In an oil refinery’s ethylene project of Indonesia, air-cooled heat exchangers are required for the gas oil hydrotreating process. The product of hydrogen cracking process is separated high-pressure hot gas which consists of hydrogen sulfide(H₂S), ammonia(NH₃), nitrogen(N₂), etc. Considering the harsh conditions, Incoloy 825(UNS N08825) materials are chosen for the manufacture of the air-cooled heat exchanger.

The design pressure and design temperature for tube-side pass are 15.2 MPa and 250°C respectively with flow media of hot gas(H₂S+NH₃+N₂ ,etc). The design pressure and design temperature for shell-side pass are 0.1 MPa and 35°C respectively with flow media of air. The air-cooler dimensions are 10.5m(length) x 3m(width).

The air cooled heat exchanger mainly consists of headers, plug-type tube bundles and joint flanges. The header is made of Incoloy 825 plates (ASTM B424 UNS N08825) in solution annealed condition. The tube bundles are made of Incoloy 825 seamless tubes manufactured to ASTM B163 Gr. N08825 also in solution annealed condition. The joint flanges shall be manufactured to ASTM B564 Gr. N08825 forgings. Especially, the tube bundles are furnished with finned tubes. The extruded aluminum fins are firmly seated on the Incoloy 825 base tubes.