Used 50 sq ft Carbon Steel shell and tube heat exchanger. Manufactured by Alabama Heat Exchanger. Rated 100PSI/FV @ 400F. (24) 3/4" OD 316L stainless steel tubes 100PSI/FV @ 400F. 6" diameter x 10'0" tube length. National Board #690. Serial #AHE-1041. Built 2007.