The Hearson Tobacco Oven has been designed to meet the stringent requirements of the industry for moisture testing. The oven provides a continuous flow of pre-heated air which passes over tared sample pans for drying purposes.

The unit comprises a cylindrical drying chamber in which is placed a stand carrying 12 circular copper trays; each tray is designed to take six stainless steel sample pans (TKE186). The top of the drying chamber is enclosed by a hinged insulated lid. In the centre of the chamber is an air distribution tube through which pre-heated air passes over the pans to facilitate the drying process.

The drying chamber is enclosed in a second, larger chamber providing a combined water reservoir and steam boiler in which is housed a copper coil. An immersion heater maintains the water at boiling point. Surplus steam is discharged from the top of this chamber to an air cooled condenser, with the condensate returning by gravity to the reservoir, thus sustaining the water level.

An electrical blower at the base of the oven passes air through the heated copper coil; it then enters the drying chamber through the air distribution tube. After passing over the sample pans, the air escapes to atmosphere via the vent provided in the centre of the lid. The oven is controlled using fused on/off switches for both the heater and air blower. An ammeter is fitted above each switch to indicate the combined load. Air flow through the drying chamber is regulated by a valve and measured by a rotameter calibrated over the range 2 to 20 litres/min