Circulation heaters are the equivalent to tube and shell heat exchangers with the particular feature that the core bundle is manufactured with electric tubular heating elements. Circulation heaters are used in applications where a process stream needs to be heated to a finely controlled set-point. Typical applications include: air/gas superheating, oil pre-heating, steam superheating, fuel pre-heating and others. Circulation heaters are designed and manufactured in accordance with ASME Section III, Class 1, 2 or 3 and stamped N according to code requirements. Immersion heaters also are designed and manufactured under ASME Section VIII, Div 1 for non nuclear code applications.