Principles of naval engineering - Historic Naval Ships Association

Chapter U-BOILER FITTINGS AND CONTROLSCHEVRON DRYERSDRY BOXHORIZONTAL STEAMSEPARATOR\STEAMBAFFLESOUTLETORIFICEBAFFLESCHEMICAL FEEDDESUPERHEATER INLET^DESUPERHEATER38.48Figure 11-8.— Arrangement of internal fittingsin newer single-furnace boiler (DE 1006 classship).Figures 11-10, 11-11, 11-12, and 11-13 showthe locations of many external fittings and connectionson a recent 1200-psi single-furnaceboiler. As you study the following information onexternal fittings and connections, you may find ithelpful to refer to these figures to see where thevarious units are installed on or connected tothe boiler. Remember, however, that the illustrationsshown here are for one particularboiler and that differences in boiler design leadto differences—in the type and location of externalfittings and connections. Drawings showingthe location of external fittings and connectionsare usually included in the manufacturer'stechnical manuals for the boilers on each ship.The maintenance of external fittings is ofvital importance to the proper operation of theboiler. Therefore, all maintenance shall beconducted in accordance with the PlannedMaintenance Subsystem of the 3-M System.Drains and VentsThe main part of the boiler, the economizer,and the superheater— in short, all the steam andwater sections of the boiler— must be providedwith drains and vents.38.49Figure 11-9.— Horizontal steam separator.The main part of the boiler may be drainedthrough the bottom blow valves (described laterin this chapter) and through water wall headerdrain valves. It is vented through the aircock,which is a high pressure globe valvel installedat the highest point of the steam drum. Theaircock allows air to escape when the boiler isbeing filled and when steam is first forming; italso allows air to enter the steam drum whenthe boiler is being emptied.The economizer is vented through a ventvalve on the economizer inlet piping. It isdrained through a drain line from the econonomizeroutlet header. Another drain line, thisone coming from the drain pan installed belowBasic types of valves are discussed in chapter 14 ofthis text.283