Pipes and tubular conduits – Repairing – Patches
Patent
1999-02-10
2000-08-08
Hook, James
Pipes and tubular conduits
Repairing
Patches
138 97, 264 3616, 405184, F16L 5516
Patent
active
060986654
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to methods and apparatus for lining a conduit. Particularly, but not exclusively, the invention relates to the relining of pipework such as underground water mains.
There are a number of known techniques for rehabilitating, rather than replacing, existing underground pipework; Traditional methods which are still widely employed involve spray coating the inner surface of a pipe with a suitable material such as epoxy resin. It is also known to reline pipework with a plastics liner pipe (typically polyethylene), which is drawn into the existing pipe. This method is referred to as "slip lining".
In known "close fit" slip lining processes, the cross section of the plastics liner is first reduced to enable it to be drawn into the existing pipe. Once in position, the liner can be expanded to a circular cross section. A number of different methods and apparatus have been proposed for each of the three basic steps of this process, i.e. deforming the liner into a reduced cross-sectional shape, maintaining the liner in the reduced cross-sectional shape whilst it is drawn into the existing pipe, and expanding the liner into a circular cross-section once it is in place.
For instance, British patent specification number 1 580 438 describes a process, in which a plastics liner is first deformed into a reduced cross-sectional form, and then wrapped in a sleeve to bold it in this form as it is drawn into a pipe. The sleeve is provided with a tear line or fuse to enable rupturing of the sleeve once the liner has been installed in the pipe to allow the liner to assume a circular cross-section. It is also suggested in this patent specification that other means might be used to hold the liner in the deformed cross-section, including coiling a filament around the liner or restraining it using spaced apart bands or tape. It is suggested that such binding can be released once the liner has been inserted into the pipe by passing a cutting means through the pipe to slice through the binding.
An object of the present invention is to provide new methods and apparatus for lining existing pipework.
According to one aspect of the present invention there is provided a method for lining a conduit with a deformable plastics liner pipe, the method comprising, external dimensions relative to the dimensions of the un-deformed liner, cross-section; substantially corresponding with the internal cross-section of the conduit;,
wherein the liner is fabricated from a plastics material and has a wall thickness in the range of about 1.5 mm to 5 mm.
The plastics material is preferably a polymeric material such as, for example, polyethylene.
Preferably the liner has a wall thickness of between 2mm and 4 mm, and more preferably still between about 2.5 mm and 3.5 mm.
The liner for lining a given conduit preferably has an initial circumference smaller than the internal circumference of the conduit, the liner being expanded beyond its initial circumference into contact with the conduit by internal fluid pressure.
Preferably the liner is deformed into a generally U-shaped or horse-shoe shaped cross-section.
The liner may be bound in said deformed cross-section by hooped restraining straps which are positioned at spaced apart locations along the length of the liner.
For instance the straps may be fabricated from a plastics material and may be approximately 0.5 mm thick and between 5 and 15 mm wide.
Alternatively the liner may be bound in said deformed cross-section by helically winding an elongate flexible clement around the liner along its length.
For instance said elongate flexible element may be a self adhesive tape. Suitable tapes are readily available. Preferably the adhesive should be one that is entirely solvent free as recommended by liner polymer manufacturers to be in contact with the liner.
Preferably the liner, is mechanically deformed by means comprising at least one pair of rollers disposed on opposite sides of the liner and a mechanical former which depresses the liner into a generally U-shaped cross-section betwe
REFERENCES:
patent: 4207130 (1980-06-01), Barber
patent: 4347018 (1982-08-01), Wrightson et al.
patent: 5042532 (1991-08-01), Gilleland
patent: 5285817 (1994-02-01), Sigel
patent: 5335872 (1994-08-01), Clubbs
patent: 5395472 (1995-03-01), Mandich
patent: 5447665 (1995-09-01), Steketee, Jr.
Hook James
North West Water Limited
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