ENGINEMAN 1 & Cdata, furnished by the contractor, should beentered in prescribed records by the ship’sengineering personnel when the ship is at the con-tractor’s yard. They should include the crownthickness readings and the clearances of theoriginal bearings, the thrust settings andclearances, and the backlash and root clearancesfor gear and pinion teeth. It is essential to havethis information available at the time when thealignment must be checked.All repairs, adjustments, readings, andcasualties should be reported in accordance with3-M system procedures. All original bearing data,as well as all additional bearing measurements,should be entered in appropriate records.The manufacturer’s technical manual, whichgives detailed information regarding repairs to bemade to reduction gears, is furnished to each ship.Special tools and equipment are normally pro-vided on board ship for (1) lifting some reduc-tion gear covers, (2) handling the gear elementswhen removing or replacing their bearings, (3)making the required measurements, and (4) rebab-bitting bearings.Figure 4-1.—Scribe lines used in measuring the crownthickness of reduction gear bearings.These special tools and equipment should beavailable aboard ship in case repairs have to bemade by repair ships or at advanced bases. Bridgegages are no longer used to check bearing wearof the main reduction gears. When bearing wearmust be checked, the crown thickness method isused.bearings are given in the manufacturer’s technicalmanual. These clearances are also shown on theblueprints for the main reduction gears.A bearing shell consists of a pressure-bearinghalf and a nonpressure-bearing half. Thenonpressure-bearing half has a radial scribe lineat one end of the geometric center. The pressure-bearing half of every main reduction gear shellhas three radial scribe lines on each end of thebearing shell (figure 4-1). As you can see one ofthese scribe lines is located at the geometric centerof the shell and the remaining lines intersect thecenter scribe line at a 45° angle.On a multishaft ship, if a main reduction gearbearing is wiped, the preferred procedure (if prac-ticable) is to secure the shaft and the reductiongear until the units can be inspected and repairedby a repair activity.A glance at figure 4-2 will indicate why thereplacement of a bearing in a main reduction gearwould be a major undertaking for the ship’s force.However, emergency conditions may requireaction by the ship’s force. When such action isto be taken, a number of factors must be takeninto consideration before repairs are attempted.The crown thickness of each shell at thesepoints should be measured with a micrometer ata prescribed distance from the end of the shell.These measurements should be recorded duringthe initial alignment and should be permanentlymarked adjacent to each scribe line.The first factor to consider would be whetheror not to attempt the repair work.The amount of bearing clearance should notbe allowed to become too great to cause incor-rect tooth contact. The designed clearances forThe EN1 or the ENC must study the manufac-turer’s instructions and the blueprints for thereduction gear, so as to have a clear understandingof the constructions details and the repair pro-cedures and to be able to decide whether or notthe work should be done by the ship’s force. Otherfactors which must be considered are the location4-4
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