Inspection Detail

Inspection: 117946434 - Pacific Scientific

Inspection Information - Office: San Francisco Ro

Investigation Summary

At 11:00 a.m. on April 9, 2003, Employee #1, Employee #2, and Employee #3, were burned in a deflagration or rapidly burning flash fire. Pacific Scientific manufactured propellant for military aircraft ejection seats at this facility. The plant was located on the Gila River Indian Community, a Native American Trust Land. At the time of the accident, employees were scraping a mixture that was about 75 to 80 percent ammonium perchlorate off the mixing blades of a five-gallon Baker Perkins mixer. The Bureau of Alcohol, Tobacco and Firearms (BATF) classified ammonium perchlorate as an explosive and this incident as a deflagration. The incident occurred in Bay 6 of Building 29. Bay 6 was about 15-feet wide by about 30-feet long. It was separated from the rest of the building by walls that ran from the floor to the ceiling. There was a door to the exterior and an interior opening to another section of the building. There were two mixers in Bay 9, a one-gallon mixer and a five-gallon Baker Perkins mixer, the one involved in the accident. The exterior walls of Bay 9 were split open and bowed slightly outward in places after the accident. The propellant mixing process called for placing a specific particle size and quantity of ammonium perchlorate in the mixing bowl, blending the mixture with the mixer's blades, mechanized removal of the blades from the mixture, manual scraping with spatulas of the ammonium perchlorate mixture from the mixing blades into the bowl, moving the bowl on rails along a table, and the addition of another particle size and quantity of ammonium perchlorate. These basic steps were repeated until the final mixture was obtained. At the time of the accident, the three employees were using spatulas to scrape the mixture off the mixer's blades. One employee used a stainless steel spatula, which was not a non-sparking tool, to scrape the mixture off the blades. According to the company's procedures only non-sparking spatulas were to be used in this process. The company's written procedures called for wooden tongue depressors. The company's safety manager and the company's production manager said that beryllium spatulas could be used. The employee who used the stainless steel spatula told BATF agents that he saw a flame start underneath his tool while he was scraping. It seems that friction from the stainless steel spatula ignited the mixture of ammonium perchlorate. Pacific Scientific consultant's report indicated that the ammonium perchlorate's particle size present at the time of the incident was very sensitive to friction. Since the source of ignition was difficult to determine and all the variables were difficult to control, automatic or remote control devices to remove the mixture from the mixer's blades and shielding of personnel appears to be the most effective way to prevent similar injuries from occurring in another incident. Violations were proposed for the failure to ensure that only non-sparking tools were used with explosives, the failure to train employees in safe work practices and the process' procedures, the failure to require the use of all the personal protective equipment to prevent burns, and the failure to lockout/tagout the controls for the mixing blades The employees had burns over about 60-percent of their bodies. Employee #1 had third-degree burns over about 30 percent of his body. Employee #2 had third-degree burns over less than 30 percent of his body. Employee #3 had third-degree burns over more than 30 percent of his body and died on April 17, 2003.

Keywords: BURN, FIRE, MIXER, LOCKOUT