Chapter 4—REDUCTION GEARS AND RELATED EQUIPMENTgrooved to accommodate the rings. As they glidethrough the reservoir of oil at the bottom, therings carry some of the oil along to the top of theshaft journal.On some steam driven ships, the most recentline shaft bearing design employs oiler discsinstead of oiler rings for lubrication. At very lowspeeds (i.e., when the shaft is jacked for 24 hourswhile the turbines are cooling), the oil rings tendto slip and lubrication is sometimes inadequate.The oiler discs are clamped to propulsion shaftand have cavities at the periphery which carry oilto the top of the bearing regardless of the shaftspeed.Spring bearing temperatures and oil levelsshould be checked hourly while underway. Atleast once each year, the bearings should beinspected, clearances taken, and any defectscorrected.STERN TUBE AND STERNTUBE BEARINGSThe hole in the hull structure for accom-modating the propeller shaft to the outside of thehull is called the stern tube. The propeller shaftis supported in the stern tube by two bearings—one at the inner end and one at the outer end ofthe stern tube—called stern tube bearings. At theinner end of the stern tube there is a stuffing boxcontaining the packing gland (figure 4-4), whichis generally referred to as the stern tube gland.The stern tube gland seals the area between theshaft and stern tube but allows the shaft to rotate.The stuffing box is flanged and bolted to thestern tube. Its casing is divided into twocompartments—the forward space which is thestuffing box proper, and the after space, providedwith a flushing connection, designed to maintaina positive flow of water through the stern tubefor lubricating, cooling, and flushing. Thisflushing connection is supplied by the firemain.A DRAIN CONNECTION is provided both fortesting for the presence of cooling water in thebearing and for permitting sea water to flowthrough the stern tube and cool the bearing whenunderway, where natural seawater circulation isemployed.The gland for the stuffing box is dividedlongitudinally into two parts. The gland bolts arelong enough to support the gland when the latteris withdrawn at least 1 inch clear of the stuffingFigure 4-4.—Stern tube stuffing box and gland.4-9
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