FOREMAN WAS WELDING ROUND SEAM INSIDE OF TANK. AUTOMATIC HUNG ON HOOK LADDER BURNT HOLE THRU SHELL, FIRE FELL DOWN ON OUTSIDE AND STRUCK EMPLOYEE. HE GOT UP TO MOVE SAFETY LANYARD CRADDLED ARO UND LEFT KNEE CAUSING HIM TO GET OFF BALANCE ANDHE FELL TO THE GROUND ABOUT FIVE FEET ON LEFT ANKLE.