BOILER No. 69. 229 



Dimensions of Boiler No. 69. 



Number of tubes 4 inches outside diameter, .... 48 



Length of tubes, 15 ft. 



Diameter of drums ( three ), 14 in. 



Length of drums, 15 ft. 



Area of water-heating surface, 848 sq. ft. 



Area of steam-heating surface, ...... 114 sq. ft. 



Area of total-heating surface, 962 sq. ft. 



Area of grate surface, ........ 27 sq. ft. 



Area through flue, . . . 3.7 sq. ft. 



Height of chimney, ......... 70 ft. 



Width of air spaces and metal bars in grates, Air 3-8 in., metal 1-2 in. 



Ratio of water-heating surface to grate surface, . . . 31.4 to 1 

 Ratio of steam-heating surface to grate surface, . . . 4.2 to 1 



Ratio of grate surface to flue area, 7.4 to 1. 



Results of Test, Boiler No. 69. 



Test No. 135. 

 Manner of start and stop and kind of run, .... Ordinary. 



Duration, 10.1 hrs. 



Coal consumed, ( including 91 pounds leather scraps taken to 



be equal to 91 pounds of coal), .... 2,972 Ibs. 



Percentage of ash, 16.4 per cent. 



Water evaporated, 23,396 Ibs. 



Coal per hour, 294 Ibs. 



Coal per hour per square foot of grate, . . . 10.9 Ibs. 



Water per hour, 2,314.1 Ibs. 



Water per hour per square foot of water-heating surface, 2.7 Ibs. 



Horse-power developed, .73.9 H. P. 



Boiler pressure, 84 Ibs. 



Temperature of feed-w^ater, ...... 150 deg. 



Temperature of escaping gases, 428 deg. 



Draught suction, . .0.12 in. 



Water per pound of coal, 7.87 Ibs. 



Water per pound of coal from and at 212 degrees, . . 8.66 Ibs. 



Water per pound of combustible from and at 212 degrees, 10.36 Ibs. 



NOTE. When the water was carried below the ordinary level, the steam was 

 superheated a few degrees. Ordinarily the thermometer failed to show any superheat. 



The test on Boiler No. 69 shows the performance of a water 

 tube boiler, using one of the small grades of anthracite coal. 

 The ratio of heating surface to grate surface is somewhat small 

 for a water tube boiler. As a result, the temperature of the 

 waste gases is above the point of the best efficiency, and the 

 evaporative result, which is 10.36 pounds of water from and 

 at 212 per pound of combustible, is somewhat unfavorable. 



