Muller Mixer Fire - Lessons Learned

The purpose of this paper is to share some of the actions taken by Morton Thiokol, Inc. to enhance safety in pyrotechnic muller mixing operations at Longhorn Army Ammunition Plant. These initiatives resulted from the investigation of a muller mixer fire which occurred on October 30, 1985. It is the safety management philosophy of Morton Thiokol Ordnance Operations that all explosive accidents and significant near miss incidents be thoroughly investigated, by the Engineering and Safety Committee, utilizing a safety systems approach. This committee was charged with identifying the causative deficiencies and ancillary procedural, equipment design and human engineering changes required to enhance the overall system. Without belaboring all the causative possibilities considered the following four were considered the most probable in order to priority Friction due to Mechanically Damaged Lip Seal in Muller Wheel Friction Between Material Contamination in Bearing Friction Between Plow Blades and Bowl and Exothermic Moisture Reaction.