EMPLOYEE WAS HELPING MECHANIC CLEAN OUT ROTARY VALVE. CORNER BOLT WAS LEFT IN FLANGE TO HOLD UP VALVE. WHILE LIFTING ROTARY VALVE TO PUT BOLTS BACK IN, FLANGE BROKE CAUSING VALVE TO FALL (VER Y HEAVY). WHEN THE VALVE FELL IT STRUCK HIM ON LEFT KNEE AND FOOT CAUSING BRUISES AND LACERATION.