Bearing failure is rarely a bearing problem. In most industrial plants, premature bearing failure traces back to how the bearing was lubricated — not a defect in the bearing itself. Studies across industrial maintenance consistently point to lubrication-related issues as the single biggest cause of avoidable bearing failure, ahead of fatigue, installation error, or normal wear.
The good news is that almost all of these causes are preventable once you know what to look for. Below are the 10 most common lubrication-related causes of premature bearing failure — and what to do about each one.
1. Over-Lubrication
More grease is not better grease. Pumping excess grease into a bearing housing increases internal pressure, generates heat through churning, and can damage seals — which then lets contaminants in. Over-lubrication is one of the most common mistakes in plants that relubricate "on schedule" without measuring actual grease volume.
Fix: Calculate the correct grease quantity for each bearing based on housing dimensions, and train staff to apply it precisely rather than "until it looks full."
2. Under-Lubrication
The opposite problem is just as damaging. Insufficient grease means metal-to-metal contact, increased friction, and accelerated wear — often showing up as overheating before total failure. Under-lubrication is especially common on bearings that are hard to access or get skipped during routine rounds.
Fix: Build relubrication into a scheduled maintenance plan, not an "as needed" judgment call.
3. Wrong Grease Type
Not all greases behave the same way under load, temperature, or water exposure. Using a general-purpose lithium grease where a calcium sulfonate complex grease is needed — or vice versa — can mean the grease breaks down well before its expected service life. We cover this in detail in Lithium vs Lithium Complex vs Calcium Sulfonate Grease.
Fix: Match the grease type to the application — load, temperature, and environment — not just what's already on the shelf.
4. Wrong NLGI Grade
NLGI grade determines a grease's consistency, and using the wrong one affects how well it stays in place and seals out contaminants. A grease that's too soft can migrate out of the bearing; one that's too stiff may not distribute properly under operating conditions. For a full breakdown, see NLGI 2 Grease Explained.
Fix: Check manufacturer specifications for the correct NLGI grade — don't assume "2" is always the safe default.
5. Contamination
Dirt, dust, and metal particles entering the bearing housing act like an abrasive, accelerating wear on both the bearing surfaces and the grease itself. Contamination is one of the leading causes of bearing failure in environments like mining, manufacturing, and heavy industry where airborne particulates are unavoidable.
Fix: Use proper seals, clean application equipment, and avoid topping up bearings in dusty or dirty conditions without protective measures.
6. Water Ingress
Water in a bearing housing washes out grease, causes corrosion, and can lead to hydrogen embrittlement in extreme cases. This is a particular risk in washdown environments, marine applications, and outdoor equipment exposed to rain. Choosing a water-resistant grease — such as calcium sulfonate complex — significantly reduces this risk.
Fix: Specify water-resistant grease for wet or washdown environments, and check seal integrity regularly.
7. Incorrect Relubrication Interval
Relubricating too often wastes grease and risks over-lubrication; relubricating too infrequently leaves bearings running on depleted or degraded grease. The correct interval depends on bearing type, speed, load, and operating temperature — it's rarely a one-size-fits-all number across a plant.
Fix: Calculate relubrication intervals per bearing based on operating conditions, rather than applying a blanket plant-wide schedule.
8. Excessive Temperature
Heat accelerates grease oxidation and shortens its effective service life. A grease rated for standard conditions can break down rapidly in a high-temperature application, losing its ability to protect the bearing. This is where upgrading to a higher dropping-point grease — such as lithium complex — often resolves recurring failures. See Lithium vs Lithium Complex vs Calcium Sulfonate Grease for a temperature comparison.
Fix: Monitor operating temperatures and select a grease rated for the actual conditions, not just the "typical" range.
9. Incorrect Storage and Handling
Grease that's been stored incorrectly — exposed to extreme temperatures, contamination, or extended shelf time — may already be degraded before it's even applied. Using dirty application equipment or decanting grease into unsealed containers introduces contamination before the grease reaches the bearing.
Fix: Store grease in sealed containers in a stable environment, and use dedicated, clean application tools.
10. Poor Lubrication Practices
Beyond the specific technical issues above, inconsistent practices across a maintenance team — different people applying different amounts, mixing incompatible greases, or skipping documentation — create unpredictable outcomes across a plant's bearing population.
Fix: Standardise lubrication procedures across your maintenance team, and document grease type, quantity, and interval for every bearing.
