AU704949B2

AU704949B2 - Method and apparatus for joining metal and polymeric pipes and pipe fittings

Info

Publication number: AU704949B2
Application number: AU60796/96A
Authority: AU
Inventors: John Bugh
Original assignee: IND PIPE SYSTEMS Pty Ltd
Current assignee: INDUSTRIAL PIPE SYSTEMS Pty Ltd
Priority date: 1995-08-04
Filing date: 1996-07-29
Publication date: 1999-05-06
Anticipated expiration: 2016-07-29
Also published as: AU6079696A

Description

-2- The present invention relates to a method and apparatus for joining metal and polymeric pipes or pipe fittings.

The invention has been developed primarily for use in joining underground polymeric pipes to copper or steel risers and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

Polymeric pipes, such as those formed from polyethylene or nylon, are easier to cut, join and bend than equivalent copper or steel pipes. For these reasons, polymeric pipes are generally used in preference to metal pipes where possible. The ease of 0o 10 handling polymeric pipes is particularly advantageous in situations where access is .limited, such as in underground piping systems. However, polymeric pipes tend to deteriorate when exposed to sunlight, which makes them undesirable for use in some S•applications. Due to this deterioration, it is often necessary to join an above ground copper or steel riser pipe to an underground polymeric pipe, thereby allowing, for example, water to be conveyed from an underground pipe system to an above ground tap. In this way, the use of polymeric piping is maximised as far as possible, whilst substantially avoiding the problems of sunlight based deterioration.

In order to join the dissimilar polymeric and metal pipes or pipe fittings together, it has been necessary in the past to use mechanical clamping or interference style fittings.

However, these known joining arrangements have a number of disadvantages associated with them. Firstly, polymeric pipe has a tendency to creep and relax over time, which tends to reduce the effective sealing forces of the surrounding clamps. Secondly, these -3arrangements entail additional costs due to the clamping componentry and the labour input required for assembly.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

According to a first aspect of the invention there is provided a method ofjoining a polymeric pipe or pipe fitting to a metal pipe or pipe fitting, said method including the steps of: applying a priming layer to a connection surface of the metal pipe or pipe fitting wherein the priming layer is a compound including epoxy phenolic resin; bringing said polymeric pipe or pipe fitting into contacting engagement with said priming layer; and heating said priming layer and said polymeric pipe or pipe fitting to a temperature sufficient to form a permanent bond therebetween.

Preferably, during step the metal pipe or pipe fitting is heated at a point 15 remote from the connecting surface to achieve the heating of the priming layer and the plastic pipe or pipe fitting by conduction through the metal pipe or pipe fitting.

In one form, step includes overmoulding the polymeric pipe or pipe fitting into contacting engagement with the priming layer. Alternatively, step may include premoulding the polymeric pipe or pipe fitting prior to engagement with the priming 20 layer.

In some cases, it may be desirable to include an additional step intermediate (a) and of preheating the metal pipe or pipe fitting prior to positioning the polymeric pipe or pipe fitting into contacting engagement with the priming layer.

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9 0505 -4- In one preferred embodiment, the polymeric pipe or pipe fitting is externally positioned in an overlapping telescopic relationship with the metal pipe or pipe fitting.

Alternatively, the metal pipe or pipe fitting may be externally positioned in an overlapping telescopic relationship with the polymeric pipe or pipe fitting.

According to a second aspect of the invention, there is provided a pipe fitting assembly including a polymeric pipe or pipe fitting and a metal pipe or pipe fitting, the metal pipe or pipe fitting including a priming layer applied to a connection surface, the priming layer and the polymeric pipe or pipe fitting being permanently fused together, wherein the priming layer is a compound including epoxy phenolic resin.

In a first preferred form the polymeric fitting is an overmoulded grooved nylon ferrule, and the metal pipe is copper.

•In a second preferred form, the polymeric fitting is a preformed grooved nylon ferrule having a cylindrical recess which receives a reduced diameter portion of the metal pipe, which is preferably formed from steel.

esee 15 In a third preferred form, the polymeric fitting is a polyethylene to nylon transition piece fused to the metal pipe, which is formed from copper or steel. The transition piece may be formed by coextruding a polyethylene outer layer and a nylon inner layer with an intermediate joining layer.

Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a sectional side view of a first embodiment of a polymeric pipe fitting S joined to a metal pipe, in accordance with the invention; Figure 2 is a sectional side view of a second embodiment of a polymeric pipe fitting joined to a metal pipe; Figure 3 is a sectional side view of a third embodiment of a polymeric pipe fitting joined to a metal pipe; and Figure 4 is a perspective view of a joining apparatus according to the second aspect of the invention.

Referring to Figure 1, there is shown a pipe fitting assembly 10 which includes a polymeric pipe or pipe fitting in the form of overmoulded nylon ferrule 12, and a metal S o 0* 0* S

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0 -6pipe or pipe fitting in the form of copper riser pipe 14. Before ferrule 12 is moulded around pipe 14, a priming layer is applied to a connection surface 16 of the pipe. The ferrule 12 is then moulded into overlapping contacting engagement with the priming layer. Once the nylon has set, the ferrule and pipe are heated to a temperature sufficient to form a permanent bond therebetween.

In this preferred embodiment, the priming layer is formed from RILPRIME P23V40, an enamel manufactured by ElfAtochem Australia Pty. Ltd. When using this primer, the priming layer is applied in liquid form to the end of the copper pipe and then baked onto the pipe. The bond between the nylon ferrule and the priming layer is S. 10 formed by heating the copper pipe 14 at a position remote from the priming layer and nylon ferrule. Conduction of heat by the copper pipe melts the priming layer and inner surface of the ferrule to form a permanent bond. A temperature of approximately 240'C •has been found to be sufficient, with the particular samples tested to date, to melt the priming layer and nylon into a permanent bond. An indication of sufficient temperature is given by a melt bead forming at both ends 18 and 20 of the bonding zone.

To facilitate subsequent gluing of the nylon ferrule to additional componentry, it is provided with internal glue grooves 22. Copper pipe 14 also includes a flared end portion 24 which serves to both strengthen the join between the ferrule and pipe in the longitudinal direction and to provide a smooth inner transition edge for mating with the internal surface of the mould to ensure that molten nylon does not pass into the interior of the pipe during production.

Turning to Figure 2, there is shown a second embodiment of a pipe fitting assembly according to the invention in which like numerals are used to designate like -7features. In this embodiment, the metal pipe or pipe fitting is in the form of a steel pipe 26 which terminates in a shouldered portion 28 of reduced external diameter. Priming layer 16 is bonded to the shouldered portion 28. To facilitate joining, the pre-formed nylon ferrule 12 is provided with a correspondingly recessed inner portion 30 which is pressed over the shouldered portion 28 and the priming layer. The priming layer and ferrule are heated after assembly, as previously described, to form a permanent bond therebetween. The ferrule 12 is again provided with internal glue grooves 22 to facilitate subsequent joining of the ferrule and associated pipe to additional componentry.

.Figure 3 shows a third embodiment of the invention in which a polyethylene to nylon transition piece 32 is bonded to a copper or metal pipe 34. In this embodiment, S"the transition piece 32 is preformed with a polyethylene outer layer 36 and a nylon inner layer 38. To join the transition piece to the copper or steel tube 34 the recessed inner nylon layer 40 is positioned over the priming layer 16 of the tube 34, and the tube is heated to bond the priming layer to the nylon. The transition piece may be formed by coextrusion of a polyethylene outer and nylon inner with an intermediate bonding layer.

It will be appreciated that this embodiment of the invention overcomes the difficulty of attempting to join polyethylene directly to copper or steel.

Turning finally to Figure 4, there is shown an apparatus 42 for use in joining the previously described polymeric and metal pipes or pipe fittings. The apparatus comprises a feed table 44, conveyor assembly 46, heating means in the form of gas burners 48, cooling means in the form of blower 50 and an exit table 52. The conveyor assembly 46 contains evenly spaced attachment links (not shown) which are adapted to sequentially pick up pipes from the feed table and carry them over the gas burners -8towards the exit table. The pipes fall free of the attachment links at the end of the apparatus into the exit table.

In use, a number of pipes are placed in the feed table 44. These pipes are individually picked up by the conveyor assembly 46 and passed over gas burners 48 in the direction shown by arrow 52. For copper pipes a sufficient fusion bonding temperature is achieved when the pipes dwell over the burners for approximately three minutes. The pipes are then passed over a cooling blower 50 prior to exit of the conveyor assembly.

The time taken for the pipes to pass over the gas burner is governed by a variable 10 speed motor (not shown) driving the conveyor assembly. This allows the heating and cooling dwell times to be adjusted for various pipe and fitting configurations.

°It is believed that whilst RILPRIME is the preferred priming layer, other such primer compositions would also be suitable.

The invention possesses advantages over prior joining methods as it provides a relatively inexpensive, repeatable and secure bond between the polymeric and metal components. In its preferred form it also obviates the need, and extra cost, of powdercoating the pipe, as the priming layer may be applied directly to the metal surfaces.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. In particular, the invention is equally suited to joining polymeric pipes to metal fittings and can be used to join other metals and polymers not described above.

-9- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A method of joining a polymeric pipe or pipe fitting to metal or pipe or pipe fitting, said method including the steps of: applying a priming layer to a connection surface of the metal pipe or pipe fitting, wherein the priming layer is a compound including epoxy phenolic resin; bringing said polymeric pipe or pipe fitting into contacting engagement with said priming layer, and heating said priming layer and said polymeric pipe or pipe fitting to a temperature sufficient to form a permanent bond therebetween.

2. A method according to claim 1, wherein during step the metal pipe or pipe fitting is heated at a location remote from the connecting surface to achieve the heating of the priming layer and the plastic pipe or pipe fitting by heat conduction through the metal pipe or pipe fitting.

3. A method according to claim 1 or claim 2, wherein step includes overmoulding 15 the polymeric pipe or pipe fitting into contacting engagement with the priming layer.

4. A method according to either claim 1 or claim 2, wherein step includes premoulding the polymeric pipe or pipe fitting prior to engagement with the priming layer.

00* A method according to any one of the preceding claims, wherein the metal pipe or pipe fitting is preheated prior to positioning the polymeric pipe or pipe fitting into contacting engagement with the priming layer.

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Claims

6. A method according to any one of the preceding claims, wherein the polymeric pipe or pipe fitting is externally positioned in an overlapping telescopic relationship with the metal pipe or pipe fitting.
7. A method according to any one of claims 1 to 5, wherein the metal pipe or pipe fitting is externally positioned in an overlapping telescopic relationship with the polymeric pipe or pipe fitting.
8. An apparatus for fusing a preassembled joint between a polymeric pipe or pipe fitting and a metal pipe or pipe fitting, the apparatus including: heating means; and a conveyor means adapted to pass the metal pipe or pipe fitting portion of the preassembled joint through said heating means for a dwell time sufficient to heat the joint to a fusion bonding temperature.
9. An apparatus according to claim 8 wherein the preassembled joint includes a S" priming layer disposed intermediate overlapping portions of the metal and polymeric pipes or fittings. An apparatus according to claim 8 or claim 9, further including cooling means :°°positioned downstream of the heating means to cool the fusion joint.
11. An apparatus according to claim 9 or claim 10, said apparatus being adapted to sequentially pass a plurality of the metal pipes or pipe fittings through the heating and cooling means.
12. An apparatus according to any one of claims 8 to 11, wherein the conveyor means is driven by a variable speed motor, the speed of which is correlated to the dwell time which the joint or joints spend passing through the heating means. 0 *00 0 0 0* 0 -11-
13. A pipe fitting assembly including a polymeric pipe or pipe fitting and a metal pipe or pipe fitting, the metal pipe or pipe fitting including a priming layer applied to a connection surface, the priming layer and the polymeric pipe or pipe fitting being permanently fused together wherein the priming layer is a compound including epoxy phenolic resin.
14. A pipe fitting assembly according to claim 13, wherein the polymeric fitting is an overmoulded nylon ferrule. A pipe fitting assembly according to claim 13, wherein the polymeric fitting is a preformed grooved nylon ferrule having a cylindrical recess which receives a reduced diameter portion of the metal pipe.
16. A pipe fitting assembly according to any one of claims 13 to 15, wherein said metal pipe or pipe fitting is formed from copper or steel.
17. A pipe fitting assembly according to claim 13, wherein the polymeric fitting is a polyethylene to nylon transition piece. 15 18. A pipe fitting assembly according to claim 17, wherein the transition piece is formed by coextruding a polyethylene outer layer and a nylon inner layer with an intermediate joining layer.
19. A method ofjoining a polymeric pipe or pipe fitting to a metal pipe or pipe fitting substantially as herein described with reference to any one of Figures 1, 2 or 3.
20. An apparatus for fusing a preassembled joint between a polymeric pipe or pipe fitting and a metal pipe or pipe fitting, substantially as herein described with reference to Figure 4. DATED this 4th day of March, 1999 INDUSTRIAL PIPE SYSTEM PTY LIMITED Attorney: CAROLINE M. BOMMER Fellow Institute of Patent Attorneys of Australia of BALDWIN SHELSTON WATERS ABSTRACT A method of joining a polymeric pipe or pipe fitting (12) to a metal pipe or pipe fitting including the steps of applying a priming layer to a connection surface (16) of the metal pipe or pipe fitting bringing the polymeric pipe or pipe fitting (12) into contacting engagement with the priming layer, and heating the priming layer and the polymeric pipe or pipe fitting to a temperature sufficient to form a permanent bond therebetween. An apparatus for performing the invention is also described. a.