SCAN DeCAMILLO (Member, STLE)
Kingsbury, Inc., 10385 Drummond Road, Philadelphia, Pennsylvania 19154
KEITH BROCKWELL (Fellow, STLE), deceased, and WALDEMAR DMOCHOWSKI (Member, STLE)
National Research Council, Institute for Aerospace Research, Montreal Road, Ottawa, Ontario, K1A 0R6, Canada
Babbitt temperatures in pivoted shoe bearings can be significantly reduced by offsetting the pad pivots in the direction of rotation. However, reverse rotation can occur in certain types of machinery under temporary or adverse conditions. The offset is then in the wrong direction and it becomes important to know if the bearing can withstand the reverse rotation operating conditions without damage. This paper compares pad temperature data from tests of a 152.4-mm, 60 percent offset bearing in forward and reverse rotation. The data indicate that the offset pivot bearing can run in reverse without damage for the operating conditions tested. Reverse rotation pad temperatures are hotter. Discussions towards the end of the paper address assessment of the data.
A number of technical papers present steady-state results from experimental work on center pivot journal bearings. The offset pivot journal bearing is not as well documented, although there is sufficient information and experience to show that pad temperatures are significantly reduced by offsetting the pad pivots in the direction of rotation (Dmochowski, et al. (1); Bouchoule, et al. (2); Simmons and Lawrence (3); DeCamillo and Brockwell (4); Brockwell, et al. (5); Nicholas (6)).
Unfortunately, there are conditions that can cause reverse rotation in certain types of machinery and applications. Some are expected and are only temporary. Others can occur under adverse or unusual conditions such as backwash through a pump from a check valve failure.
When designing for an offset pivot application, reverse rotation is a concern because the offset is then in the wrong direction. As pad temperatures improve, going from a center to an offset pivot design, it is logical that the reverse rotation will run worse, and so it becomes important to assess if the offset design can withstand the reverse rotation operating conditions without damage.
This is the fifth in a series of papers that present results from an extensive study of parameters that affect the performance of pivoted shoe journal bearings. The first paper compares test results of direct lube leading edge groove (LEG) lubrication to a conventional, flooded design (Dmochowski, et al. (1)). Subsequent papers report on the effects of oil flow, pivot offset, load orientation, and oil viscosity grade (DeCamillo and Brockwell (4), Brockwell, et al. (5), (7)).
The purpose of this paper is to provide information from pivot-shoe journal bearing tests comparing pad temperatures of a 60 percent offset bearing in forward and reverse rotation.
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