Laboratory-scale testing of titanium powder fire extinguishment using water

Metal powders, such as those used in additive manufacturing, can pose a high fire hazard due to faster heating times relative to larger ingots or parts. Current industrial standards recommend special agents for manual extinguishment of metal powder fires and not automatic protection systems such as sprinklers. In this work, laboratory-scale experiments were conducted to understand the behavior of titanium powder fires when subjected to water sprays. Aluminum powder, although combustible when dispersed in air, could not be ignited in the configurations tested. Powder was ignited in a straight channel to evaluate flame propagation rate and characteristics during spray application. Additionally, piles of powder were ignited to assess the possibility of extinguishment in scenarios with larger flames. These exploratory experiments revealed that upon water delivery, ejected powder plumes caused intensification of the fire. These powder plumes were caused by the vaporization and expansion of water trapped beneath the powder surface. Most importantly, it was determined that a water flux threshold exists where cooling from the water spray can overcome intensification effects and yield effective fire suppression. Contrary to existing recommendations, automatic sprinkler protection may be effective for metal powders in storage applications, however future investigation is required at larger scales.