). An under-tightened adapter won’t generate a sufficient interference fit between the shaft and bearing bore, which results in the bearing becoming loose on
the shaft.

Conversely, an over-tightened adapter will generate excessive amounts of “hoop” stress (i.e., pressure exerted around the circumference of the shaft) on the inner race of the bearing. This often results in an inner race fracture and ultimately, bearing failure.

A second type of failure associated with adapter mounted bearings is excessive thrust loading when the bearing is slightly displaced along the shaft during installation.

When using two fixed bearings (the most common scenario for unit handling conveyors) improper installation will result in the two bearings being thrust against one other, leading to premature failure due to increased bearing operating temperatures.

For proper installation procedures for these and all styles of Rexnord bearings, visit Rexnord.com or check out our YouTube channel.

Dale Stallard

Dale Stallard started with Rexnord in 1988 and has held different positions in Quality Control and Product Design and Development at multiple facilities. Dale is a Senior Application Engineer supporting Rexnord's bearing business. In his current role, he provides customers with support such as helping them select the proper bearing, onsite assistance, maintenance and installation training, and troubleshooting with any issues.