Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGmmm^ummmmmi38.45Figure 11-4.— Cutaway view of cyclone steamseparator.INLETBAFFLESTEAMWATER38.46Figure 11-5.— Plan view of cyclone steamseparator.Before reinstalling the fittings, wirebrush,clean, and hose down the steam drum. Be surethat it is clean and free of any oil or otheraccumulation.When replacing the fittings in the steamdrum, be sure that all the bolts are drawn tight.The desuperheater flanges must be thoroughlycleaned before the desuperheater is fitted intoplace and bolted. New gaskets must be installed.The flanges must be drawn up evenly and tightlyto prevent any leakage from the flanged joints.The internal fittings used in newer singlefurnanceboilers differ from those used in olderboilers and also differ among themselves. Figure11-7 shows the arrangement of fittings usedin the steam drum of a boiler on a DLG 9-15class ship. A little study of this illustrationshows several new or different features.To begin with, notice that there is no desuperheater,even though this is a single-furnaceboiler. The boiler does have a desuperheater,but it is installed in the water drum rather thanin the steam drum.Another interesting feature illustrated infigure 11-7 is the vortex eliminator. A vortexeliminator consists of a series of grid-likeplates arranged in a semicircular shape to conformto the shape of the lower half of the steamdrum. One vortex eliminator is located at thefront of the steam drum (as shown in fig, 11-7)and another is located at the rear of the drum.In each case, the eliminator is fitted over thenecks of the downcomers. The purpose of thevortex eliminators is to reduce the swirlingmotion of the water as it enters the downcomers.The arrangement of internal fittings in thesteam drum of a boiler on one of the newer destroyerescorts is shown in figure 11-8. Noticethat there are two feed pipes, each of which runslengthwise in the drum. The discharge holes aredrilled along the inner side of each feed pipe sothat the incoming feed water is discharged horizontallytoward the middle of the drum. Noticealso that the internals in this steam drum includehorizontal steam separators rather thancyclone steam separators.A horizontal steam separator is shown infigure 11-9. These separators are installed inmuch the same way as the cyclone steam separators—thatis, one row of separators is installedalong each side inside the steam drum.Each horizontal steam separator has a machinedflange which is bolted to a matching flangeattached to a girth baffle. The mixture of steam280