January 8 2013 -
David M. Casper, Engineering Service Coordinator, Kingsbury, Inc.
There is always some degree of thrust bearing misalignment due to housing and bearing machining tolerances, or misalignment between the shaft and housing. This is considered static misalignment since the bearing is misaligned before a load is applied. This static misalignment is different from dynamic misalignment that may occur when thermal expansion and mechanical deflection causes shifts in the housing and shaft position while in operation.
Joseph Wilkes is Kingsbury's Vice President of Engineering. He is currently responsible for overseeing all aspects of the engineering department, including bearing design, analysis, troubleshooting, research and development, and testing. Wilkes has traveled around the world to give technical presentations and troubleshoot bearing problems.
Electrical pitting damage, caused by intermediate arcing between stationary and rotating machine components, erodes the babbitted surface of a bearing, causing it to fail. With the right precautions, however, this type of damage can be prevented.
The purpose of thrust bearing end play is to provide axial clearance between the thrust collar and the thrust bearing assemblies. The end play allows room for the formation of an oil film, misalignment, and thermal expansion of the bearing components. End play is the total distance the shaft can move between the two thrust bearings and is sometimes called float, thrust bearing clearance or axial clearance.
Typical values of end play can be calculated by the following formula: