Guideline values for factor ηc for different level of contamination
| Conditions | Factor ηc1) | |||
| for bearings with diameter | ||||
| dm < 100 | dm ≥ 100 mm | |||
| Extreme cleanliness | 1 | 1 | ||
| Particle size of the order of the lubricant film thickness | ||||
| Laboratory conditions | ||||
| High cleanliness | 0,8 ... 0,6 | 0,9 ... 0,8 | ||
| Oil filtered through an extremely fine filter | ||||
| Typical conditions: sealed bearings that are greased for life | ||||
| Normal cleanliness | 0,6 ... 0,5 | 0,8 ... 0,6 | ||
| Oil filtered through a fine filter | ||||
| Typical conditions: shielded bearings that are greased for life | ||||
| Slight contamination | 0,5 ... 0,3 | 0,6 ... 0,4 | ||
| Typical conditions: bearings without integral seals, coarse
filtering, wear particles and slight ingress of contaminants |
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| Typical contamination | 0,3 ... 0,1 | 0,4 ... 0,2 | ||
| Typical conditions: bearings without integral seals, coarse
filtering, wear particles, and ingress from surroundings |
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| Severe contamination | 0,1 ... 0 | 0,1 ... 0 | ||
| Typical conditions: high levels of contamination due to excessive
wear and/or ineffective seals |
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| Bearing arrangement with ineffective or damaged seals | ||||
| Very severe contamination | 0 | 0 | ||
| Typical conditions: contamination levels so severe that values
of ηc are outside the scale, which significantly reduces the bearing life |
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- 1) The scale for ηc refers only to typical solid contaminants. Contamination by water or other fluids detrimental to bearing life is not included. Because of strong abrasive wear in highly contaminated environments (ηc = 0), the useful life of the bearing can be significantly shorter than the rating life.
