Spiral wound liners 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. The process was initially developed in Australia to 'manufacture' pipes in remote locations and allow the construction of pipelines using conventional open cut techniques. However, its advantages as a pipe relining system were soon realised.Application
All pipelines and culverts, particularly in the water industry.Technology Description
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 (or steel reinforced PVC or HDPE) 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 as shown in the diagram. The rotational action pushes the liner through the host pipe – 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 smaller diameter pipes, the liner can be expanded by reversing the winding machine to form a tight fit with the host pipe, thus maximising the available cross-sectional area and minimising the grout volumes and in some cases eliminating the need for grout.
The winding machine remains stationary at the manhole or inserting pit in line with the host pipe, however for larger diameter circular or non-circular applications, the machine usually travels along the host pipe. The travelling machine installs 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, however due to the uneven surface within underground pipelines, grouting the void is recommended to form a composite lining with the host pipe. Alternatively the liner may be installed with a fixed dimension and the annular space between the spiral wound liner and host pipe grouted.
By use of the differing methods of installation, pipes of diameter 150mm to 3000mm can be relined.
Grouting of the annular space is required to secure the liner in place thus avoiding potential 'floating' of the liner and effectively transferring the external load from the existing pipe onto the composite liner. Such lining designs include the presence of the grout layer so that the ability of the pipeline to withstand existing and possibly future external loads is maintained.
Within non man-entry pipelines, lateral connections are located by measurement and after lining remade by cutting through the lining using robotic equipment, ensuring that a watertight reconnection is made with a 'standard' trenchless technique. For man-entry pipelines, this can be achieved by manual methods however the sealing of the connection against external water ingress is just as important and necessary.