Establishing wear particle limits using the theory of Dynamic Equilibrium Condition (DEC) to predict when abnormal wear modes are taking place in machinery
The basis of modern oil analysis programs is the use of optical emission spectroscopy (OES) to measure the ppm (parts per million) levels of wear metals, contaminants, and additives in oil samples. Whatever an oil lab may need to measure, multi-elemental analysis is the core of an in-service oil analysis program. This paper gives an overview of Rotating Disc Electrode Optical Emission Spectroscopy (RDE-OES), its applications, and the SpectrOil Series family of products, which combine the latest innovations for increased performance and reliability with 30+ years of experience in military and laboratory applications.
Sometime after World War II, the Denver and Rio Grande Railroad, now defunct, began analyzing diesel locomotive engine oil by looking at the spectral lines emitted by an in service oil sample when excited by a strong electric arc using carbon electrodes. Early tests proved that monitoring the elements attributed to wear and contamination provided early warnings of chronic equipment failure.
Elemental spectroscopy is the backbone of an oil analysis program as it is widely applicable to a closed loop lubricating system such as those found in gas turbines, diesel and gasoline engines, transmissions, gearboxes, compressors and hydraulic systems. In practice, an oil sample is periodically taken from a system and analyzed. The resulting data, when compared to previous analyses and allowable limits, may indicate a sound mechanical system showing only normal wear, or it may point out a potentially serious problem in its early stages. With this advanced warning, steps may be taken to correct the situation before serious damage or injury occurs.
Spectroscopic oil analysis works by detecting the fine particles generated by relative motion of metallic parts in an oil-wetted system. Contaminants are also detected and lubricant mix-ups, or badly degraded lubricants, are identified by the concentration of additive elements. Multi-element analysis, coupled with knowledge of the materials used to build the engine, often allows identification of a specific component in distress. Table 1 shows that typical metal elements can be analyzed by spectroscopy and their typical sources.