Filled Tank not Explosive.—If a tank is entirely filled with gasoline, it cannot explode. It may leak, and the escaping gasoline is thus brought into contact with sufficient air to aërate it. When this burns it develops a heat; this in turn increases the temperature of the gasoline and increases the rate of evaporation, so that it now begins to issue forth in greater volume, thus adding to the intensity of the flame; and as the evaporation increases, it reaches a point where the tank openings are not large enough to permit it to escape fast enough, and an explosion follows.
Why Gasoline will not Burn Within a Closed Tank.—Now this explosion is attributed to the burning of the gasoline within the tank. Such is not the case, for the reasons stated. It will be found that the difficulty lies in allowing the tank to become filled with an explosive gas, and it is brought about in this way:
If all the gasoline is drawn from a tank, the sides of the tank will retain enough gasoline to form a heavy vapor of hydro-carbon gases. This gas is heavier than air, and, like water, will remain in the bottom. Sooner or later some of the gas will pass out, particularly the lighter portions, and air will intermingle with the gas, and it is then in a ripe condition for an explosion.
It is obvious, therefore, that the first duty is to see that there are no leaks, and when discovered, to repair immediately.
Filling Tanks Having Dried Out Gasoline.—The second, and more important care, is, to be sure and not attempt to fill a tank which has been allowed to run dry, without first blowing out the vapor, if there is any danger from lights. If there is still oil in the tank when you refill, there is no danger from explosions, because the vapor within is too heavy, and requires too much air to explode.
To Extinguish Gasoline Fires.—When a fire actually takes place in a gasoline tank, do not use water in trying to extinguish it. Dry sand, or a woolen blanket will be far more serviceable. The latter should not be applied haphazard, as so many do in the excitement of the moment. Try and remember what it is that the blanket is used for. The object is to try and prevent air from reaching the flame, hence the effort should be to so arrange the blanket that air cannot reach the burning part.
Ammonia as an Extinguisher.—It is better, therefore, to place the blanket around the lower part of the tank, or below the flame itself, so as to prevent air from rushing up into the burning zone. The air coming in from above will soon be inadequate to aërate the flame, and it will be smothered.
A bottle of ammonia, and one should always be kept handy, is the best, in the absence of regular extinguishers, to kill the flame.
The lesson learned from the experiments show, that a large amount of air is necessary to make an explosive compound.
Leaks.—Leaks in tanks can be repaired temporarily, with tire cement, and patches, but as gasoline affects the rubber it should be properly soldered up at the first opportunity.