GB2431611A

GB2431611A - Method of forming a sterilised and sealed pipe

Info

Publication number: GB2431611A
Application number: GB0521823A
Authority: GB
Inventors: Alan Lloyd Headford; Keith Andrew Wilson; David John Hill; Edward Terry; Michael Shepherd
Original assignee: Glynwed Pipe Systems Ltd
Current assignee: Glynwed Pipe Systems Ltd
Priority date: 2005-10-26
Filing date: 2005-10-26
Publication date: 2007-05-02
Anticipated expiration: 2025-10-26
Also published as: GB2431611B; WO2007049047A1; GB0521823D0

Abstract

A method of manufacturing pipe coils 1 comprises extruding molten polymer 3 compound through a tool 5, 7, 9; cooling and cutting the polymer 3 to form a pipe 1; sterilising the inside of the pipe 1 and sealing each end 19 of the sterile pipe 1 with at least one sealing means (29, 33, 35; figures 3a,3b,4a,4b,5a,5b); wherein the at least one sealing means maintains the sterility of the pipe 1. The pipe 1 is preferably sterilised by passing sterilised gas through a nozzle 13 in the extrusion tool. The gas is preferably heated, but may alternatively be sterilised by UV radiation or membrane filtering.

Description

SEALING METHOD FOR COILED PIPE

The present invention relates to water pipes and in particular to methods of sterilisation of such pipes for the conveyance of potable water.

Polyethylene (PE) pipe for conveyance of water are well known. Long lengths of PE pipe are available in coiled form, to allow for faster installation because fewer joints are required than with other forms of pipes and those made from alternative materials. PE pipe is used for laying of new pipelines and also to replace or reline existing pipelines. * .* * * S S..

When PE pipe is newly installed, installed as a liner or as a replacement pipe it must be sterilised prior to carrying potable water. * Existing methods of sterilising pipes include flushing out the pipes for a number of hours following installation or treating with a sterilising agent, SSS * such as sodium hypochlorite solution. Such a sterilisation process increases the time required for installation and so increases labour costs, the disruption caused by Street works and the period of interruption to consumers' water supply.

Alternatively, the sterilisation process can be carried out on pipe coils prior to installation. This reduces the time required for installation but further treatment of joints and fittings is required after installation.

There are further disadvantages of this method because of the complexity in planning the number of coils required. This method is cumbersome to carry out on coils, which become very heavy when filled with sterilising solution. The method is also relatively costly and disposal of the used sterilising solution is difficult.

The present invention sets out to provide an improved method of pipe manufacture which overcomes the problems described above.

The invention provides a method of manufacturing pipe coils comprising extruding molten polymer compound through a tool; cooling and cutting the polymer to form a pipe; sterilising the inside of the pipe and sealing each end of the sterile pipe with at least one sealing means, wherein the at least one sealing means maintains the sterility of the pipe.

By sealing the pipe immediately following manufacture the bore of the pipe is kept in a clean and sterile condition and the need for carrying out a separate sterilisation process is removed. There is minimal: .".

interference with the standard output rate for the product because this method makes use of the time window between extrusion of successive pipe lengths or coils. Although extrusion is a continuous process, there is a short gap necessary for completion of each pipe coil, for example to cut and remove the pipe coil from the cooler.

The term "sterile" is used to refer to both absolute and relative sterility. Even if absolute sterility is not maintained, the method of manufacture reduces the further measures necessary to achieve a required level of sterility, such as the level of sterility required for the safe transport of potable water.

Preferably, extruding the molten polymer compound through the tool sterilises the inside of the pipe.

By sterilising the pipe during extrusion the need for a separate sterilising step is not required and the cost, time involved and complexity of pipe manufacture is reduced.

Preferably, the tool is heated.

More preferably, the tool is heated to between 170 and 2500 C. Preferably, the sealing means provides resistance up to 0.5 bar of pressure.

Preferably, the sealing means comprise a cap.

Preferably, the cap is heat shrinkable.

Alternatively, the sealing means comprises a sleeve and/or a plug. * .* *.*

Preferably, the plug is cylindrical.

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Preferably, the plug is tapered. *S*. *

* .* S Preferably, the sleeve and/or plug comprises a layer of heat sensitive adhesive.

Preferably, the tool comprises a hollow cylinder and a mandrel.

More preferably, the mandrel comprises at least one aperture.

Preferably, the inside of the pipe is sterilised by passing heated gas through the tool and the pipe.

Preferably the gas passing through the tool is sterilised by heat before entering the pipe.

More preferably, the gas passing through the pipe maintains the sterility of the pipe.

Alternatively the gas passing through the pipe is sterilised by any of UV radiation or membrane filtering.

Preferably the gas passing through the pipe is air or nitrogen.

Preferably, gas exits the tool and enters the pipe through the at least one aperture of the mandrel.

More preferably the exit of gas through the at least one aperture draws gas through the pipe. :...:. * o. *

Preferably gas is drawn through the pipe from the tool to an open end of the pipe.

During the transit time when the pipe material passes through the heated extrusion tool it is effectively sterilised. The positive gas pressure at an aperture, acting as a bleed hole, forces gas through the pipe to exit at the open end of the pipe. The heated gas maintains the sterility of the pipe.

Preferably, the time between cutting the pipe and sealing the pipe is less than 120 seconds.

Preferably sterile gas continues to enter the pipe after cutting.

The continual passage of sterile gas through the pipe tool prevents non-sterile gas entering an open end of the pipe, which has just been cut, prior to sealing.

The shape and dimensions of the sealing means can be adapted according to the outer diameter of the pipe.

Preferably the plug has an outer diameter substantially equal to the inner diameter of the pipe.

Optionally, the plug comprises a compressible material and whilst in a relaxed state may have a diameter greater than the inner diameter of the pipe.

Preferably, the plug is made of a low mass, resilient material.

More preferably, the plug is made of closed cell PE foam. * .* * * S *S.

The plug is selected to be robust and secure enough to withstand the considerable force exerted when heavy pipe coils are manoeuvred and to resist any mild internal pressurisation due to thermal expansion of the gas within the pipe coils. S... S...

Preferably, the plug is removably retained by retaining means. : By providing retaining means the plug is retained in the desired position and further resistance is provided to internal pressurisation of the pipe during storage.

Preferably, the outer diameter of the pipe is between 25mm and mm.

The methods of sealing the pipe using any of a heat shrinkable cap, a sleeve and/or a plug can easily be adapted for different outer diameters of pipes and also is easily adapted for possible variations in the "standard" outer diameter of pipes. The standard outer diameter of pipes is likely to vary because of the permitted tolerance of the nominal outer diameters.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic view showing a cross-section of an extruded pipe constructed in accordance with the present invention, using a heat shrinkable cap; Figure 2 is a flow chart of the method of manufacture of the pipe of Figure 1; * *

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Figure 3a is a schematic side view of a sealed end of the pipe of Figure 1 according to a first embodiment of the present invention;

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Figure 3b is a cross-sectional view of the sealed end of the pipe of Figure 3b; * SIS * S..

Figure 4a is a schematic side view of a sealed end of the pipe of Figure 1 according to a second embodiment of the present invention; Figure 4b is a cross-sectional view of the sealed end of the pipe of Figure 3b; Figure 5a is a schematic side view of a sealed end of the pipe of Figure 1 including towing means; and Figure 5b is a cross-sectional view of the sealed end of the pipe of Figure 5a.

Referring to Figure 1 the polyethylene (PE) pipe 1 is formed from molten PE polymer compound 3 forced through an extrusion tool 5. The extrusion tool 5 comprises a cylindrical die 7 and mandrel 9, with an annular gap 11 between the die 7 and mandrel 9, which, together with the haul-off speed, determines the wall thickness of the extruded pipe 1. The mandrel 9 includes a central bleed hole 13 which is typically 5 to 10 millimetres in diameter.

In manufacture of the pipe, molten PE is extruded under pressure and passes into a vacuum cooling chamber 17a via a perforated calibration sleeve 15. The perforated calibration sleeve 15 controls the outer diameter of the pipe 1 whilst the pipe 1 is simultaneously cooled by the vacuum cooling chamber 17a. When the pipe 1 is extruded, a forward end of the pipe 19 is open to the air. Air passes through the bleed hole 13 in the mandrel 9 and exits through the forward end of the pipe 19. : :.

The air passing through the bleed hole 13 is rapidly heated to the temperature of the extrusion tool 5, which is between 170 and 250 C. The air is sterilised at this temperature and acts to sterilise the pipe 1 during extrusion. *S,. S... * S S

As shown in Figure 2, following extrusion of the pipe 1 through the extrusion tool 5 and the calibration sleeve 15, the pipe is cooled in a vacuum cooling chamber 17a. The cooling chamber 17a precedes one of more cooling tanks 17b. The dimensions of the cooled pipe 1 are monitored by a gauging means 21 between the vacuum cooling spray chamber 17a and a cooling spray 17b. The gauging means 21 is an ultrasonic calibration device which measures the wall thickness of the extruded pipe 1. The pipe 1 then reaches a haul-off 23 which draws the pipe 1 through the line to a marker 24 where it is marked according to a product specification. The pipe 1 is cut by a cutting means 25, such as a saw, to the required length and is coiled.

As shown in Figures 3a and 3b, the pipe 1 is sealed using a heat shrinkable cap 29. The heat shrinkable cap 29 has a heat sensitive adhesive coating 31 on the inner surface of the cap 29.

As shown in Figures 4a and 4b, in an alternative embodiment of the invention, the pipe 1 is sealed using a heat shrinkable sleeve 33. The sleeve is open-ended with a heat sensitive adhesive coating 31 on the inner surface of the sleeve 33. The heat shrinkable sleeve 33 is used in combination with a closed cell foam plug 35, particularly for pipes of greater outside diameter. The dimensions of the plug 35 are determined to allow for compression when the plug 35 is inserted into the pipe end.

In use, the plug 35 is inserted into the pipe end and is loosely fitting. The heat shrinkable sleeve 33 is fitted over the end of the pipe end and the plug 35. The heat shrinkable sleeve 33 and the heat sensitive I.'.

adhesive coating 31 are heated to removably fix the sleeve 33 to the pipe end and the plug 35. This seals the pipe 1.

After the pipe 1 is transported to an installation site, the heat pg* shrinkable cap 29, or heat shrinkable sleeve 33 and plug 35, is peeled away from the pipe end or cut and removed from the pipe end. The pipe * bore is relatively clean and sterile. Although the pipe 1 may not be absolutely sterile, the level of treatment required to achieve the required water quality will be much reduced due to the sealing of the pipe 1 following extrusion.

In further embodiments, as shown in Figures 5a and 5b, a pulling means 37 is used with the pipe and is attached to a towing end of the pipe 1. Prior to installation following removal of the seals 29, 33 from the pipe ends a temporary replacement seal is removably attached to the towing end of the pipe 1 to maintain sterility until installation is complete.

The temporary replacement seal is formed by inserting the loosely fitted plug 35 further into the pipe. The towing end of the pipe is then left free and towing means 37 are attached.

The above described embodiments have been given by way of example only, and the skilled reader will naturally appreciate that many variations can be made thereto without departing from the scope of the present invention. * *

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Claims

Claims 1. A method of manufacturing pipe coils comprising extruding

molten polymer compound through a tool; cooling and cutting the polymer to form a pipe; sterilising the inside of the pipe and sealing each end of the sterile pipe with at least one sealing means, wherein the at least one sealing means maintains the sterility of the pipe.

2. A method of manufacturing pipe coils according to claim 1 wherein extruding the molten polymer compound through the tool sterilises the inside of the pipe. * a, * * **.

3. A method of manufacturing pipe coils according to claim 1 or claim 2 I.. ** wherein the tool is heated. S. S * S * S.

4. A method of manufacturing pipe coils according to claim 3 wherein the S...

tool is heated to between 170 and 250 C. *:::: 5. A method of manufacturing pipe coils according to any preceding claim wherein the sealing means provides resistance up to 0.5 bar of pressure.

6. A method of manufacturing pipe coils according to any preceding claim wherein the sealing means comprises a cap.

7. A method of manufacturing pipe coils according to claim 6 wherein the cap is heat shrinkable.

8. A method of manufacturing pipe coils according to any of claims 1 to 5 wherein the sealing means comprises a sleeve and/or a plug.

9. A method of manufacturing pipe coils according to claim 8 wherein the plug is cylindrical.

10. A method of manufacturing pipe coils according to claim 8 wherein the plug is tapered.

11. A method of manufacturing pipe coils according to any preceding claim wherein the sealing means further comprises a layer of heat sensitive adhesive.

12. A method of manufacturing pipe coils according to any preceding claim wherein the tool comprises a hollow cylinder and a mandrel.

13. A method of manufacturing pipe coils according to claim 12 wherein *s.SS.

the mandrel comprises at least one aperture. * S. * . S .5

14. A method of manufacturing pipe coils according to any preceding claim wherein the inside of the pipe is sterilised by passing heated gas through the tool and the pipe. : .. S... * 5 S...

15. A method of manufacturing pipe coils according to any preceding claim wherein the gas passing through the tool is sterilised by heat before entering the pipe.

16. A method of manufacturing pipe coils according to any of claims 1 to 14 wherein the gas passing through the pipe is sterilised by any of UV radiation or membrane filtering.

17. A method of manufacturing pipe coils according to any of claims 14 to 16 wherein the gas passing through the pipe maintains the sterility of the pipe.

18. A method of manufacturing pipe coils according to claim 17 wherein the gas passing through the pipe is air or nitrogen.

19. A method of manufacturing pipe coils according to any of claims 14 to 18 wherein gas exits the tool and enters the pipe through the at least one aperture of the mandrel.

20. A method of manufacturing pipe coils according to any or claims 14 to 19 wherein the exit of gas through the at least one aperture draws gas through the pipe.

21. A method of manufacturing pipe coils according to claim 20 wherein gas is drawn through the pipe from the tool to an open end of the pipe.

22. A method of manufacturing pipe coils according to any preceding claim wherein the time between cutting the pipe and sealing the pipe is: :::* less than 120 seconds.

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23. A method of manufacturing pipe coils according to any of claims 14 to: 22 wherein sterile gas continues to enter the pipe after cutting. .S.. * S S * S

24. A method of manufacturing pipe coils according to any of claims 8 to 23 wherein the plug has an outer diameter substantially equal to the inner diameter of the pipe.

25. A method of manufacturing pipe coils according to any of claims 8 to 23 wherein the plug comprises a compressible material and in a relaxed state the plug has a diameter greater than the inner diameter of the pipe.

26. A method of manufacturing pipe coils according to any of claims 8 to wherein the plug is made of a low mass, resilient material.

27. A method of manufacturing pipe coils according to any of claims 8 to 26 wherein the plug is made of closed cell PE foam.

28. A method of manufacturing pipe coils according to any of claims 8 to 27 wherein the plug is removably retained by retaining means.

29. A method of manufacturing pipe coils according to any preceding claim wherein the outer diameter of the pipe is between 25mm and 180 mm.

30. A pipe coil manufactured by the method as claimed in any of claims 1 to 29.

31. An apparatus for a method of manufacturing pipe coils as claimed in *.S.S.

anyofclaimslto29. S..

32. A method substantially as described herein and with reference to a.....

the accompanying drawings 1 to 5. a... * * a... *SS* * S S