WO1994025789A1

WO1994025789A1 - Improvements relating to the manufacture of tubular structures

Info

Publication number: WO1994025789A1
Application number: PCT/GB1994/000494
Authority: WO
Inventors: Mick Askin
Original assignee: Insituform Licensees BV; Insituform Netherlands BV; INA Acquisition Corp
Current assignee: Insituform Licensees BV; Insituform Netherlands BV; INA Acquisition Corp
Priority date: 1993-05-01
Filing date: 1994-03-14
Publication date: 1994-11-10
Anticipated expiration: 1995-11-01
Also published as: AU6213094A; GB9309087D0; DK145794A

Abstract

The invention provides that a reinforced resin impregnable flexible tubular structure (68) is manufactured by feeding an inner layer (12) in tubular form over a floating mandrel (62) which is held magnetically suspended so that the layer (12) can be fed onto one end and off the other end of the mandrel (62). As the inner layer (12) is being so fed, reinforcing filaments (44-50) onto which adhesive has been sprayed, are helically wound round the inner layer (12). An outer resin absorbent layer (58) is then applied and that layer has an outer impermeable coating (59) so that the inner and outer layers (12, 58) of the resulting structures (68) can be impregnated with resin in which the reinforcement (44-50) is immersed by charging the resin into the inside of the structure (68).

Description

Improvements Relating to the Manufacture of Tubular Structures

This invention relates to the manufacture of tubular structures which in one particularly advantageous form, are suitable for the lining of underground pipelines and passageways. Such tubular structures will be referred to hereinafter as lining pipes, but the invention as will be appreciated from the following has wider application.

The tubular structures to which the invention relates typically will be of a flexible character but will be constructed so as to have circumferential strength so as to be provided with a hoop stress capability so that the structure can be used in some instances as pipes in their own right, as opposed to lining pipes, in which latter case the pipes are applied against existing structures such as underground pipelines and passageways. The tubular structures to which the invention relates are furthermore of a type including one or more layers of a material which can absorb curable synthetic resin such as a polyester or epoxy resin. By this arrangement, the tubular structure can be changed from the flexible and shapable condition into a rigid form by impregnating the said layer or layers with the curable synthetic resin followed by the curing of the resin with the tubular structure held in the configuration which it is to retain when the resin is rigid.

Thus, the tubular structures may, when in the dry state i.e. without any resin impregnating said layer or layers, or when in the impregnated but uncured state, be folded to a flat condition and wound or stacked for storage or transportation, but in subsequent use, the structures are inflated whilst impregnated with resin, so as to take a circular or other cross section, and the resin is then cured in order to form a rigid tubular strcuture.

The use of tubular structures to which the invention relates is well known in the lining of underground pipelines and passageways. The very early inventions in this field date from the late 1960's and early 70's, and reference is made to two specific U.S. Patents Nos. 4,009,063 and 4,064,211 for a detailed disclosure of typical tubular structures to which the invention relates. Since these early inventions, many modifications have been made as to the materials to be used for the tubular structures, the design of the tubular structures, and the resins to be used for impregnating the tubular structures. Additionally, many methods of installation have been devised, some of which involve applying the curable resin to the tubular structure whilst it is being positioned in an underground pipeline or passageway, and improvements in resin systems have meant that the tubular structure can be impregnated with the resin in a condition in which it will not cure until initiated for example by a separate initiator or catalyst, or by some other means.

Thus, it is known that a resin curable by ultraviolet light can be adopted for these tubular structures, the structures being pre-impregnated with the resin and only caused to cure when exposed to ultraviolet light which may be applied from a source which is drawn through the tubular structure after it has been inflated and placed in a pipeline or passageway.

Again, suggestions have been made for curable synthetic resins to provide that the catalyst or initiator or the resin is contained in microcapsules, and the microcapsules are ruptured at the appropriate time in order to release the initiator or catalyst to cause the resin to harden. Other resins have been designed to have a long shelf life in the uncured state, but be capable of rapid curing when desired. All of these resins are usable in connection with the present invention.

Although there have been developments in the tubular structures to which the invention relates, over the last twenty years or so, there has continued to be used as the main body of the tubular structure a resin absorbent felt material, specifically a polyester felt which is of needled construction. This material has been used largely according to the method set forth in said U.S. Patent No 4,064,211 for producing pipe linings, and depending upon the required thickness of the pipe lining, so one or more layers of said felt material is used. The layer, or the outermost layer, has applied to its outermost surface a coating or membrane of a relatively impermeable material such as polyurethane which bonds to the felt, and also forms a shell for retaining the resin which impregnates the felt.

As this lining pipe when impregnated with uncured resin is typically applied to the pipeline or passageway surface by eversion of same using fluid pressure as described in said U.S. Patent No. 4,064,211 the outer coating or membrane performs yet a further function of acting as a barrier between the everting fluid medium (air or water or both) and the impregnated felt layer or layers so that the pipe lining can be everted into and along the pipeline or passageway and directly onto the pipeline or passageway surface.

The present invention is concerned with tubular structures and methods of their manufacture whereby the structures will be usable in the said method of pipelining as described in said U.S. Patent No. 4,064,211, although as explained hereinbefore the invention has wider application. There is an increasing demand for tubular structures to provide lining pipes which have increased structural strength so as to withstand increased internal pressures, such as exist in gas pipes. Increased strength also enables the lining pipes to withstand increased external pressures for example from ground water, when the pipe is located underground under the water table.

General proposals have been made for the reinforcing of the tubular structures hereinbefore described but in particular no proposal has been made for the efficient and rapid manufacture of same.

An object of the present invention is to provide tubular structures with improved hoop stress so that the resulting structures when impregnated with synthetic resin which is cured, will have enhanced hoop strength to make the tubular structures more capable of holding internal pressure and withstanding external pressure before fracturing or buckling.

Additionally, a further object is to provide that the tubular structures are reinforced circumferentially in a most effective and economic manner by a novel method of manufacture.

In accordance with a first embodiment of the invention, a tubular structure comprises an inner resin absorbent layer, and at least one outer resin absorbent layer provided with a realtively impermeable coating or membrane, and between said inner and outer layers is reinforcement in the form of helically wound filamentary material.

Preferably, the helically wound filamentary material is positioned at an angle to provide maximum increase in hoop strength in the resulting tubular structure and maximum improvement in tensile strength consistant with a minimum utilisation of the filamentary material.

The filamentary material is preferably laid in oppositely handed helical windings, and there may be two or more layers of helically wound filamentary material.

Each layer of helically wound filamentary material may be made up of single or multiple filament strands of a suitable reinforcing material such as nylon or like strength synthetic plastics material and/or glass fibres.

The inner and outer layers of absorbent material preferably are of fibrous felt and typically will be of polyester or similar felt. The outer coating may typically be of polyurethane or the like.

There may be more than one inner layer of absorbent material, and equally there may be more than one outer layer of absorbent material, but only the outermost layer in such case will be provided with said impermeable membrane or coating.

In a particular arrangement there are three sections of absorbent material namely an inner section, a middle section and an outer section and the filamentary reinforcement may be between the inner section and middle section and/or between the middle section and outer section on the other hand. Any or each section may be made up of one or more layers.

It is usual to produce the felt layers from felt in the order of 6mm thickness and therefore if a 18mm nominal size lining pipe is required, each of the inner, middle and outer absorbent layers may typically be a 6mm thick felt. The coating thickness is measured in microns. The inner layer in such case may either be preformed or formed into tubular configuration by being wrapped so that the free edges butt and the butted edges are sewn together to form a seam. The inner layer thus formed into tubular configuration is then fed over a mandrel so as to retain a circular form whilst the filamentary material or a first layer of filamentary material is applied typically by winding a supply of the filamentary material around the mandrel and inner tubular layer whilst the tubular layer moves axially over the mandrel. When provided the middle layer of felt may be applied and a second layer of filamentary material may be applied by a similarly rotating supply of the material around the mandrel but in the opposite direction from the first supply so that the helically wound materials of the respective layers are of opposite hand. The helix angle of the filamentary material in relation to the inner tubular layer on which it is wound can be varied by varying the speed of rotation of the supply of filamentary material, and the speed of feed of the inner tube.

The inner tube preferably is used in connection with a magnetically suspended mandrel so that there are no mechanical connections between the mandrel and any surrounding support so that the feeding of the inner tube over the mandrel is simplified.

As the inner tube and middle layer if provided is or are fed over the mandrel, and after the application of the filamentary material, the outer layer of absorbent material may be applied around the assembly with the filamentary material thereon, and the free edges of the outer layer may be butted and sealed by means of a strong reinforcement tape.

As the filamentary material is being applied, it or the inner and/or middle layer may be sprayed with a suitable adhesive whereby it will bond to the inner/middle tubular layer at the correct helix angle and will remain so bonded in subsequent use of the resulting tubular structure.

The mandrel may be disposed horizontally or vertically as required, and vertical disposition is most suitable when the inner layer is preformed.

The resulting tubular structure is particularly suitable for forming a lining pipe in a process as described in said U.S. Patent No. 4,064,211, and the resulting structure in such case would be used by being impregnated with the synthetic resin, the resin being introduced to the interior of the resulting tubular structure so as to impregnate the inner and outer absorbent layers and so that the filamentary reinforcement becomes embedded in the resin. In this connection it may be appropriate or desirable to work the tubular structure for example through nip rollers in order to spread the resin effectively throughout the absorbent layers. Additionally, and preferably, the interior of the tubular structure may have a vacuum applied thereto in order to remove any air therein again to enhance the thoroughness of the impregnation. When the tubular structure has been so impregnated, it is then ready for use in the manner described in siad U.S. Patent. The tubular structure can in fact be applied by the method and means as described in U.S. Patent 4,778,553 or European Patent Application No. 91902304.4 or European Patent Application No. 90905593.1 incorporated herein by reference.

An embodiment of a method of manufacturing the tubular structure and the tubular structure per se and modifications thereof are now described with reference to the accompanying diagrammatic drawing of which the single figure illustrates a manufacturing process for a tubular structure and a detail of the structure itself.

Referring to the drawing, which is a schematic representation, production of the tubular structure comprises the use of a roll 10 of needled felt material, typically polyester felt of a thickness in the order of 6mm. The roll of felt 10 is supported by means not shown so that the felt can be unwound from the roll as indicated by reference 12 and guided round guide rollers 14 and 16 which are rotatable about their horizontal axes.

The felt is led from the guide rollers 16 to a ploughing or shaping device 18 which starts to shape the felt into tubular configuration so that by the time the felt reaches a sewing machine head 20 it is in tubular configuration with the free edges of the web in butting contact. The sewing machine head 20 arranges, as described in U.S. Patent 4,446,181, for the sewing together of the butting edges to complete the tubular form of the felt 12, which felt forms the inner layer of the resulting tubular structure as will be clear from the following. The felt is of course designed to absorb synthetic resinous material for the reasons explained above.

The thus formed inner tube of the final structure is fed over a magnetically suspended round mandrel 22 and in fact is drawn over the mandrel by means of a pull-through device 24 which may typically comprise a pair of rollers defining a nip through which the tubular structure is drawn, the rollers being driven by a suitable motor 25.

As the formed inner tube, which is indicated by reference 26 in the figure, is drawn over the mandrel 22, at a preselected speed (which can be varied) filamentary material is simultaneously wound around the inner tube 26 in a helical manner from each of, in this example, two heads 28 and 30. Each of the heads 28 and 30 as shown comprises a cup-shaped casing having a drive boss 32, 34 by which the casing may be rotated around the axis of the mandrel 22. The axis of each of the cup-shaped casings is coincident with the mandrel axis.

Inside the cup-shaped casing of each head are two supplies or bobbins 36, 38 in the case of cup 28 and 40 and 42 in the case of cup 30.

These bobbins carry filamentary materials in the form of glass rovings, and the rovings, as indicated by references 44 and 46 in the case of winding cup 28, and 48 and 50 in the case of winding cup 30 are helically wound onto the inner tube 26 as it progresses as indicated by arrow 52 along the mandrel 22.

The rovings are unwound as shown, and are helically wound on the inner tube, and whilst they are being wound, a special adhesive is sprayed onto each layer of reinforcement on the inner tube 22 by a spraying device (not shown), so that the reinforcement rovings will be held in position during subsequent handling of the resulting tubular structure.

The winding cups 28 and 30 are rotated in opposite directions so that the rovings 44 and 46 will be wound on the inner tube 26 helically with the helix angle of one hand, whilst the rovings 48 and 50 will be wound on the inner tube with the rovings helically wound in the opposite hand.

The inner tube 22 will travel smoothly over the mandrel 22 in that the mandrel is suspended so as to float by a pair of magnets 54 and 56 which ensures that there is no mechanical obstruction on the mandrel to impede the progress of the inner tube over same.

The emerging inner tube with the glass rovings reinforcement would thereon is overwrapped whilst on the mandrel by a second web material 58 from a roll 60 of same. The second web of material 58 is a coated felt material as referred to herein, and as shown in the ringed detail comprises the felt 57 and has on its outer surface 62 a coating or layer (59) of relatively impermeable material such as a polyurethane film or membrane which is bonded to a layer of felt similar to felt 12. The felt side is applied over the rovings 44 to 50, and a suitable plough device wraps the web 58 around the inner tube and rovings so that the free edges of the outer layer as the web 58 is wrapped, are butted together and then are sealed by means of a sealing tape 64 supplied from a reel of same 66, thereby producing the resulting tubular structure which is pulled from the machine by means of the pull-through device 24.

The finished tubular structure which has a degree of stiffness but still is flexible is folded and stacked in a stack pile 68 as shown.

The finished tubular structure 68 subsequently will be used as hereinbefore described by being impregnated with resin, and then applied to a pipeline or passageway, when a pipe lining is to be formed, or can be used for the creation of a new pipe.

The tubular structure 68 will have enhanced hoop strength and tensile strength properties by virtue of the application of the glass rovings.

Instead of glass rovings any suitable filamentary material can be used which will provide the required strength characteristics.

The effective production of the tubular structure is achieved by the use of the smooth magnetically supported mandrel 22, which is of appropriate diameter to smooth out the inner tube 26 as it is pulled over the mandrel.

As many winding cups or machines 28 and 30 as are required can be provided to give the desired reinforcement to the tubular structure, and intermediate layers of felt may be applied between the cups for example to ensure that the filamentary reinforcement is located close to the inner surface and/or outer surface of the tubular structure which is the most effective location of the reinforcement.

The tape 64 preferably is of a reinforced type in order to withstand the inflation pressures which will subsequently be applied to the tubular structure in its utilisation.

The helix angle of each roving or reinforcement can be controlled by varying the rotational speed of the winding machine, and/or by varying the linear speed of the feed of the tubular structure through the machine as indicated by arrow 52. This variation capability enables the provision of optimisation of the use of the reinforcement in providing the correct relationship between hoop strength, longitudinal strength, and the angle of the reinforcement to minimise creasing at bends in an underground pipeline or passageway in which the tubular structure is eventually installed. This optimisation results in lowest material cost by using reinforcement in its most efficient form.

When the tubular structure is eventually impregnated with curable resin as described herein, the reinforcement will be fully encapsulated within the impregnating resin, and any appropriate technique for impregnation of the tubular structure and installation of same may be adopted such as that for example described in European Patent Application No. 90905593.1.

In^' a modified arrangement the inner layer 26 may be preformed into tubular configuration, so that the sewing machine would not be required. This can save down time of the machine which may. arise due to running difficulties with the sewing machine, which are not unusual.

Also, the machine can be arranged with the mandrel vertical if required; this is a particularly suitable arrangement when the inner layer is pre-formed as decribed above.

If the machine is designed to operate with the mandrel vertical it may be necessary to provide a reaction means, such as a roller, to the other side of the mandrel to support the pressure which will be applied to the mandrel by the sealing roller which seals the tape 64 to the outer layer film 62.

Claims

1. A tubular structure comprising an inner resin absorbent layer (12) and at least one outer resin absorbent layer (58) provided with a relatively impermeable coating or membrane (59) characterised in that between said inner and outer layers (12, 58) a reinforcement (44,46,48,50) in the form of helically wound filamentary material.

2. A structure according to claim 1, characterised in that the helically wound filamentary material (44-50) is positioned at an angle to provide maximum increase in hoop strength and maximum improvement in tensile strength consistant with a minimum utilization of filamentary material.

3. A structure according to claim 1 or 2 characterised in that the filamentary material (44-50) is laid in oppositely handed helical windings.

4. A structure according to any of claims 1 to 3, characterised in that there are two or more layers of helically wound filamentary material (44-50).

5. A structure according to claim 4, characterised in that each layer of helically wound filamentary material is made up of single or multiple strands (44-50) of a plastics material and/or glass fibres.

6. A structure according to any of claims 1 to 5 characterised in that the helically wound filamentary material (44-50) is adhered to the inner layer (12).

7. A structure according to any of claims 1 to 6 characterised in that the inner layer (12) and/or outer layer(s) (58) are/is of fibrous felt.

8. A method of producing a tubular structure comprising an inner resin absorbent layer (12) and filamentary material (44-50) helically wound therein characterised in that the inner layer (12) in tubular form is fed over a floating mandrel (62) and the filamentary material (44-50) is applied by rotating means (36, 38,40,42) forming a supply of such material around the mandrel (62).

9. A method according to claim 8, characterised in that the inner layer (12) is formed by coiling a flat web of resin absorbent material so that the edges come together, followed by connection of such edges to make the web tubular before it is fed over the mandrel (62).

10. A method according to claim 8 or 9, characterised in that there are two of said means (36-42) which rotate round the mandrel (62) in opposite directions to apply filamentary material (44-50) wound helically in opposite directions on said inner layer (12) .

11. A method according to claim 8, 9 or 10, characterised by applying adhesive to the filamentary material (44-50) before it is applied to the inner layer (12) .

12. A method according to any of claims 8 to 11, characterised by the step of magnetically suspending the mandrel (62) .

13. A method according to any of claims 8 to 12, including the step of applying an outer layer (58) of resin absorbent material over the filamentary material (44-50).

14. A method according to claim 13, characterised in that the outer layer (58) is formed by a web which is wrapped round the inner layer (12) and the filamentary material (44-50) until the edges meet and such edges are connected together.

15. A method according to claim 14, characterised in that the outer layer (62) has an outer coating (59) in the form of an impermeable membrane (59) and the edges are connected together by adhering a scaling tape (64) to said edges.

16. A method according to claim 14 or 15, characterised in that the outer layer (58) is wrapped round the inner layer (12) whilst on the mandrel (62).

17. A method according to any of claims 8 to 16, characterised in that the tubular structure is engaged by variable speed drive means (24) which moves the inner layer (12) and the filamentary material (44-50) and the outer layer (58) when provided over the floating mandrel (62).