Abstract: On November 16, 2011, Employee #1 and Employee #2 of Titanium Metals Corp of America were removing the four large bolts, from a magnesium recovery electrolytic cell, that connected the cell to a flexible direct current buss system. The Magnesium Recovery Operator (MRO) had reduced the current from 83,000 amperes and was holding it at zero amperes with a control circuit. The operator locked it out. Employee #1 and Employee #2 placed their locks on a group lockout device. The MRO had failed to place the control circuit (43MA switch) on the rectiformer main panel, back into semi-automatic after tapping down the amperage from 83,000 to zero. With the rectiformers in auto mode, rectiformer #1 unexpectedly energized the direct current buss system. Employee #2 removed the nuts from the first three shunt bolts with an uninsulated three foot cheater bar. Employee #1 was between the direct current buss system and the cell. He was removing locking pins from each bolt with an uninsulated center punch and an insulated brass hammer. Employee #1 removed the locking pin from the third bolt and upon striking it with the center punch there was a small flash and he was temporarily blinded. Employee #2 asked to switch places with him and attempted to remove the locking pin from the fourth bolt. Employee #1 went to the outside of the cell, in-line with the fourth bolt. Employee #2, between the buss system and the cell, struck the locking pin with the center punch and there was a large arc flash. Witnesses stated that they heard three explosions (arc flashes). Employee #1 was burnt over 50 percent of his body and Employee #2 suffered burns over 20-30 percent of his body.