The invention relates to an apparatus for inserting a new pipe into an old pipe by means of a self-driven impact device, which simplifies the insertion of a new pipe into an old pipe, and wherein blocking elements of an apparatus according to the invention engage with the inside wall of an old pipe in order to prevent any movement of the self-driven impact device in a direction opposite the direction of advance, as well as a method for using the device. The apparatus according to the invention has blocking elements, which are disposed on at least one base body, but preferably four base bodies, which are in turn releasably mounted on the self-driven impact device. This method is characterized in that the base bodies together with the blocking elements and the self-driven impact device are salvaged by the new pipe.

A method of sealing a casing comprising the steps of deploying a thin wall tube in the region the casing is to be sealed, melting a low temperature alloy and allowing it to flow into the annulus between the thin wall tube and the casing, and allowing the low temperature alloy to solidify. The thin wall tube may include protrusions on its outer surface, of similar height so as to centralise the thin wall tube in the casing.

Segments are linked in the circumferential direction to assemble a pipe unit, which is linked to another pipe unit in the pipe-length direction to assemble a rehabilitation pipe inside an existing pipe. Before the pipe unit is assembled or after the pipe unit has been assembled, a spacer is attached to the segment using a spacer holder to prevent the spacer from falling down from the segment. The pipe unit having the spacer attached to the segment is linked to the pipe units that have already been linked. The rehabilitation pipe is positioned relative to the existing pipe using the spacer that is attached to the segment. A filler is injected between the positioned rehabilitation pipe and the existing pipe.