360 FARM MOTORS 



gines, kerosene is largely used. Kerosene is also good to 

 remove scale already formed. Where a sight-feed lubri- 

 cator is available, kerosene may be fed through it, but 

 when not the kerosene may be put into a boiler before 

 filling. The kerosene floats, and as the water rises it 

 adheres to the sides and tubes. Avoid using a compound 

 except when absolutely necessary. 



500. Blister. A blister in a boiler is identical with a 

 blister on the hand. On account of imperfect material or 

 dirt, the metal will separate and one part will swell. 

 Wherever there is a blister it is best to cut this part out 

 and patch. If the blister is around the fire, a new half 

 sheet should be put in. 



501. Bag in a boiler. A boiler is likely to bag if dirty, 

 or if a quantity of oil has found its way into it. The oil 

 will stick in one place and keep the water away. Then 

 the fire will overheat this place and the inside pressure 

 force it out. In forcing out the place it breaks the oil 

 scales and allows the water to run in and cool it off. 

 Sometimes it is best to put in a new half sheet where a 

 bag is formed, but often it can be repaired by heating the 

 place and driving it back. 



502. Cracks sometimes form in the flue sheet because 

 the flues are expanded too much. They are often formed 

 in riveting. Whenever a crack is discovered it can be 

 mended by drilling a hole in the end of the crack and 

 putting in a rivet. This keeps the crack from getting 

 larger; then the crack can be filled in. 



503. Laying up a boiler. In laying up a boiler, always 

 clean it thoroughly. Scrape and wash it inside and out, 

 and then paint the outside with black asphaltum or 

 graphite and oil. 



