GB2303680A

GB2303680A - Liner pipe

Info

Publication number: GB2303680A
Application number: GB9515425A
Authority: GB
Inventors: Alan Headford
Original assignee: Victaulic Co PLC
Current assignee: Victaulic Co PLC
Priority date: 1995-07-27
Filing date: 1995-07-27
Publication date: 1997-02-26
Anticipated expiration: 2015-07-27
Also published as: GB9515425D0; GB2303680B

Abstract

The liner pipe 1 is secured against axial displacement along the bore of a surrounding outer pipe member 2, by inserting the pipe 1 such that an end portion 4 protrudes beyond the end of the outer pipe member 2, positioning expanding means 21, 22 into the end portion 4, actuating the expanding means 21, 22 to expand the end portion 4, inserting a reinforcing hoop 31 into a circumferential groove 5 extending around its radially inner surface and removing or radially contracting the expanding means 21, 22 such that the reinforcing hoop 31 is held securely in the circumferential groove 5; the reinforcing hoop 31 being of such dimensions that it anchors the expanded end portion of the liner pipe 1 against axial displacement into and along the bore of the outer pipe member 2. The expanding means 21, 22 may be a turnbuckle hoop in a groove of the pipe 1 or a pneumatic or hydraulic pipe expanding head. The pipe end portion 4 may be heated for the expansion.

Description

IMPROVEMENTS IN OR RELATING TO 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 as a result of the presence of 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.

A further aspect of the invention is to provide a method of forming a reinforced end formation in situ.

Accordingly, in a first aspect, the invention provides a method of anchoring a liner pipe member formed of a plastics material against axial displacement along the bore of a surrounding outer pipe member; which method comprises arranging the liner pipe member in the outer pipe member such that an end portion of the liner pipe member protrudes beyond the end of the outer pipe member; positioning expanding means into the protruding end portion of the liner pipe member; actuating the expanding means to expand the protruding end portion; inserting a reinforcing hoop into a circumferential groove extending around the radially inner surface of the protruding end portion; and removing or radially contracting the expanding means such that following the removal or radial contraction of the expanding means, the reinforcing hoop is held securely in the circumferential groove; the reinforcing hoop being of such dimensions that it anchors the expanded end portion of the liner pipe against axial displacement into and along the bore of the outer pipe member.

The protruding end portion of the liner pipe member may be created by simply inserting the liner pipe member into the outer pipe member such that a short length of liner pipe extends outwardly from the end of the outer pipe. Alternatively, the line pipe member may be initially arranged within the outer pipe member such that a longer portion of liner pipe member extends outwardly from the end of the outer pipe member, the liner pipe member then being cut down to give a protruding end portion of the desired size.

The expansion of the protruding end portion may be accomplished with or without the application of heat to soften the plastics material, but preferably it is accompanied by the application of heat. For example, the protruding end portion may first be heated with a suitable heating means such as a heating plate, heating jacket or heating mandrel, the heating means then being removed once the desired temperature has been reached. Expanding means can then be positioned within the protruding pipe end to expand and stretch the softened plastics material.

In an alternative form, the expanding means itself may be provided also with heating means.

The term "pipe member" as used herein refers not only to "pipes" per se, but also to any pipe-like member such as pipe fittings, junctions etc.

In one particular embodiment, the expanding means is an expandable hoop which is arranged to be seated in a second circumferential groove disposed axially outwardly of the first circumferential groove within which the reinforcing hoop is retained.

The expandable hoop may be expandable by virtue of having a turn buckle.

As an alternative, a pneumatically or hydraulically driven pipe expanding head can be used as the expansion means.

The reinforcing hoop is typically formed from a metal material, for example a suitable steel material. The reinforcing hoop can have a circular cross-section, or a distorted circular cross-section such as an ovular crosssection, or may have a regular or irregular polygonal cross-section. Preferably however the reinforcing hoop has either a circular cross-section or a rectangular crosssection.

The reinforcing hoop will generally have an outer diameter which is equal to or greater than the inner diameter of the outer pipe member.

Where the protruding end portion of the liner pipe member is provided with two circumferential grooves, an annular region of the protruding portion may be removed by cutting at a position axially between the first and second grooves following expansion and insertion of the reinforcing hoop.

In a further aspect, the invention provides a liner pipe formed from a plastics material, the liner pipe having first and second circumferential grooves in a radially inner surface of an axial end portion of the liner pipe; the first circumferential groove being disposed axially inwardly of the second circumferential groove and being dimensioned to retain therein a reinforcing hoop, and the second circumferential groove being dimensioned to receive therein a turn buckle.

In a still further aspect, the invention provides a combination of an outer pipe member having a liner pipe disposed within its bore, an axial end portion of the liner pipe protruding from the end of the outer pipe, wherein the protruding end portion of the liner pipe is flared radially outwardly and wherein the radially outwardly flared end portion has a circumferential groove in the radially inner surface thereof, which groove has retained therein a reinforcing hoop, the reinforcing hoop and radially outwardly flared end portion serving to anchor the liner pipe against axial displacement into and along the bore of the outer pipe.

The invention will now be illustrated, but not limited, by reference to the specific embodiments shown in Figures 1 to 4 of which: Figure 1 is a partial sectional elevation of the end of a liner pipe positioned within the end of an outer pipe; Figure 2 is a partial sectional elevation illustrating the expansion of the end of the liner pipe in Figure 1 using an expandable hoop; Figure 3 illustrates the expanded liner pipe end of Figure 2 but with a reinforcing hoop inserted; and Figure 4 illustrates the liner pipe arrangement of Figure 3 following removal of the expandable ring and trimming of the end.

Referring now to Figure 1, it can be seen that in accordance with the invention, an inner liner pipe member 1 is inserted into an outer pipe member 2. Outer pipe member 2 may, for example be formed from metal such as steel. Outer pipe member 2 has a chamfer 3 on its radially inner edge.

Liner pipe 1 in this embodiment is formed of an appropriate grade of polyolefin material, for example polyethylene. An end portion 4 of the liner pipe protrudes from the end of the outer pipe 2. The protruding end portion 4 of the liner pipe has two circumferential grooves 5 and 6 cut in to the radially inner surface thereof.

The two circumferential grooves have a similar profile. Thus each groove has an axially inner surface 5a, 6a, which is radially outwardly inclined with respect to the axis A of the liner pipe. Each groove 5,6 also has on its axially outermost side a circumferential lip 5b, 6b.

Circumferential lips 5b and 6b act to retain a reinforcing hoop and a turn buckle ring respectively as will be described below. Circumferential lip 6b is cut away over a region 6c on its circumference to make room for the insertion of a turn buckle.

As an alternative to the angled grooves shown in the drawings, the grooves may be formed such that when the end portion 4 of the liner pipe is in the non-expanded condition, the walls of the groove are generally normal to the axis of the pipe members 1, 2.

As shown in Figure 2, a turn buckle ring 21 is inserted into annular groove 6, the turn buckle 22 being accommodated within the enlarged recess 6c of the circumferential groove 6. Turn buckle ring 21 consists of a discontinuous metal hoop having two threaded ends of which one 23 is shown in Figure 2. The two threaded ends are threadingly engaged by the turn buckle 22 which has a socket arrangement 24 within which a lever (not shown) may be inserted to rotate the turnbuckle and thus expand or contract the turn buckle ring 21.

In Figure 2, the turn buckle 22 has been rotated so as to cause the ring 21 to expand thereby forcing the protruding end 4 of the liner pipe member 1 radially outwardly to give a conical end formation on the liner pipe.

Prior to expanding the ring 21, it is preferable to heat the liner pipe by means of a suitable heating means (not shown) e.g. a heating collar, plate or mandrel, so as to soften the polyolefin to render it easier to deform.

Once the protruding end portion of the liner pipe 1 has been expanded to the required extent, a reinforcing hoop 31 is inserted as shown in Figure 3. Reinforcing hoop 31 is of a fixed radius, and is formed from a suitably stiff material, typically a metal such as steel.

As an alternative to the reinforcing hoop 31 illustrated in Figure 3, in which the radial width of the reinforcing hoop is greater than its axial width, the reinforcing hoop 31 could instead be formed such that its axial width is greater than its radial width, i.e. the reinforcing hoop has a cylindrical form. In a still further alternative, rather than being rectangular, the reinforcing hoop could be of circular or distorted circular cross-section.

Once the reinforcing hoop 31 has been fitted into place, the turn buckle 22 is rotated to contract the turn buckle ring 21 allowing removal from groove 6. As the turn buckle ring 21 is contracted, so the flared end portion 4 of the liner pipe 1 shrinks onto the reinforcing hoop 31 thereby holding it firmly in place.

An annular portion 32 containing the circumferential groove 6 may then be removed from protruding end portion 4 by cutting along line 33.

The end result is a liner pipe which is anchored in the end of outer pipe 2 and wherein the reinforcing ring 31 serves to stiffen the end formation 4' and prevent the liner pipe from being displaced axially into the liner pipe 2 when subjected to axial end loads.

The advantage of the process of the present invention is that it avoids the need for the retaining groove 5 to be machined to close tolerances. Thus in order to accommodate the reinforcing hoop, it is simply necessary to expand the protruding end portion 4 to a suitable extent and then snap the reinforcing hoop 31 into place. Thus the method can accommodate considerable deviations from the nominal size of both of the reinforcing hoop and the retaining groove.

It will readily be apparent that numerous modifications and alterations may be made to the embodiments shown in the accompanying drawings without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.

Claims

1. A method of anchoring a liner pipe member formed of a plastics material against axial displacement along the bore of a surrounding outer pipe member; which method comprises arranging the liner pipe member in the outer pipe member such that an end portion of the liner pipe member protrudes beyond the end of the outer pipe member; positioning expanding means into the protruding end portion of the liner pipe member; actuating the expanding means to expand the protruding end portion; inserting a reinforcing hoop into a circumferential groove extending around the radially inner surface of the protruding end portion; and removing or radially contracting the expanding means such that following the removal or radial contraction of the expanding means, the reinforcing hoop is held securely in the circumferential groove; the reinforcing hoop being of such dimensions that it anchors the expanded end portion of the liner pipe against axial displacement into and along the bore of the outer pipe member.

2. A method according to claim 1 wherein the protruding end portion of the liner pipe member is created by inserting the liner pipe member into the outer pipe member such that a short length of liner pipe extends outwardly from the end of the outer pipe.

3. A method according to claim 1 wherein the liner pipe member is initially arranged within the outer pipe member such that a longer portion of liner pipe member extends outwardly from the end of the outer pipe member, the liner pipe then being cut down to give a protruding end portion of the desired size.

4. A method according to any one of the preceding claims wherein the expansion of the protruding end portions is accomplished with the application of heat.

5. A method according to claim 4 wherein the protruding end portion is first heated with a heating plate, heating jacket or heating mandrel, the heating means being removed once a desired temperature has been reached, and prior to expansion of the protruding end portion.

6. A process according to any one of claims 1 to 4 wherein the expanding means itself is provided with heating means.

7. A method according to any one of the preceding claims wherein the expanding means is an expandable hoop which is arranged to be seated in a second circumferential grove disposed axially outwardly of the first circumferential grove within which the reinforcing hoop is retained.

8. A method according to claim 7 wherein the expandable hoop is expandable by virtue of having a turn buckle.

9. A method according to any one of claims 1 to 6 wherein a pneumatically or hydraulically driven pipe expanding head is used as the expanding means.

10. A method according to any one of the preceding claims wherein the reinforcing hoop is formed from a metal material.

11. A method according to claim 10 wherein the metal material is a steel material.

12. A method according to any one of the preceding claims wherein the reinforcing hoop has either a circular cross-section or a rectangular cross-section.

13. A method according to any one of the preceding claims wherein the reinforcing hoop has an outer diameter which is equal to or greater than the inner diameter of the outer pipe member.

14. A method according to claim 7 or claim 8 wherein, following expansion of the protruding end portion of the liner pipe and insertion of the reinforcing hoop, an annular region of the protruding end portion is removed by cutting at a position axially between the first and second groove.

15. A liner pipe formed from a plastics material, the liner pipe having first and second circumferential grooves in a radially inner surface of an axial end portion of the liner pipe; the first circumferential groove being disposed axially inwardly of the second circumferential groove and being dimensioned to retain therein a reinforcing hoop, and the second circumferential groove being dimensioned to receive therein a turn buckle.

16. A combination of an outer pipe member having a liner pipe disposed within its bore, an axial end portion of the liner pipe protruding from the end of the outer pipe, wherein the protruding end portion of the liner pipe is flared radially outwardly and wherein the radially outwardly flared end portion has a circumferential groove in the radially inner surface thereof, which groove has retained therein a reinforcing hoop, the reinforcing hoop and radially outwardly flared end portion serving to anchor the liner pipe against axial displacement into and along the bore of the outer pipe.

17. A method of anchoring a liner pipe member sebstantially as described herein with reference to the accompanying drawings.

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

19. A combination of an outer pipe member having a liner pipe disposed within its bore substantially as described herein with reference to the accompanying drawings.