Chapter 4 Reduction Gears and Related Equipment

CHAPTER 4 REDUCTION GEARS AND RELATED EQUIPMENT This chapter contains information on the operation, care and maintenance of reduction gears and related equipment found on Navy ships. All EN1s and ENCs must be familiar with the design and construction details of naval reduction gears and related equipment. When more detailed information is needed, refer to the manufacturer’s technical manual. REDUCTION GEARS The main reduction gears are the largest and most expensive single units of machinery found in the engineering department. When the main reduction gears are installed properly and are operated properly they give years of satisfac- tory service. However, when casualties occur to the main reduction gears they put any ship out of operation or force it to operate at reduced speed. Main reduction gear repairs are very costly. Usually they must be accomplished by a shipyard. FACTORS AFFECTING GEAR OPERATION Proper lubrication is essential for the efficient operation of reduction gears. This includes supplying the proper amount of oil to the gears and bearings, and keeping the oil clean and at the proper temperature. All abnormal noises and vibrations must be investigated and corrective action must be taken immediately. Gears and bearings must be inspected in accordance with cur- rent instructions issued by NAVSEA, the type commander, or other proper authority. Lubrication of Gears and Bearings The correct quantity and quality of lubricating oil must be available at all times in the main sump. This oil must be clean and it must be supplied to the gears and bearings at the pressure specified by the manufacturer. In order to supply the proper quantity of oil, several conditions must be met. The lubricating oil pump must deliver the proper discharge pressure, and all relief valves in the lubricating system must be set to function at their designed pressure. Too small a quantity of oil will cause the bearing to run hot. On the other hand if too much oil is delivered to the bearing, the excessive pressure will cause the oil to leak at the seal rings, and may also cause the bearing to overheat. Lubricating oil must reach the bearing at the proper temperature. If the oil is too cold, there will be insufficient oil flow. If the oil supply is too hot, some lubricating capacity is lost. For most main reduction gears, the normal temperature of oil leaving the lube oil cooler should be between 120°F and 130°F. For full power operation, the temperature of the oil leav- ing the bearings should be between 140°F and 160°F. The maximum temperature rise of oil passing through any gear or bearing, under any operating condition, should not exceed 50°F, and the final temperature of the oil leaving the gear or bearing should not exceed 180°F. Temperature rise and limit may be monitored by a thermometer or by a resistance temperature element installed where the oil is discharged from the bearings. Cleanliness of lubricating oil cannot be overstressed. The oil must be free from such impurities as water, grit, metal, and dirt. Par- ticular care must be taken to remove metal flakes 4-1