Babbitt Bearings Information
Babbitt bearings are rotary bearings (no rolling elements) made from special alloys poured into place in the bearing housing. A Babbitt bearing is made of Babbitt metal, a soft alloy of tin, antimony, and lead. Babbitt bearings are produced by the deposition of a thin layer of Babbitt metal onto plain bearings. The structure of Babbitt metal consists of small, hard crystals dispersed in a matrix of softer alloy. As the Babbitt bearing wears, the harder crystals are exposed. With the erosion of the matrix, a path is provided for the lubricant to reach the bearing surface.
There are many types of Babbitt bearings. Examples include:
- self equalizing bearings
- sleeve bearings
- thrust bearings
- tapered bearings
- tilting shoe bearings
A self equalizing bearing can adapt to different angles and accommodate varying loads. A sleeve bearing operates on the principle that the rod that fits a shaft rests upon a very thin layer of lubricant during rotation. Without a thin layer of lubricant between the rotating shaft and sleeve, the bearing material would wear away from the friction. A thrust bearing can cope with thrust along the axis of the supported shaft. Tapered bearings are used in pairs to accommodate axial thrust in either direction. A tapered bearing may also be used with radial loads.
Tilting shoe bearings are Babbitt bearings that can be used in turbomachinery to sustain axial thrust on a horizontal rotor assembly. Equalizing tilting shoe thrust bearings can be mounted vertically or horizontally. Their diameters range from 4 to 17 inches (in.). Equalizing titling shoe thrust bearings have standard or large bores, and use either two-shoe or six-shoe configurations. Non-equalizing tilting shoe thrust bearings are also 4 to 17 in. in diameter. Standard thrust bearings have a split to facilitate installation and replacement. Often, standard thrust bearings are interchangeable with other types of thrust bearings. Custom tilting shoe thrust bearings with a 60-in. outer diameter (OD) are available.
Babbitt bearings are used in many applications. Examples include high-speed rotating equipment such as:
- electric motors
- gear drives
- marine applications
In some cases, however, Babbitt type bearings have been replaced by rolling-element bearings such as ball bearings or roller bearings.