350 cox. 



absorbed when a low steam pressure is used, there is a limit 1}elow which 

 one can not go, for new losses appear which more than compensate 

 the gain. 



Badiation. — A portion of the heat value is lost bj' radiation through 

 the fire doors and furnace walls. By the use of a larger furnace and 

 boiler the exothermic loss would be less. More favorable figures than 

 mine have been attained by the Manila Electric Light and Eailroad 

 Company for Australian coal of the same source and similar comjDOsi- 

 tion as that of tests Nos. 1 and 2, Table II; however, it must be remem- 

 bered that they operate their steam boilers in large units and that my 

 figures are thoroughly representative of plants of 75-horsepower rating. 



Other factors. — Tliere are many other factors which enter into con- 

 sideration such as the physicial condition of the coal,-'' small experimen- 

 tal errors in its use, personal variables, air leaks which dilute and cool 

 the gases before absorption takes place, relative load carried, moisture 

 from the air and the water of combustion which must be expelled through 

 the stack as superheated steam, etc. Perhaps the greatest of these 

 variables are the fireman and the moisture of the air. 



As a rule; the fireman is a cheap laborer secured more for his muscle than 

 his brains, is indifferent to liis work and does it in the way that requires the 

 least energy and initiative on his part. A fireman must be intelligent or have 

 constant intelligent supervision to obtain good results. In hand firing, instead 

 of carefully spreading the coal or coking it and then working it back gradually, 

 a stoker will often spread over the fire a tremendous amount of green coal. 

 In this way the flames are smothered, the instantaneous evolution of combustible 

 gases is out of all proportion to the supply of air, they are cooled perhaps below 

 their ignition temperature and thus a large quantity leaves the system uuburned. 

 A deep fuel bed is called for in a producer-gas plant, but in steam boiler practice 

 where a complete combustion is desired so that all of the carbon of the fuel 

 will be converted into carbon dioxide a thin fuel bed is needed. When it is 

 noticed that the steam pressure does not respond to the new supply of coal, 

 the fireman with a slice bar or hoe will stir up the new fuel togttlier with 

 that already on the grate, the result being still further loss of coal. Greath* 

 increased evaporation and saving of coal will be obtained by prohibiting these 

 practices. The tendencj' of most stokers is toward a too frequent use of the 

 bar. If Philippine coal is properly stoked it is not necessary to poke the fire 

 at all. I have made a test of seven hours on this coal without once putting a 

 bar in the fire box. 



The great difference in the moisture going into a furnace day by day, 

 largely due to the variation of the daily humidity as well as that Ijetween 

 the dry months and the rainy season, had often been noted; but it was 

 left for Mr. Gayley'^ to obtain definite data and show the considerable 



" There is a marked tendency of the coal from certain parts of the Philip- 

 pines to fall to pieces. Care must be exercised to prevent the production of a 

 large amount of slack in handling for it reduces the value for steaming 

 purposes. 



'^'IroH and Steel Inst. (1904), October. 



