New device for analysis of metal particles in oil

Abstract

A portable graphite furnace atomic absorption (AA) spectrometer, developed under a contract for this laboratory, has been evaluated using powdered metal particles suspended in oil. The portable wear metal analyzer (PWMA) was designed to support the deployed aircraft requirement for spectrometric oil analysis. The PWMA is a microprocessor-controlled automatic sequential multielement AA spectrometer packaged in two cases having a total weight of 49 kg. The PWMA will analyze for nine elements (nickel, iron, copper, chromium, silver, magnesium, silicon, titanium and aluminum) at a rate of 4 min per sample. The graphite tube and modified sample introduction system increase the detection of particles in oil when compared with the currently used techniques of flame AA or spark atomic emission spectroscopy and represent the major reason for this work — the qualification and calibration of the PWMA with known “wear metal” samples in turbine engine oil. Five (nickel, iron, copper, chromium and silver) of the nine elements analyzed by the PWMA are reported here owing to space limitations. These five elements represent the minimum and maximum concentration ranges of all nine elements. The PWMA shows good-to-excellent response for particles in the size ranges 0–5 and 5–10 μm and fair response to particles of 10–20 and 20–30 μm. All trends in the statistical variations are easily explained by system considerations. Correction factors to the calibration curves are necessary to correlate the analytical capability of the PWMA to the performance of existing spectrometric oil analysis instruments.