Burning of pools of electrical-insulating oils

The spread of flame from a wick across pools of two electrical-insulating oils and the subsequent burning of the pools have been studied in the presence and absence of flame retardants added to the oils. The time required for the flame to spread across the pool, the ensuing rate of burning of the complete flame, and the composition of the burnt gases have been measured with no additive present. The times required for the flame to spread have been compared with between zero and a range 0.2 to 20% by volume of halogen-containing inhibitors present. The times required for flame spread with the untreated oils are governed by the interaction of heat transfer from the wick flame to the pool, the growth of convection currents in the pool, and the resultant evaporation of the more volatile fractions of the oil from the surface of the pool. The relative efficiency of the additives, CH₂I₂ >CH₂Br₂ >CCI₄ >CICHCCI₂, suggests that in the mechanism of inhibition the more efficient act as chemical inhibitors.