Instrumental neutron activation analysis in support of implementation of quantitative filter debris analysis

Abstract

Aircraft engines and transmissions are regularly monitored by several integrated techniques such as periodic analysis of the metallic wear debris deposited in the lubricating oil, termed Aircraft Oil Analysis (AOA). Trending of these results indicate to the fleet manager the operational health of each aircraft. Instrumental neutron activation analysis (INAA) provides similar results and for a greater range of metals than the analytical techniques used in the field laboratories. However, for new oil-lubricated systems with fine filtration, the wear debris collects on the oil filter and little debris remains in the oil for analysis. The wear debris must be removed from the filter and ends up as a solid sample. Ultrasonic cleaning is used and the wear debris may be inspected qualitatively to determine the wear mechanism, termed Filter Debris Analysis (FDA). Quantitative analysis follows, termed Quantitative Filter Debris Analysis (QFDA) and, for techniques other than INAA, the sample must be dissolved. A combination of three acids and microwave digestion are then used. Then, to use the present field technique, this aqueous sample is then converted to an appropriate organic matrix before analysis. Again, INAA has been used to develop and monitor this QFDA technique for field application.