A. M. Mikula
R. S. Gregory
Vice President and Manager, Research and Development
Assoc. Mem. ASME
Kingsbury, Inc., Philadelphia. Pa. 19154
This paper compares three different lubricant supply methods-pressurized supply (flooded), spray feed, and leading edge distribution groove-and analyzes their influence on the performance of tilting pad, equalizing thrust bearings. The paper presents experimental data on 267 mm (10-½ in.) o.d. bearings, operating at shaft speeds up to 13,000 rpm with loads ranging up to 3.45 MPa (500 psi). The data presented demonstrate the effect each lubricant supply method has on bearing power loss and temperature. Conclusions are drawn, based upon the effectiveness of each design, to guide the potential user.
There are a wide variety of thrust bearing types available to machinery designers. In addition to initial cost, each type of thrust bearing has its own unique set of performance characteristics which serve as the evaluation criteria for identical operating conditions. The two primary indicators of bearing performance are power loss and babbitt temperature of the pads, or "shoes." Rising energy costs have made bearing power loss a very critical yardstick in the evaluation of relative performance. The maximum babbitt temperature effectively gages the degree of bearing operating risk, and can even limit the bearing's suitability for a specific application. The approach of this paper will be limited to a thorough discussion of power loss values and bearing operating temperatures attained in similar bearings employing three different lubricant supply methods.
In order to evaluate the three different lubricant supply methods - pressurized supply, spray feed, and leading edge distribution groove - each method was tested under identical conditions of applied load, shaft speed, inlet oil temperature, and oil viscosity. A detailed description of the test rig can be found in reference . By reporting the effect of each lubricant supply method on bearing power loss and babbitt temperature, it is hoped that this paper will provide the necessary information for the designer to make a well-reasoned thrust bearing selection, based upon actual performance data.
All three bearings were evaluated in comprehensive tests using a light turbine oil with a viscosity of 0.027 Pa·S @ 37.8°C and 0.006 Pa·S @ 98.9°C (150 SSU @ 100°F and 43 SSU @ 210°F) supplied at 46°C (115°F), for applied loads ranging from 0-3.45 MPa (0-500 psi) and shaft speeds ranging from 4000-13,000 rpm.
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