GB2584008A

GB2584008A - Method of protecting the end of a pipe

Info

Publication number: GB2584008A
Application number: GB2003796.6A
Authority: GB
Inventors: Millward Keith; Lang John; Taylor Mike
Original assignee: Polypipe Ltd
Current assignee: Polypipe Ltd
Priority date: 2012-08-28
Filing date: 2012-08-28
Publication date: 2020-11-18
Anticipated expiration: 2032-08-28
Also published as: GB202003796D0; GB2584008B

Abstract

A method of protecting the end face of a metal composite pipe of the kind having an inner plastics layer, an outer plastics layer and a central metal layer. The method comprises the first step of removing an end portion of the central metal layer at a free end of the pipe, so that the central metal layer is recessed from the inner and outer layers at the free end of the pipe. The inner and/or outer plastics layer of the pipe is then formed to cover the recessed central metal layer. The formed free end of the pipe is then inserted into a socket on a pipe connector.

Description

Method of protecting the end of a pipe

Field of Invention

The present invention relates to a method of protecting the end of a pipe, for example a metal composite pipe.

Background

Figure 1 shows a known arrangement of pipe connector 1010, plastics pipe 1012 and pipe insert 1014. The arrangement is shown in exploded form to the left as viewed in Figure 1 and in assembled form to the right as viewed in Figure 1.

In this instance, the pipe connector 1010 defines an elongate body 1016 having opposing sockets 1018, 1020. Each socket 1018, 1020 is configured for receiving the free end of a pipe 1012 and includes a collet 1024 (mounted in the connector by means of a cap 1022) for gripping the pipe 1012 in a manner known in the art. The pipe insert 1014 is located in the free end of the pipe 1012 prior to insertion into one of the sockets 1018, 1020, and serves to stiffen the free end of the pipe 1012. In order to provide a seal between the pipe 1012 and the connector 1010, an 0-ring 1026 is positioned between two washers 1028 inside each socket 1018. 1020. The 0-ring 1026 acts between the pipe 1012 and an internal surface 1019 of the respective socket 1018, 1020. to prevent leakage from the connector 1010.

Figure 2 illustrates another known arrangement, which uses a grab ring 2032 instead of a collet 1024. Other features are similar, and so will not be described further here. Similar features are given similar reference numerals as the features of Figure 1, but with a prefix of 2 instead of 1.

The grab ring 2032 is arranged between two washers 2030, 2031 within the respective socket 2018, 2020 and includes a plurality of teeth (not shown) for gripping the pipe 2012 in a manner known in the art. The pipe insert 2014 serves to stiffen the free end of the pipe 2011 and an 0-ring 2026 within the connector 2010 provides a seal between the pipe 2012 and an internal surface 2019 of the respective socket 2018. 2020.

Problems may arise if the stiffener is used with a metal composite pipe (MCP), e.g. of the kind having outer and inner layers of plastics material and a metal central layer (generally aluminium), since the end of the pipe may become exposed to fluid flow within the connector. This is problematic because contact with the fluid can cause corrosion of the metal layer. Moreover, the fluid may cause &lamination of the inner and outer plastics layer away from the central metal layer. Delamination can result in blistering of the inner layer. In some cases, pressure failure of the pipe can occur, e.g. if the relatively thin outer plastics layer is subject to the full or near full pressure of the fluid flow through the connector without the reinforcing effect of the central metal layer and the inner plastics layer.

Attempts have been made to overcome this problem by using a connector of a different configuration to that shown in Figures 1 to 2. Such a connector is illustrated generally at 3010 in Figure 3. The connector 3010 has at least one spigot 3034 with a plurality of barbs 3036 formed on the outer surface thereof. Two 0-ring seals 3026 are positioned on the spigot 3034 and a stainless steel sleeve 3038 is arranged about the spigot 3034 -initially spaced from the spigot 3034. To attach a pipe to the connector 3010, the pipe is fitted onto the spigot 3034 and the sleeve 3038 is then deformed into an interference fit with the outside of the pipe. This forces the inside of the pipe into close contact with the 0-ring seal 3026 on the spigot 3034 to create a seal, and the barbs 3036 on the spigot 3034 provide axial restraint against the pull-out forces generated by internal hydraulic pressure when the connector 3010 is in use. It can be seen that the connector 3010 seals against the inside of the pipe, and so fluid cannot come into contact with the end of the pipe (overcoming the potential for corrosion or delamination at the exposed end of an MCP).

However, a problem with this design of connector is that it requires complex equipment to attach a pipe to the connector, instead of a simple push-fit operation that is possible using the types of connectors shown in Figures 1 and 2.

Summary of the invention

There is a need to address one or more of the above-mentioned problems.

According to one aspect of the invention there is provided a method of protecting the end face of a metal composite pipe (e.g. of the kind intended to be received in the socket of a pipe connector and subjected to fluid flow), the method comprising the steps of: providing a metal composite pipe of the kind comprising inner and outer plastics layers and a central metal layer; providing a pipe insert of the kind having first and second ends and defining a flow path between the first and second ends for allowing fluid to flow along a longitudinal axis of the insert, wherein the first end of the insert defines a body configured for insertion into the free end of the pipe and the second end of the insert defines a head configured to project from the free end of the pipe and limit the degree of insertion of the insert into the pipe, wherein the second end of the insert includes an abutment surface intended for abutment with an end face of the pipe, and wherein the diameter of the abutment surface is sufficient cover at least part of the outer plastics layer of the pipe; the method further comprising the steps of: locating the first end of the insert inside a free end of the pipe; arranging said abutment surface of the head in abutment with an end face at the free end of the pipe, and immovably fixing the abutment surface of the head in contact with the end face of the pipe, in order to seal the central metal layer at the end face of the pipe against fluid contact.

Sealing the central metal layer against fluid contact in this manner overcomes problems of corrosion and/or delamination at the end of an MCP.

In exemplary embodiments, the abutment surface is welded or fused with the end face of the pipe so as to encapsulate the central metal layer at the end of the pipe, thereby sealing the metal layer against fluid contact.

This aspect of the invention may also be applicable to conventional plastics pipes, wherein the abutment surface of the insert has a diameter sufficient to extend over at least part of the end face of the pipe. Accordingly, a further aspect of the invention provides a method of protecting the end face of a pipe, the method comprising the steps of: providing a pipe; providing a pipe insert of the kind having first and second ends and defining a flow path between the first and second ends for allowing fluid to flow along a longitudinal axis of the insert, wherein the first end of the insert defines a body configured for insertion into the free end of the pipe and the second end of the insert defines a head configured to project from the free end of the pipe and limit the degree of insertion of the insert into the pipe, wherein the second end of the insert includes an abutment surface intended for abutment with an end face of the pipe, and wherein the diameter of the abutment surface is sufficient cover at least part of an end face of the pipe; the method further comprising the steps of: locating the first end of the insert inside a free end of the pipe; arranging said abutment surface of the head in abutment with an end face at the free 10 end of the pipe, and immovably fixing the abutment surface of the head in contact with the end face of the pipe, in order to seal the end face of the pipe against fluid contact.

According to another aspect of the invention there is provided a method of protecting the end face of a metal composite pipe (e.g. of the kind intended to be received in the socket of a pipe connector and subjected to fluid flow), the method comprising the steps of: providing a metal composite pipe of the kind comprising inner and outer plastics layers and a central metal layer, the pipe having a free end; providing a washer of the kind having first and second ends and defining a flow path between the first and second ends for allowing fluid to flow along a longitudinal axis of the washer, wherein the washer includes an abutment surface intended for abutment with an end face of the pipe, and wherein the diameter of the abutment surface is sufficient cover at least part of the outer plastics layer of the pipe; the method further comprising the steps of: locating the abutment surface of the washer in abutment with an end face of the 25 pipe, and immovably fixing the abutment surface of the washer in contact with the end face of the pipe, in order to seal the central metal layer at the end face of the pipe against fluid contact.

Sealing the central metal layer against fluid contact in this manner overcomes problems 30 of corrosion and/or delamination at the end of an MCP.

Again, this aspect of the invention may also be applicable to conventional plastics pipes, wherein the abutment surface of the washer has a diameter sufficient to extend over at least part of the end face of the pipe. Accordingly, a further aspect of the invention provides a method of protecting the end face of a pipe, the method comprising the steps of: providing a pipe having a free end; providing a washer of the kind having first and second ends and defining a flow path between the first and second ends for allowing fluid to flow along a longitudinal axis 10 of the washer, wherein the washer includes an abutment surface intended for abutment with an end face of the pipe, and wherein the diameter of the abutment surface is sufficient cover at least part of the outer plastics layer of the pipe; the method further comprising the steps of: locating the abutment surface of the washer in abutment with an end face of the 15 pipe, and immovably fixing the abutment surface of the washer in contact with the end face of the pipe, in order to seal the end face of the pipe against fluid contact.

According to a further aspect of the invention, there is provided a method of protecting the end of a metal composite pipe of the kind having an inner plastics layer, an outer plastics layer and a central metal layer, the method comprising the steps of: removing an end portion of the central metal layer at a free end of the pipe, so that the central metal layer is recessed from the inner and outer layers at the free end of the pipe; forming the inner and/or outer plastics layer of the pipe to cover the recessed central metal layer; and inserting the formed free end of the pipe into a socket on the pipe connector.

In an exemplary embodiment the method may comprise forming and welding together the inner and/or outer plastics layers of the pipe to encapsulate and seal the recessed metal 30 layer.

According to a still further aspect of the invention, there is provided a method of protecting the end of a metal composite pipe of the kind having an inner plastics layer, an outer plastics layer and a central metal layer, the method comprising the steps of: providing a metal composite pipe of the kind having an inner plastics layer, an outer plastics layer and a central metal layer; providing a cap for the end of the pipe, the cap comprising a body defining an annular channel for fitting onto the free end a pipe, wherein the annular channel comprises an inner wall for extension inside the pipe, an outer wall for extension outside of the pipe, and an end wall defining a closed end of the channel; fitting the cap on the free end of the pipe so that outer wall extends outside of the pipe and the inner wall extends inside the pipe, with the inner wall defining a bore for fluid to flow through the cap along a longitudinal axis of the pipe; and using the cap to provide a seal between the cap and the pipe, in order to seal the end of the pipe against fluid contact.

Again, this aspect of the invention may also be applicable to conventional plastics pipes, wherein the cap seals the end of the pipe against fluid contact. Accordingly, a further aspect of the invention provides a method of protecting the end of a pipe, the method comprising the steps of: providing a pipe; providing a cap for the end of the pipe, the cap comprising a body defining an annular channel for fitting onto the free end a pipe, wherein the annular channel comprises an inner wall for extension inside the pipe, an outer wall for extension outside of the pipe, and an end wall defining a closed end of the channel; fitting the cap on the free end of the pipe so that outer wall extends outside of the pipe and the inner wall extends inside the pipe, with the inner wall defining a bore for fluid to flow through the cap along a longitudinal axis of the pipe; and using the cap to provide a seal between the cap and the pipe, in order to seal the end of the pipe against fluid contact.

Description of drawings

Embodiment(s) of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a sectional exploded and assembled view of a pipe connector assembly of the prior art incorporating a collet for gripping a pipe received in the connector; Figure 2 shows a sectional exploded and assembled view of another pipe connector assembly of the prior art incorporating a grab ring for gripping a pipe received in the connector; Figure 3 is a sectional view of a further pipe connector assembly of the prior art, wherein the connector has a deformable sleeve for retaining the pipe on a spigot of the fitting; Figure 4 shows a sectional view of a connector and pipe end cover assembled using a method according to an embodiment of the invention; Figure 5 is similar to Figure 4 and shows a connector and pipe end cover assembled according to another embodiment of the invention; Figure 6 shows a sectional view of steps in a method of providing cover for the end face of a metal composite pipe, according to a further embodiment of the invention; Figure 7 shows a sectional view of a pipe fitted in the socket of a pipe connector, with the free end of the pipe sealed by a cap; Figure 8 shows a sectional view of part of a cap for use in the assembly shown in Figure 7; and Figure 9 shows a sectional view of an alternative embodiment of cap for use in sealing the free end of a pipe.

Detailed description

Referring to Figure 4, a pipe connector is indicated generally at 10a. The pipe connector 10a is similar to the kind shown in Figure 1. As such, it defines a body 16a having first and second sockets 18a, 20a, each configured for receiving the free end of a pipe 12a. A channel 1 la extends between the first and second sockets 18a, 20a, e.2. for permitting fluid to pass through the body 16a from one pipe 12a to another. In this embodiment, the connector body 16a is made from polybutylene. However, in alternative embodiments the connector body may be made from other suitable plastics (e.g. such as acetal or polysulphone) or metals such as brass, DZR brass or stainless steel.

In this embodiment, the sockets 18a, 20a are of identical configuration. However, for ease of illustration, only the internal structure of the socket 18a as defined by body 16a of the connector 10a is shown to the right as viewed in Figure 4, whereas the full detail of socket 20a is shown to the left as viewed in Figure 4.

S

Socket 20a includes a cap 22a which serves to locate a conventional collet 24a in the connector 10a. The collet 24a is used for gripping the outer surface of a pipe 12a in a manner known in the art. The cap 22a is mounted on an annular end part 40a of the body 16a (e.g. by snap-fit or threaded engagement). The end part 40a defines a first chamber 42a within the respective socket 18a, 20a. The first chamber 42a includes an annular internal surface 44a. Axially inwardly of the first chamber 42a (e.g. to the left when viewing socket 18a in Figure 4), the body 16a defines a second chamber 46a within the respective socket 18a, 20a. The second chamber 46a includes an annular internal surface 48a, which terminates at a stop surface 49a adjacent the channel 1 la. The internal diameter of the first chamber 42a is greater than the internal diameter of the second chamber 46a.

An 0-ring 26a is arranged within the first chamber 42a of the socket 20a, between two washers 28a, for providing a seal between the pipe 12a and the internal surface 44a of the socket 20a. In particular, the 0-ring 26a is intended for preventing fluid leakage between the external surface of the pipe 12a and the connector 10a.

In use, a free end of the pipe 12a is inserted into the socket 20a. The free end of the pipe 12a passes through the collet 24a, through the first chamber 42a and into the second chamber 46a, as illustrated to the left as viewed in Figure 4. As can be seen, the 0-ring 26a is axially spaced from the free end of the pipe 12a, when the pipe 12a is inserted in the manner illustrated in Figure 4.

The collet 24a is configured to permit the pipe 12a to slide into the connector 10a with case. The collet 24a acts to prevent the pipe being pulled from the connector. However, the connector 10a is removable from the pipe 24a, by moving the collet 24a in a conventional manner, e.g. in an axial direction towards the socket body 16a, to cause the collet 24a to release its grip with the pipe 1 2a.

A pipe insert 14a is shown fitted in the free end of the pipe 12a. The insert 14a defines a bore along a longitudinal axis of the insert 14a for allowing fluid to flow into or out of the bore of the pipe 12a. The insert 14a has a first end which defines a generally tubular main body or barrel 50a configured to extend within the pipe 12a, and a second end which defines a head 52a configured to limit the extent of insertion of the insert 14a into the pipe 12a. Inserts of this kind have been found to improve performance during pipe connector pull-out tests, and are more commonly referred to as pipe 'stiffeners'.

In this embodiment, the head 52a is arranged in the second chamber 46a of the connector 10a when the pipe 12a and insert 14a are fully assembled with the connector 10a, e.g. as viewed in Figure 4. Typically, the pipe 12a will be pushed into the socket 20a until the exposed end of the insert 14a abuts the stop surface 49a.

In the illustrated embodiment, the main body 50a has an outer surface configured for frictional contact with the inside of the pipe 12a. The head 52a of the insert 14a defines a radial flange having a surface 54a, orthogonal to the longitudinal axis of the insert. 14a, that is intended to be arranged in abutment with the end face of the pipe 12a. In exemplary embodiments, the outer diameter of the surface 54a is dimensioned to be at least a substantial match for the outer diameter of the pipe 12a into which the insert 14a is to be fitted, e.g. in order to extend radially over at least a significant proportion of the exposed end face of the pipe 12a (in particular, over at least the central metal layer of an MCP, and more preferably over at least part of the outer plastics layer of an MCP).

The outer surface of the head 52a defines a curved end of the insert 14a, to ease insertion of the pipe 12a and insert 14a into the connector 10a (e.g. to pass through a collet or other pipe gripper on the connector). In alternative embodiments, the end of the insert 14a may include angled surfaces (e.g. defining an end of the insert which is trapezoidal in cross-section).

In an exemplary method of assembly, first end 50a of the insert is fitted within the pipe 12a, to an extent that the orthogonal surface 54a of the head 52a abuts against an end face of the pipe 12a. The insert 14a is then welded to the pipe 12a to immovably fix the head 52a relative to the end face of the pipe 12a.

In this embodiment, the step of welding the insert 14a to the pipe 12a requires a tool to rotate the insert 14a with respect to the free end of the pipe, to create heat at Ihe interface between the insert and the pipe (i.e. spin welding). The tool may be a hand-held power drill, for example. The head 52a of the insert 14a is positioned with the surface 54a in abutment with an end face of the pipe and an axial pressure is applied in a direction towards the pipe 12a, whilst the insert 14a is rotated. The heat generated causes engaged parts of the insert and pipe to soften to a point at which a weld can be formed upon cooling. For example, a weld may be formed between the head of the insert and at least part of an end surface of the pipe, and/or between the barrel of the insert and the inside of the pipe.

In alternative embodiments, the insert 14a may be welded using localised butt welding, socket fusion or electro fusion.

Welding the insert 14a to the pipe 12a immovably fixes the insert with respect to the pipe 12a.

In this embodiment, the insert 14a is made from the same material as the portion of the pipe 12a to which it is intended to be welded or fused. However, in alternative embodiments any suitable material may be selected to manufacture the insert 14a, e.g. suitable to weld or fuse the insert to the end of the pipe.

A tool engagement formation (not shown in the Figures) may be formed in the second end of the insert, for engagement by the tool intended to rotate the insert relative to the pipe. For example, the tool engagement formation may take the form of one or more recesses or ribs for engaging complimentary projections on a tool head (e.g. the free end of an appropriately configured drill bit).

In exemplary embodiments, the pipe 12a is an MCP having a central metal layer (e.g. of aluminium) arranged between an inner plastics layer and an outer plastics layer, and the weld or fusion occurs between the end surface 54a and the exposed inner and outer plastics layers at the free end of the pipe 12a, so as to encapsulate the metal layer and seal the end of the pipe against fluid contact from within the pipeline.

An alternative embodiment is shown in Figure 5. Features of the embodiment of Figure 5 that are similar to those of Figure 4 are given a similar reference numeral, but with a suffix "1)". Only the differences will be described here.

II

In this embodiment, a washer 14b is positioned on an end face of the pipe 12b. The washer 14b is an annulkff or ring-type member having an end face configured to cover at least a major proportion of the end face of the pipe 12b.

The washer 14b defines a bore intended to be at least generally concentric with the bore of the pipe 12b, to allow fluid to flow through the pipe 12b and washer 14b without significant disruption at the interface between the pipe 12b and the washer 14b. Furthermore, the washer 14b has inner and outer surfaces intended to be arranged at least generally in alignment with the inner and outer surfaces at the free end of the pipe 12b.

This is particularly important if the pipe 12b is an MCP of the kind having a central metal layer (e.g. of aluminium) arranged between an inner plastics layer and an outer plastics layer, since the washer 14b is intended to be immovably fixed against an end face of the pipe 12b, in order to encapsulate and seal the exposed metal layer at the end of the pipe.

This may be achieved by spin welding, e.g. in the manner described with reference to Figure 4, so that a weld is formed at the interface between the washer 14b and the pipe 12b. Accordingly, the washer may include one or more tool engagement portions of the kind described above with reference to Figure 4, e.g. for use in rotating the washer against the free end of the pipe using a powered hand drill and an appropriately configured drill bit, in order to generate the heat necessary to soften the plastics parts at the interface and permit a weld to be formed therebetween.

Other methods may be used for immovably fixing and sealing the washer 14b to the end of the pipe (in order to protect the end face of the pipe against fluid contact from within the pipeline), such as localised butt welding, ultrasonic welding, socket fusion or electro fusion.

In this embodiment, the washer 14h is made from the same material as the portion of the pipe 12b against which it is intended to be welded or fused, but in alternative embodiments any suitable material may be selected to manufacture the washer, provided that it is also suitable to form a weld or fuse with the end face of the pipe (in particular both the inner outer plastics layers, if the pipe is an MCP).

In exemplary embodiments, the pipe 12b is an MCP having a central metal layer (e.g. of aluminium) arranged between an inner plastics layer and an outer plastics layer, and the weld or fusion occurs between the end surface 54b and the exposed outer and inner plastics layers at the free end of the pipe 12b, so as to encapsulate the metal layer and seal the end of the pipe against fluid contact from within the pipeline.

An alternative method of coveting the end of a pipe is shown in Figure 6.

In this embodiment, the pipe 12c is an MCP having inner and outer plastics layers 60c, 62c and a central metal layer 64c (e.2. of aluminium). As will be described in more detail below, the plastics layers 60c, 62c are used to cover the central metal layer 64c, instead of using the insert of Figure 4 or the washer of Figure 5.

It will be understood that the pipe 12c defines an annulus about a central axis (shown by the dotted line 13c in Figure 6), although only one side of the cross-section is shown for ease of illustration.

In a first step, a circumferential portion 66c of the metal central layer 64c at. the end face of the pipe 12c is removed. In this embodiment, this is achieved using a powered hand drill with a shaped cutter attached thereto. This results in the central metal layer 64c being recessed or axially set-back from the plastics layers 60c, 62c at the free end of the pipe 12c.

The free end of the MCP 12c is then heated to soften the outer and inner plastics layers 60e. 62c, making them easier to form. The outer and inner layers 60c, 62e are then folded over so as to cover the end of the metal central layer 64c. The end of the MCP 12c is then cooled, allowing the ends of the outer and inner plastics layers 60c, 62c to set in the folded position. This ensures that the central metal layer 64c is encapsulated and sealed against exposure to fluid flow in the pipeline, reducing the risk of corrosion and/or delamination.

Referring now to Figures 7 and 8, a pipe connector assembly is shown similar to Figures 1 and 4. However, in this embodiment, a cap 14d is positioned on the free end of the pipe 12d.

The cap 14d has inner and outer walls 54d, 56d separated from one another by an end wall 52d, so as to define an annular channel having a closed end and configured for receiving the end of the pipe 12d, i.e. with the inner wall 54d extending into the bore of the pipe 12d and the outer wall 56d extending over an outer surface of the pipe 12d.

When so located, it will be understood that the cap 14d covers an exposed end face of the pipe 12d.

The inner wall 54d of the cap 14d may have a greater axial length than the outer wall 56d, as this has been found to improve the performance during pull-out tests.

Projections 58d (in this embodiment, two projections) are positioned on an inner surface of the outer wall 56d and on an outer surface of the inner wall 54d. The projections 58d are arranged and dimensioned to provide an interference fit with the pipe 12d, i.e. for gripping the pipe 12d. hi this embodiment, the projections 58d are barbs positioned at an angle to a longitudinal axis of the cap 14d. The projections are arranged to permit the cap to be pushed onto the end of the pipe 12d. but to resist the cap being pulled off the end of the pipe 12d. In alternative embodiments, barbs may be provided on only the outer wall 56d or only the inner wall 54d, which may simplify manufacture and ease fitting of the cap onto the end of a pipe.

In this embodiment, the cap 14d is manufactured from stainless steel sheet of approximately 0.1 mm thickness. The cap 14d is formed by pressing the stainless steel sheet. Using such a relatively thin sheet material enables the outer diameter of the cap to be minimised, which enables a pipe with an cap on the end to be easily fitted through the 0-ring seal 26d and collet 24d of the connector 20d (i.e. the cap does not significantly obstruct passage through the collet 24d). Of course, other thicknesses of material could be used.

In other embodiments, different metals may be used, e.2. brass or copper, in which case other thicknesses may be appropriate.

A washer 50d is fitted in the closed end of the channel, e.g. against the end wall 52d of the cap 14d, and is held between the inner and outer walls 54d, 56d. In this embodiment, the washer 50d is a sealing washer manufactured from a soft plastics (e.g. polybutylene or PEX), thermoplastic elastomer or rubber. When the cap 14d is pushed onto the end of the pipe 12d, the end of the pipe is brought into sealing engagement with the washer 50d (i.e. by compression of the washer 50d), so as to create a seal with the end of the pipe.

This arrangement reduces the risk of the end of the pipe being exposed to fluid contact.

The projections 58d on the inner and/or outer walls 54d, 56d prevent movement of the cap relative to the pipe and so ensure that the seal remains compressed.

In alternative embodiments, an adhesive, for example a high temperature adhesive or a mastic sealant may be used instead of a washer. Using an adhesive or mastic sealant also provides a method for connecting the cap to the pipe, in addition to or as an alternative to using projections 58d.

In other alternative embodiments, the cap 14d may be used without a sealing washer or an adhesive/mastic sealant in the channel.

The channel formed between the inner and outer walls 54d, 56d may define a taper or other reduction in diameter in the direction away from the free end of the walls 54d, 56d, for providing a sealing interference fit with the pipe 12d. Such configurations may provide an alternative or additional means for providing a seal to prevent or reduce the risk of fluid contact with the end of the pipe 12d.

The free end of the inner and/or outer walls 54d, 56d may have a tapered portion or otherwise angled surface to define a 'lead in', for reducing the likelihood of the cap causing damage to a pipe 12d during fitting of the cap 14d (in particular for those embodiments where the inner and/or outer wall 54d, 56d is configured to provide a sealing interference fit with the pipe 12d, and so requires greater force to push the cap onto the end of the pipe).

Advantageously, the cap 14d can be positioned onto the end of a pipe 12d without the need for tooling, or at least without the need for bespoke tooling. However, using a tool to force the cap on the pipe may, in some instances, increase a compressive force applied by the cap onto the pipe walls and thereby improve the sealing effect of the cap on the Pipe.

Figure 9 shows an alternative embodiment of cap 14e. Similar reference numerals are used as for Figures 7 and 8, but with a suffix "e" instead of "d", and only the differences will be described.

The cap 14e is configured to define a loose fit on the end of the pipe 12e, i.e. the channel defined by the inner and outer walls 54e, 56e is enlarged relative to the diameter of the pipe 12e, when compared to the channel defined in the cap 14d. In this embodiment, the outer wall 56e is angled so that the width of the channel is greatest at the open end of the channel.

For this kind of embodiment, the cap 14e is connected to the end of the pipe using a press tool, i.e. to radially compress the inner and outer walls 54e, 56e onto a respective inner and outer surface of the pipe 12e.

The inner wall 54e of the cap 14e has a greater axial length than the outer wall 56e, which can improve the performance of connected pipes 12e in a pull-out test. However, the walls may be of equal length in other embodiments.

Although the connectors described with reference to Figures 4, 7, 8 and 9 include a collet, the embodiments of the invention desciibed can equally be used with connectors having an alternative gripper, for example a grab ring of the kind shown in Figure 2.

Typically, the invention described herein is intended for use in plumbing systems and the like, in which the free end of a pipe needs to be fitted in a socket on a connector within the system. In exemplary embodiments, the invention is intended for use in central heating systems. In other embodiments, the invention is intended for use in other water supply applications, including indoor and outdoor applications (domestic and/or commercial). The connectors for use with or in the invention may be of any suitable shape and may be configured with one, two or more sockets for receiving the free end of a pipe. This will include conventional elbow and T-sections, as well as 'straight' or double-ended connectors (e.g. of the kind illustrated herein), radiator valves and socket blank ends. The connectors may be of any suitable material, such as plastics, brass, copper or stainless steel.

Claims

Claims 1. A method of protecting the end of a metal composite pipe of the kind having an inner plastics layer, an outer plastics layer and a central metal layer, the method comprising the steps of: removing an end portion of the central metal layer at a free end of the pipe, so that the central metal layer is recessed from the inner and outer layers at the free end of the Pipe; forming the inner and/or outer plastics layer of the pipe to cover the recessed central metal layer; and inserting the formed free end of the pipe into a socket on the pipe connector.
2. The method according to claim 1 wherein the end portion of the central metal layer is removed using a drill and/or a shaped cutter.
3. The method according to claim 1 or claim 2 wherein the method comprises folding the inner and/or outer layer of the pipe to cover the recessed central metal layer.
4. The method according to any preceding claim, comprising the step of heating an end of the pipe so as to soften the inner and/or outer plastics layers of the pipe so as to ease forming of the inner and/or outer layers of the pipe over the recessed central metal layer.
5. The method according to claim 4, comprising the subsequent step of cooling the free end of the pipe to form the cover over the recessed central metal layer.