Used 61 sq.ft. horizontal shell & tube heat exchanger, Mfg. by Doyle & Roth, U-tube type. 316L stainless steel shell rated for 100 psi @ 350 Deg. F, -20 Deg. F @ 100 psi, 316L stainless steel tubes rated for 100 psi @ 350 Deg. F, -20 Deg. F. @ 100 psi. Serial #J-6318-3, National Board #14994, Year Built: 1990, Previous Service: Carbon Treatment, Heater/Cooler - Multi-purpose.