Used 50 sq. ft. 316L Stainless Steel shell and tube heat exchanger. Mfg. by Alabama Heat Exchanger. Carbon steel shell, 100FV @ 400 F. (24) 3/4" OD tubes, 316L stainless steel, 100FV @ 400 F. 6" diameter x 10'0" tube length. Serial #AHE-1037. National Board #686. Built 2007.