Radial bearings on centrifugal compressors are usually pressure lubricated. For ease of maintenance, they are horizontally- split with replaceable liners or pads. The liners or pads are usually steel backed with a thin lining of babbitt.
Since centrifugal rotors are relatively light, bearing loads are low. This often leads to instability problems which must be compensated for by the bearing design. Due to instability, the straight-sleeve bearing is used only in some slow-speed units with relatively short bearing spans. The pressure-dam sleeve bearing, and the tiltingpad bearing are two commonly used designs which improve rotor stability.
The top half of the pressure-dam design is relieved as shown in Figure 200-35, creating a pressure point where the dam ends. This conversion of oil-velocity into pressure adds to rotor stability by increasing the bearing load.
The tilting-pad bearing shown in Figure 200-36 is usually made up of five individual pads, each pivoted at its midpoint. By adjustments to the shape of the pads and bearing clearance, bearing stiffness and damping characteristics can be controlled. This bearing is successful in applications where the pressure-dam design is inadequate.