Examples of other casualties which may affect propulsion plant operation are described below.

OVERHEATING MAIN SHAFT BEARINGS

Hot bearings may generally be traced to one of the following causes:

1. Insufficient lubrication.

2. Defective oil ring.

3. Grit or dirt in the oil.

4. Bearing out of line.

5. Bearing improperly fitted.

6. Poor condition of bearing or journal surface.

If the trouble is due to insufficient lubrication and is discovered before the bearing metal has wiped, an abundant supply of oil should gradually bring the bearing back to its normal operating temperature.

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 continued operation.

If the main shaft bearing is out of line or improperly 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 adjustments 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 indicating 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 manufacturers 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 excessively, 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 trying 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.