184 



BOILER TESTS. 



Boiler No. 51 is a verti- 

 cal tubular boiler of the 

 so-called "Rolling Pin" 

 form, the principal features 

 of which are shown in the 

 following cut. In this 

 boiler the main shell is 

 completely filled with tubes, 

 with the exception of the 

 central space extending be- 

 tween the water le and 



o 



the dome. The grate sur- 

 face forms an annular ring 

 surrounding the water leg. 

 The brick setting consists 

 of a plain brick Avail, sur- 

 rounding the shell, and 

 extending up to a height of 

 about 10 feet above the 

 upper tube sheet. This is 

 surmounted by a wrought 

 iron smoke stack. The 

 water line is ordinarily car- 

 ried to a point about 3 feet 

 below the top of the main 

 shell, and above this point 

 the tubes are uncovered. 

 A considerable portion of 

 the heating surface is thus 

 made steam heating surface, and the boiler produces steam 

 which is in a more or less superheated condition. This form 

 of vertical boiler has a proportion of 30 square feet of total 

 heating surface to one of grate, and about two thirds of this is 

 water-heating surface. 



BOILER No. 51, VERTICAL ELEVATION. 



