The function of a Plummer Block is to mount bearings safely enabling their outer ring to be stationary while allowing rotation of the inner ring. The housing is bolted to a foundation through the holes in the base. The bearing housings are split, usually a two piece housings where the cap and base can be detached. The Plummer Block can be used with Self-Aligning Ball Bearings or high capacity Spherical Roller Bearings. They are manufactured from high strength cast iron as standard, but other materials such as cast steel are available. The Plummer Block has a re-lubrication facility, and can be used with either grease or oil. By using the correct bearing Plummer Blocks can accept both metric and imperial shaft sizes.
To prevent dust and other contaminants from entering the houseing the Plummer Block can be fitted with one of the various designs of seals that are available. This ensures that the Plummer Block provides a clean environment for the bearings to freely rotate, hence increasing their performance and duty cycle.
A typical arrangement would be to have two Plummer Blocks, one at each end of a shaft. The Blocks would each contain a bearing and seals. One block would also have locating rings to lock the bearing in place, whilst the Plummer Block at the other end of the shaft would not have the locating rings. This would allow the bearing inside that Block to move linearly (for example, in order to compensate for any change in the shaft length due to the expansion and contraction of metal at different temperatures).