EMPLOYEE WAS CUTTING BOLTS OFF OF THE CYLINDERS OF A CRUSHER MANTLE WITH AN OXY-ACETYLENE TORCH. HOT SLAG BURNED A HOLE THROUGH THE ACETYLENE GAS HOSE AND CAUSED A FIRE THAT BURNED THE EMPLOYEE'S RIGHT KNEE. HIS PANT LEG HAD SOME OIL ON IT WHICH CAUSED THE FIRE TO BURN THROUGH HIS CLOTHING.