Examination of Errors in the Joint Oil Analysis Program (JOAP) Trending Procedures - Suggested Improved Techniques for Trend Analysis of Wear Metal Measurements.
Interim rept. Jan-Oct 79,
SOUTHEASTERN CENTER FOR ELECTRICAL ENGINEERING EDUCATION INC WRIGHT-PATTERSON AFB OH
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The JOAP methodology for evaluating wear metal concentration measurement is examined in depth and its limitations are defined in a quantitative manner. Their trending procedures are subject to an inherent error, introduced by the allowable tolerance in the concentration measurements, and tend to increase with decreasing operating time between samples. They are not considered to be a reliable index of engine wear for sampling intervals less than 10 hours and of little or no value for trends less than 5 hours. Revised criteria for abnormal trends are proposed to increase the utility of trend determinations in such circumstances. The masking effects of oil consumption on wear metal measurements and their interpretation are delineated and demonstrated to further decrease the validity and usefulness of the JOAP evaluation methodology. A corrected concentration concept is advanced to compensate for these effects. Linear regression analysis is applied to wear metal concentration measurements to deduce valid trends and is shown to be greatly superior to JOAPs qualitative trending procedures. Furthermore, the use of corrected concentrations to determine steady-state wear metal concentrations and trends as an engine approaches this condition is illustrated. Author
- Lubricants and Hydraulic Fluids