Glovebox Fire Suppression Experimental and Computational Characterization

Abstract

Gloveboxes are generally used to protect workers from the potential hazards that arise in the materials they are working with. In the middle of the 20th century gloveboxes were mainly used to protect workers against radioactive materials. Factory Mutual investigated accidents involved in gloveboxes at nuclear facilities from 1956 to 1965 that resulted in damages and contamination clean up efforts reported at $1,232,000 ($8.5 million in 2012 dollars) [1]. Fire suppression systems are therefore a key aspect to glovebox safety. Use of water based systems generally result in undesired transport of hazardous materials [2]. Halon suppression systems were used but due to its large potential to deplete ozone was phased out in the latter part of the 20th century. Activation tests of a commercial automatic fire suppression system (Fire Foe™) containing heptaflouropropane (FE-36) fire suppressant were conducted within a glovebox at the University of Texas Fire Research Group’s burn structure. Ten tests were conducted at four different fire sizes: three 13 kW, one 20 kW, three 25 kW, and three 50 kW. Activation times and gas temperatures were recorded. Gas temperatures from experiments were compared against NIST’s Fire Dynamics Simulator (FDS) gas temperatures with good agreement. More stratification was observed in experimental temperatures compared to FDS temperatures. The time and spatially averaged net heat flux on a virtual Fire Foe™ tube from the FDS simulations were passed to a thermo-physical semi-empirical submodel to predict activation. The submodel did not capture the exponential nature observed in the data of activation times versus fire heat release rate. Work is continuing on improving the submodel to capture the observed events.