Inliner rehabilitation with annular space: Laying further media in the annular space

The various methods of trenchless pipe rehabilitation can be distinguished, among other things, with regard to the retention of a cavity, the so-called annular space, between the host pipe and the inserted liner or pipe.

The Primus Line^® system was deliberately developed with an annular space design (loose fit), because this not only results in decisive advantages for the installation of the inliner, but also makes line rededications, targeted cross-section reductions and increases in the pressure rating possible. Last but not least, other media such as micro cable pipes can be laid in the annular space as empty conduits for fibre optic cables, signal cables or locating tapes.

The annular space design of Primus Line^®

The liner is designed in such a way that it has to be considered as a new pressure pipe in an existing pipe. This is due to its unique three-layered structure. It unites robustness against mechanical forces with a high chemical resistance with wall thicknesses of just six to eight millimetres.

The outer layer of polyethylene (PE) protects the liner from external influences during transport and from abrasion during insertion.

Depending on the field of application, the inner layer is made of PE or thermoplastic polyurethane (TPU). It protects the host pipe from the corrosive effect that liquid and gaseous media can have.

By its seamless reinforcement made of aramid fibres between inner and outer layer, the Primus Liner is statically self-supporting. This means that it does not require any time-consuming gluing with the host pipe and can absorb the operating pressure completely itself. This will extend the pipeline’s lifetime by at least 50 years. In depressurised conditions, the liner will keep its form. The stability of the system is demonstrably given (classification according to DIN EN ISO 11295).

In principle, this even allows Primus Line^® to be used completely independently of existing pipelines. Based on this concept, the Primus Line F-Liner was developed which is optimised particularly for free above-ground installation and is characterised by even more flexible material for easier handling during the unrolling and rolling up process from the reel and multiple use.

Laying further media in the annular space

The existing annular space between liner and host pipe can also be used for the parallel insertion of further media such as micro cable pipes as empty conduits for fibre optic cables, signal cables or locating tapes.

The additional medium is already included during the factory folding process of the liner in a U-shape and inserted into the host pipe with the liner. After pressurisation, which gives the inliner its circular shape, the empty pipe is placed in the annular space between the liner and the host pipe. At the ends of the rehabilitated section, the empty pipe is led out of the host pipe via a project-specific adapter piece. The fibre optic cable is blown in after the rehabilitation.

The Primus Line® system has already been installed several times with empty conduits for micro cable pipes. Like in case of the rehabilitation of a cast iron potable water pipeline DN 500 on a stretch of about 3.5 km in North Rhine-Westphalia. The combined installation had very much convinced the client there, because an additional flush drilling or even the open trench laying of the fibre optic cable would have been much more time-consuming and costly.