binding, replacing faulty parts, adding oil tohydraulic type trips, or adjusting the speed sen-sitive element, always in accordance with the in-struction manual. If the trip has been damaged,it is advisable to install a spare overspeed trip andcompletely rebuild or overhaul the damaged one.REPAIR OF INTERNALCOMBUSTION ENGINESThe Navy uses so many models of dieselengines that it is not possible to describe in anydetail all the overhaul procedures used by theNavy. Detailed repair procedures are listed in themanufacturers’ technical manuals and in yourPMS. Always consult the manuals and themaintenance requirement cards (MRCs) beforestarting any type of repair work. Pay particularattention to installation tolerances, wear limits,adjustments, and safety procedures. Also be sureto follow the general rules, listed below, whichapply to all engines.1. Observe the highest degree of cleanlinessin handling engine parts. Engines have been com-pletely wrecked by the presence of abrasives andvarious objects which have been carelessly left inthe engines after overhaul. Make sure that anyengine assembled for post-repair running isscrupulously free of foreign matter prior to run-ning. Too much emphasis cannot be given to thenecessity for maintaining engines clean both in-ternally and externally. Since dirt entering theengine during overhaul causes increased wear andpoor operation, it is essential that all repair workbe done under clean conditions. When overhaulor repair of precision parts and surfaces is re-quired, the parts and the surface should bethoroughly cleaned and wrapped in a clean clothor suitable paper. The parts should then be storedin a dry place until reinstalled. During installa-tion, parts should be wiped with a cloth free oflint and coated, where applicable, with cleanlubricating oil. When removing or installing partssuch as pistons, connecting rods, camshafts, andcylinder liners, make sure that these parts are notnicked or distorted. Take precautions to keep dirtand other foreign material in the surroundingatmosphere from entering the engine while it isbeing overhauled. As an example, during shipyardoverhaul periods the engine should be protectedwhen sandblasting is occurring in areas adjacentto the ship.2. Before starting repair work, make sure thatall required tools and spare parts are available.Plan ahead for repair periods so everythingneeded is available to ensure successful and ex-peditious completion of the work.WARNINGNever attempt to jack the engine over by handwithout first disabling the starter circuit.3. Disable the starter circuit and tagout thestarter before you start working, particularly whenthe jacking gear is to be engaged.4. Keep detailed records of repairs, includingmeasurements of worn parts (with hours in use),and the new parts installed. Later, an analysis ofthese records will indicate the number of hoursof operation that may be expected from thevarious parts and will facilitate prediction as towhen they should be renewed before a failureoccurs. Measurement of new parts are needed todetermine whether or not they come within thetolerances listed in the manufacturers’ instructionbooks or the wear limit charts. In addition, beforeinstallation, all replacement parts should be com-pared with removed parts to ensure that they aresuitable.5. Do not test an overhauled diesel engine at125% of full load or any other overload beforethe engine is returned to service. It has beenreported that some overhauled diesel enginesused for driving generators are being tested at125% of full load before being returned to serv-ice. The original purpose for this test was todemonstrate a 25% overload capability for a2-hour period to absorb occasional electrical peakloads. The nameplate rating of many of the oldergenerator sets indicates a 25% temporary overloadcapacity. (More recent generator sets have a singlerating with no stated overload requirement.) Theearlier practice was a reasonable approach sincethe engine was frequently capable of substanti-ally greater power than could be absorbed by thegenerator and the 125% test was not likely to bedetrimental to the engine. Now that these engineshave aged, the margin of excess power availableChapter 3—ENGINE MAINTENANCE3-25
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business