Mining Publication: Ignition Hazard From Internally-generated H2 in Sealed Mining Equipment

A number of ignition incidents involving mining and farm equipment have illustrated the surprising danger of drilling, cutting, or otherwise penetrating sealed compartments or frames that are filled with metal scrap for ballast. The presence of chemically-reactive metals (or electrochemically-active pairs), such as zinc in galvanized steel, can produce hydrogen from moisture in the steel scrap, and the resulting pressure, due to the internally-generated hydrogen, can produce an easily-ignited gas jet when the sealed component is penetrated. Hydrogen or methane production is also possible in contaminated steel scrap by microbial action. Thus, the simple act of drilling a hole in such equipment can have disastrous consequences to the operator behind the drill. The lesson learned from these incidents is that sealed and filled equipment components must be treated as if they contained a flammable gas at considerable pressure. Penetration of such equipment should be done remotely, in a safe area, or with a drill used to penetrate high-pressure natural gas lines safely (the method that both NIOSH and the Australian investigators used). The above potential hazard can be minimized by providing a vent hole or valve in such sealed systems, or insuring that only clean and dry-carbon steel scrap is used.