Air Heater tube, recovers heated air or preheats before expelling this air into a boiler’s combustion chamber, thereby making the boiler more efficient. Air temperatures can range from 150 to 200° Celsius depending on the heater’s design specifications. The design will dictate whether air passes either within the tube or outside between the tubes. In designs where air or gas flows over the tube, the air heater is often designed such that the tubes are positioned horizontally which if the tube are long, could lead to them sagging. These designs often necessitate that soot blowers to be employed to clean or blow off the ash deposits on the air heater tube in so as not to compromise it’s efficiency.
Air Heater design and it’s influence on Air Heater Tube
Where gas flows through the tube, the air heater is often designed such that the air heater tube is positioned vertically. The risk of ash deposits plugging the tube becomes an issue, therefore larger diameter air heater tube is sometimes specified.
Tube diameter tends to be 50.8mm or 63.5mm OD with gauges ranging from 2.0mm to 2.8mm and sometimes even 3.0mm. Smaller diameter tube sizes, can result in increased pressure drops across the air heater as well as ash clogging which can sometimes be a challenge to overcome. Neven Matthews (Pty) Ltd produces air heater tube to BS 6323 as well as other international al specifications. In order to prolong the lifespan of the tube, Corten-AF steel is sometimes specified as this offers additional protection against cold end corrosion.