subject: Pipe Extrusion Line [print this page] Pipe extrusion line Pipe extrusion line
A tubular liner for a pipe is collapsed on itself to define a pair of lobes. The lobes are folded into a central region so that bending modulus and radius are reduced. The liner can be stored in a tighter coil and can be introduced into an underground pipe to be lined at a more acute angle.
This pipe extrusion line relates to pipe lining for renovating or rehabilitating pipes or other conduits bearing, for example, water, gas, sewage or other fluids. The corrugated pipe extrusion line is particularly applicable to pipe extrusion liners for underground pipes.
When such underground pipes have deteriorated by, for example, corrosion, ageing or other damage, repair or renewal by methods which require the digging of a trench along the full length of the pipe are expensive, timeconsuming and cause disruption especially in urban areas.
Various methods exist to rehabilitate pipes by the in situ insertion of a pipe extrusion liner which fits closely within the pipe and which may be bonded to the inside of the pipe. Several processes exist whereby relatively rigid plastics lining pipes made by corrugated pipe extrusion machine, are treated to reduce their original diameter sufficiently so that they can be pulled into the existing pipe and then further treated to regain their original diameter and form a close internal fit with the existing pipe.
A previously proposed collapsed corrugated pipe production line is illustrated in FIG. 1 of the drawings. Such liners have a smaller bend radius than a circular cross-section liner, require lower pull-in loads and may be used for lining pipes which are not truly circular in cross-section. However, such liners need to have relatively thin walls in order to be deformable into the described cross-sections and this limits their mechanical performance in terms of their ability to withstand internal or external pressure when unsupported. By way of clarification external pressure may be considered to be derived from loads transmitted through a saturated sub-soil from, for example, the vehicles on a roadway above. This external pressure can result in collapse of the liner if it is not sufficiently rigid.
A disadvantage with such systems is that the liners have a large bending radius due to their rigidity and circular cross-section. The diameter is only slightly less than the diameter of the pipe extrusion line to be lined and, thus, long lengths of liner have very large coil diameters which is both inconvenient for delivery and use on site. Furthermore, insertion is difficult because of the small diameter difference between the pipe and the liner.
