Advanced condition monitoring of tapered roller bearings, part1

Abstract

A new condition monitoring technique is under development which is basedon electrostatic charge. This was originally employed for the detection of debris in thegas path of jet engines and gas turbines, and is now being developed for lubricatedsystems. Previous investigations have demonstrated the viability of this technique indry and lubricated tribo-contacts using laboratory-based equipment. This paperreports on the evolution of wear during a tapered roller bearing test, using a suite ofcondition monitoring techniques, that incorporated electrostatic wear-site sensors toidentify charge during surface wear and oil-line sensors to detect debris in oilscavenge lines. The multi-sensor arrangement also included a vibration accelerometer,thermocouples, inductive and ferromagnetic particle counters. Additionally, oilsamples were taken during various stages of the test and were analysed for sub-100?m debris content. Off-line debris analysis included optical particle counting,ferrography, spectrometric oil analysis and electron microscopy. Further tribologicalassessments included mass loss calculations and photographic evidence of damage.During the initial 7 hours, running-in wear was identified by dynamic wear sitecharge, acceleration and temperature. Also at this time, increases in oil-line chargecorrelated with debris detection by the inductive sensor, optical particle counter andferrographic analysis. Following running in, benign wear was indicated by a reductionin wear site charge, acceleration and temperature, as well as reductions in oil-linecharge, inductive and optical particle counts. Around 42 hours, increases in inductiveand optical particle count were considered to be an early indicator (or precursor) ofthe impending wear out phase. At 53.5 hours, wear out was identified by increases inwear site charge, acceleration and temperature. Evidence of wear debris was shownby increases in oil-line charge, inductive and ferromagnetic particle count. The debriswas further corroborated by optical particle count, ferrography and spectrometry. Thetest was then stopped after 63 hours and post-test analysis confirmed outer race androller spallation