A bearing that failed from lack of lubrication. The bearing was on a conveyor roller, mounted inside a steel frame. The grease nipple was on the outside of the frame — but the installer routed the grease gun to the wrong fitting. The bearing ran dry for 6 months. The customer greased the wrong zerk every month. The correct zerk was hidden behind a guard. This is about lubrication access and how to design for maintainability.
The access problem
A bearing that can’t be greased will fail. It doesn’t matter how good the bearing is — without lubrication, the rolling elements wear. The design must place the grease nipple where a maintenance technician can reach it with a standard grease gun (300 mm long nozzle). If the nipple is behind a guard, under a chute, or inside a machine frame, it won’t get greased.
The failed bearing was on a 50 mm diameter roller, mounted in a pillow block inside a conveyor frame. The grease zerk pointed downward, into the frame. The technician couldn’t get the grease gun on it. The zerk on the outside of the frame was for a different bearing (the drive side). The technician greased the drive side every month. The idler bearing ran dry.
What was changed
1. Installed a grease line extension. A 1/8 inch tube ran from the bearing zerk to a remote mounting point on the outside of the frame. The remote zerk was at waist height, visible and accessible. The technician greased the correct bearing. The bearing life extended to 5 years.
2. Grouped all zerks in one location. For a 10-roller conveyor, all 10 remote zerks were mounted on a single manifold plate. The technician walks to one location and greases all 10 bearings in 2 minutes. No crawling under the conveyor. No missing a zerk. The manifold plate is labeled with bearing numbers.
3. Used an automatic lubricator. For critical bearings (drive side, high load), a single-point automatic lubricator (spring-driven, 12-month supply) was mounted directly on the bearing. The lubricator dispenses 1 ml of grease per day. No manual intervention. The technician replaces the lubricator once a year during scheduled maintenance. The bearing never runs dry.
The grease type consistency
When multiple bearings are greased by different technicians, the grease type varies. One uses lithium EP2, another uses calcium soap. The greases are incompatible — they react and turn into a goo that blocks the lubrication path. The fix: label every zerk with the grease type. Use a single grease type for the entire machine (lithium complex EP2 is the universal choice). The automatic lubricators are pre-filled with the correct grease.
The lubrication schedule
| Bearing type | Relubrication interval | Amount |
|---|---|---|
| Deep groove ball, low speed | 6 months | 20% of free space |
| Spherical roller, conveyor | 3 months | 30% of free space |
| Linear guide, continuous | Monthly | 5 ml |
| Fan bearing, 1500 RPM | Annually | 10% of free space |
The lubrication rule: if a zerk can’t be reached with a grease gun in 10 seconds, install a remote line. The failed bearing wasn’t defective — it was greased at the wrong fitting. Group all zerks on a labeled manifold. For critical bearings, use automatic lubricators. A bearing that can’t be greased is a bearing that will fail.
