CHANGING DISCHARGE SCREENS INSIDE #5 BALL MILL. WASHER WAS WELDED TO NEW SCREEN AND ANOTHER WASHER WELDED TO SCREEN ABOVE. CONNECTED TO EACH OTHER BY CHAIN HOIST TO LIFT SCREEN INTO POSITION. WHILE LIFTING AND PUSHING SCREEN INTO PLACE, THEUPPER WELD BROKE, AND THE CHAIN HOIST FELL KNOCKING EMP HARD HAT OFF AND STRIKING HIM ON THE HEAD.