A CREW WAS WORKING INSIDE OF CYCLONE, ONE WORKER WAS RECEIVING A 10'SCAFFOLD LEG TO PLACE INSIDE THE CYCLONE WHEN IT CAUGHT ON THE INSIDE RING. AS HE PULLED IT AWAY FROM THE RING A LARGE PIECE OF REFRACTORY BROKE LOOSE. INJURED EE WAS WORKING BELOW THIS WORKER AT THE TIME & WAS STRUCK BY THE FALLING REFRACTORY ON HIS RT. THUMB.