GB2407857A

GB2407857A - Pipe insulating apparatus and method

Info

Publication number: GB2407857A
Application number: GB0424574A
Authority: GB
Inventors: Alan David Foxton
Original assignee: Subsea 7 BV
Current assignee: Subsea 7 BV
Priority date: 2003-11-08
Filing date: 2004-11-08
Publication date: 2005-05-11
Anticipated expiration: 2024-11-08
Also published as: US20050103393A1; GB0424574D0; US6981525B2; BRPI0406126A; GB2407857B; NO20044848D0; NO20044848L; GB0326118D0

Abstract

A tubular insulating apparatus 10 for insulating a first pipe 8 from a second pipe 20, the apparatus comprising at least one pair of longitudinally spaced rigid spacers 16 providing support for the first pipe within the second pipe, an insulating member 4 surrounding the inner pipe between the spacer members, and a resilient member 2 associated with an outermost face of the insulating member, where the insulating member and resilient member are helically arranged. The spacers preferably consist of a toroidal ring, and the helical arrangement may be provided by a helically arranged cut 6 in the insulating and resilient members. The resilient layer and insulating layers may be joined by an adhesive bond. Also claimed are methods of manufacturing and installing a tubular insulating apparatus.

Description

1 "Apparatus and Method" 3 The present invention relates to an insulating

4 apparatus and a method of installing the apparatus, and particularly but not exclusively relates to an 6 insulating apparatus and method of installing the 7 apparatus for use in insulating oil and gas 8 pipelines.

In the oil and gas exploration industry it is often 11 necessary to transport oil and gas over long 12 distances underwater. This is often done using a 13 pipeline installed at or near the sea bed. In order 14 to allow the oil to flow through the pipeline easily, it is usually necessary to keep the oil 16 relatively hot (generally at a temperature of 17 between 80 C and 100 C). Maintaining the oil at this 18 temperature prevents "waxing" (solidification) of 19 the oil from occurring whilst flowing through the pipeline, thereby helping to prevent blockages in 21 the pipeline.

1 As the environment surrounding the pipeline is much 2 cooler than the temperature of the oil flowing 3 through it, it is beneficial to provide some form of 4 insulation to surround the pipeline. This is often done using a pipe-in- pipe insulation system where an 6 outer pipe (of greater diameter than the inner oil 7 containing pipe) is positioned around the inner oil 8 containing pipe such that a cavity is created 9 between the two, the cavity typically being filled with an insulating material. Mineral wool offers a 11 cost effective, and therefore widely used insulant 12 for this purpose. One type of insulating unit is 13 Fibashield_ offered by Rockwool Limited of Bridgend, 14 Glamorgan, Wales, UK which consists of mineral wool insulant surrounded by a rigid polymer sheath.

16 Sections of the insulating unit, approximately 2.5 17 metres long, are placed around the oil containing 18 pipeline, either by sliding the insulating unit onto 19 one end of the pipeline, or by cutting through one wall of the insulating unit along its longitudinal 21 axis and "clipping" the unit over the pipeline 22 section.

24 Annular ring centralizers such as those offered by Devol Engineering of Greenock, U.K., are spaced 26 apart (typically by approximately 2.5m) along the 27 length of the longitudinal axis of each insulating 28 unit, such that in use, the centralisers extend 29 radially outwardly between the inner and outer pipe walls, and their purpose is to transfer load (e.g. 31 gravity acting upon the inner oil containing pipe) 32 from the inner pipe to the outer pipe without 1 compressing the insulation material. The 2 centralizers also therefore act to maintain the 3 central longitudinal axis of the pipeline in a 4 parallel and co-axial relationship with the longitudinal bore of the surrounding insulating 6 material. This prevents the situation where the 7 inner oil containing pipeline becomes closer to one 8 wall of the outer pipe, and hence has poorer 9 insulation at that point due to compression/ destruction of the surrounding insulating material.

11 Each section of pipeline and associated insulating 12 unit(s) are typically transported and stored on 13 large reels.

The problem with such insulation systems is that 16 when in transit and/or storage on the reels, the 17 compression exerted on the insulation at the inner 18 radius or intrados of the curved length of 19 insulation unit is sufficient to permanently deform the insulation. Therefore, when the length of 21 insulation unit is off-loaded from the reel and is 22 straightened, the non-elastic behaviour of the 23 mineral wool results in areas where the insulation 24 is reduced, typically between each centraliser location. This reduction in insulation is often 26 substantial.

28 According to a first aspect of the present invention 29 there is provided a tubular insulating apparatus for insulating a first tubular within a second tubular, 31 the apparatus comprising: 1 at least one pair of substantially rigid spacer 2 members adapted to provide support for the first 3 tubular within the second tubular, wherein the 4 substantially rigid spacer members are longitudinally spaced apart within the apparatus; 6 an inner insulating member suitable for 7 substantially surrounding the outer circumference of 8 the first tubular between the pair of longitudinally 9 spaced apart spacer members; a substantially resilient member associated 11 with an outer most face of the inner insulating 12 member wherein the inner insulating member and 13 substantially resilient member are helically 14 arranged in order to allow tensile and compressive stresses caused by a bending moment acting along the 16 longitudinal axis of the apparatus to be 17 substantially relieved.

19 Preferably, the or each spacer member comprises a transverse spacer which provides an annular wall 21 between the first and second tubulars. More 22 preferably, the or each spacer member comprises a 23 toroidal ring.

Preferably, the helical arrangement is provided by a 26 helically arranged cut provided in the inner 27 insulating member and substantially resilient 28 member.

Preferably, the relief of the tensile and 31 compressive forces is provided by the helically 1 arranged cut opening into apertures along an 2 extrados of the insulating apparatus.

4 Preferably, the resilience of the resilient member is capable of urging the inner insulating member 6 radially inward toward a substantially central 7 longitudinal axis of the apparatus. More 8 preferably, the resilience of the resilient member 9 is such that when the bending moment is removed from the apparatus, the inner insulating member is urged 11 to return to its original shape and form prior to 12 the application of the bending moment, thereby 13 substantially closing said apertures and re 14 establishing the radial dimension of the insulating member.

17 Typically, the association between the resilient 18 member and the inner insulating member is provided 19 by an adhesive bond therebetween.

21 Typically, the first tubular is a pipeline.

23 Preferably, the helically arranged cut circumscribes 24 the apparatus at an angle of between 30 and 60 with respect to an axis transverse to the 26 longitudinal axis of the apparatus.

28 Optionally, the substantially resilient member and 29 inner insulating member are formed from a substantially continuous longitudinal strip.

1 According to a second aspect of the present 2 invention there is provided a method of 3 manufacturing a tubular insulating apparatus for 4 insulating a first tubular within a second tubular, the method comprising: 6 cutting, in a helical arrangement, an 7 insulating apparatus comprising an insulating inner 8 member suitable for substantially surrounding the 9 outer circumference of the first tubular and a substantially resilient member associated with an 11 outer most face of the inner member.

13 According to a further aspect of the present 14 invention there is provided a method of installing a tubular insulating apparatus on a first tubular to 16 be insulated within a second tubular, the insulating 17 apparatus having a helically arranged insulating 18 member suitable for substantially surrounding the 19 outer circumference of the first tubular and a helically arranged substantially resilient member 21 associated with an outer most face of the insulating 22 member, the method comprising: 23 partially opening out one end of the helically 24 arranged insulating apparatus in the opposite direction to the bias of the outer resilient member 26 in order to create an aperture between the opened 27 out portion of the helically arranged insulating 28 apparatus and the remaining portion of the helically 29 arranged insulating apparatus, the aperture being of a dimension large enough to accommodate the diameter 31 of the first tubular; 1 resting the opened out portion of the helically 2 arranged insulating apparatus on the first tubular 3 such that the opened out portion of the insulating 4 apparatus is attached to the first tubular; rotating the insulating apparatus relative to 6 the first tubular about the longitudinal axis of the 7 insulating apparatus in order to transfer the 8 remaining unattached portion of the insulating 9 apparatus onto the first tubular; and inserting the first tubular and insulating 11 apparatus into the second tubular.

13 An embodiment of the present invention will now be 14 described, by way of example only, with reference to the accompanying drawings, in which: 17 Fig. 1 is a transverse cross-sectional view 18 showing the helical cut pipe-in-pipe insulation 19 prior to installation on the sea bed and reeling; 21 Fig. 1A is a cross-sectional view of the pipe 22 in-pipe insulation taken through the section A; 23 Fig. 2 is a transverse cross-sectional view 24 showing the helical cut pipe-in-pipe insulation during transit on a reel; and 26 Fig. 3 is a transverse cross-sectional view 27 showing the helical cut pipe-in-pipe insulation 28 system, after transit and installation on the 29 seabed.

1 Figs. 1 to 3 generally show an oil/gas/water or 2 multiphase pipeline 8 which is to be installed onto 3 the seabed within an exterior protective pipe 20.

Figs. 1 to 3 also show a preferred embodiment of an 6 insulating apparatus, in accordance with the present 7 invention, generally designated 10 for insulating 8 the pipeline 8, the apparatus comprising 9 centralizers or spacers 16, and a resilient sheath 2 (best seen in Fig. la) surrounding mineral wool 11 insulant 4, the resilient sheath 2 and mineral wool 12 insulant 4 each having a radially extending cut 6 13 and being located, in use, within the exterior pipe 14 20.

16 The resilient sheath 2 is generally cylindrical or 17 tubular in shape, and is formed from a material such 18 as a suitable polymer.

The mineral wool insulant 4 is in the form of an 21 annular ring such that it has an 'O' shaped cross 22 section to enable it to fill the cavity (not shown) 23 produced between the resilient sheath 2 and the 24 pipeline 8 to which the insulating apparatus 10 is to be installed upon, and may be bonded to the 26 internal bore of the resilient sheath 2 by any 27 suitable means such as a suitable adhesive (not 28 shown).

In the embodiment shown, the radially extending cut 31 6 is cut at an angle of between 30 and 60 relative 32 to an axis transverse to the longitudinal axis 14 of 1 the insulating apparatus 10 such that a helicoidal 2 cut 6 is created around the circumference of the 3 insulating apparatus 10. The skilled reader will 4 appreciate that other angles of the cut 6 may be provided without substantially affecting the 6 operation of the apparatus 10. The helicoidal cut 6 7 passes through one wall of the tubular resilient 8 sheath 2 and the tubular mineral wool insulant 4.

The skilled reader will note that the apparatus 10 11 may be formed by cutting a standard 2.5 metre length 12 section of insulating unit such as Fibashield_ 13 insulation offered by Rockwool Limited of Bridgend, 14 Glamorgan, Wales, UK at the required angle in order to create the helicoidal arrangement described 16 above. This may be done by rotating a suitable 17 cutting device around the apparatus 10 at the 18 required angle. A suitable cutting device may be a 19 rapidly oscillating or rotating blade, however the reader will realise that other cutting devices could 21 be used here.

23 Positioned between each section of insulating 24 apparatus 10 are transversely arranged nylon centralisers 16 which provide a rigid support for 26 the lower half of the pipeline 8 to rest upon from 27 one point of view, and a rigid support for the upper 28 half of the resilient sheath 2 to rest upon from 29 another point of view. Accordingly, the centralizers 16 provide support in the radial 31 direction, and thus are capable of bearing and 32 transferring load in the radial direction between 1 the exterior pipe 20 and the outer surface of the 2 pipeline 8. Furthermore, the centralisers 16 ensure 3 that the annular gap created between the inner 4 circumference of the exterior pipe 20 and the outer circumference of the interior pipeline 8 is 6 maintained. The centralizers 16 have a toroidal 7 ring shape and are located between the mineral wool 8 insulation 4 of each insulating section.

9 Installation of the insulating apparatus 10 on the pipeline 8 may be performed by placing a 11 transversely arranged nylon centraliser 16 onto the 12 bare pipeline 8 and then partially uncoiling the 13 helical cut of a length (typically of around 2.5m 14 long) of insulating apparatus 10 at one end until a gap (not shown) is created which is big enough to 16 allow that end of the insulating apparatus to slip 17 onto the pipeline 8. The insulating apparatus 10 18 can then be progressed onto the pipeline 8 by 19 rotating the remainder of the insulating apparatus 10 until the full length of the section of 21 insulating apparatus 10 has been transferred onto 22 the pipeline 8. It should be noted again that the 23 resilience of the resilient sheath 2 is important to 24 ensure that the resilient sheath 2 and mineral wool insulant 4 return to their original shape once 26 installed on the pipeline 8. Another transversely 27 arranged nylon centralizer 16 is then placed onto 28 the pipeline 8 adjacent the end of the insulating 29 material 4 of the insulating apparatus 10. Another length of insulating apparatus 10 may then be placed 31 onto the pipeline 8 in the same process as 32 previously described. This process is repeated 1 until the desired length of pipeline is surrounded 2 by the insulating apparatus 10. This length may 3 typically be in the region of between 0.5km and 4 1.5km, however the skilled reader will realise that this process could be repeated for any length of 6 pipeline 8.

8 The length of pipeline 8 with the apparatus 10 9 (comprising the centralizers 16, insulation 4 and sheath 2) installed thereon is then located within 11 the protective outer tubular 20 by sliding the 12 protective tubular 20 there over.

14 In use, when a continuous length of the insulating apparatus 10, exterior pipe 20 and the associated 16 and surrounded inner pipe 8 is coiled onto a reel 17 (not shown) for storage or transport prior to 18 installation on the sea bed, the resilience of the 19 apparatus 10 provided by the helicoidal cut 6 allows relief of the tensile force acting on the outer side 21 (extrados) and the compressive force acting on the 22 inner side (intrados) of the insulating apparatus 10 23 via the opening of slots 18 as shown in Fig. 2.

24 This is possible since any compressive force acting on the insulant 4 between faces A and B (as shown in 26 Fig. 2) of the transverse nylon centralisers 16 will 27 (rather than attempting to compress the insulant 4) 28 tend to open apertures 18 on the extrados of the 29 apparatus 10 instead. This therefore allows the insulating apparatus 10 and the associated and 31 surrounded inner pipe 8 to be coiled onto the reel 32 (not shown) without irretrievably or permanently 1 deforming the mineral wool insulant 4.

2 Additionally, the longitudinally spaced apart but 3 transversely arranged centralizers 16 prevent radial 4 collapse of the insulating material 4 located therebetween. Furthermore, when the continuous 6 length of the insulating apparatus 10 is removed 7 from the reel (not shown), the resiliency of the 8 resilient sheath 2 will tend to return the resilient 9 sheath 2 and therefore the mineral wool insulant 4 to their original shape. In this regard any 11 localized compression which does occur at the end of 12 the insulant 4 due to compressive forces present 13 between the centralizers 16 will be minimised. In 14 addition any gaps in the insulant 4 which would otherwise have been created between the centralisers 16 16 will be closed due the apparatus 10 reforming 17 into its original configuration when the compressive 18 force is removed.

Modifications and improvements may be made to the 21 embodiments hereinbefore described without departing 22 from the scope of the invention. For instance, 23 whilst the preferred embodiment described above has 24 the helicoidal cut 6 formed in the insulating apparatus 10 prior to installation of the apparatus 26 10 onto the pipeline 8, it may be possible to 27 install the cylindrical insulating apparatus 10 28 uncut on the pipeline 8 first, and then form the 29 helicoidal cut 6 with a suitable cutting implement or mechanism.

1 Alternatively, the insulating apparatus 10 may be 2 provided as a continuous resilient strip on a reel 3 (not shown). Installing the continuous strip on the 4 pipeline 8 may be performed by wrapping the strip around the circumference of the pipeline 8 whilst 6 progressing down the length of the pipeline 8, 7 resulting in a similar installed apparatus to the 8 substantially tubular insulating apparatus 10.

Claims

1 CLAIMS: 3 1. A tubular insulating apparatus for insulating a 4 first

tubular within a second tubular, the apparatus comprising: 6 at least one pair of substantially rigid spacer 7 members adapted to provide support for the first 8 tubular within the second tubular, wherein the 9 substantially rigid spacer members are longitudinally spaced apart within the apparatus) 11 an inner insulating member suitable for 12 substantially surrounding the outer circumference of 13 the first tubular between the pair of longitudinally 14 spaced apart spacer members; a substantially resilient member associated 16 with an outer most face of the inner insulating 17 member wherein the inner insulating member and 18 substantially resilient member are helically 19 arranged in order to allow tensile and compressive stresses caused by a bending moment acting along the 21 longitudinal axis of the apparatus to be 22 substantially relieved.

24 2. A tubular insulating apparatus according to claim 1, wherein the or each spacer member comprises 26 a transverse spacer which provides an annular wall 27 between the first and second tubulars.

29 3. A tubular insulating apparatus according to either of claims 1 or 2, wherein the or each spacer 31 member comprises a toroidal ring.

1 4. A tubular insulating apparatus according to any 2 preceding claim, wherein the helical arrangement is 3 provided by a helically arranged cut provided in the 4 inner insulating member and substantially resilient member.

7 5. A tubular insulating apparatus according to 8 claim 4, wherein the relief of the tensile and 9 compressive forces is provided by the helically arranged cut opening into apertures along an 11 extrados of the insulating apparatus.

13 6. A tubular insulating apparatus according to any 14 preceding claim, wherein the resilience of the resilient member is capable of urging the inner 16 insulating member radially inward toward a 17 substantially central longitudinal axis of the 18 apparatus.

7. A tubular insulating apparatus according to 21 either of claims 5 or 6, wherein the resilience of 22 the resilient member is such that when the bending 23 moment is removed from the apparatus, the inner 24 insulating member is urged to return to its original shape and form prior to the application of the 26 bending moment, thereby substantially closing said 27 apertures.

29 8. A tubular insulating apparatus according to any preceding claim, wherein the association between the 31 resilient member and the inner insulating member is 32 provided by an adhesive bond therebetween.

2 9. A tubular insulating apparatus according to any 3 preceding claim, wherein the first tubular is a 4 pipeline.

6 10. A tubular insulating apparatus according to any 7 of claims 4 to 9, wherein the helically arranged cut 8 circumscribes the apparatus at an angle of between 9 30 and 600 with respect to an axis transverse to the longitudinal axis of the apparatus.

12 11. A tubular insulating apparatus according to any 13 of claims 1 to 3, wherein the substantially 14 resilient member and inner insulating member are formed from a substantially continuous longitudinal 16 strip.

18 12. A method of manufacturing a tubular insulating 19 apparatus for insulating a first tubular within a second tubular, the method comprising: 21 cutting, in a helical arrangement, an 22 insulating apparatus comprising an insulating inner 23 member suitable for substantially surrounding the 24 outer circumference of the first tubular and a substantially resilient member associated with an 26 outer most face of the inner member.

28 13. A method of installing a tubular insulating 29 apparatus on a first tubular to be insulated within a second tubular, the insulating apparatus having a 31 helically arranged insulating member suitable for 32 substantially surrounding the outer circumference of 1 the first tubular and a helically arranged 2 substantially resilient member associated with an 3 outer most face of the insulating member, the method 4 comprising: partially opening out one end of the helically 6 arranged insulating apparatus in the opposite 7 direction to the bias of the outer resilient member 8 in order to create an aperture between the opened 9 out portion of the helically arranged insulating apparatus and the remaining portion of the helically 11 arranged insulating apparatus, the aperture being of 12 a dimension large enough to accommodate the diameter 13 of the first tubular;

14 resting the opened out portion of the helically arranged insulating apparatus on the first tubular 16 such that the opened out portion of the insulating 17 apparatus is attached to the first tubular; 18 rotating the insulating apparatus relative to 19 the first tubular about the longitudinal axis of the insulating apparatus in order to transfer the 21 remaining unattached portion of the insulating 22 apparatus onto the first tubular; and 23 inserting the first tubular and insulating 24 apparatus into the second tubular.

26 14. A tubular insulating apparatus substantially as 27 hereinbefore described with reference to the 28 accompanying drawings.

15. A method of manufacturing a tubular insulating 31 apparatus substantially as hereinbefore described 32 with reference to the accompanying drawings.

1 16. A method of installing a tubular insulating 2 apparatus substantially as hereinbefore described 3 with reference to the accompanying drawings.