PRINCIPLES OF NAVAL ENGINEERING 



SWIVEL TUBE 

 PACKING 



PACKING 



ELEMENT 



38.54 



Figure 11-24.— External view of multi-nozzle soot blower. 



vary somewhat in design details. Detailed in- 

 formation on the water gage glasses installed 

 on any particular boiler may be obtained from 

 the manufacturer's technical manual. 



An older type of water gage glass is shown 

 in figure 11-26. Figure 11-27 illustrates the 

 construction of this gage. The frame is the 

 centerpiece of the assembly. Hollow stems at 

 each end of the frame connect with the cutout 

 valves at top and bottom, thus allowing water 

 and steam to enter the gage. Two glass plates 

 or strips, ground to flat parallel faces, are 

 used in each water gage. The glass strips are 

 backed up by thin sheets of mica which sep- 

 arate the glass from the high temperature 

 water and steam. The mica sheets serve two 

 purposes. First, they keep the glass from be- 

 coming etched by the action of the hot water 

 and steam. And second, they prevent shatter- 

 ing of the glass in case of breakage. 



The entire assembly of frame, glass strips, 

 and mica sheets is supported between two steel 

 cover plates which are held together by studs. 

 Asbestos gaskets, 1/32 inch in thickness, are 

 used on each side of the frame. Asbestos cush- 

 ions, 1/16 inch in thickness, are used between 

 the cover plates and the glass strips. The ar- 

 rangement of cushions and gaskets is shown in 

 figure 11-27. 



The drain connection shown in figure 11-26 

 permits the water gage to be blown down and 

 also permits it to be drained. The regulator 

 connections shown at the top and bottom of 

 this gage are not found on all gages; they are 

 installed only on boilers whichwerenot orignal- 

 ly designed to use feed water regulators but 

 which were later fitted with the regulators. 



A more recent type of water gage glass is 

 shown in figure 11-28. The gage is assembled 

 springs, as shown in the illustration. This type 

 of assembly makes it unnecessary to retorque 



298 



