Explosion Prevention in Dry Dust Collection Systems

To reduce the risk of dust explosions in propellant and explosive manufacturing plants, dust is captured as it is generated and transported through ducts to filters, separators, or collectors. However, the dust collection systems may potentially contribute to the accident potential within the plant. A series of site visits was made to measure the electrostatic potential buildup and the dust concentration levels in ducting actually present during normal plant operations. These data provide a base of plant operating conditions upon which one may evaluate the safety of dry dust collection systems. A survey was conducted to determine if off-the-shelf instrumentation exists which will measure dust concentrations dynamically at levels within the explosive range. Most dust explosive characterizations are conducted using the Hartmann apparatus. This instrument is useful for evaluating relative characteristics of dusts. However, it has been shown that this instrument underpredicts both the peak pressure and the pressure rise rate for full-scale explosions. In designing explosion venting or explosion-resistant structures, data obtained in larger chambers are needed to allow the prediction of full- scale trends. A series of experiments was conducted using 40- and 1000-liter vessels to characterize the peak pressure and pressure rise rate for several explosive dusts.