GB2300243A

GB2300243A - Liner pipe

Info

Publication number: GB2300243A
Application number: GB9506800A
Authority: GB
Inventors: Alan Lloyd Headford
Original assignee: Victaulic Co PLC
Current assignee: Victaulic Co PLC
Priority date: 1995-04-01
Filing date: 1995-04-01
Publication date: 1996-10-30
Anticipated expiration: 2015-04-01
Also published as: GB9506800D0; GB2300243B

Abstract

The pipe 11, of plastics, had a radial outwardly extending or flared formation 12 at an axial end thereof for anchoring the pipe end in a pipe connector or in an end of an outer pipe, the formation 12 having a circumferential groove 15 in a surface facing generally axially away or radially inwardly of the pipe 11; the groove 15 containing a reinforcing hoop 18 for assisting the formation 12 to resist radially inward forces, the reinforcing hoop 18 being provided with adjustment means for adjusting the circumference thereof.

Description

LINER PIPES This invention relates to pipes, such as liner pipes formed of plastics materials for lining existing pipelines.

More particularly the invention relates to pipes having an end formation suitable for terminating and anchoring the pipe against axial displacement from a joint by an end load applied to the pipe, the end formation being provided with a reinforcing hoop to assist it to resist radially inward forces.

It is known to provide plastics pipes with stub flanges having an annular reinforcing hoop embedded therein. Such pipes are disclosed in our earlier Patent Specification EP-B-0441619. The purpose of the annular reinforcing hoop is to assist the stub flange to resist radially inward forces, e.g. forces produced by the backing rings of stub flange joints during the application of longitudinal forces to the plastics pipes. In the absence of the reinforcing hoops, the radially inward forces can be such as to distort the stub flanges to an extent whereby they can pull through their associated backing rings.

Whereas the reinforcing hoops illustrated in EP-B0441619 are highly effective in performing their intended purpose, a drawback is that in general the hoop, and the groove in the stub flange within which the hoop is located, need to be machined to relatively fine tolerances. The need for precision almost inevitably pushes up the cost of manufacture, which in turn mitigates against the use of the reinforcing hoop in certain more cost-sensitive sectors of the market.

It is an object of the invention to provide a pipe having an end formation such as a stub flange which incorporates a reinforcing hoop, but wherein the need to manufacture the hoop and retaining groove to close tolerances is avoided.

In a first aspect, the invention provides a pipe formed of a plastics material and having a circumferential radially outwardly extending formation at an axial end thereof for anchoring the pipe end in a pipe connector or in an end of an outer pipe; the circumferential radially outwardly extending formation having a circumferential groove in a surface facing generally axially away from the pipe; the circumferential groove having disposed therein a reinforcing hoop for assisting the said formation to resist radially inward forces, the reinforcing hoop being provided with adjustment means for adjusting the circumference thereof.

It is to be understood that by the expression "pipe" as used herein is meant any pipe-like member such as a pipe per se, and additionally pipe fittings such as "T"junctions, elbows, bends, reducers and valve inlets, for example.

The term "facing generally axially away" as used herein means that there is at least an axial component to the direction in which the surface faces. Thus the surface need not be perpendicular to the axis but could, for example, be at an inclined angle relative to the axis.

In one embodiment, the radially outwardly extending circumferential formation can be in the form of a radially outwardly extending stub flange which is generally perpendicular with respect to the longitudinal axis of the pipe. In this embodiment, the groove is formed in an axial end face of the stub flange.

In another embodiment, the radially outwardly extending circumferential formation can be in the form of a flared pipe end. In this embodiment, the groove is formed in a radially inner surface of the said pipe end.

The reinforcing hoop may comprise a metal rod curved into a circular form and having adjustment means comprising a screw-thread arrangement for connecting the ends of the rod together. For example, the metal rod may have two threaded ends, and the adjustment means may comprise a turn buckle having a complementary thread for controlling the distance between the two ends of the rod, e.g. by drawing together or separating the ends of the rod.

The circumferential groove preferably has a circumferential retaining lip on the radially outer side thereof for preventing dislodgement of the hoop from the groove as the hoop is expanded radially.

An advantage of the present invention is that it avoids the need for the circumferential groove to be cut to a very close tolerance to the reinforcing hoop, the groove being dimensioned so as to provide a relatively loose fit initially about the reinforcing hoop, which may then be expanded to the appropriate radius. It is envisaged that such an arrangement will be simpler and cheaper to manufacture.

The pipe may be preformed with the radially outwardly extending circumferential formation, and this is particularly appropriate when the said formation is in the form of a stub flange generally perpendicular to the longitudinal axis of the pipe. However, the radially outwardly extending circumferential formation may alternatively be formed in situ by warming a pipe end to soften the plastics material and then actuating the adjustment means to radially expand the reinforcing hoop to deform the end of the pipe radially outwardly into a flared formation.

The present invention is particularly applicable for use with plastics pipes of the type used to line existing pipelines. Accordingly, in one embodiment, the invention provides a liner pipe for lining an existing pipeline, the liner pipe being formed of a plastics material and having a radially outwardly extending circumferential formation at an axial end thereof for holding the liner pipe against axial displacement along the existing pipeline; characterised in that the radially outwardly extending circumferential formation is provided with a circumferential groove within which is disposed a reinforcing hoop having adjustment means for adjusting the circumference thereof.

In the aforementioned embodiment, the adjustment means typically may be arranged to allow the reinforcing hoop to be expanded such that its outer diameter is equal to or greater then the inner diameter of the pipeline.

In the case of the flared pipe end arrangement described hereinabove, the reinforcing hoop may have an outer diameter (OD) smaller than the inner diameter (ID) of the pipeline.

In another aspect, the invention provides a pipe coupling assembly comprising an outer pipe, a connector for connecting the outer pipe to another pipe element; and a liner pipe; the liner pipe being as hereinbefore defined.

The invention will now be illustrated, but not limited, by reference to the specific embodiments shown in the accompanying drawings, of which: Figure 1 is a partial longitudinal sectional view through a pipe joint incorporating a liner pipe according to one embodiment of the invention; Figure 2 is an end view of a sector of the liner pipe shown in Figure 1; Figure 3 is a sectional elevation along line A-A in Figure 2; Figure 4 is a longitudinal sectional view of a liner pipe prior to forming; and Figure 5 is a longitudinal sectional view illustrating the liner pipe of Figure 4 after heat-softening and forming.

Referring now to Figure 1, there is illustrated a mechanical pipe joint incorporating a liner pipe according to the present invention. The pipe coupling is formed between the end of an unlined pipe 1 and a lined pipe 2.

The pipes are coupled together by means of a mechanical pipe coupling 3 of conventional type. Mechanical pipe coupling 3 comprises a steel sleeve or barrel 4 having flared ends 5 within which are located annular gaskets 6.

A pair of flanged collars 7, 8 are linked by flange bolts 9, and the coupling is tightened on to the ends of the respective pipes 1, 2 by tightening the flange bolts thereby drawing the collars 7, 8 together which leads to compression of the gaskets 6 against the outer diameters of the pipes 1, 2. Such a pipe coupling is entirely conventional and examples of such pipe couplings can be obtained from Viking Johnson Limited of Hitchin, UK.

Pipe 2 has a liner 11 formed from an appropriate grade of polyethylene. Polyethylene liners are generally used to reline pipes which, through corrosion or other defects acquired over many years of use, are no longer considered to have sufficient mechanical strength or integrity for the intended purpose.

Referring now to Figure 3, liner 11 has a radially outwardly extending stub flange 12 which is generally perpendicular to the axis A of the pipeline. The rear surface 13 of the flange 12 abuts against an axial end face of the pipe 2 and serves to anchor the liner 11 against axial displacement along the pipe 2.

The axial end face 14 of the flange 12 has a groove 15 which extends around the entire circumference of the liner pipe 11. The groove 15 has an annular lip 16 on its radially outer side. The annular lip 16 extends around the greater part of the circumference of the flange but is cut away at location 17 for reasons which will become apparent below.

Disposed within the groove 15 is a reinforcing hoop 18 formed from steel. Reinforcing hoop 18, which may conveniently be formed from a steel rod formed into shape by means of rollers, has threaded ends 19, 20 as shown in Figure 2. Threaded ends 19, 20 are linked by, and engage, complementary threads in turn buckle 21. Turn buckle 21 is provided with holes 22 for receiving an end of a torque bar.

The steel reinforcing rod is initially curved to suit approximately the nominal size of the intended host pipe.

The groove 15 is machined into the end face 14 of the flange so as to accommodate the steel reinforcing hoop.

Once the steel hoop has been fitted in place, the turn buckle is turned by means of the torque rod to adjust the radius of the hoop to expand the hoop radially outwardly and into firm contact with the radially outer surface 23 of the groove 15. Once the hoop has been expanded, it is held securely within the groove 15 by means of the lip 16.

Reinforcing hoop 18 serves to stiffen the flange 12 and prevents the flange 12 from being deformed radially inwardly and into the bore of pipe 2 as a result of axial end loads on the liner 11.

The advantage of the arrangement illustrated in the Figures is that the groove 15 machined into the face 14 of the flange 12 does not need to be of a close tolerance, any slack being taken up by virtue of the adjustability of the reinforcing hoop 18. The result is an arrangement which is potentially far cheaper and more flexible than factory machining a recess into a stub flange face and then fitting a bespoke hoop ring into the recess. With this latter approach, good tolerances are essential to guarantee a close fit of the hoop ring and adequate retention.

A second embodiment of the invention is illustrated in Figures 4 and 5. In Figure 4, a pipe 30 is provided with a liner pipe 31 formed from a suitable grade of plastics material, e.g. polyethylene. An annular groove 32 is machined into the radially inner surface 33 of the liner pipe 31. Groove 32 is provided with an annular lip 34 which extends around the greater part of the circumference of the liner pipe 31, but wherein a section 35 is cut away to permit access to a turn buckle 36.

Pipe 30 in this embodiment has a chamfered edge 30a, the purpose of which will become apparent below. However, the edge need not be chamfered but could equally be a right-angle edge or a radiussed edge.

In order to fit the reinforcing hoop 38 the protruding portion 31a of the liner pipe is warmed by a suitable heating means (not shown) to give a through-wall temperature of not more than 125so, and most preferably between 60"C and 1200C. The reinforcing hoop 38, which is of substantially the same form as reinforcing hoop 18 in Figures 1 to 3, is then inserted in a radially contracted form, and the turn buckle 37 is rotated to expand the hoop 38. Expansion of the hoop 38 forces the end 31a of the liner pipe radially outward and into a flared configuration. The reinforcing hoop 38 is expanded until its outer diameter is typically equal to or greater than the inner diameter of the pipe 30. The chamfer 30a at the end of the pipe 30 assists the flaring process.

As with the embodiment shown in Figures 1 to 3, the reinforcing hoop 38 acts to stiffen the radially outwardly extending end formation and provides a means of anchoring the liner pipe against retraction into the pipe 30 under the influence of end loads.

It will readily be apparent that numerous modifications and alterations may be made to the liner pipe illustrated in the Figures, without departing from the principles underlying the invention. For example, although the invention has been illustrated by reference to liner pipes, it is also applicable to stand-alone pipes. Also, whereas the adjustment means for adjusting the circumference of the reinforcing hoop has been illustrated by reference to a turn buckle, alternative methods may be employed to give the same result.

All such modifications and alterations are intended to be embraced by this Application.

Claims

1. A pipe formed of a plastics material and having a circumferential radially outwardly extending formation at an axial end thereof for anchoring the pipe end in a pipe connector or in an end of an outer pipe; the circumferential radially outwardly extending formation having a circumferential groove in a surface facing generally axially away from the pipe; the circumferential groove having disposed therein a reinforcing hoop for assisting the said formation to resist radially inward forces, the reinforcing hoop being provided with adjustment means for adjusting the circumference thereof.

2. A pipe according to Claim 1 wherein the radially outwardly extending circumferential formation is in the form of a radially outwardly extending stub flange which is generally perpendicular with respect to the longitudinal axis of the pipe, the circumferential groove being formed in an axial end face of the stub flange.

3. A pipe according to Claim 1 wherein the radially outwardly circumferential formation is in the form of a flared pipe end, the circumferential groove being formed in a radially inner surface of the pipe end.

4. A pipe according to any one of the preceding claims wherein the reinforcing hoop is a metal rod curved into a circular form and having adjustment means comprising a screw-thread arrangement for connecting the ends of the rod together.

5. A pipe according to Claim 4 wherein the metal rod has two threaded ends, the adjustment means comprising a turnbuckle having a complimentary thread for controlling the distance between the two ends of the rod.

6. A pipe according to any one of the preceding claims wherein the circumferential groove has a circumferential retaining lip on the radially outer side thereof for preventing dislodgement of the hoop from the groove as the hoop is expanded radially.

7. A pipe according to any one of the preceding claims which is a liner pipe for lining an existing pipeline, the radially outwardly extending circumferential formation being arranged to hold the liner pipe against axial displacement along the existing pipeline.

8. A liner pipe according to Claim 7 wherein the adjustment means is arranged to allow the reinforcing hoop to be expanded such that its outer diameter is equal to or greater than the inner diameter of the pipeline.

9. A pipe coupling assembly comprising an outer pipe, a connector for connecting the outer pipe to another pipe element; and a liner pipe; the liner pipe being as defined in Claim 7 or Claim 8.

10. A pipe substantially as described herein with reference to the accompanying drawings.

11. A liner pipe substantially as described with reference to the accompanying drawings.

12. A pipe coupling assembly substantially as described herein with reference to the accompanying drawings.