The HET heater is an indirect fired unit designed for most applications where there is a requirement to heat ambient process air to temperatures of up to 300°C in one lift. The unit consists of a stainless steel concentric tube type heat exchanger mounted in a mild steel chamber.

The outer casing of the unit is generally manufactured from carbon steel; it is double skinned and insulated with mineral wool. The unit can be constructed totally in stainless steel.

The inner assembly consists of a stainless steel combustion chamber and concentric cylinder heat exchanger; these are independently mounted within the casing to allow for differential expansion. The chamber is fitted with end inspection covers to facilitate cleaning.