Geometries
Journal bearings installed in industrial machinery today generally fall into two categories: full bearings and partial arc bearings. Full bearings completely surround the shaft journal with many differing geometries such as elliptical, lobed, or pressure dam configurations and usually are two pieces, mated at a split line. Partial arc bearings have several individual load bearing surfaces or pads and are made up of numerous adjustable components.
The bearing inner surface is covered with a softer material, commonly called babbit. Babbit, which is a tin or lead based alloy, has a thickness that can vary from 1 to 100 mils depending upon the bearing diameter. A babbit lining provides a surface which will not mar or gouge the shaft if contact is made and to allow particles in the lubricant to be imbedded in the liner without damaging the shaft.
https://youtu.be/7OY170iaGSA
Plain Bearing
The plain bearing is the simplest and most common design with a high load carrying capacity and the lowest cost. This bearing is a simple cylinder with a clearance of about 1-2 mils per inch of journal diameter. Due to its cylindrical configuration it is the most susceptible to oil whirl. It is a fairly common practice during installation to provide a slight amount of "crush" to force the bearing into a slightly elliptical configuration.
Lemon Bore Bearing
The lemon or elliptical bore bearing is a variation on the plain bearing where the bearing clearance is reduced on one direction. During manufacture this bearing has shims installed at the split line and then bored cylindrical. When the shims are removed the lemon bore pattern is results. For horizontally split bearings, this design creates an increased vertical pre-load onto the shaft.
This bearing has a lower load carrying capacity that plain bearings, but are still susceptible to oil whirl at high speeds. Manufacturing and installation costs are considered low.
Pressure Dam
Pressure Dam BearingA pressure dam bearing is basically a plain bearing which has been modified to incorporate a central relief groove or scallop along the top half of the bearing shell ending abruptly at a step. As the lubricant is carried around the bearing it encounters the step that causes an increased pressure at the top of the journal inducing a stabilizing force onto the journal which forces the shaft into the bottom half of the bearing.
This bearing has a high load capacity and is a common correction for machine designs susceptible to oil whirl. Pressure dam bearings are a unidirectional configuration.
Another unidirectional bearing configuration is the offset bearing. It is similar to a plain bearing, but the upper half has been shifted horizontally. Offset bearings have increasing load capacities as the offset is increased.
Tilting Pad Bearing
Tilting pad bearings is a partial arc design. This configuration has individual bearing pads which are allowed to pivot or tilt to conform with the dynamic loads from the lubricant and shaft. This type of bearing is a unidirectional design and is available in several variations incorporating differing numbers of pads with the generated load applied on a pad or between the pads.
Tilting Pad Preloads
https://123project.ir/wp-content/uploads/2021/01/TILTING-PAD-BEARING-DESIGN-872763.pdf
Tilting Pad Thrust Bearing
https://vlaves.bg/html/upload/files/katalozi/lageri/VLAVES-Tilting-Pad-Thrust.pdf