Chemical Analysis of Hydrocarbon Grease from Spin Bearing Tests

Abstract

The rotor bearing running torqzie levels of certain spin bearing an attempt to determine whether lubricant failure was the z~nils were found to increase s~pzijicantl ~ during extended life test- sole cause of the increased torque levels or a symptoln of illg. Sn7np/es of the greases from t/tese tests were analyzed to de- adverse n1echanic:al conditions in the bearings. During the lelrnilze if lzLbricalzl degradation was linked!he increased course of the analyses, useful techniques for assessing grease torque levels. By means of chromatographic and spectroscopic tech- degradation developedt and interesting characteristics concerning the chemistry of the degradation were ttiques, we were able to determine that oxidation of some of the revealed. greases had occurred and that the oxidative degradation was most easily obserued in the soap-thickener portion of the grease. A correlation betwee?z the disappeamnce of the fatty acid salts and the appearance of degradation products was obserued. Polymerization EXPERIMENTAL, PROCEDURES of the greases war observed in all samples. We also determined that Lubricant the grease degradation was a symptom of adverse mechanical con- The lubricant employed in the tests was a specially forditiom in the bearings and not the primary cause of mechanical mulated naphthe:nic-oil-based sodium-complex soap-thickproblems. ened grease. Prclperties of the oil and the analogous commercial grease arc: given in Table 1. No details on the thickener composition were available.