Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGMANUALOPERATION-LEVERACTUATINGLINEACTUATORTO ATMOSPHEREACTUATINGVALVEATMOSPHERETO ATMOSPHEREDRUM PRESSURE SUPERHEATER OUTLET PRESSURE104.2?Figure 11-22.— Three-valve superheater outlet safety valve assembly (Consolidated).Before instructing fireroom personnel toblow tubes, the engineering officer of the watchmust obtain permission from the officer of thedeck. Under some conditions, tubes cannot beblown without covering the upper decks with soot;hence the need for obtaining permission from theofficer of the deck.Soot blowers are installed on the boiler withtheir nozzles projecting into the furnace betweenthe boiler tubes or adjacent to them. The sootblowers are arranged so that operation in theproper sequence will sweep the soot progressivelytoward the uptakes.The number of soot blowers installed, theway in which they are arranged, and the blowingarcs for each unit differ from one type of boilerto another. Figure 11-23 shows the arrangementof soot blowers used on one of the newer 1200-psisingle-furnace boilers; one of the soot blowershas a blowing arc of 220° and the others haveblowing arcs of 360° F, on this particular boiler.One common type of soot blower is shown infigure 11-24. The part of the soot blowerthat maybe seen from the outside of the boiler is calledthe head. The soot blower element, a long pipewith nozzle outlets, is the part of each sootblower that projects into the tube banks of theboiler. The soot blower shown in figiire 11-24 isoperated by an endless chain; when the chain ispulled, the element is rotated and superheatedsteam is admitted through the steam valve. Thesteam discharges at high velocity from thenozzles in the elements. The nozzles direct thejets of steam so that they sweep over the tubes.The soot is thus loosened so that it can be blownout of the boiler.Some soot blowers are operated by turning acrank or handwheel, instead of by an endlesschain. On some recent ships, the soot blowers areoperated by pushbuttons. One pushbutton is providedfor each unit. Pressing the pushbutton^admits air to an air motor which drives the units.296