AU733262B2

AU733262B2 - Electrically conducting pipes

Info

Publication number: AU733262B2
Application number: AU67075/98A
Authority: AU
Inventors: Craig Meredith; Phillip Thicthener; Robert Whalan
Original assignee: A C Whalan & Co Pty Ltd
Current assignee: Ac Whalan & Co Pty Ltd
Priority date: 1997-12-24
Filing date: 1998-05-18
Publication date: 2001-05-10
Anticipated expiration: 2018-05-18
Also published as: AU6707598A

Description

AUSTRALIA

Patents Act 1990 A.C. WHALAN CO PTY LIMITED *9*e 9- '9 99 99.4 a.

9* 4 9* 9 9 9* 9 9* *9*9~9.

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Electrically conducting pipes The following statement is a full description of this invention including the best method of performing it known to us:-

I.

2 Technical Field The invention concerns a pipe which has electrically-conductive walls, and in particular, pipes used in mining applications.

Background Art In order to improve safety in underground mines, pipes used in mining applications are required to have a relatively high burst strength. Such pipes may also be required to withstand negative pressures within the pipe. One method of making suitably strong pipes has been to wind a laminate consisting of a fibre glass resin matrix, around a mandrel, and to wrap additional glass fibre reinforcement rings around the outside of the laminate at intervals along the pipe before the resin has set.

In Australia, all plastic pipes to be used in coal mining applications for **air ventilation and gas drainage must also be capable of passing the Department of Mineral Resources Fire Resistant and Anti-Static Testing (AS1180.13A.1983). This standard requires pipes to be able to conduct electrical charge in order to reduce the build-up of static electric charge on the pipes. In the past this requirement has been achieved by coating pipes with a graphite-impregnated resin matrix. While this method allows the pipe to conduct electrical charge, it has the disadvantage that the graphiteimpregnated resin coating is black or grey colour, which reduces pipe visibility and increases the chance of the pipe being damaged in underground situations. Furthermore, it is difficult to make such pipes more visible by .painting them other colours while retaining antistatic properties.

Disclosure of Invention Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

In a first aspect the present invention is a pipe, wherein the walls of the pipe contain a laminate composed of resin, glass fibres, and carbon fibres such that the laminate conducts electrical charge.

In a second aspect the present invention is a method of making a pipe wherein the walls of the pipe contain a laminate composed of resin, glass fibres, and carbon fibres such that the laminate conducts electrical charge.

The ratio of the number of carbon fibres to the number of glass fibres in the laminate may be in the range from 1:99 to 99:1, and the average strand thickness of the carbon fibres may be least 600 tex.

In a preferred embodiment, the ratio of the number of carbon fibres to the number of glass fibres in the laminate is 1:19.

The pipe may be a layered composite structure in which the laminate is one of the layers. Alternatively, the walls of the pipe may be substantially composed of the laminate.

Optionally, the resin may include one or more pigments.

An advantage of at least some embodiments of is invention are that a pipe with an outside layer of this laminate has a more visible appearance than a pipe coated in a graphite-impregnated resin. Furthermore, the option of using a resin with pigments allows the visibility and colour of the laminate to be enhanced while maintaining the antistatic properties.

In one embodiment of the present invention, the walls of the pipe S comprise the laminate.

One embodiment of a method according to the present invention wherein, the walls of the pipe are constructed from the laminate, includes the step of winding layers of glass fibre, carbon fibre, and resin around a mandrel until the required wall thickness is built up.

In another embodiment of the invention, the walls of the pipe 25 comprise a composite structure which has one continuous outer layer of the laminate and reinforcement bands placed inside the laminate at intervals along the length of the pipe, wherein the reinforcement bands consist of a matrix of glass fibre and resin, the interval between bands is in the range from 100 mm to 2000 mm, and the width of the bands is in the range from mm to 100 mm.

An advantage of at least some embodiments is that they provide an electrically-conductive pipe which is able to withstand higher pressures while weighing less than prior art pipes in which the reinforcement bands are bonded to the outside of a layer composed of a glass fibre resin matrix.

In a particular embodiment of the invention, the walls of the pipe comprise a composite structure which has one continuous outer layer of the laminate and reinforcement bands placed inside the laminate at intervals along the length of the pipe, wherein the reinforcement bands consist of a matrix of glass fibre, carbon fibre, and resin, the interval between bands being 600 mm, and the width of the bands being 55 mm.

One embodiment of a method of making a pipe in which the pipe walls comprise a composite structure according to the invention includes the steps of wrapping resin-impregnated reinforcement bands around a cylindrical mandrel at intervals along the mandrel, and winding the laminate layer around the reinforcement bands before the resin in the reinforcement bands has hardened. In this method, the reinforcement bands and the laminate bond together, forming a conductive pipe with high burst strength.

The laminate may be wound around the mandrel at a helix angle in the range from 900 to 170' to the axis of the mandrel.

Preferably, the laminate is wound around the mandrel at a helix angle in the range from 1250 to 1260 to the axis of the mandrel.

A pipe in which the laminate is wound with a helix angle close to 900 will be stronger but less flexible than a pipe wound with a helix angle closer to 1800. It has been found that pipes in which the laminate is wound at a helix angle in the range 1250 to 1260 have a good balance between strength and flexibility.

Optionally, one end of the pipe may be used as a spigot and the other S.end may be enlarged to form a socket, the inner diameter of the socket being large enough to allow the spigot end of another identical pipe to fit S. contiguously into the socket.

One embodiment of method of making a pipe which has a socket end and a spigot end includes the steps of: -centring a cylindrical socket profile around the centre of a cylindrical mandrel, the inner diameter of the socket profile being that of the socket to be formed, and the length of the socket profile being twice that of the socket to be formed; -winding the laminate in a helix over the mandrel and socket profile; -allowing the laminate to harden; -removing the hardened laminate with socket profile from the mandrel, the laminate being bonded to the socket profile; -cutting the hardened pipe into two lengths through the laminate and socket profile, the cut being in the direction perpendicular to the central axis of the pipe and at a location half-way along the centre of the socket profile.

This method forms two lengths of pipe, each length having a spigot end and a socket end.

Optionally, the spigot may be coated in a carbon-enriched resin.

Brief Description of Drawings The present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a longitudinal cross-sectional view of a pipe of a first embodiment of the invention.

Figure 2 is a side view of the embodiment of Figure 1.

Figure 3 is a longitudinal cross-sectional view of a second embodiment of a pipe of the invention.

15 Figure 4 is a longitudinal cross-sectional side view of the mandrel and socket profile used to construct a third embodiment of a pipe according to the invention.

S. Figure 5 is a longitudinal view of the mandrel and socket profile with reinforcement bands which form part of the third embodiment of a pipe of the invention.

"Figure 6 is a cross-sectional end-view through plane 1-1 in Figure S. Figure 7 is a longitudinal view of the third embodiment of a pipe according to the invention.

Best Mode for Carrying Out the Invention In each of the following embodiments of the pipe according to the invention, the pipe contains a laminate consisting of a matrix of resin and glass fibres interwoven with carbon fibres, the ratio of the number of glass fibres to the number of carbon fibres being 19:1, and the carbon fibres having an average strand thickness of 600 tex.

The first embodiment of the pipe according to the invention is shown in figures 1 and 2. The pipe 10 is formed by winding strips 20 of glass fibre interwoven with carbon fibre and impregnated with resin around a cylindrical mandrel 30 at a helix angle 0 of 1260 to the central axis of the mandrel. When the resin has hardened the pipe 10 may be removed from the mandrel 30 by sliding it off the mandrel 30 along the central axis.

Referring to Figure 3, the walls of the pipe 40 in the second embodiment of the invention are strengthened with glass fibre reinforcement bands 50 consisting of glass fibre and interwoven with carbon fibre in the ration of 19:1. The pipe 40 is formed by firstly wrapping resin-impregnated reinforcement bands 50 around the mandrel 30 at substantially 900 to the central axis of the mandrel, at intervals along the length of the mandrel The width of the reinforcement bands 50 is 55 mm and the spacing between adjacent and edges 55 is 600 mm. Strips 20 of glass fibre interwoven with carbon fibre 20 and impregnated with resin are then wound around both the mandrel 30 and reinforcement bands 50 at a helix angle of 1250 to the central axis of the mandrel 30 before the resin in the reinforcement bands 50 has .".hardened throughout the pipe 40. The resin in the pipe 40 is then allowed to harden. The hardened resin bods the reinforcement bands 50 to the strips of glass fibre and carbon fibre 20, and the pipe 40 can be removed from the mandrel Referring to Figures 4 to 7, a third embodiment of the pipe 60 has a socket end 70 and a spigot end 80. Each pipe 60 is formed by using a S. cylindrical mandrel 30' which is at least twice as long as the length of pipe to be formed. A socket profile 100 is used to form the socket shape at one end 70 of each pipe 60. The socket profile 100 is a hollow cylinder with an outer diameter selected to form the socket with the appropriate inner diameter. Each end 110 of the cylindrical socket profile 100 has a passage which is large enough for the mandrel 30' to contiguously fit through. The o pipe 60 is formed by firstly inserting the mandrel 30' through the passages in S 25 the socket profile 100, and sliding the socket profile 100 to the centre of the mandrel 30'. Resin-impregnated reinforcement bands 50' consisting of a matrix of glass fibre and carbon fibre in the ration of 19:1, each band having a width of 55 mm, are then wrapped around the mandrel 30' at 600 mm intervals along the length of the mandrel 30'. Strips 20' of glass fibre interwoven with carbon fibre and impregnated with resin are then wound in a continuous layer over the reinforcement bands 50' and socket profile 100 along the length of the mandrel 30' before the resin in the reinforcement bands 50' has hardened. The strips 20' are wound at a helix angle of 1250 to the central axis of the mandrel 30'. The resin in the pipe is then allowed to harden. The hardened resin bonds the reinforcement bands 50' to the strips of glass fibre and carbon fibre, and this structure can be removed from the mandrel 30' in one piece. A cut 140 is then made perpendicular to the axis of the pipe, right through the centre of the socket profile. The cut 140 is the final step in the production of two lengths of pipe 60, each length of pipe having a spigot end 80 and a socket end 70. The socket profile halves are then removed from the socket ends Numerous other embodiments of the pipe are envisaged in which one or more ends of the pipe are structured in known ways which allow the pipe to be joined to other pipes or components. Known techniques of forming joints in fibre glass pipes may be applied to the present invention, the difference being that the carbon fibre/glass fibre laminate of the present invention is used instead of glass fibre. For example, the ends of the pipe of the present invention may be formed with either threads, shoulders, flanges, or combinations of these. However, the technique used to join the pipes of the present invention should be such that it allows electrical charge to be 15 conducted through the joint, into the next pipe or component.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in :the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A pipe, wherein the walls of the pipe contain a laminate comprising a matrix of resin, glass fibres, and carbon fibres such that the laminate conducts electrical charge.

2. The pipe of claim 1, characterised in that the resin includes a pigment.

3. The pipe of either claim 1 or 2 characterised in that the average carbon fibre strand thickness is at least 600 tex, and in that the carbon fibres and glass fibres are at least partially interwoven.

4. The pipe of any one of claims 1 to 3 characterised in that the ratio of the number of carbon fibres to the number of glass fibres in the laminate is in the range from 1:99 to 99:1.

5. The pipe of any one of claims 1 to 3 further characterised in that the ratio of the number of carbon fibres to the number of glass fibres in the laminate is 1:19.

6. The pipe of any one of claims 1 to 5 characterised in that the walls of the pipe consist substantially of the laminate. S7. The pipe of any one of claims 1 to 6 characterised in that the walls of the pipe are of a layered composite structure in which the laminate is one of the layers.

8. The pipe of claim 7 characterised in that the composite structure comprises a continuous outer layer of the laminate bonded to cylindrical reinforcement bands inside the outer layer.

9. The pipe of claim 8 characterised in that the reinforcement bands are made from a second laminate composed of resin, glass fibres, and carbon fibres. The pipe of claim 9 characterised in that the ratio of the number of carbon fibres to the number of glass fibres in the second laminate is in the range from 1:99 to 99:1.

11. The pipe of claim 9 characterised in that the ratio of the number of carbon fibres to the number of glass fibres in the second laminate is 1:19.

12. The pipe of any one of claims 8 to 11 characterised in that the reinforcement bands are located at substantially equal intervals along the length of the pipe.

13. The pipe of claim 12 characterised in that the interval between reinforcement bands is in the range from 100 mm to 2000 mm, and in that L the width of the reinforcement bands as measured along the central axis of the pipe is in the range from 10 mm to 100 mm.

14. The pipe of claim 12 characterised in that the interval between reinforcement bands is substantially 600 mm and that the width of the reinforcement bands as measured along the central axis of the pipe is substantially The pipe of any one of claims 8 to 14 characterised in that the continuous outer layer of laminate is formed from at least partially- overlapping strips of the laminate wound in a helix.

16. The pipe of claim 6 characterised in that the walls of the pipe comprise a continuous layer of laminate is formed from at least partially-overlapping ~strips of the laminate wound in a helix.

17. The pipe of either claim 15 or 16 characterised in that the strips of laminate are wound at an angle in the range from 900 to 1700 to the central axis of the pipe.

18. The pipe of either claim 15 or 16 characterised in that the strips of laminate are wound at an angle in the range from 1250 to 1260 to the central "'"axis of the pipe.

19. The pipe of any one of the preceding claims characterised in that one end of the pipe comprises a spigot and the other end of the pipe is formed as a socket, the inner dimensions of the socket being such that the spigot end of a second identical pipe will fit contiguously into the socket. A method of making the pipe of claim 16, comprising the steps of: -winding strips of the laminate in a helix around a mandrel such that a 25 continuous layer of the laminate is formed, until the walls of the pipe are of a required thickness; -hardening the resin in the layers of laminate; -removing the pipe from the mandrel.

21. A method of making the pipe of claim 15, comprising the steps of: -wrapping the resin-impregnated reinforcement bands around a mandrel at fixed intervals along the mandrel; -winding strips of the laminate in a helix around a mandrel such that a continuous layer of the laminate is formed, until the walls of the pipe are of a required thickness; -hardening the resin in the layers of laminate; -removing the pipe from the mandrel.

22. A method of making the pipe of claim 19 wherein the pipe includes reinforcement bands, comprising the steps of: -centring a socket profile around the central axis of a mandrel at a location halfway along the length of the mandrel, wherein the outer diameter of the socket profile is the inner diameter of the socket to be formed, and the length of the socket profile along the axis of the mandrel is double the length of the socket to be formed; -wrapping the resin-impregnated reinforcement bands around the mandrel at fixed intervals along the length of the mandrel; -winding strips of the laminate in a helix around a mandrel such that a continuous layer of the laminate is formed, until the walls of the pipe are of a "required thickness; -hardening the resin in the layers of laminate; -removing the pipe and socket profile together from the mandrel; 15 -cutting the hardened pipe into two lengths through the laminate and socket profile, the cut being in a direction perpendicular to the central axis of the pipe and at a location half-way along the length of the socket profile; -removing the socket profiles from the sockets. S23. A method of making the pipe of claim 19 wherein the pipe has no reinforcement bands, comprising the steps of: -centring a socket profile around the central axis of a mandrel at a location halfway along the length of the mandrel, wherein the outer diameter of the socket profile is the inner diameter of the socket to be formed, and the length of the socket profile along the axis of the mandrel is double the length of the socket to be formed; -winding strips of the laminate in a helix around a mandrel such that a continuous layer of the laminate is formed, until the walls of the pipe are of a required thickness; -hardening the resin in the layers of laminate; -removing the pipe and socket profile together from the mandrel; -cutting the hardened pipe into two lengths through the laminate and socket profile, the cut being in a direction perpendicular to the central axis of the pipe and at a location half-way along the length of the socket profile; -removing the socket profiles from the sockets.

24. The method of any one of claims 20 to 23 wherein the step of winding strips of laminate in a helix around the mandrel is further characterised in Q 11 that the laminate is wound at an angle in the range from 900 to 1700 to the central axis of the pipe. The method of any one of claims 20 to 23 wherein the step of winding strips of laminate in a helix around the mandrel is further characterised in that the laminate is wound at an angle in the range from 1250 to 1260 to the central axis of the pipe.

26. A pipe as claimed in claim 1 substantially as hereinbefore described and with reference to the accompanying drawings.

27. A method as claimed in any one of claims 20 23 substantially as hereinbefore described and with reference to the accompanying drawings. Dated this Eighteenth day of May 1998 A.C. WHALAN CO PTY LIMITED Patent Attorneys for the Applicant: F B RICE&CO O *oeo*eo