Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGSWIVEL TUBEPACKINGPACKINGELEMENTFigure 11-24.— External view of multi-nozzle soot blower.38.54vary somewhat in design details. Detailed informationon the water gage glasses installedon any particular boiler may be obtained fromthe manufacturer's technical manual.An older type of water gage glass is shownin figure 11-26. Figure 11-27 illustrates theconstruction of this gage. The frame is thecenterpiece of the assembly. Hollow stems ateach end of the frame connect with the cutoutvalves at top and bottom, thus allowing waterand steam to enter the gage. Two glass platesor strips, ground to flat parallel faces, areused in each water gage. The glass strips arebacked up by thin sheets of mica which separatethe glass from the high temperaturewater and steam. The mica sheets serve twopurposes. First, they keep the glass from becomingetched by the action of the hot waterand steam. And second, they prevent shatteringof the glass in case of breakage.The entire assembly of frame, glass strips,and mica sheets is supported between two steelcover plates which are held together by studs.Asbestos gaskets, 1/32 inch in thickness, areused on each side of the frame. Asbestos cushions,1/16 inch in thickness, are used betweenthe cover plates and the glass strips. The arrangementof cushions and gaskets is shown infigure 11-27.The drain connection shown in figure 11-26permits the water gage to be blown down andalso permits it to be drained. The regulatorconnections shown at the top and bottom ofthis gage are not found on all gages; they areinstalled only on boilers whichwerenot orignallydesigned to use feed water regulators butwhich were later fitted with the regulators.A more recent type of water gage glass isshown in figure 11-28. The gage is assembledsprings, as shown in the illustration. This typeof assembly makes it unnecessary to retorque298