WEAR OF BEARING LINERS AT LOW-SPEED ROTATION OF SHAFTS WITH CONTAMINATED OIL

An experimental and theoretical investigation was carried out to inves tigate the relationship between wear of bearing liners and low shaft s peed, contamination, oil temperature, bearing load and time. Experimen tally, it was found that oil with no external debris added produced on ly slight polishing of the liners. When the oil was contaminated with 0.02 wt.% iron or quartz particles of a known distribution (less than 32 mum diameter), increased wear was detected. Also, comparison of the results of the clean and iron-contaminated tests with those for quart z-contaminated oil show that the character of the worn liner area has changed from evenly rubbed zones to equally divided polished stripes i n the circumferential direction. During the tests, the bearing frictio n was measured. In no test did the friction rise drastically, as would have been the case if severe wear and scoring had appeared. In actual applications, though, this sometimes occurs. This may be explained by severe contamination in industrial lubricating systems, with larger p articles and higher debris concentration. A clean lubricating system i s thus crucial in order to avoid heavy wear at low speeds. The experim ental results were then compared with those indicated theoretically fo r film thickness at low speed. The theoretical minimum film thickness at low speed was much smaller than the size of the debris. The results indicate that if So-1 less-than-or-equal-to 340, B/D greater-than-or- equal-to 0.73 and C greater-than-or-equal-to 0.18 mm, no severe wear w ill occur.