Gas Explosions Mitigation by Ducted Venting

The mitigation of effects of gas and dust explosions within industrial equipment is effective if venting the combustion products to safe location. The presence of relief duct is however likely to increase the severity of the explosion with respect to equipment vented to open atmosphere, due to secondary explosions occurring in the initial sections of duct, frictional drag and inertia of the gas column, acoustic and Helmholtz oscillations. The weights of these phenomena on explosion enhancement in terms of peak pressure and rate of pressure rise are still uncertain. As a consequence, appropriate design of duct-venting configuration is still a matter of debate. We recently found that the main phenomenon among those cited is the burn-up occurring in the initial section of duct, which leads to the backflow from the duct towards the protected vented equipment, thus restricting the effective vent section and turbulizing the flame within the combustion chamber. Starting from this result, we have identified dimensionless numbers which quantifies the burn-up effects and then we identified engineering correlations for the appropriate design of relief section in the presence of duct.