154 STEAM BOILERS 



thus set free. This pipe will also serve to lead off the air in 

 the upper part of the tank during the operation of filling, and 

 will thus prevent undue pressure from accumulating. The 

 cross-sectional area of the ventilating pipe should be equal to 

 that of the rilling pipe. Care should be taken in locating the 

 ventilating pipe to see that no naked light can approach its 

 upper end; moreover, the openings in this end should be pro- 

 tected by a return elbow having wire gauze firmly fastened 

 over it. The gases rising from the oil, when mixed with air in the 

 correct ratio, form an explosive mixture, and could be ignited 

 by a naked flame. This flame, however, would not pass 

 through the fine meshes of the gauze, and the latter therefore 

 forms a safety device; also, the downward curving of the elbow 

 prevents any sparks from dropping into the opening. In addi- 

 tion to the ventilating pipe there should be a telltale, which is 

 a device for indicating the amount of oil in the tank at any 

 specified time. 



Installation of Oil Tanks. To conform with the require- 

 ments of underwriters and city ordinances, any oil-storage 

 tank located above the surface of the ground should be at least 

 200 ft. from inflammable property. Moreover, the top of the 

 tank should be at a lower level than the lowest pipe in the oil- 

 burning system, so that, in case a valve is inadvertently left 

 open, the plant will not be flooded with oil. If the tank is 

 placed underground, as is usually the case, its top should be 

 at least 2 ft. below the surface of the ground, and it should be 

 30 ft. distant from the nearest building; also, the top of the 

 tank should not be at a higher level than the lowest pipe in the 

 oil system. These, precautions in locating the tank or tanks 

 are necessary because of the highly inflammable nature of crude 

 oil and fuel oil. 



Separation of Water From Oil. The crude oils invariably 

 contain water in greater or less proportions. When the oil is 

 run into the storage tank, the water, being heavier, sinks to 

 the bottom of the tank and gradually accumulates. If the 

 suction pipe extends to the bottom of the tank, some of this 

 water will be drawn to the pump and forced to the burners, 

 extinguishing the fires. To prevent this trouble, provision 

 should be made for the removal of water from the oil tanks. 



