Fluid Film Bearings vs. Rolling Element Bearings

Relative Motion

A bearing 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.

Half-section diagram of integral rib tilt pad journal bearing

Bearing Life

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.

Read More About How Fluid Film Bearings Work

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
Tilting pad journal bearing with floating seal and 'Directed Lubrication' (TJ series bearing)

Journal Bearings

Waukesha Bearings custom engineers fluid film bearings in both fixed profile and tilt pad designs. Bearing geometry and materials are carefully considered to provide minimum power loss and optimum dynamic performance for the given operating conditions.

Hydrodynamic fluid film thrust bearings

Thrust Bearings

Waukesha Bearings offers fixed profile fluid film thrust bearings for lightly loaded applications and advanced tilting pad solutions for more demanding operating conditions. Tilt pad designs may be non-equalizing or self-equalizing with flooded or ‘Directed’ lubrication to support the equipment’s unique requirements.