The Use of Radioactive Tracer Technology in Studying Lubricant Chemistry to Enhance Bearing and Ring Wear Control in an Operating Engine

Radioactive tracer technology (RAT) is an important tool in measuring component wear in an operating engine on a real-time basis. This paper will discuss the use of RAT to study and evaluate boundary lubricant and surfactant chemistries aimed at providing benefits in wear control. In particular, RAT was employed to study ring and bearing wear as a function of engine operating condition (speed, load, and temperature) and lubricant characteristics. Prior to testing, the engine's compression rings and connecting rod bearings were subjected to bulk thermal neutron bombardment in a nuclear reactor to produce artificial radioisotopes that were separately characteristic of the ring and bearing wear surfaces. The irradiated parts were installed in the test engine, after which testing to a specific test matrix was accomplished. During testing, these radioisotopes acted as detectable tracers as irradiated wear particles abraded from the rings and bearings and circulated in the lubrication system. Radiation associated with these particles was measured by a gamma ray spectrometer; the amount of radioactivity present being proportional to the number and mass of wear particles in the oil at the time of measurement. Thus, the radiation measurements were directly proportional to the amount of ring and bearing wear during a given test period. With this technology, it was possible to measure ring and bearing wear simultaneously, in real-time, without disassembling the engine for inspection.