GB2221741A

GB2221741A - Lining pipes

Info

Publication number: GB2221741A
Application number: GB8819063A
Authority: GB
Inventors: Brian Edward Mcguire
Original assignee: British Gas PLC
Current assignee: British Gas PLC
Priority date: 1988-08-11
Filing date: 1988-08-11
Publication date: 1990-02-14
Anticipated expiration: 2008-08-11
Also published as: MX171346B; GB2221741B; GB8819063D0; BR8904032A

Abstract

The invention relates to the reduction of the diameter of liner pipe 3 intended for use as a liner for existing pipework such as ground embedded gas, oil or water pipes. In use, the liner pipe 3, which is of plastics material e.g. polythene of external diameter greater than the internal diameter of the pipework to be lined, is drawn through a swaging die 1 to reduce its diameter sufficiently to enable the liner pipe 3 to be drawn through the pipework. The swaging dye 1 is provided with lubricating means to reduce the friction between the liner pipe 3 and the swaging surface 4. The lubricating means may be liquid or gas fed through channels e.g. channel 6 in the die or may be a pt fe insert (e.g. 17, Fig. 2) in the die 1. Liquid lubricant may be fed to a brush, swab or a spray ring to be applied to a liner pipe prior to entry to the die 1. Monoethylene glycol, detergents and soaps may be employed. <IMAGE>

Description

CASE NUMBER 8 PIPELINING AND LINER PIPE SWAGING DIES This invention relates to improvements in methods and apparatus for reducing the diameter of liner pipes intended for use as liners to existing pipework such as ground embedded gas, oil or water pipes.

When lining existing ground embedded pipework, it is known to draw a hot liner pipe of plastics tube through a die to reduce the diameter and then into a length of the existing pipework wherein the swaged liner pipe is caused to expand within the embedded pipework by the application of internal heat or elevated internal pressure thus providing a close fitting liner within the pipework.

Further methods of lining installed pipework using improved methods and/or improved dies are described in our co-pending United Kingdom Patent Applications all filed on the 9th May 1988. For the purposes of this Specification, the said Applications are identified by reference to "Case Numbers" as set out below: Application No.8810892.3 Case 1 Application No.8810893.1 Case 2 Application No.8810894.9 Case 3 Application No.8810895.6 6~~~~~~~~~~~~~~~~~ Case 4 Application No.8810896.4 .................. Case 5 Application No.8810897.2 Case 6 Application No.8810891.5 Case 7.

The present invention provides an improved method of lining installed pipework using a modified swaging die to reduce the diameter of the liner pipe prior to its being drawn into installed pipework. By "installed pipework" is meant pipework that has already been installed in position to carry out its intended purpose, such as for example, ground embedded pipework for gas, oil, water or sewerage, pipework forming part of a larger installation, or pipework resting on ground or other support and laid down to connect a source of supply to the recipient such as an oil pipe connecting a well to a refinery or port.

The present invention also relates to an improvement to swaging dies for use in pipelining operations.

According to the present invention, there is provided a method of lining installed pipework which comprises drawing a liner pipe of plastics material of external diameter greater than the internal diameter of the pipework to be lined through a swaging die to reduce its diameter sufficiently to enable the liner pipe to be drawn through the pipework using pulling means under tension attached to the leading end of the liner pipe and threaded through the pipework wherein the internal swaging surface of the swaging die is provided with lubricating means whereby the swaging surface is lubricated so as to reduce the friction between the liner pipe and such swaging surface.

The present invention also relates to a die for use in reducing the diameter of plastics liner pipe prior to its insertion into installed pipework having an internal swaging surface provided with lubricating means adapted to effect lubrication of the swaging surface so as to reduce the friction between the swaging surface and the liner pipe to be drawn through it.

The lubricating means may be provided by modifying the swaging surface of the die by the incorporation thereon of a skin or layer of material having a low coefficient of friction, for example polytetrafluorethylene (PTFE).

Alternatively, the lubrication means may be constituted by the provision of means whereby a liquid lubricant may be introduced under pressure to form a lubricating film between the liner pipe and the swaging surface during the swaging operation.

A further alternative lubricating means may be provided by providing for the introduction of a gas, typically air, under pressure to form a lubricating film between the liner pipe and the swaging surface during the swaging operation.

It will be appreciated that the method of the present invention can be applied both to the prior art known methods of reducing the diameter of liner pipes by swaging and also to the several methods described and claimed in each of the several United Kingdom Patent Applications referred to above and given the designation for the purposes of the present Specification of Case 1 to Case 7 inclusive.

Furthermore, dies made according to the present invention may be constituted by the dies as used and known in accordance with the prior art or, preferably, as described and claimed in Case 6 and/or Case 7 as referred to above, modified by the provision on or in relation thereto of any of the lubricating means of the present invention.

It will be appreciated that, for the present purposes, the matters set out in the respective SpecificationSof Case 1 to Case 7 inclusive are and are to be deemed to be read in conjunction with the disclosure made in the present Specification.

The present invention may be illustrated by reference to the accompanying drawings in which: Figure 1 represents in cross section the upper part of a swaging die provided with means for injection into the die and onto the swaging surface of a liquid lubricant.

Figure 2 represents in cross section the upper part of a swaging die where the swaging surface is provided with a layer having a low coefficient of friction vis a vis the liner pipe.

Figure 3 represents in cross section the upper part of a swaging die provided with means for injection into the die and onto the swaging surface of a gaseuos lubricant.

Figure 4 is an enlarged cross sectional view of the circumferential groove of Figure 3.

In Figure 1, 1 represents in cross section the upper part of a swaging die disposed around its axis 2, through which passes a liner pipe 3 whose diameter is reduced by the swaging surface 4 as the liner pipe passes through the die in the direction A to B. The swaging surface 4 is provided with a continuous circumferential groove 5 adjacent to and downstream of the point where the liner pipe engages with the swaging surface. Such groove 5 is connected to a plurality of symmetrically disposed supply channels 6 passing through the body of the swaging die and connected to injection means whereby liquid lubricant may be injected into channels 6 and may pass therefrom into the groove 5 and onto the surface of liner pipe 3 as it passes through the die. On drawing the liner pipe across the circumferential groove 5, a seal is formed.

In operation, a liquid lubricant, for example, CASTROL (registered Trade Mark) D416 is introduced under pressure into the circumferential groove 5 through the respective channels 6 and forms a film of lubricant around the liner pipe 3 as it moves downstream of the circumferential groove 5 thus reducing the friction between the liner pipe 3 and the swaging surface 4 during the swaging operation.

The dimensions of the circumferential groove 5 and its supply channels 6 will depend upon the dimensions of the die and the particular conditions of the operation. Typically, in the case of a swaging die intended for swaging a liner pipe having an initial diameter in the order of 300mm, the groove may have a depth in the order of 2mm and a downstream radiused edge and may be supplied by four symmetrically disposed lubricant supply channels 6 each of 3mm diameter.

In Figure 2, 11 represents in cross section the upper part of the swaging die that is disposed around its axis 12, and the swaging surface 14 is constituted along at least part of its length by a layer 17 of a material e.g. "Teflon" (registered Trade Mark), having a low coefficient of friction in relation to the material of the liner pipe 13 that is drawn in the direction A to B through the die.

In Figure 3, the die, disposed around its axis 22 and represented in this case by its upper part 21 seen in cross section, is provided with a circumferential groove 25 connected to one or more radial supply channels 26 through which air may be introduced under pressure e.g. from the inwardly facing channel of ring 28 firmly clamped onto the outer surface of the die or forming part of the die housing and which is adapted to receive and transmit to channels 26 a supply of air under pressure from a suitable source. As in the case of the embodiments described by reference to Figure 1, the liner pipe 23 on engaging and passing along the swaging surface 24 seals off, at least in part, the groove 25 from the upstream aperture of the die.Air under pressure from groove 25 passes downstream along the swaging surface 24 of the die in the form of a gaseous film that lubricates the passage of the liner pipe 23 through the die.

The operation of the invention described by reference to Figure 1 and Figure 3 may be enhanced by providing the groove 5 or 25 as the case may be, with a sharp acute angle or flange like upstream edge 25a and a large angled or large diameter radiused downstream edge 25b (Figure 4). This arrangement facilitates the passage of the lubricating fluid or gas in the downstream direction to form a lubricating film between the liner pipe 25 and the swaging surface 24 during the course of the swaging operation.

The above methods of lubrication of the passage of the liner pipe through a swaging die may be put to use in connection with the methods of any of Cases 1 to 7 inclusive above. In particular, they may be used in conjunction with those operations where the liner pipe is heated prior to the swaging operation. One method of pre-heating the liner pipe prior to swaging is described in our co-pending Patent Application GB2,186,340A which discloses passing the liner pipe prior to swaging through a heating chamber into which is supplied hot gas from a burner. In the case of the method described by reference to Figure 1 above, the liquid lubricant (which in general would be a combustible product) is sealed off from the hot gases and from the burner.

According to a modification of the present invention, there is provided a method of installing lined pipework which comprises drawing a liner pipe of plastics material of external diameter greater than the internal diameter of the pipework to be lined through a swaging die to reduce its diameter sufficiently to enable the liner pipe to be drawn through the pipework using pulling means under tension attached to the leading end of the liner pipe and threaded through the pipework wherein a non-aqueous lubricant adapted to wet the surface of the liner pipe is applied to the liner pipe prior to its entry into the passage through the swaging die and in which the liner pipe enters the swaging die at ambient temperatures or heated otherwise than using a high intensity source of heat.

By the expression "high intensity source of heat" is meant a flame or gas such as combustion gases emerging from a flame or an electrical or other source of heat used to heat the liner pipe before it enters the die and having a temperature that is higher than the flash point of the lubricant employed.

Such modification of the present invention may usefully be employed in conjunction with the method of Case 2 as referred to above and the methods of each of Case 3, 4, 6 and 7 in so far as the same do not involve the use of a high intensity source of heat as referred to above. In particular, the method of this modification of the present invention may advantageously be put to use in conjunction with the use of any of the dies of the Specification of Cases 6 and/or 7 as referred to above.

Care should be exercised in the choice of any liquid lubricant used in putting the inventions of the present Application, including the above mentioned modification thereof, into effect. One useful liquid lubricant as already mentioned is the proprietary product CASTROL D416. Another is Monoethylene Glycol. Certain soaps and detergents will also provide a lubricating effect.However, the use of surface active or detergent compositions other than soaps is not recommended in conjunction with polyethylene liner pipes since their long term effect can be to bring about stress cracking of the pipes. The application of the lubricant to the liner pipe prior to entry of the liner pipe into the swaging die according to the aforesaid modification of the present invention may be effected by projecting the lubricant from an annular ring surrounding the liner pipe and provided with means for directing jets or sprays of liquid lubricant which impinge upon the pipe. Further or alternatively, the pipe may be passed through a ring shaped brush with inwardly directed bristles bearing against the pipe or else a continuous annular swab which bears on the pipe, the brush or swab being fed by a supply of liquid lubricant and, if desired, continuously rotated around the pipe.

Claims

What we claim is: 1. A method of lining installed pipework which comprises drawing a liner pipe of plastics material of external diameter greater than the internal diameter of the pipework to be lined through a swaging die to reduce its diameter sufficiently to enable the liner pipe to be drawn through the pipework using pulling means under tension attached to the leading end of the liner pipe and threaded through the pipework wherein the internal swaging surface of the swaging die is provided with lubricating means whereby the swaging surface is lubricated so as to reduce the friction between the liner pipe and such swaging surface.
2. A method as claimed in Claim 1 in which the die swaging surface is provided with a skin or layer or a material having low surface friction characteristics.
3. A method as claimed in Claim 2 in which the material is polytetrafluorethylene.
4. A method as claimed in Claim 1 in which a liquid lubricant is supplied within the die under pressure to the swaging surface.
5. A method as claimed in Claim 1 in which a gaseous lubricant under pressure is supplied within the die to the swaging surface.
6. A method as claimed in Claim 5 in which the gaseous lubricant is air.
7. A method as claimed in any of claims 4, 5 or 6 in which the lubricant concerned is supplied under pressure to a circumferential groove on the swaging surface.
8. A method as claimed in Claim 7 in which the edge of the groove on its upstream side in relation to the direction of movement of the liner pipe during swaging is acute angled or flange like with its apex as seen in cross section pointing in the downstream direction.
9. A modification of the invention as claimed in any of the preceding Claims being a method of installing lined pipework which comprises drawing a liner of plastics material of external diameter greater than the internal diam##ter of the pipework to be lined through a swaging die to reduce its diameter sufficiently to enable the liner pipe to be drawn through the pipework using pulling means under tension attached to the leading end of the liner pipe and threaded through the pipework wherein a non-aqueous lubricant adapted to wet the surface of the liner pipe is applied to the liner pipe prior to its entry into and passage through the swaging die and in which the liner pipe enters the swaging die at ambient temperatures or heated otherwise than using a high intensity source of heat as herein defined.
10. A method as claimed in any of Claims 1 to 9 inclusive in which the die employed is a die as described and claimed in our co-pending Application Number 8810892.2.
11. A method as claimed in any of Claims 1 to 9 inclusive in which the die employed is a die as described and claimed in our co-pending Application Number 8810891.5.
12. A method as claimed in any of the preceding claims characterised in addition by the features of any of the methods described and claimed in any of our aforesaid co-pending Patent Applications, that is to say: Application Number 8810892.3 Application Number 8810893.1 Application Number 8810894.9 Application Number 8810896.6 Application Number 8810896.4
13. A die for use in reducing the diameter of plastics liner pipe prior to its insertion into installed pipework having an internal swaging surface provided with lubricating means adapted to effect lubrication of the swaging surface so as to reduce the friction between the swaging surface and the liner pipe to be drawn through it.
14. A die as claimed in Claim 13 in which the swaging surface is provided with a layer of skin of material having low surface friction characteristics.
15. A die as claimed in Claim 14 in which the material is constituted by polytetrafluorethylene.
16. A die as claimed in Claim 13 which is provided with means for supplying a lubricant to the swaging surface during the swaging operation.
17. A die as claimed in Claim 16 in which the means include a circumferential groove in the swaging surface to which a lubricant may be supplied under pressure during the swaging operation.
18. A die as claimed in Claim 17 in which the upstream edge of the groove nearest the larger diameter aperture of the die is acute angled or flange like with its apex as seen in cross section pointing in the downstream direction.
19. A die as claimed in any of Claim 13 to 18 characterised by the features of any of the dies claimed in our co-pending Application Number

8810892.2.
20. A die as claimed in any of Claims 13 to 18 characterised by the features of any of the dies claimed in our co-pending Application Number

8810891.5.
21. A method as claimed in Claim 1 substantially as described by reference to the accompanying drawings.
22. A die as claimed in any of Claims 13 to 21 substantially as described herein by reference to the accompanying drawings.