The Silent Killer of Bearing Life
Contamination is responsible for a significant proportion of premature bearing failures — and it's often preventable. Once dirt or water enters a bearing, the damage is done: abrasive particles score the raceways, water corrodes the steel and degrades the grease, and chemical process fluids attack the cage and seals.
#Choosing the Right Sealing Arrangement
The seal is your first line of defence. Here's how to choose:
##Contact Seals (2RS)
- Best for: General industrial, dusty environments, moderate speed
- Pros: Excellent contaminant exclusion, grease retention
- Cons: Friction generates heat; speed limit ~50% of open bearing
- Typical: SKF 2RS1, FAG 2RSR, NSK DDU
##Non-Contact Shields (ZZ)
- Best for: Clean environments, high-speed applications
- Pros: Low friction, high speed capability
- Cons: Limited protection against fine dust and water
- Typical: SKF ZZ, FAG ZR, NSK ZZ
##Labyrinth Seals
- Best for: Very dirty or wet environments — aggregate, food, outdoor
- Pros: Non-contact (no friction), excellent exclusion if well-designed
- Cons: Requires more axial space; needs grease purge to work
##V-Ring Seals
- Best for: Axial shaft sealing against dust and splash
- Pros: Simple, effective, self-adjusting
- Cons: Not for pressurised environments
#Storage Best Practice
Bearings arrive from the manufacturer coated with preservative and sealed in plastic. That protection doesn't last forever. Follow these rules:
1. **Store flat** — never stand bearings on end on a shelf; the anti-corrosion oil migrates and the bearing runs dry on one side. 2. **Keep sealed** — leave the original packaging intact until the bearing is needed. Opening it exposes the preservative to air and moisture. 3. **Climate control** — store at 20–25°C with <60% relative humidity. Damp stores cause condensation inside the packaging. 4. **First-in, first-out** — rotate stock. Preservative oil degrades over 2–3 years. 5. **Don't wash before mounting** — the factory preservative is compatible with most greases. Washing introduces contamination.
#When Contamination Has Already Occurred
If you open a bearing and find contamination:
- Dry dust — flush with clean solvent, dry with compressed air (filtered), re-grease immediately.
- Water — the bearing is likely already corroded internally. Replace it.
- Process chemical — depends on the chemical. Acid or alkali exposure usually means replacement.
Never re-install a bearing that has had water ingress, even if it looks clean. The corrosion has already started and will accelerate rapidly once back in service.
