Arrangement for supporting a rotary drum

An arrangement for supporting a rotary drum, said rotary drum having at least three riding rings distributedly arranged along the axial direction of the rotary drum, the arrangement comprising a pair of relatively spaced rollers for supporting a riding ring, at least one bearing for each roller, a support for each bearing mounted for movement of the roller toward and away from the shell of the rotary drum and spring means exerting a spring force acting on the support so as to counteract the weight of the rotary drum resting on the rollers, wherein the spring means comprise a pressure vessel charged with a compressed gas that exerts the spring force and wherein the rotary drum comprises at least three riding rings and only at least one middle ring arranged between two outer rings is supported by a pair of relatively spaced rollers that are equipped with said spring means comprising the pressure vessel charged with the compressed gas.