Experimental investigation on PMMA dust explosion venting at elevated static activation pressure

Vented PMMA dust explosions were conducted in a 20-L spherical chamber with a venting diameter of 80 mm. The flame behaviors and overpressure characteristics at different dust concentrations and static activation pressure were studied. The development mechanism of external flame and the comparison results with two standards were analyzed. The results showed the reduction of dust concentration was necessary for mitigating the external flame, while blindly decreased the static activation pressure would bring greater risk. The characteristics of reduced explosion pressure inside the chamber were analyzed combined with external pressure. Then the rupture mechanism of the venting diaphragm was established based on the elastoplastic analysis. Two empirical modified equation for NFPA68 and EN14491 was established. For NFPA68, the volume correction coefficient of size effect was introduced and the inapplicability of NFPA68 at elevated static activation pressure was attributed to ignoring the compressibility and the choking phenomenon of high-speed fluid.