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, and 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 which 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 inches 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-inch outer diameter (OD) are available.
Babbitt bearings are used in many applications. Examples include high-speed rotating equipment such as compressors, chillers, turbines, electric motors, gear drives, locomotives, marine, and pumps. In some cases, however, Babbitt type bearings have been replaced by rolling-element bearings such as ball bearings or roller bearings. Babbitt bearings often adhere to standards from the American Society of Mechanical Engineers (ASME) and the International Standards Organization (ISO).