Statistical Trend Analysis of Wear Metal Concentration Measurements - Calculation of Significant Wear Metal Production Rates

摘要

The JOAP Methodology for the evaluation of wear metal concentration measurements has been examined and its inadequacies arising from its lack of quantitative procedures to account for the effects of data scatter and oil consumption have been delineated. The use of wear metal production rates, calculated on a sample-to-sample basis, advocated as an improvement over JOAP methods has also been investigated. These are shown to be subject to the same type of error as the JOAP 10 hour trend, though they do make allowance for the effect of oil consumption and replenishment on wear metal concentration. Linear regression analysis of concentration measurements are demonstrated to be greatly superior to both the foregoing methods for performing quantitative trend analysis. A 'corrected' concentration concept is advanced and utilized to obtain a meaningful interpretation of concentration measurements on oil-consuming engines. Variance analysis techniques are described to deduce statistically valid regimes of constant wear rate from a set of concentration measurements. The use of this procedure to formulate guidelines for maintenance action is discussed. (Author)