Measurements of Maximum Temperature in Tilting-Pad Thrust Bearings

One of the important restrictions governing the design of tilting pad thrust bearings is the maximum allowable white metal temperature. However, adequate guidance on typical pad operating tempatures has not been available in established lubrication hand books. New pad tempature data from 12 test bearings have been combined with previously published work to provide a source of information covering a diverse range of proven bearing types and sizes.

The collected information has been presented as the difference between maximum pad and oil supply tempatures at fixed values of bearing pressure against mean sliding speed. Clear trends have been found in the data which have enabled curves of typical bearing performance to be drawn through the test results. The difference between the type of lubricant feed (“flooded” or “low loss directed”) and the pivot position (center or offset) have been highlighted.

Introduction

Tilting-pad thrust bearings are a very efficient means of transferring large thrust loads from rotating shafts to sur­rounding structures. Since the generation of the lubricating film is entirely automatic, and its presence eliminates wear, tilting-pad units have proved to be the most appropriate type of bearing in many areas of industry.

As with all technologies, there are a number of funda­mental limitations that define a tilting-pad’s range of suit­able applications. One such limit is the maximum safe work­ing temperature of the traditional white metal face; hence, the assessment of pad temperature is an essential part of bearing performance prediction. Consequently, a statement of performance must be considered incomplete if it does not contain an estimate of pad temperature.

The successful introduction of tilling-pad technology was largely due to the good agreement between the operation of modest size pads and the predictions of simple hydro­dynamic theory. With the general trend for larger bearings and more arduous duties, the prediction of pad tempera­ture has gained importance. Although the laws of thermodynamics are well understood, there is no complemen­tary simple thermodynamic model of bearing performance for the prediction of operating temperatures. Historically, experimental results have been the only reliable source of pad temperature information. Early formulae for predict­ing pad temperatures were based on bearing observations, and even today’s computer models rely heavily on test data for setting up a number of parameters used in the performance calculations; hence; the consolidation of experimen­tal results into coherent pad temperature information is of prime importance to lubrication engineers.

For many years, various technical journals have published temperature data obtained from bearing tests, but very few anicles have drawn together the results from different bear­ings to see if there is a consistent overall pattern to the reported results. This paper uses previously unpublished test results from the authors’ company in combination with other published work, to form a general source of infor­mation on typical bearing temperatures.