EMPLOYEE WAS STANDING ON GUARD RAIL OF TAIL PULLEY OF C2 CONVEYER ATTEMPTING TO INSTALL A NEW BELT ON THE CONVEYER. EE HAD POSITIONED ON THE GUARD RAIL OF TAIL PULLEY AND QUARRY MANAGER INSTRU CTED HIM TO GET OFF GUARD. WHILE DOING SO, A WELD BROKE ON THE PIPE GUARD SUPPORT BRACE AND EE FELL TO THE GROUND.