Failure Guide

Most bearings are removed long before they reach their natural fatigue life, and nearly every premature failure traces back to a handful of causes: lubrication problems, contamination, mounting errors, misalignment, overload and electrical damage.

Quick Symptom Index

Grease & Lubrication Signs

IN PLAIN TERMS Lubrication and contamination together cause the large majority of premature failures. If you remember nothing else: use the right grease, the right amount, on time — and keep dirt and water out.

The Failure Modes (ISO 15243)

ISO 15243 classifies bearing damage into six groups. Identifying the mode tells you the root cause — and fixing the cause is what stops the failure recurring after replacement.

1. Rolling-Contact Fatigue

Appearance — Flaking, pitting or spalling — material breaking away from the raceway or rolling elements. May start below the surface (normal end of life) or at the surface where dents or poor lubrication concentrate stress.

Root Causes — Natural fatigue at end of life; or accelerated by overload, contamination dents, or too thin a lubricant film.

Action — Replace. If it appeared early, correct overload, contamination and lubrication or the new bearing fails the same way.

2. Wear (Abrasive & Adhesive)

Appearance — Abrasive: dull, matt, scratched surfaces from hard particles. Adhesive (smearing): material transferred and smeared, often discoloured, when surfaces slide under poor lubrication.

Root Causes — Contamination (dirt, dust, debris); inadequate or wrong lubricant; sliding under load with too little oil film.

Action — Improve sealing and cleanliness; correct lubricant type, quantity and interval; eliminate the contamination path.

3. Corrosion (Moisture & Frictional)

Appearance — Moisture corrosion: red/brown staining and pitting. Fretting corrosion: reddish-brown oxide at fit surfaces from micro-movement. False brinelling: shallow dents at rolling-element spacing from vibration while stationary.

Root Causes — Water/condensation ingress; poor sealing; loose fits; vibration during transport or standstill.

Action — Upgrade seals; control condensation in storage; correct the fit; protect idle and in-transit machines; use the correct preservative on stored bearings.

4. Electrical Erosion

Appearance — Tiny arc craters; over time, regular grey/dark fluting (washboard) marks across the raceway, and darkened grease.

Root Causes — Stray current through the bearing — common on variable-frequency-drive (VFD) motors, and from poor earthing or welding currents.

Action — Provide a proper current path: shaft grounding rings, insulated (ceramic-coated or hybrid) bearings on the affected end, correct earthing. Never weld with the return path through a bearing.

5. Plastic Deformation

Appearance — True brinelling: dents at rolling-element spacing from static overload or impact. Debris/handling indentations: scattered dents from particles or rough handling.

Root Causes — Hammering or pressing on the wrong ring; shock load; dropping the bearing; hard debris in the raceway.

Action — Press only on the interference-fitted ring; use the correct sleeve, press or induction heater; keep clean; never load through the rolling elements.

6. Fracture & Cracking

Appearance — Cracked or split rings; chipped flanges; in thermal cracking, discoloured rings with cracks across the raceway.

Root Causes — Forced fracture: excessive mounting force / oversized interference. Fatigue fracture: stress concentration over time. Thermal cracking: friction heat (slipping fit, severe under-lubrication).

Action — Verify shaft/housing tolerances against the catalogue; mount with controlled force or heat (not flame); address the heat source for thermal cracking.

FOR BUYERS & REPLACEMENTS When ordering a replacement, build the failure lesson into the spec: if heat was the issue, confirm the right clearance (often C3); if contamination, move from shields to contact seals (2RS); if a VFD motor with fluting, quote an insulated or hybrid bearing. For obsolete or hard-to-find sizes, the Bearings Exchange is the place to source them.

Prevention Checklist