ECONOMICAL USE OP FUEb IN CREAMERIES. 45 



ashes or sand or some similar material, thus reducing heat losses, and 

 should cracks form in the walls, this fine material will run into and 

 fill them and prevent the air from leaking into the furnace or com- 

 bustion chamber. The exposed top of the boiler should also be cov- 

 ered with a layer of sand or ashes, or a layer of asbestos blocks or 

 insulating brick may be substituted. By properly insulating the 

 boiler setting, uptakes, and breeching the heat loss can be easily 

 reduced one-half or more. 



The heat lose through incomplete combustion is an extremely 

 variable quantity in creameries where the firing of the boiler is done 

 at irregular intervals. In most of the smaller plants no regular fire- 

 man is employed, hut some one engaged in other work around the 

 plant is depended upon to fire the boiler; consequently the firing 

 is not given the proper attention. In the larger and better-managed 

 plants, however, this loss is not more than about 2 per cent, which 

 can be practically eliminated .through careful firing. 



There is a certain amount of heat loss in the stack that is neces- 

 sary to maintain the dr'aft for burning the fuel, and hence can not be 

 eliminated. In practice it is found that twice the theoretical amount 

 of air is necessary for complete combustion of the fuel. Assuming 

 that twice the theoretical amount of air is supplied and that the coal 

 used has a heat value of 13,500 B. t. u. per pound, then the neces- 

 sary heat lost in the stack, as given in the table, is 19.15 per cent. It 

 is impracticable to reduce this loss to any appreciable extent. 



The greatest operating loss is that due to excess air which is allowed 

 to leak into the furnace and combustion chamber through cracks in 

 the walls of the setting, firing doors, doorframes, and other points. 

 This is a loss that can be entirely eliminated if all cracks are care- 

 fully stopped and the air supply through the openings in the ash pit 

 and firing doors is properly controlled. 



The loss due to. heating the moisture in the coal is one that is im- 

 practicable to eliminate or- reduce. The loss depends, of course, upon 

 the amount of moisture contained in the coal, but seldom exceeds 2 

 or 3 per cent. 



Soot is one of the best-known insulators. Consequently if allowed 

 to collect on the heating surfaces of the boiler it will reduce mate- 

 rially the amount of heat passing through the heating surfaces to the 

 water inside the boiler. The loss from this source may be entirely 

 prevented. The remedy lies in keeping all heating surfaces clean. 



Nearly all boilei'-feed water contains scale-forming impurities. 

 Rain water, while not containing scale-forming material, always 

 contains carbonic and often sulphuric acid, and hence should never 

 be used as boiler- feed water on account of pitting and corroding the 

 boiler plates. The heat loss f ronl scale deposit depends, of course, on 

 the thickness and nature of the scale formed. While in the foregoing 



