Abstract: Employee #1 and two coworkers, members of the company's sanitation crew, had cleaned the filter in the plant's water filtering system. After setting it back in the bottom section of the 18 in. diameter tank, they put on the cap and tightened down the ring clamp, sealing the cap to the bottom. During the tightening process only one nut on the ring was tightened all the way down; the other nut had an approximately 1 1/4 in. gap between the two sections of the ring. When the water was turned on to fill the tank, pressure built up in the tank because the bleed off valve was not open. The tank cap blew off, striking Employee #1 on the left side of his forehead. He was killed.