ECONOMICAL USE OP FUEL IN CREAMERIES. 



17 



where leakage of air through the walls may occur and to give as 

 smooth a surface inside as possible so as to lessen the resistance to 

 the flow of escaping gases. 



The area of the chimney should be approximately 20 per cent 

 greater than the combined flue area of the boiler or boilers which it 

 is to serve. Table 3 gives the size of chimney for steam boilers. 



.Table 3. — Size of chimney for steam boilers. 

 [Calculated from Kent's formula assuming 5 pounds of coal per horsepower-hour.] 





Diam- 

 eter 

 (inches. ) 



Height in feet. 



Equiv- 

 alent 



Area 



(square 



feet). 



30 



40 



50 



60 



70 



80 



90 



100 



110 



125 



150 



175 



200 



square 

 chim- 

 ney- 





Commercial horsepower. 



side of 

 square. 



1.23 



15 

 18 

 21 

 24 

 27 

 ' 30 

 33 

 36 

 39 

 42 

 48 

 54 

 60 



10 



18 



12 

 20 

 31 



'44 



13 



23 

 25 

 49 

 65 

 84 



14 

 25 

 38 



54 

 72 

 92 

 115 

 141 



16 

 27 

 41 

 58 

 78 

 100 

 125 

 152 

 183 

 216 











| | 



13 



1.77 



29 

 44 

 62 

 83 

 107 

 133 

 163 

 196 

 231 

 311 









i 1 



16 



2.41 









i 



19 



3.14 



66 

 88 

 113 

 141 

 173 

 208 

 245 

 330 

 427 

 536 







I 



22 



3.98 











24 



4.91 







119 

 149 

 182- 

 219 

 258 

 348 

 449 

 565 









27 



5.94 







156 

 191 

 229 

 271 

 365 

 472 

 593 





1 



30 



7.07 









204 

 2*5 

 289 

 389 

 503 

 632 







32 



8.30 









2b8 

 3i6 

 426 

 551 



692 









35 



9.62 











342 

 460 

 595 



748 







492 

 636 

 800 



38 



12.57 











42 



15.90 















48 



19.64 















54 



















For pounds of coal burned per hour for any given size of chimney, multiply the figures in the table by 5. 



DAMPERS. 



Each boiler should be provided with a damper in the uptake or 

 breeching which should have an effective opening of at least 25 per 

 cent greater area than that of the combined area of the tubes. It 

 should be arranged for convenient manipulation by the fireman; 

 otherwise there will be a tendency to neglect its use. The control 

 of the draft should be done through the manipulation of this damper 

 rather than by the ash-pit doors. 



BRIDGE WALL. 



The wall just back of the grates is known as the bridge wall and 

 extends across the entire width of the furnace to a height somewhat 

 above the level of the bars. It has for its object the directing of the 

 hot furnace flames and gases, forcing them to rise toward the shell 

 of the boiler, and also to hold the fuel at the rear of the grates. The 

 distance between the top of the bridge wall and the boiler shell de- 

 pends on the kind of fuel used. With anthracite, or hard coal, the 

 distance should be less than if soft coal or wood is used. As the 

 bridge wall above the grate bars is in the direct path of the flames 

 and hence is subjected to a very high temperature, it should be faced 

 with fire brick, as ordinary brick soon fuses or crumbles. 



82693°— 19 3 



