 The mass of a typical 6 x 60 m kiln, including refractories and feed, is around 1100 tonnes, and would be carried on three tyres and sets of rollers, spaced along the length of the kiln.The longest kilns may have 8 sets of rollers, while very short kilns may have only two.Kilns usually rotate at 0.5 to 2 rpm, but sometimes as fast as 5 rpm.