A  defective  oil  ring  should  be  repaired  or replaced. Should the trouble be caused by grit, dirt, or foreign matter in the bearing, the oil should be renewed. The new oil may flush out the impurities in the bearing surfaces sufficiently to permit con- tinued operation. If the main shaft bearing is out of line or im- properly fitted, or if the bearing or journal is not in proper condition, only temporary relief can be obtained from use of the various means suggested above. The most effective treatment will probably be the operation of the main engines at low or moderate speeds until such time as the proper ad- justments or repairs can be made. Abnormal temperatures of a bearing can be lowered by slowing down the main shaft and thus decreasing the amount of friction in the bearing. If the trouble has reached an advanced stage, it may be necessary to stop the main shaft. In an emergency, cold water may be used on a bearing to reduce the temperature so that it will be within safe  operating  limits;  it  must  be  remembered, however, that cold water will cause contraction of the bearing. Also, care must be taken to see that water does not contaminate the bearing oil. Once a bearing has wiped, it should be recon- ditioned. If it has wiped out slightly, it can prob- ably be scraped to a good bearing surface and restored to service. If badly wiped or burned out, the  bearing  will  require  replacement.  Inspect  the journal and remove any high spots by lapping the journal. UNUSUAL  NOISE  IN  REDUCTION GEAR This information applies to diesel-driven ships that have main reduction gears. The action taken will  depend  upon  the  two  following  conditions: 1. When noise and conditions indicate that tooth failure is not probable: a. Slow the engine immediately and stop it if the noise persists. b. Check the oil discharge pressure, the temperature of the bearing, and the operation of oil sprays and strainers. Look for the presence of babbitt or other foreign matter. 2. When there is a loud or roaring noise in- dicating gear tooth damage: a.  Stop  the  engine  and  check  the  shaft immediately. b. Lock the main shaft in accordance with EOSS/EOCC procedures or the manufacturer’s instruction. c. Make a preliminary investigation of the gear teeth and other parts of the main reduction gear. PROPULSION  SHAFT  VIBRATES EXCESSIVELY When  the  propulsion  shaft  vibrates  exces- sively, take the following actions: 1. Slow the shaft. If the vibration continues, stop and lock the shaft. 2. Investigate to determine the cause of the vibration. Take necessary action to correct the cause of the vibration. Frequently,  the  circumstances  under  which  a ship is operating should be considered when try- ing to determine the probable cause for excessive vibration. For example, if the ship is in shallow water or close to a beach, the vibration may be caused by the propeller striking ground. ELECTRICAL  CASUALTY  CONTROL Since Enginemen and Electrician’s Mates are assigned  duties  in  operating  diesel-driven  emer- gency generating plants on steam-driven ships, and all electrical generating plants on diesel-driven ships, they must have a general knowledge of the purpose of electric generating plants, their opera- tion under various conditions, and the types of casualties  that  will  interfere  with,  or  disrupt,  the normal operation of an engineering plant. THE ELECTRICAL PLANT The  ship’s  power  and  lighting  plant  consists of  generators,  switchboards,  power  panels,  cables, circuit breakers, and other equipment necessary for the generation, distribution, and control of power  supplies  to  electrically  driven  auxiliaries, ENGINEMAN  1  &  C 9-10