Abstract: On December 6, 2016, an operations employee had already locked out the suction and discharge valves for pump AC-11. It was discovered that the drain line valve for AC-01 was faulty and could not open to drain hot monomer. A Safe Work Permit that called for a line break using an Unusual Job Permit (UJP) was issued on December 6, 2016 at 7:30 am. The pump jacket was drained of its heat transfer medium (HTM) oil into a black 55-gallon drum, prior to maintenance mechanics splitting open pump AC-11 for the first line break at around 12 noon to drain hot PET monomer. Once the maintenance mechanics had completed the first line break by separating the volute from the pump, hot PET monomer was expected to spill onto the floor around the pump, cool and solidify. Around 12:10 pm, a pressure blast occurred that blew out the right side of the pump about 10-15 feet through the air. The employee was struck by the blast and smashed into the adjacent concrete block wall. The employee was killed from the blast.