An oil disc (ring) clamped to the shaft is used in eachbearing to deliver oil to the upper bearing and journalsurfaces. As the disc rotates, it picks up oil from thebearing reservoir and carries it to the oil scraper on theupper shell. The scraper removes oil from the disc anddirects it to the upper bearing lining. A clear sight coveron the bearing housing allows visual confirmation of theoil disc operation. Figure 3-7 shows a typical disc-oiledline shaft bearing.All bearing pedestals have an oil level rod and anoil reservoir thermometer for checking oil level andtemperature. A resistance temperature detector (RTD)is installed in the lower bearing shell of eachoil-lubricated bearing. The RTDs provide for remotereadouts of each bearing’s temperature on the digitaldemand displays.Clearances are taken with a depth micrometerthrough a port in the upper bearing housing, whichcontains the anti-rotation pin. The original installationreadings are stamped into the flat surface adjacent to thisport. You must take readings according to PMSrequirements or when an abnormal condition exists.For information on maximum wear limits and repairprocedures, you should consult the appropriatemanufacturer’s technical manual and NSTM, chapter244, “Shafting, Bearings, and Seals.”STRUT AND STERN TUBE BEARINGSEach propeller shaft extending aft of the stern tubeis supported by two struts, each containing aseawater-cooled bearing. Figure 3-8 shows a typicalstrut bearing.Stern tube bearings are in constant contact with theseawater surrounding the stern tubes. The cleanseawater that passes through the stem tube seals fromthe ship’s seawater service system or firemain system(in emergencies) also flows through the stern tubebearings. Stern tube bearings are identical to forwardstrut bearings. However, aft strut bearings are roughly5 inches larger in diameter and twice as long as stemtube bearings. Remember that stem tube bearings arenot remotely monitored.PROPULSION SYSTEMSThe ship’s propulsion thrust is provided byhydraulically actuated propellers. In the Gas TurbineSystems Technician (Electrical) 3/Gas Turbine SystemsTechnician (Mechanical) 3, volume 1, NAVEDTRA10563, you were provided with a complete descriptionof propulsion systems and how they operate. As a gasturbine supervisor you need to be knowledgeable andexperienced with a variety of gas turbine propulsionFigure 3-7.—Disc-oiled line shaft bearing,3-11
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business