Lubrication Technology Guides: Lubricants, Intervals, Service Life

Lubrication Technology: Why Lubrication Determines Service Life

Over 50 % of all rolling bearing failures are attributable to lubrication errors — wrong lubricant, insufficient quantity, or exceeded intervals. Correct lubrication extends machine service life and significantly reduces maintenance costs.

Quick Orientation

Grease-lubricated for compact units → NLGI 2–3 multipurpose grease. Gearbox oil fill → ISO VG 220–460. High-temperature range (> 120 °C) → Synthetic lubricants.

Grease or Oil?

Lubricating Greases

Greases consist of base oil, thickener (lithium, calcium, polyurea), and additives. Advantages: easy handling, sealing function, no leakage. Used in rolling bearings, linear guides, and sealed gearbox units. Consistency grade NLGI 2 covers the majority of industrial applications.

Lubricating Oils

Oils cool better than greases and are suitable for circulating lubrication, high speeds, and splash lubrication in open gearbox housings. Viscosity selection per ISO VG: lower VG value for high speeds, higher VG value for slow-running high-load gearboxes.

Property	Grease	Oil
Cooling	Low	Good
Sealing	Self-sealing	Seal required
Relubrication	Periodic	Change or circulation
Typical Application	Rolling bearings, linear guides	Gearboxes, high-speed applications

Rolling Bearing Service Life: L10 Fundamentals

L10 Service Life (nominal)

 
L10 = (C / P)^p × 10&sup6; / (60 × n)

(L10 in hours, C = dynamic load rating [N], P = equivalent load [N], n = speed [rpm], p = 3 for ball bearings, 10/3 for roller bearings)

The nominal service life L10 indicates the number of operating hours that 90 % of a bearing series will exceed under identical conditions. For modified service life (L10mh) per ISO 281, reliability factor, system parameters, and lubrication ratio are taken into account.

Lubrication Intervals: Influencing Factors

Operating temperature: Every 15 °C increase above 70 °C halves the grease service life
Speed: High speeds require more frequent relubrication or oil circulation lubrication
Vibration: Vibration loading accelerates lubricant degradation
Contamination: Moisture, dirt, or aggressive media → shortened intervals

Avoid Over-Lubrication

Too much grease increases running resistance and operating temperature — this accelerates aging and can cause leakage. Follow the manufacturer's specifications for relubrication quantities.