138 BOILER TESTS. 



test shows regarding the quality of fuel, rate of combustion, 

 or the temperature of the flue gases, for these are such as 

 ordinarily give good results. 



Boiler No. 31. 



Kind of boiler, . . . ' . . . Horizontal return tubular. 



Number used, . . Three. 



Horse power ( collective basis 12 square feet ), Three hundred and twelve. 



Age, ........ One month. 



Boiler No. 31 consists of a plant of three horizontal tubular 

 boilers, set in one battery of brick work. The general feat- 

 ures of the setting are similar to those shown in the cut of 

 Boiler No. 5, with the exception that the bridge walls are 

 arched upward to conform to the curve of the shell. These 

 boilers are deficient in flue area, this being about one third of 

 the area for draught through the tubes . As a consequence, a 

 strong draught is required in the flue to secure a relatively 

 slow rate of combustion and small capacity. 



Dimensions of Boiler No. 31. 



Diameter of shell, . 66 in. 



Length between heads and length of tubes, ... 15 ft. 



Number of tubes ( collective ) 3 inches outside diameter, . 306 



Area of heating surface, 3,374 sq. ft. 



Area of grate surface, ........ 90 sq. ft. 



Area through tubes, 12.6 sq. ft." 



Area through flue, 4.6 sq. ft. 



Height of chimney, 75 ft. - 



Width of air spaces and metal bars in grates, ... 1-2 in. 



Distance of grate to shell, . . . . . . 24 in. 



Distance of curved bridge to shell, . . . . . 12 in. 



Ratio of heating surface to grate surface, .... 41.6 to 1 



Ratio of grate surface to tube area, 7.1 to 1 



Ratio of grate surface to flue area, 18.3 to 1 



