Full definition
Presence of solid particles, water, air or other contaminants that degrade lubricant and accelerate abrasive and corrosive wear. 80% of bearing failures are attributed to lubricant contamination. Sources: ingress through defective seals, moisture condensation, wear products and cross-contamination during maintenance. Detected by oil analysis (ferrography, particle counting). Control: proper seals, ISO 4406 filtration, correct lubrication practice, hermetic caps.