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Fluid Film Solutions


How does a fluid film bearing differ from a rolling element bearing?


A bearing is a machine part that allows relative motion between two surfaces with minimal friction.

In a rolling element bearing, the primary motion is a rolling motion using a ball or roller. There is direct contact between the ball/roller and the inner and outer surfaces (races).

In a fluid film bearing, the relative motion between the two surfaces is a sliding motion on a shear of film (the lubricant). There is no contact of the surfaces except during start-up or shutdown.

A key difference between rolling element and fluid film bearings is the expected life of the bearings. Rolling element bearings typically have a predictable life based on the operating conditions; fluid film bearings, when properly designed and maintained, can operate for decades.

Waukesha Bearings specializes in the engineering, design and manufacture of hydrodynamic fluid film bearings.


  Hydrodynamic Fluid Film Bearings Rolling Element Bearings
Life Expectancy Indefinite Limited Life (L10)
Impact Loads Excellent Poor
Damping Excellent Poor
Speed Limitations Approaches Burst Limit Limited to DN
Noise Quiet Can Be Noisy
Start-up Torque High Low
Operating Friction Low Low
Lubrication Pressure Fed Simple
Cost Low to High Low to Moderate
Position Control Fair Good
Assembly/Repair Easy to Difficult Easy
Tolerance for Misalignment  Tolerant Intolerant
Operating Temperature Cryogenic to High Cryogenic to Extreme
Power Loss Moderate to High Low to Moderate
Lubricant Requirements Minimal to High None to Low
Oil Quality Moderate High
Oil Pressure Low to High None to High
Natural Frequency Control   Good Poor
Unbalance Response Good Poor
Stability Good Fair