Water reactive chemical incident

In 1996, an OSHA office investigated an explosion and fire which occurred at a custom chemical blending ("toll blending") facility, resulting in the deaths of five employees and the destruction of the facility. The report mentions that "The employees were in the process of making "Gold Precipitating Agent" by blending 5,400 lbs. of sodium hydrosulfite, 1,800 lbs. of aluminum powder, 900 lbs. of potassium carbonate, and 8 liters of benzaldehyde. Sodium hydrosulfite and aluminum powder are highly water reactive and aluminum powder in this quantity has catastrophic potential. Neither of these materials are covered by 29 CFR 1910.119. The employer's representatives stated that they relied on the information in the material safety data sheets (MSDSs) to perform a brief hazard review. This review failed to identify the hazards of that mixture. The mixing was done in a 125 cubic foot blender that had a water-cooled mechanical seal. It is very likely that water inadvertently entered the blend. Mechanical seals are known throughout the industry to be prone to this type of failure. Symptoms of a leak were noted and reported, but only to employees who did not know that water reactive chemicals were to be blended. A mechanical problem developed with the liquid feed system, which had not been checked prior to the addition of the dry ingredients. This caused a deviation from the standard operating procedures and the dry ingredients remained in the blender for a much longer period than originally anticipated. Water entering the subsurface caused the sodium hydrosulfite and possibly the aluminum powder to react, slowly at first. The large volume of powder did not conduct heat readily and the exothermic reaction intensified. In response to noxious gases being released, the employer decided to unload the blender, based upon the information in the MSDS for the finished blend. During the unloading process, an ignition and explosion occurred, propelling the vessel and its concrete supports approximately 48 feet. The pressure wave destroyed part of the facility and caused four of the five deaths; the fifth employee was killed by the ensuing fire, which destroyed most of the plant"
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