Abstract: A device for removing irregularities in or enlarging a buried duct comprises a cylindrical housing corresponding approximately in diameter to the required diameter of the duct, an expandable shell comprising a plurality of tapered leaf members pivotally attached at their rear ends to the front of the housing, and remotely controllable drive means for moving the leaf members between contracted and expanded configurations. In operation, the apparatus is drawn through the duct with the leaf members in a contracted configuration in which they enter a portion of the duct of a diameter less than the required diameter. The drive means is operated to force the leaf members outwardly against the sides of the duct to expand the duct. The leaf members are then retracted and the apparatus is drawn forward. The apparatus is particularly intended for preparing damaged sewers prior to fitting an inner, lining pipe.