CLASSIFICATION OF BEARINGS

Bearings can be classified in the following ways,

1. Direction of load to be supported

 a) Radial bearings and

 b) Thrust bearings.

In radial bearings, the load acts perpendicular to the direction of motion of the moving element.

In thrust bearings, the load acts along the axis of rotation.

2. The nature of contact

1. Sliding contact bearings and

2. Rolling contact bearings.

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In sliding contact bearings, the sliding takes place along the surfaces of contact between the moving & fixed elements. The sliding contact bearing are known as plain bearings.

In rolling contact bearings, the steel balls & rollers are interposed between the moving and fixed elements. The balls offer rolling friction at two points for each ball or roller

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3. Sliding contact bearings

The sliding contact bearing in which the sliding action is guided in a straight line & carrying radial loads may be called slipper or guide bearings. Such types of bearing are found in crosshead of steam engines.

The sliding bearing in which the sliding action is along the circumference or an arc of a circle or an arc of a circle and carrying radial loads are known as journal or sleeve bearings.

The sliding bearings, according to the thickness of layer of the lubricant between the journals, may also classified as follow.

1. Thick film bearings are those in which the working surfaces are completely separated from each other by the lubricant. Such bearings are also called hydrodynamic lubricated bearings.

2. Thin film bearings are those in which although lubricant is present, the working surfaces partially contact at least part of the time. Such type of bearings are also called boundary lubricated bearings.

3. Zero film bearings are those which operate without any lubricant present.

4. Hydrostatic or externally pressurized lubricated bearing are those which can support steady loads without any relative motion between the journal and bearing. This is achieved by forcing externally pressurized lubricant between the members.