Spirally Wound Lining
Spirally wound linings can be used to rehabilitate gravity pipeline applications such as sewers, culverts and process pipes. The liner is installed in-situ within the host pipe from a manhole or insertion pit, thus minimising excavation needs e.g. a slip trench is not required.
Installation is simple and quick with a minimal set-up, usually from a single access point. The lining is produced by introducing a profiled strip of PVC (which may reinforced with a steel band or rolled steel section) from a spool located at ground level to a winding machine, which rotates causing the edges of the profile strip to interlock thus forming a water-tight liner.
The rotational action pushes the liner through the host pipe. In a traditional version the finished lining then requires grouting of the void between the external surface of the liner and the internal pipe wall. The formed liner is smooth on the inside wall and ribbed on the outside which provides strength for this thin walled profile and a key for the grouting process.
In later versions, with a slightly modified liner material and a strip interlock, once the liner has been extended through the host pipe the free end is anchored and the machine continues to wind the liner thus expanding it to form a close fit lining with the host pipe reducing if not eliminating the need to grout the annulus.
At smaller diameters the winding machine remains stationary at the manhole or insertion pit with the liner extruding from it. However for larger diameter circular or non-circular applications, the winding machine may travel through the host pipe creating the liner behind it as it moves leaving the spiral wound liner in contact with the host pipe forming a close-fit liner that generally conforms to the profile of the host pipe. Grouting the annulus is recommended to form a composite lining with the host pipe. This may also have the added benefit of creating a composite pipe of equal or greater structural integrity than the original unlined pipe