Dust explosion venting of small vessels at the elevated static activation overpressure

Four venting diameters were chosen to carry out the simple venting experiments of 70 μm lycopodium dust explosions in a 20-L chamber at the elevated static activation overpressures ranging from 1.2 bar to 6 bar to evaluate the vent sizing correlations proposed by NFPA 68:2007 and EN 14491:2006. Before conducting dust explosion venting experiments, the static activation overpressures of the membranes at different vent diameters and different membrane layers were firstly determined. The linear relationship was quantified versus membrane layer at four venting diameters. The experimental results in a confined 20-L chamber represent that the maximum overpressure is 6.5 bar at 750 g·m− 3 and the maximum rate of pressure rise is 283.0 bar·m·s− 1 at about 1000 g·m− 3 for 70 μm lycopodium dust. The comparison of simple venting results and the calculated results according to NFPA 68 and EN 14491 at the elevated static activation overpressures shows that NFPA 68 results have a good predictive ability in a certain range of vent diameters. The predictive results tend to be conservative for small vent diameters and dangerous for large ones. EN 14491 results are too conservative and unreliable. The reasons of vent sizing divergence between the NFPA 68 results and EN 14491 results at the elevated static activation overpressures were analyzed according to the empirical functions.