The Function of Plummer Blocks
The function of plummer blocks 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. Plummer Blocks have 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. They are manufactured from high strength cast iron as standard, but other materials such as cast steel are available.
To prevent dust and other contaminants from entering the housing, Plummer Blocks can be fitted with one of the various designs of seals that are available. This ensures that Plummer Blocks provide a clean environment for the bearing to freely rotate, hence increasing its performance and duty cycle.
A typical arrangement would be to have two Plummer Blocks, one at each end of a shaft. The Plummer 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).
In extremely hostile environments Plummer Block bearing units with plain bearings can be used. In these cases the housings are designed to hold a solid or split plain bearing made from a material such as Gunmetal, Phosphor Bronze, Oilite or Plastic. This removes the need to provide the bearings with lubrication and enables them to operate for long periods of time without requiring any maintenance. In some instances it may be necessary to also make the entire housing from a material that is resistant to the environment that the bearings will be used in. For example, a bearing unit that is to be used in an underwater application would typically be made entirely of plastics.
All of our catalogues are available to download in PDF format. To view our catalogues see links to the main Bearings and Bushes catalogue and main Plummer Blocks sections below.
Bearings, Plummer Blocks and Self Lube
SNL & SNH Plummer Blocks Catalogue Sections
Plummer Blocks – Full Range