Pipes and tubular conduits – Repairing – Patches
Utility Patent
1999-01-13
2001-01-02
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Repairing
Patches
C138S097000, C264S269000, C405S150100
Utility Patent
active
06167913
ABSTRACT:
TECHNICAL FIELD
This invention relates to thermoplastic liners for lining cylindrical or tubular pipe lines, either initially or as a repair, for protecting the pipe lines, particularly pressure pipe lines, from deterioration and preventing the pipe lines from leaking and particularly relates to a novel and unique pipe liner having a profile on one side which serves as an anchor for mechanical bonding to a cementitious substrate and a generally folded cross-sectional configuration to facilitate insertion within a pipeline and which liner is inflatable or expandable into a cylindrical or tubular configuration to line the pipe. The invention also relates to methods of forming the pipe liner from a continuously extruded flat sheet material into a cylindrical or tubular shaped thermoplastic liner by spirally winding the sheet material and bonding the overlapping joints, either as single liners or multiple liners.
BACKGROUND
Large sums of money are spent annually on water mains refurbishment, however this has been directed at water quality rather than leakage control. The problem is really twofold, namely corrosion and leakage control. Ideally therefore, the refurbishment solution should offer both corrosion protection to the existing host pipe as well as affording a high level of leakage control. The available refurbishment options do not address both problems. It is a fact that all water distribution systems leak. Leakage can be at the joints or through the pipe structure itself where internal pitting causes pinholes and subsequently accelerated external corrosion of the pipe walls. The majority of water mains installed prior to the mid 1960's were cast iron pipes which were either unprotected or were treated with a bituminous coating which has not proven to be an effective long term corrosion treatment resulting in problems such as:
1. Leakage due to faulty joints.
2. Internal metallic corrosion leading to failure of the pipe itself as a result of leakage or loss of hydraulic capacity owing to build-up of corrosion products.
3. Internal corrosion due to microbial growths results in bacterial oxidation of ferrous iron, especially at low pH values with biological factors producing periodic concentrations of iron as high as 8 mg/L.
Currently, there are a substantial number of various apparatus and methods for lining pipe lines that involve forming a cylindrical thermoplastic liner into a reduced cross-section such that the liner can be inserted into and moved through a pipe to be lined and subsequently expanded into a cylindrical configuration approximating the diameter of the pipe to be lined whereby the thermoplastic material forms the interior surface of the pipe for transporting fluid or other material through the pipe. One such method for protecting the interior of pipe lines is disclosed in French Patent No 81 07346 to Laurent in the patent, there is disclosed a cylindrical liner formed of a thermoplastic material having historic time-memory properties, ie, shape-memory characteristics. That is the liner is initially formed in a cylindrical configuration and is then folded at an appropriate temperature to reduce the cross-section off the liner, enabling introduction of the folded liner into the pipe to be lined. The folded liner in the pipe is then expanded by the introduction of pressurised hot fluid, eg steam, and at a temperature such that the folded liner assumes its original shape or the shape given to it by the host pipe. With the applied steam pressure the liner conforms to the interior contour of the pipe.
There are various types of liners relating to the application of the shape-memory characteristics of thermoplastic materials where the liners are folded for subsequent reformation or expansion within a generally cylindrical shaped pipe or conduit to provide a lined pipe. Other types of thermoplastic liners are also known. For example, in British Patent Specification 1580438, as well as in PCT application PCT/AU86/00362, WO87/03840, there are disclosed liners having generally U-shaped configurations (an X-configuration being further shown in British Patent No 1,580,438). In British Patent Application No 2,084,686 an oversized round semi-rigid plastic tube is flattened or otherwise reduced in cross-sectional area at the job site and then inserted cold and semi-rigid into the existing host pipe whereupon it is expanded against the host pipe using internal pressure and heat. All of the liners of these documents employ semi-rigid material in cylindrical form which is forcibly mechanically collapsed or folded by creating longitudinal depressions along the pipe liner material and maintaining this profile by means of strapping. Later, when the folded liner is installed in a pipe, the strapping is released such that the folded liner returns to its original cylindrical configuration thus creating a liner in the host pipe.
In U.S. Pat. No. 5,034,180 there is disclosed a method for installing a liner of plastic material in a pipe. In that patent, a thin flexible tubular membrane providing a heat containment tube is first inserted into an underground pipe to be repaired. The thermally folded liner is then inserted into the tube while the liner is heated and flexible. Hot steam is then injected into the liner and the tube to heat the liner along its entire length externally and internally whereupon pressure is applied to expand the liner against the walls of the pipe with a flexible tubular membrane therebetween.
All of these known methods fold or deform or mechanically collapse the generally cylindrical thermoplastic liners into a reduced cross-sectional shape enabling the liner for insertion into the pipe being lined. The thermoplastic liners use the shape-memory characteristics both in manufacturing the liner as well as in the reformation process to reconstitute the liner to its cylindrical configuration. The mechanically deformed liners rely on a manufacturing process which introduces substantial stress into the liner and which inhibits the formation of liners for lining large diameter pipes and restricts the wall thickness of the liners. In many instances the reliability of the lined pipe is adversely affected. Many of the stresses introduced into the liners during manufacture are often difficult to relieve upon installation. Flat spots and loose fitting liners often occur as a result of inadequate relief of the stresses, especially at the point on the liner where the concave peak formed during the deforming yields the highest magnitude of residual stresses. The nature of the materials prohibit the lining of bends, large diameters and very long lining lengths. Also, all of these liners do not provide any active corrosion prevention of the host pipe, which is generally a metal such as steel, ductile iron or cast iron, thus residual corrosion of the host pipe is free to continue and as the liners are designed to function with structural enhancement from the host pipe, the premature failure of the host pipe will result in the failure of the lining as the lining will have nothing suitably strong enough to line.
While the above refers to semi-rigid or semi-flexible linings, there are also used methods of lining pressure pipes with flexible linings. In such processes a flexible liner is fixed to the walls of a host pipe by means of an adhesive. As the adhesive is placed between the lining and the internal walls of the host pipe and this adhesive either cures at ambient temperatures, when the adhesive contains volatile components, or two part component adhesives are used which are free of volatile. In this case the adhesive setting and hardening is promoted by the use of heating during installation of the liner. Also, there are methods which require the impregnation of coated needle felt fabrics with thermosetting resins and by using inversion techniques, the uncured resin impregnated tubes are inserted into the pipe to be lined and thereupon cured by means of heat using either steam or hot water. Various patents relate to these method sometimes referred to as ‘cured-in-place
Broadwood Michael Leopold Erictschudi
Cirket Edward John
Hopkins Geoffrey David
Wood Peter Trevor William
Brinson Patrick
Cempipe Ltd.
Zarley McKee Thomte Voorhees & Sease
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