Steam Engines. 



509 



636. Construction of Steam Boilers. Steam boilers are 

 usually made of strong sheet stcjl * i> or A incl es 

 thick which are rolled into cylindrical forms, securely 

 riveted and often braced as represented in Fig. 245. The 

 fire-box is placed in one end and is entirely surrounded by 

 water so as to lessen the loss of heat. The boiler repre- 

 sented in Fig. 245 is designed specially for burning straw 

 as fuel, which is introduced into the fire-box A, from which 

 the flame passes forward through the main large flue B 

 into the combustion chamber C. From the combustion 

 chamber the flame is sub-divided, returning to the smoke 



FIG. 24 -i. -Construction of steam boiler. 



stack E through the small flues D. In the same figure 

 FF and FF represent the steam dome from which the dry 

 steam is taken by the supply pipe G to the steam chest at 

 H, not represented. At the bottom of the boiler at KK 

 and KKKK are represented hand holes to be used in clean- 

 ing it out. The construction of the valve for closing 

 the hand hole is shown at A in Fig. 243 and also the 

 relation of the flues to the water being heated by them. 

 In the arrangement of the flues in the boilers, particular- 

 ly in the horizontal forms, it is important to have them 

 placed in vertical rows rather than one flue above the 

 space between the two below, in order that there may be 

 as free and rapid a circulation of water as possible. It is 



