THE THREE MEN WERE IN THE PROCESS OF REPLACING A WORN PIPE IN THE PREP PLANT AT THE TIME OF THIS INCIDENT HAD REMOVED A 27"" X 33"" PIECE OF METAL GRATING FROM THE FLOOR. CO-WORKER WAS CUTTING T HE BOLTS OUT OF THE OLD PIPE AND INJURED WAS WATCHING HIM. HE ASKED INJURED TO GET HIM A WRENCH. HE TURNED FORGETTING THE HOLE & WALKED INTO IT. HE APPARENTLY FELL FORWARD STRUCK HIS CHEST ON