USED APPROXIMATELY 800 SQ. FT. HORIZONTAL HEAT EXCHANGER. CARBON STEEL SHELL. 316 S/S STAINLESS STEEL TUBE SIDE. CARBON STEEL FLAT HEADS. APPROXIMATELY 20" DIAMETER X 12' STRAIGHT SIDE. (340) 3/4" 16 GA TUBES MANUFACTURED BY GRAHAM. SHELL RATED 75 PSI @ 250 deg. TUBES RATED 50 PSI @ 250 deg F. BUILT 1975. NATIONAL BOARD #6953. S/N 5090-74-2.