This SA516 Grade 70, three-pass, shell-to-tube heat exchanger is 30" in diameter and approximately 13-1/2' in overall length. It has an internal pressure rating of 136 PSIG at 500°F and an external pressure rating of 15 PSIG (full vacuum) at 100°F. Internally, it has 188 tubes (1/4" diameter) rolled into the tube sheets. The internal pressure rating of the tubes is 103 PSIG at 500 degrees Farhenheit.