BOILER No. 77. 231 



The test on Boiler No. 70 shows the performance of a water 

 tube boiler, using Cambria bituminous coal. The power 

 developed is somewhat more than its nominal capacity, and a 

 high rate of combustion prevails. The temperature of the 

 escaping gases is above the economical limit, and the evapora- 

 tive result is correspondingly low. The quantity of ash 

 contained in the coal, viz. 10.5 per cent., is higher than is 

 found in the best grades of bituminous coal, and to this 

 indication of inferior quality of fuel may be attributed in some 

 measure the low degree of economy which was obtained. 



Boiler No. 71. 



Kind of boiler, Water tube. 



Number used, ...... Two. 



Horse-power ( collective, basis 12 sq. ft. ), One hundred and fifty-seven. 



Kind of coal, George's Creek Cumberland. 



Age, Four years. 



Boiler No. 71 is a water tube boiler, having the general 

 features shown in the cut of Boiler No. 66. It embraces two 

 boilers set in one battery of brick work. 



Dimensions of Boiler No. 71. 



Number of tubes 4 inches outside diameter, ... 96 



Length of tubes, ........ 16 ft. 



Diameter of drums (two), . . . ... . 30 in. 



Length of drums, . . . . . . . . 16 ft. 6 in. 



Area of heating surface, , 1,886 sq. ft. 



Area of grate surface, 38.9 sq. ft. 



Area through flue, . . . . . . . . 9.2 sq. ft. 



Width of air spaces and metal bars in grates, Air 5-8 in., metal 3-8 in. 



Ratio of heating surface to grate surface, . . . . 48.4 to 1 



Ratio of grate surface to flue area, 4.3 to 1 



Results of Test, Boiler No. 71. 



Test No. 137 

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



Duration, 10 hrs. 



Coal consumed, dry ( including wood equivalent ), . 6,812 Ibs. 



Percentage of ash, 6.4 per cent. 



Water evaporated, . 59,113 Ibs. 



Coal per hour, 634.9 Ibs. 



Coal per hour per square foot of grate, . . . . .163 Ibs. 



Water per hour, 5,510.6 Ibs. 



Water per hour per square foot of heating surface, . .2.9 Ibs. 



