Plain or Rolling Bearings – Which is Best?

Plain bearings are available for an extremely wide variety of applications. Most are used in sliding or oscillating roles: door hinges, ball joints on cars, the fifth wheel on a tractor trailer. But when full rotation is required, plain bearings change shape to a “sleeve” that fits around the shaft. In addition to being called sleeve bearings, other names include plane, journal or babbitt bearings.

1. The high startup torque requirement usually means plain bearings aren’t suitable for machines that start and stop frequently.

2. The full fluid film in plain bearings requires up to 3x more energy to operate, even if startup losses are excluded.

3. Plain bearings have difficulty with grease lubrication – they need a constantly replenished thick oil film.

4. Vertical or thrust applications require special Kingsbury or Mitchell designs, which can add to cost. Alternate types of rolling bearings, made in standard sizes, can often be used to accommodate thrust.

5. Plain bearings are generally optimized for a single speed, while rolling bearings can tolerate a wider speed range, more suitable for variable speed drives.

When power density is extremely high, as in power generation stations, the heavy loads might result in permanent plastic raceway deformation in a rolling element bearing – plain bearings are a better choice. The API 610 Standard has guidance for the recommended use of plain bearings versus rolling element bearings in industrial machines.

Find the original article here on SKF’s website 

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