Chemical Analysis of Hydrocarbon Grease from Spin Bearing Tests

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Abstract
The rotor bearing running torque levels of certain spin bearing units were found to increase significantly during extended life testing. Samples of the greases from these tests were analyzed to determine if lubricant degradation was linked with the increased torque levels. By means of chromatographic and spectroscopic techniques, we were able to determine that oxidation of some of the greases had occurred and that the oxidative degradation was most easily observed in the soap-thickener portion of the grease. A correlation between the disappearance of the fatty acid salts and the appearance of degradation products was observed. Polymerization of the greases war observed in all samples. We also determined that the grease degradation was symptom of adverse mechanical condition in the bearings and not the primary cause of mechanical problems.