Fire Safety Science Digital Archive

A series of tests have been carried out on the extinction of a transformer oil tire 30 cm diameter by water sprays applied from single nozzles situated 8 ft. above the plane of the fire. It was found that an increase in the rate of flow and the velocity of the entrained air stream in the spray decreased the extinction time, but within the range of drop size of practical interest in this problem an increase in drop size increased the extinction time. The fire was extinguished more easily when it was not placed directly underneath the spray nozzles. The predominant mechanism of extinction was by cooling the liquid to the fire point. No evidence was obtained that in these experiments extinction took place by the formation of an oil in water emulsion. It is concluded that nozzles should be designed to project water sprays to surfaces where they may cool the liquid to the fire point. The entrained air velocity of the spray assists fine sprays to do this, but there is probably an upper limit to the size of the fire and to the degree of extraneous disturbance beyond which this factor will not operate satisfactorily.