An apparatus for keeping a slotted tubular liner in axial alignment with a seamer head through which it is passing adjusts the spatial position of the seamer head in response to inputs from liner centerline sensors. The seamer head is mounted on a seamer head carrier that is vertically movable relative to a seamer head frame, which in turn is horizontally movable relative to a base structure. A programmable logic controller is programmed to continually poll the liner centerline sensors to determine the position of the seamer head relative to the liner, and to instruct vertical and horizontal axis positioners to move the seamer head as necessary to make the seamer head's rotational axis substantially coincident with the centerline of the liner as the liner passes through the seamer head.