The arrangement is for positioning equipment in association with an opening in a boiler wall and has a rotation mechanism that rotates the equipment around a virtual rotation axis that lies within the outer wall of the boiler. During the use of a liquor spreader for the introduction of combustible material, the opening of the liquor spreader is arranged in the virtual center of rotation so that the point at which the combustible material is introduced is retained independently of the angle of rotation. The liquor spreader is united either with a glide device or the guide in the rotation mechanism.