Chapter 3—ENGINE MAINTENANCEAnother source of trouble during installationis due to the interchanging of the upper and lowershells. The installation of a plain upper shell inplace of a lower shell, which contains an oilgroove, completely stops the oil flow and leadsto early bearing failure. The resulting damage notonly may ruin the bearing but may also extendto other parts, such as the crankshaft connectingrod, piston, and wrist pin.8. Failure to follow recommended proceduresin the care of lubricating oil. Lack of properamount of lubricating oil will cause theoverheating of a bearing, causing its failure (seefigure 3-22). In large engines, the volume of thelubricating oil passages is so great that the timerequired to fill them when starting an engine couldbe sufficient to permit damage to the bearings.To prevent this, separately driven lubricating oilpriming pumps are installed, and by their action,the oil is circulated to the bearings before anengine is started. Priming pumps should besecured prior to starting the engine when theprescribed pressure has been obtained.circulation, and sufficiently low to preventexcessive oxidation of the lubricating oil. Nor-mally, the manufacturer’s technical manualshould be followed as to the correct lubricatingoil temperature to maintain. However, if nomanual is available, the temperature of the oilleaving the engine should be maintained between160° and 200°F. When possible, oil must beanalyzed at recommended intervals to determineits suitability for further use. In addition, regularservice of oil filters and strainers must be main-tained, and oil samples must periodically be drawnfrom the lowest point in the sump to determinethe presence of abrasive materials or water. Thelube oil purifier should be used in accordance withrequired procedures. Strict adherence to recom-mended practices will reduce the failure of bear-ings and other parts because of the contaminatedoil or insufficient supply of clean oil.FRICTIONLESS BEARINGSMaintenance of recommended oil pressures isessential to ensure an adequate supply of oil atall bearing surfaces. Refer to the oil pressure gageas it is the best source of operational informationto indicate satisfactory performance.Figure 3-23 lists the troubles that may beencountered with all types of (antifriction fric-tionless) bearings.Use Navy-approved, low-corrosive lubricatingoils at recommended oil temperatures. Recom-mended temperatures have been determined byextensive tests in laboratory and in service.They are sufficiently high to assure satisfactorySince dirty bearings will have a very short serv-ice life, every possible precaution must be takento prevent the entry of foreign matter into bear-ings. Dirt in a bearing which has been improperlyor insufficiently cleaned may be detected by noisewhen the bearing is rotated, by difficulty inrotating, or by visual inspection. Do not discardan antifriction bearing until you have definitelyestablished that something in addition to dirt hascaused the trouble. You may determine this byproperly cleaning the bearing.Spalled or pitted rollers or races may be firstrecognized by the noisy operation of the bearing.Upon removal and after a very thorough clean-ing, the bearing will still be noisy when rotatedby hand. (Never spin a frictionless bearing withcompressed air.) Roughness may indicate spall-ing at one point on the raceway.Figure 3-22.—Overheated bearing.121.6Pay particular attention to the inner surfaceof the inner race, since it is here that most sur-face disintegration first occurs. Since pits may becovered with rust, any sign of rust on the rollersor contact surfaces of the races is a probableindication that the bearing is ruined.3-35
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