Boilover 4
Boilover 4 : Crude oil often contains some entrained water and/or an emulsion layer. In addition, crude-oil storage tanks will have some accumulations of water on the uneven tank bottoms. In a fire when a heat wave is formed and comes in contact with great force. The evolution of the steam explosion can be understood by examining the reaction of water to high temperatures. When water is heated to its boiling point of 212F., water vapor, or steam, us generated. the steam that is produced expands approximately 1,700 times in volume over the volume of the water that boiled away. Should a heat wave of a temperature well above 212 F. contact any water entrained in the oil, or some of the bottom water, which is usually in larger quantities, it can be readily imagined that this instantaneous generation of steam will act like a piston, causing the oil to be flung upward with considerable violence. When the reaction is so strong, it causes the oil to overflow the tank shell. This sudden eruption is what is known as a boilover. Boilovers of sufficient magnitude, to cascade enough burning crude oil out of the tank to not only cover the entire dike area but even enough to overflow the dike wall as well, have occurred. When the hot oil and steam reaction takes place, the oil is made frothy, or sudsy, which in turn further increases its volume. The reaction resulting from the heat wave contacting entrained water can be expected to be of lesser activity than from contact with bottom water. The reason for this difference is that the quantities of water converted to steam in a given spot are usually less. Of course, with entrained water, there possibly can be several of these "frothover" - type eruptions during the progress of the fire
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