WO1999046092A1

WO1999046092A1 - Lining pipes

Info

Publication number: WO1999046092A1
Application number: PCT/GB1999/000444
Authority: WO
Inventors: Nicholas Jason John Preston
Original assignee: United Utilities Plc
Priority date: 1998-03-11
Filing date: 1999-02-11
Publication date: 1999-09-16
Also published as: AU2533899A; GB9805146D0

Abstract

A method for forming an aperture in a polymeric liner which is in contact with a thermally conductive container wall (1) such that the aperture is in register with an opening (2) defined in the container wall (1). The liner is heated such that a portion (6) of the liner which bridges the opening is thermally degraded to an extent that it is effectively destroyed. Portions of the liner in contact with the container are not thermally degraded as they are cooled by contact with the container.

Description

1

LINING PTPES

The present invention relates to a method for forming an aperture in a liner within a container such as a buried metal pipe.

Techniques have been developed to line the inside of pipes, for example buried cast iron water mains, with polymeric liners formed of materials such as polyethylene. Linings have been inserted into buried pipes using various techniques, for example by pulling in partially folded tubes and then expanding the tubes into contact with the buried pipe, or where relatively thin liners are being installed by evertion. In circumstances where the liner has a relatively thick wall so that it is self supporting, it is not necessary to adhere the liner to the pipe wall. With relatively thin liners however it is highly desirable to adhere the liner to the pipe wall so as to ensure that the liner cannot collapse after installation.

Regardless of the method used to install the liner, after its installation the liner obstructs any openings provided for the purposes of making connections to the original pipe. In the case of cast iron water mains, such openings receive ferrules which are screwed into the openings and connected to service connections for delivering water to premises served by that main. Apertures must be made through the lining to enable the restoration of services. Typically, this is achieved by digging an excavation to expose the ferrule, removing the existing ferrule, cutting out the liner which obstructs the opening in which the ferrule was previously installed, and then inserting a new ferrule which forms a seal against the liner and is clamped onto the edge of the opening in the pipe. Such techniques are satisfactory when used on large diameter mains with thick-walled liners but are more difficult to use on relatively small diameter mains with thin-walled liners.

It is an object of the present invention to provide an improved method for forming apertures in liners which have been installed within containers such as buried water mains.

According to the present invention, there is provided a method for forming an aperture in a liner which is in contact with a thermally conductive container wall such that the aperture is in register with an opening defined in the container wall, wherein the liner is heated such that the aperture is formed by thermal degradation of a portion of the liner which bridges the opening and such that portions of the liner in contact with the container are not thermally degraded.

Heat may be applied in a manner sufficient to completely destroy the liner where it bridges the opening, or in a manner which causes thermal degradation to an extent that the liner is so weakened that it will be destroyed if pressure is subsequently applied to it. For example, the liner may be heated at and adjacent the location of the opening such that portions of the liner cooled by contact with the container are not thermally degraded whereas the portion of the liner which bridges the opening is heated to a temperature which the physical properties of the liner material are degraded. An elevated pressure may be applied to the interior of the liner to encourage displacement of the portion of the liner which obstructs the opening. Heat may be applied by a radiant heater located within the liner.

In an alternative embodiment of the invention, the liner is heated by placing a heated tool in contact with the portion of the liner which bridges the opening. A tool similar to a soldering iron could be appropriately positioned so as to contact part of the liner where it bridges the opening, portions of the lining not cooled by contact with the pipe being thermally degraded as a result.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which;

Figure 1 is a sectional view through an opening in a cast iron main which has been lined with a thin wall liner;

Figure 2 is a view corresponding to that of Figure 1 after heating;

Figure 3 is a view corresponding to that of Figure 2 after the application of pressure to the interior of the liner;

Figure 4 is a section through a lined cast iron main such as that shown in Figure 1 immediately after insertion of a heated tool into the opening; and

Figure 5 is a view similar to that of Figure 4 after the destruction of the liner adjacent the opening as a result of heating by the inserted tool. Referring to Figures 1 to 3, a cast iron main 1 has an opening 2 formed through its wall. That opening will generally receive a ferrule connector (not shown), or may simply be open as illustrated as a result of the removal of such a ferrule. A liner 3 has been introduced into the pipe 1 by an evertion process such that the liner 3 is adhered to the inner surface of the pipe by an adhesive material 4. The liner 3 could be for example formed from polyethylene with a wall thickness of 500μm. The adhesive 4 may be butyl rubber. In the evertion process, the interior of a tubular liner is initially coated with butyl rubber and then that liner is turned inside out by the evertion process so that the side of the liner carrying the butyl rubber is pressed into contact with and adheres to the wall of the pipe. The pipe 1 will of course have been cleaned if appropriate before insertion of the liner.

Referring to Figure 2, after insertion of the liner a radiant heater is passed along the lined pipe and the liner is heated in the vicinity of the opening 2. Such heating is represented in Figure 2 by arrows 5. As a result the liner which bridges the opening 2 and the liner adjacent the opening 2 is heated. Contact between the liner adjacent the opening 2 and the pipe 1 cools the liner and prevents it reaching a temperature at which its physical properties are degraded. In contrast, the portion of the liner bridging the opening 2 is not in contact with the thermally conductive pipe 1 and therefore its temperature rises until the portion 6 of the liner which bridges the opening is physically degraded. At that stage in the process the portion 6 of the liner has been converted from a robust condition to a condition in which it can be readily displaced.

Referring to Figure 3, this shows the structure after internal pressure has been applied to the liner 3 so as to displace the liner portion 6 of Figure 2. It will be seen that a clean aperture having an edge 7 has been formed in perfect register with the opening 2 in the pipe 1.

In the embodiment of the invention described with reference to Figures 1 to 3, heating in the general area of the opening 2 is relied upon to form the necessary aperture in the liner 3. As an alternative, it is possible to apply heat only to the portion of the liner which bridges the opening as illustrated with reference the Figure 4.

Referring to Figure 4, this shows the structure of Figure 1 after the insertion of a heated tool 8 from inside the pipe into the opening 2. The tool 8 could be electrically heated in the manner of a soldering iron. Assuming that the liner 3 is relatively thin the position of the opening can be visually determined by for example using a video camera mounted on a carriage which also supports the tool 8 and a mechanism for extending the tool. Providing the tool 8 penetrates the opening 2, it does not matter whether or not the tool is centrally located within the opening. Thus precise positioning of the tool 8 is not necessary.

Initially the tool will readily penetrate the liner 3 as shown in Figure 4, making a relatively small hole as compared with the cross-section of the opening 2. After insertion however heat will continue to radiate from the tool 8 and will burn back those portions of the liner 3 which are not cooled by contact with the pipe 1. Thus the liner will be burn back to the edge 9 as shown in Figure 5, the end result being exactly the same as that achieved as illustrated in Figure 3.

It will be appreciated that the present invention may be applied to the formation of apertures in liners of any containers in which openings have been formed in thermally conductive container walls. The liners may be formed of any material which can be readily thermally degraded and yet which have a thermal conductivity and thickness such that they can be protected against degradation by being in contact with a thermally conductive cool material such as cast iron. Generally the liners should be adhered to the container wall so that it prevents fluid within the liner penetrating the space between the liner and the container. The present invention could be used however in circumstances where a liner is used which is sufficiently self supporting to be positioned in intimate contact with the container but thereafter relies upon the use of a ferrule or similar clamping device to form a seal with the liner.

Although in the described embodiments of the invention heat is applied from within the liner, it will be appreciated that heat could be applied from outside through the opening in the container wall. Depending of the nature of the liner material, it may or may not be necessary to apply physical force in the form of for example a differential pressure to dislodge a thermally degraded portion of the liner where it bridges the opening. The invention is particularly applicable to thin wall linings but may be used on thicker wall linings, for example linings with a wall thickness of 3mm. Heat may be applied using a mechanical tool as described with reference to Figures 3 and 4 or by any alternative means, for example, by an infrared or UV radiation source.

Where the liner is formed from polythene, the invention is equally applicable to axially and biaxially oriented material. The invention is equally applicable to single film liners or composite structures in which a liner is made up of several layers of different materials. Any convenient method may be used for locating openings in the lined pipe, for example electromagnetic flux leakage or ultrasonic devices.

Once an aperture has been formed in the liner, it may be appropriate to increase the size of the aperture using an appropriate mechanical cutting tool.

Claims

1. A method for forming an aperture in a liner which is in contact with a thermally conductive container wall such that the aperture is in register with an opening defined in the container wall, wherein the liner is heated such that the aperture is formed by thermal degradation of a portion of the liner which bridges the opening and such that portions of the liner in contact with the container are not thermally degraded.

2. A method according to claim 1, wherein the liner is heated at and adjacent the location of the opening such that portions of the liner cooled by contact with the container are not thermally degraded, whereas the portion of the liner which bridges the opening is heated to a temperature at which the physical properties of the liner material are degraded.

3. A method according to claim 2, wherein an elevated pressure is applied to the interior of the liner to encourage displacement of the portion of the liner which bridges the opening.

4. A method according to claim 2 or 3, wherein the liner is heated by a radiant heater.

5. A method according to claim 1, wherein the liner is heated by placing a heated tool in contact with the portion of the liner which bridges the opening.

6. A method for forming an aperture in a polymeric liner which is in contact with a thermally conductive container wall substantially as hereinbefore described with reference to Figures 1 to 3 or with reference to Figures 4 and 5 of the accompanying drawings.