Figure 2-1. Wearmetal Concentration Vs. Operating Hours
2-5. Identification and Measurement of Wearmetals. Wearmetals produced in fluid lubricated mechanical
assemblies can be measured in extremely low concentrations by spectrometric analysis of fluid samples taken
from the assembly. The analytical instrument currently used for spectrometric oil analysis by the services are
atomic emission rotrode instruments.
a. Atomic Emission Spectrometer. An emission spectrometer is an optical instrument used to determine
the concentration of wearmetals in lubricating fluid. The analysis is accomplished by subjecting the sample to a
high voltage spark or plasma which energizes the atomic structure of the metallic elements, causing the emission
of light. There are two commonly used types of emission spectrometers, Atomic Emission Rotrode (AER), and
Inductively Coupled Plasma (ICP). Laboratories certified under the Joint Oil Analysis Program utilize the AER
spectrometer. The emitted light is subsequently focused into the optical path of the spectrometer and separated
by wavelength, converted to electrical energy and measured. The intensity of the emitted light for any element is
proportional to the concentration of wear metal suspended in the lubricating fluid.
b. Atomic Absorption Spectrophotometer. An atomic absorption spectrophotometer is an optical
instrument used to determine the concentration of wearmetals in the lubricating fluid. The sample is aspirated into
a flame and vaporized. The molecular structure of the wear-metal compounds is reduced to ground state atoms
by the high temperature. Light energy having the same characteristic wavelength of the element being analyzed
is radiated through the flame. The resultant light which is not absorbed is converted to electrical energy and
measured electronically. The amount of light absorbed by the elements in the flame is proportional to the
concentration of wearmetal suspended in the lubricating fluid.
c. Spectrometric Oil Calibration Standards. JOAP oil standards consist of a base oil containing precisely
controlled quantities of dissolved metallo-organic elements and stabilizing agents, with controlled viscosity and
flash point for calibrating/standardizing both atomic emission and atomic absorption spectrometers.
(1) JOAP oil standards are available in 8-ounce bottles through normal supply sources as stock