INADEQUATE REPAIR OF AN AMMONIA VESSEL KILLS 3

The 109D-C was one of three identical vessels at the facility that removed moisture and carbon monoxide from a synthesis gas used in the manufacture of ammonia. The 109D-C, which had been taken off line to replace its desiccant material, had been online for approximately 11 1/2 hours when the vessel exploded into flame. One employee was killed instantly in the explosion and 6 more suffered severe burns. Another employee, a crane operator, suffered from severe burns and was hospitalized for several weeks before he died. An ammonia operator, was standing on the catwalk above the 109D-C when it exploded. He also suffered severe burns and died several weeks later. Subsequent inspection of the vessel revealed a cracked weld. Apparently, an inadequate repair job had been made to the weld two days before the accident. 

Source:osha.gov