Abstract: A lined conduit formed by decorrugating a corrugated liner conduit inside a first conduit is described. A method and apparatus for forming the lined conduit are also described. The corrugated liner conduit may be positioned inside the first conduit. Each end portion of the corrugated liner conduit may be coupled to a hydraulic expander. Each hydraulic expander may include a hydraulic cylinder. Each hydraulic cylinder may include a piston rod with an opening along the length of the piston rod. The corrugated liner conduit may be evacuated through a valve assembly coupled to the passageway in one of the piston rods. The evacuated corrugated liner conduit may be pressurized with fluid from a fluid source coupled to the valve assembly. Pressurizing the corrugated liner conduit may expand corrugations in the corrugated liner conduit to form a decorrugated liner in the first conduit.

Abstract: A conduit modifier may be used to corrugate at least a portion of a conduit. The conduit modifier may include at least a first plurality of rollers arranged in a first pattern around a passageway. The first plurality of rollers may form ridges and grooves lengthwise along a conduit passing through the passageway. A second plurality of rollers arranged in a second pattern around the passageway may compress ridges formed by the first set of rollers. The ridges may be formed such that a distance from a central axis of the conduit to a highest portion of an outer surface of a ridge is substantially equal to a distance from the central axis of the conduit to an outer surface of the un-corrugated portion of the conduit. The corrugated portion of the modified conduit may be expandable.