Abstract: EMPLOYEE #1 WAS POSITIONED ON TOP OF A PRESSURIZED VESSEL, READING THE PRESSURE GUAGE TO INSURE PROPER INSTALLATION. HE WAS STANDING ON TOP OF A 4 FOOT BY 4 FOOT BY HALF-INCH STEEL PLATE BOLTED TO A 36 INCH DIAMETER PIPE FLANGE. THE PIPE FLANGE WAS IN TURN BOLTED AT THE FLANGES WHERE A MECHANICAL JOINT AND GASKET WERE JOINED TO A 36 INCH BLANKED-OFF BUTTERFLY VALVE. THE VESSEL WAS INFLATED TO A PRESSURE WHICH EXCEEDED THE DESIGN LIMIT. IMPROPER TESTING PROCEDURE WAS USED. THE VESSEL EXPLODED, THROWING EMPLOYEE #1 INTO THE AIR. HE RECEIVED EXTENSIVE INTERNAL INJURIES, WHICH RESULTED IN HIS DEATH.