Pressure Dam Bearing, Multi-Pocket Bearing, or Step Bearings

In addition to the standard lobed bearings with preload and offset, pressure dam (pocket) and relief track are introduced in these types of bearings. The following figures are shown for a typical 2 lobes pressure dam bearing. However, this option allows you to have as many lobes as you like and each lobe can have preload, offset, pressure pocket or relief track. The following design rules for the pressure dam bearings have been suggested by Dr. John Nicholas, a leading researcher in pressure dam bearings.

1. The optimum Sommerfeld number range for designing a pressure dam bearing to increase stability is S >= 2.0
   
   
2. The optimum Clearance Ratio is around 3.0. A slightly larger clearance ratio (3.0-6.0) is recommended to avoid the sudden drop in load capacity for clearance ratios below 3.0.
   
   
3. Steps should be located at about 75% of the total arc length of the pad. The optimum step location for stability is between 125 and 160 degrees for 2 lobes bearings depending upon the Sommerfeld number. A reasonable compromise value is 140 degrees.
   
   
4. Relief track in the loaded pad should be avoided due to the high operating eccentricity ratio.
   
   
5. Pocket axial length should be 65% to 70% of the total axial bearing length.

To use these types of bearings, the Advanced Features must be checked in the input. The positive relief track axial length indicates that the relief track is in the center and the negative relief track axial length indicates that the relief track is on both sides as shown below.

Note that this bearing type can be de-generated into a standard multi-lobe bearing, if PocketArc, PocketDepth, PocketAxL, and ReliefAxL are zero, as shown below:

Also, if PocketAxL = Bearing Axial Length, then, the pocket has open ends and it becomes a step bearing as shown below:

See also Coordinate Systems, Fixed Lobe Bearing Geometry, and Examples.

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