Rotary kilns are used in various industries for a range of applications such as drying, calcining, sintering, burning and agglomeration type processes within iron & steel, cement, coking, aggregates, mineral processing industries. Rotary kilns consist of a cylindrical carbon steel rolled plate outer shell with cast steel tyres which run on support rollers and usually driven by a girth gear and pinion arrangement. The inside of the shell is typically refractory lined to protect the shell against thermal damage while preventing heat loss from the process within.
Flame temperatures inside a rotary kiln for the cement industry can approach 2000 °C, with clinker temperatures reaching 1450 °C, while the steel outer shell is kept below 350 °C by the lining. With such high temperatures, some parts of the rotary kiln are prone to distress that can include structural damage through distortion, blistering and potential thermally induced fatigue cracks in the shell, tyres and support rollers.