WO1997007359A1

WO1997007359A1 - Pipe jointing

Info

Publication number: WO1997007359A1
Application number: PCT/GB1996/001938
Authority: WO
Inventors: Thomas William Cowley
Original assignee: Cambridge Water Company
Priority date: 1995-08-11
Filing date: 1996-08-08
Publication date: 1997-02-27
Also published as: AU6706296A; GB2304168A; GB9516536D0

Abstract

In buried utility pipe runs comprising jointed pipe sections (2A, 2B, 2C), joints are replaced in situ. The existing joint is revealed and cut away. A gap (7) is formed between the ends of the adjacent pipe sections and a sleeve type joint (3A, 3B, 3C) inserted into the gap (7). At least one pipe section is moved axially through the surrounding soil (6) to close the gap and seal the ends into the sleeve joint.

Description

TITLE : PIPE JOINTING

The invention relates to a method of in situ jointing of sections of an existing pipe line or pipe run laid in soil.

Pipe lines laid into soil are very widely used for the distribution of fluids between separated sites. For example, pipes are used for distributing water from reservoirs and water treatment facilities to consumers.

In many cases, the pipes used for such distribution systems have been in place for a number of years, and need to be replaced or repaired. In some cases this arises because of catastrophic failure of part ofthe piping system, as a result of which that part will need to be replaced. In other cases experience shows that parts of pipe work systems of particular types, laid in certain conditions, are susceptible to failure, and it is desirable to replace parts or all of the pipe work system before a catastrophic failure occurs.

Many such piping systems include pipe runs which are made up of separate sections of pipe. These sections are joined by a joint, which may be integral with one ofthe ends of the pipe sections or a discrete item used to seal the adjacent pipe sections together.

An example of such a pipe system is one in which the pipe runs are made up of asbestos cement based pipe sections, for example, straight sections of about 4 metres in length. These sections are cylindrical, and adjacent sections can be jointed by placing a sleeve with an integral seal over the ends ofthe adjacent pipes.

One particular design of such pipe sections uses asbestos cement sections of about 200 mm diameter and a sleeve joint, the internal diameter of which is similar to the external diameter ofthe asbestos cement pipes, and contains a suitably profiled "O" ring mounted a short distance internally of each end ofthe sleeve. The sleeve is then slid over the end ofthe asbestos cement pipe section, and forms an effective seal. In another type of joint rubber "O" rings are placed over the ends of adjoining pipe sections, and a metal sleeve placed between the "O" rings, overlapping the ends of both pipe sections. Clamping rings, placed on the pipe sections before the "O"rings are then clamped together by bolts forcing the "O" rings against the metal sleeve, and creating a seal against the pipes. A further type of joint is a screwed gland joint.

In the past, the "O" rings used in such seals have been made of natural rubber, or partly of natural rubber, and tbis rubber is susceptible to biological degradation as a result of bacteria in the soil or in the water. Degradation of the seals results in leaking from the pipes and possible failure of the joints.

It is desirable to replace these sleeve joints in order to reduce the risk of leakage, and to increase the useful life ofthe piping system.

At present, thesejoints are generally replaced by identifying the location underground of the joint, and excavating around the pipe run. The sleeve is then cut off, and is replaced in situ by a sleeve which can be assembled over the existing junction between the two pipe sections. In practice, this method can be very effective in replacing joints which are to be replaced on a single basis, for example, joints which have failed catastrophically.

However, where continuous pipe runs are concerned, such jointing systems are relatively expensive. In addition, it is often less convenient to test joint integrity of individual joints when a continuous pipe run is being replaced, and any faults in the assembly may not be identified until much later, and additional costs will be incurred in rectifying such faults.

Accordingly, there is a substantial need for a method of jointing pipe sections which is more economical and less susceptible to risk of failure than the existing system. A system has now been found which enables such pipe sections to be jointed in situ using sleeve type joints. The present invention provides a method of forming a sealed joint between two adjoining pipe sections forming part of a pipe run buried in soil, characterised in that a sleeve type joint is applied in situ to seal the two pipe sections together; and, in particular, a method of forming a sealed joint between two pipe sections in a buried pipe run in which a gap is provided between the ends of the two pipe sections, of sufficient width to permit insertion of the sleeve type seal between the ends of the two pipe sections, and at least one ofthe two pipe sections is moved axially towards the other through the surrounding soil to locate it for sealing engagement with the sleeve type joint.

Pipe runs to which this method can be applied may be buried in any solid medium through which some axial movement of the pipe sections can be secured. Generally, they will be buried in soil of some type, for example, soil underlying roads and pavements or in fields, or the beds of roads or pavements. In the method the major part ofthe pipe sections remain buried, and are moved through the soil or surrounding solid medium (referred to generally in this application as "soil").

Pipe runs for which the method has particular application are pipe runs made up of sections of pipe, particularly runs where the pipe sections or the majority of them are generally straight sections of cylindrical shape, although some degree of curvature may be acceptable. Usually the pipe sections will have a generally circular cross-section.

Preferably the pipe sections are more than 2 metres in length, particularly 3 metres or more as, for shorter pipe sections, the procedure is rather less attractive. Pipe sections may be long; however, it is desirable to be able to move the pipe sections physically through the soil in an axial direction. Depending on the type of soil and whether any treatment ofthe soil or the pipe can be used to improve axial mobility, the length of pipe section to which the method can be applied should be such as to permit axial movement of the pipe sections for a distance sufficient to close the gap between pipe sections for engagement with the joint. Preferably such pipe sections are not more than 8 metres in length for diameters generally used in utilities, such as water distribution, particularly not more that 6 metres in length. Suitable pipe sections are ones 4 metres in length, or a length close to 4 metres.

The material from which such pipes are made may also affect whether they can effectively be moved without damage to the pipe section. Suitable materials may include plastic pipe sections. However, in practice, such sections may be too long for effective movement and may be subject to damage by abrasion when moved through the soil. Often plastic pipe sections are somewhat bowed when laid and this may inhibit axial movement, or mean that it is more difficult to apply sufficient axial force over the necessary length ofthe pipe without distortion. The method is particularly suitable for pipe sections made from mineral materials, such as steel, cast iron and especially cement pipe sections and, also, metals such as steel or cast iron. One area of particular interest for the method is in relation to asbestos cement pipe sections, for example, asbestos cement pipe sections produced in approximately 4 metre lengths.

The technique can be used with any relatively rigid pipe sections, with any particular bore. It is particularly suitable for bores of the size often found for water and sewerage systems, particularly water mains distribution systems.

Such sections are sometimes used in pipe runs forrning part of water mains or water distribution systems buried in the soil. Frequently asbestos cement pipe sections of the type described above will be used in pipe runs, and will be jointed together by placing a sleeve joint between the two sections and butting them into the sleeve.

A sleeve type joint can be any joint the body or principal parts of which, when inserted into the gap between the two pipe sections, are not split along the axis of the pipe. Joints which do have a split body, for example, sleeves which have been cut axially in two, will usually be fitted to joint pipes by assembling the two parts over the ends of the pipe sections to be jointed and securing the parts together with a seal between the two parts and also between the joint parts and the pipe ends. However, suchjoints maybe used partly assembled, with the body parts secured together in that state and, when so used, fall within the scope of what is meant by a sleeve type joint. Likewise, cast iron detachable joints in which the various elements including the 'O" rings are slid onto the pipe ends before tightening may be regarded as sleeve type joints.

In practice, the method preferably uses sleeve type joints which are specifically designed for sliding sealing engagement with the pipe ends. A common design of such a sleeve joint is a generally cylindrical sleeve having an internal diameter similar to (usually slightly larger) than the external diameter ofthe pipe sections. Inward of each end ofthe sleeve, an annular groove is provided in which a specially designed "O" ring is seated. The "O" ring is generally made of a synthetic or partly synthetic rubber type polymer, particularly one which is resistant to bacterial degradation especially from bacteria found in soil and/or water. The pipe section can be slid axially into such a sleeve so that the end of the pipe section passes the "O" ring, and the "O" ring provides an effective seal against the pipe section. The surface of the pipe section may be prepared in advance to improve the quality of the seal achieved.

Such sleeve joints may be of plastic or other materials. In practice, at least for cement based pipe sections, it is convenient to use cement based sleeves, such as asbestos cement based sleeves. An example of such a sleevejoint is that manufactured under the tradename Widnes.

When there is a need to replace the sleeve, the soil is removed from around the sleeve area and the existing sleeve cut off, leaving the two pipe sections butted more or less closely together.

The invention further provides a method by which a gap is provided between two such butted together pipe sections, by cutting a section from one or both pipe sections to leave a gap sufficient for the insertion of a sleeve type joint into the gap. At least one pipe section is then moved axially through the soil partially to close the gap for engagement with the sleeve type joint. Conveniently, the pipe section to be moved can be moved by removing soil around the next adjacent joint, and applying the necessary force to the pipe section in the area of the excavation. For example, the next adjacent joint can be removed, revealing the end of the relevant pipe section, and the pipe section can be clamped or a pressure plate inserted against its end, so as to apply a force sufficient to move it the desired distance. The force may be applied by specifically adapted jacking means, for example, specially adapted hydraulic jacking means.

By moving the pipe section axially in this manner, a further gap is provided between that pipe section and the next adjacent pipe section, and the invention further provides a method of replacing joints in which the gap is provided by moving an intermediate pipe section axially into its position for engagement with a first joint thereby to open up a gap for insertion of a second joint.

It will be appreciated that, in some cases, pipe sections of generally cylindrical shape may have protrusions which would prevent axial movement of the pipe section. In that case, it may be necessary to excavate partially around the area ofthe protrusion to allow its relatively free movement.

A further aspect ofthe invention is a pipe run made or repaired in accordance with the method of the invention, particularly a pipe run for water transmission; and a piping system including such a pipe run.

The invention is illustrated by the following specific description and by reference to the Figures 1 to 4. The invention may be used in many other applications.

Figure 1 is a general view ofthe application ofthe method.

Figures 2, 3 and 4 are part cross-sectional views of stages of the procedure.

A water main (1) comprises piping runs made up of existing pipe sections (2A, 2B, 2C) buried in surrounding soil (6). Each pipe section is a cylindrical asbestos cement pipe, length 4.0 metres, and external diameter 0.5 metres. Adjoining pipe sections (2A, 2B, 2C) are jointed with Widnes type sleeve joints (3A, 3B, 3C) with perishable natural rubber seals (not shown). The pipe runs are buried under a roadway (4).

In order to replace the joints (3 A, 3B, 3C), a first joint (3A) is located by suitable means, such as a probe inserted from a local access point. The soil around the first joint (3 A) is cleared (7), and the area ofpipe section in the immediate vicinity ofthe joint cleaned off. A grinder with a fixed depth cut is used to cut a slit lengthwise in the jointing sleeve (3 A), taking care not to damage the underlying pipe section, at one or two radial locations, and the sleeve (3A) opened up, and the sleeve elements, including the seals, are removed.

A section is then cut from one end of one pipe section (2 A or 2B) of sufficient length to leave a gap (5) into which a new Widnes sleevejoint (8) can be inserted. The new sleeve (8) is inserted and slid over the end (9) of one ofthe pipe sections (2A), after that end (9) has been prepared by cleaning away excess dirt and soil, and any remnants of the old seal, and treating the surface. The sleeve joint (8) then seals against that pipe section. A collar (10) is fastened over the pipe section end (9) adjacent to the sleeve joint (8) so as to inhibit further axial movement of the sleeve joint (8) onto the pipe section (2A).

The other pipe section end (11) is cleaned likewise, and the next adjacent joint (3B) located, and excavated in the same manner as the first joint. The next sleeve joint is removed as described above, and a hydraulic jack (13) engaged with the intermediate pipe section (2B), and used to force that section (2B) through the surrounding soil (6) into the previously partially installed sleevejoint (8), until a sealing engagement is achieved.

The procedure is then repeated (Figure 4) until the end of the relevant section of the pipe run, for example, a branch point or inspection point which cannot be moved. Jointing to the pipe work which is not to be moved can then be carried out using a conventional split sleeve joint, or a specially designed split sleeve joint which can accommodate the increased separation ofthe two components to be jointed.

Claims

Claims:

1. A method of fomiing a sealed joint between two adjoining existing pipe sections forrning part of a pipe run buried in soil, characterised in that a sleeve type joint is applied in situ to seal the two pipe sections together.

2. A method according to claim 1 in which a gap is provided between the ends of the two pipe sections, of sufficient width to permit insertion ofthe sleeve type seal between the ends ofthe two pipe sections, and at least one ofthe two pipe sections is moved axially through the surrounding medium towards the first pipe section to locate the other pipe section for sealing engagement with the sleeve type joint.

3. A method according to claim 2 in which the axial movement ofthe pipe section slides that pipe section into sealing engagement with the sleeve type joint.

4. A method according to claim 3 in which a collar is provided around the end of one pipe section to brace the sleeve against movement onto that pipe section beyond the location of the collar.

5. A method according to any of claims 2, 3 or 4 in which the sleeve type joint is moved axially into sealing engagement with the other pipe section.

6. A method according to any ofthe preceding claims 2 to 5 in which the gap is provided by removing a section ofpipe including an end of one or both pipe sections.

7. A method according to any of claims 2 to 5 in which the gap is provided by moving one pipe section axially through the soil, in a direction away from the other pipe section.

8. A method of forming a sequence of two or more sealed joints in accordance with any of claims 2 to 7 in which the gap between adjacent pipe sections for insertion of one sleeve type joint is provided by the axial movement of one of the pipe sections, being the axial movement which locates that pipe section for sealing engagement with the sleeve type joint for the, or a, previous joint.

9. A method in accordance with any of the preceding claims in which the pipe sections are asbestos cement pipe sections.

10. A method according to any of the preceding claims in which the pipe sections are from 3 to 5 metres long.

11. A method according to any ofthe preceding claims in which the sleeve type joint is an asbestos cement sleeve type joint with "O" ring seals which are a slide fit to produce a seal.

12. A pipe run which has been modified according to any of the preceding claims.

13. A pipe run according to claim 12, containing water.

14. A jack adapted to move a partially buried asbestos cement pipe axially in the surrounding soil.

15. A method according to any of claims 1 to 11, and as described by reference to any ofthe drawings.