(2 EMPLOYEES WERE INJURED IN THIS ACCIDENT.) WHILE CHANGING HL LEG JACK ON #72 SHIELD, BLOWING UP NEW LEG TO INSTALL KEEPER, THE VALVE EXPLODED SENDING PIECES OF METAL FLYING. METAL STRUCK EE IN HIS RIGHT HAND AND THUMB AND THE VALVE STRUCK HIS LEFT KNEE. (VALVE ON TOP STAGE WAS SHUT OFF.)