STUDIES ON THE BURNING BEHAVIOR OF METAL-POWDER FIRES AND THEIR EXTINGUISHMENT .2. MAGNESIUM POWDER HEAPS ON INSULATED AND CONDUCTING MATERIAL BEDS

This paper is the second in a series and covers the burning behaviour of individual heaps of magnesium powder on a sand bed, and on aluminiu m, copper and mild steel sheets and bowls. Ignition followed the proce dure described in Part I of this paper. It is found that beds of insul ated and conducting materials influence the burning behaviour of the m agnesium powder heap significantly. Thus, the severity of a fire in 10 0 g of magnesium powder is greatest on a sand bed and least on a metal bowl bed. Analyses of the temperature-time distribution curves reveal that if the shape of the bed is not flat, then temperatures attained in the top and bottom layers of the powder heaps are less than the cor responding values obtained when the beds are flat surfaces. Studies of individual heaps of magnesium powder on sand beds has established tha t the burning behaviour of heaps containing less than 100 g is differe nt from those with 100 g or more. During the burning of 400 and 800 g metal powder heaps, white flames of about 225-300 mm height were obser ved.