Fire Safety Science Digital Archive

It is commonplace in industrial installations to have duct vented vessels, the design of which is often based upon the premise that central ignition will provide the worst case scenario. This research investigates duct-vented explosions using a vented test chamber of 200 l capacity fitted with a 1m long vent pipe, discharging into a large (50 m³) dump volume with rear and central ignition. Propane-air mixtures over a range of concentrations (?=0.8-1.6) have been used. Results show that while there is no significant difference in maximum pressure in the test vessel for rear and central ignition, rear ignition consistently produces the worst case in terms of rates of pressure rise and flame-speeds in the duct. In addition, the detailed records of pressure traces and flame position showed a direct relationship between the induced gas velocity in the duct prior to the flame arrival and the subsequent rate of pressure rise in the vessel. The implications of the findings for practical systems are briefly discussed.