GB2326687A - Double walled pipe structure - Google Patents

Double walled pipe structure Download PDF

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Publication number
GB2326687A
GB2326687A GB9713168A GB9713168A GB2326687A GB 2326687 A GB2326687 A GB 2326687A GB 9713168 A GB9713168 A GB 9713168A GB 9713168 A GB9713168 A GB 9713168A GB 2326687 A GB2326687 A GB 2326687A
Authority
GB
United Kingdom
Prior art keywords
pipe
outer sleeve
insulated
system according
outer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9713168A
Other versions
GB9713168D0 (en
Inventor
Stuart John Welch
Derek Guy Glover
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
British Steel Corp
Original Assignee
British Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Steel Corp filed Critical British Steel Corp
Priority to GB9713168A priority Critical patent/GB2326687A/en
Publication of GB9713168D0 publication Critical patent/GB9713168D0/en
Publication of GB2326687A publication Critical patent/GB2326687A/en
Application status is Withdrawn legal-status Critical

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16LPIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L59/00Thermal insulation in general
    • F16L59/14Arrangements for the insulation of pipes or pipe systems
    • F16L59/143Pre-insulated pipes

Description

DOUBLE WALLED PIPE STRUCTURES The present invention relates to double walled pipe structures.

Such double walled pipe structures are often used for undersea pipelines in the oil extraction industry. Such pipelines lead from the undersea oilfield extraction point to a floating or subsea distribution point.

The crude oil carried by these pipes normally emanates from beneath the surface at an elevated temperature, typically up to 1 900C. If the crude oil is allowed to cool, lower melting point fractions will solidify and prevent further flow along the pipe. Hence, it is important to maintain the elevated temperature of the crude oil, at least until an initial separation stage can be effected.

This is normally achieved by insulating the pipeline, and Figure 1 shows a known double walled pipe structure comprising an inner flow pipe 10 held concentrically within an outer sleeve pipe 12. Crude oil 14 flows within the flow pipe 1 0. An insulating material 1 6 is placed in the annular region between the flow pipe 10 and the sleeve pipe 12. The entire assembly is shown resting on the seabed 1 8.

As exploration of oil fields continue, easily accessible oil fields approach exhaustion and therefore oil extraction companies turn to less accessible fields in order to satisfy continuing production demands. Such fields are commonly in deeper water, and therefore the depth at which some pipelines are required to operate generally increases. Deep water can be defined as deeper than about 300 metres. The deepest waters currently being considered are approximately 3000 metres.

A problem encountered with the use of double walled pipe systems in deep water is the increasing hydrostatic pressure exerted on the outer sleeve pipe. At depths over about 1000 metres (depending on the specific design) the wall thickness of the outer sleeve pipe needs to become relatively thick if it is to resist hydrostatic collapse. Figure 2 shows the effect of not increasing this thickness; it can be seen that at the points marked A there is little or no insulation. This will eventually cause the pipe to clog through wax accumulation.

If the thickness of the outer sleeve is increased then the inevitable effect of this is to increase the submerged weight of the pipeline system.

This has a knock-on effect, in that during laying of the pipeline the tension that the pipe lay vessel must exert on the pipe is proportional to the submerged weight of the pipeline system. Double walled pipe systems with thick walls can become so heavy that the required tension during pipelaying is greater than existing pipe lay vessels can supply. This effectively serves to rule out the use of double walled pipe systems.

If the insulation material is a so-called "compliant" material such as alumina-silicate microspheres, these offer support to the sleeve pipe. In this way, the thickness of the sleeve can be safely reduced without prompting collapse in deep water. However, in very deep waters, such as over about 1 500 metres, even compliant insulation material cannot prevent the sleeve pipe from collapsing.

It is an object of the invention to provide a double walled pipe system which is capable of operating safely in deep or very deep waters.

The present invention therefore provides an insulated pipe work system comprising an outer sleeve, an inner flow pipe and insulating material in the space therebetween, wherein the insulating material provides mechanical support to the outer sleeve when the latter is under compression, the system being installed under water at a depth of 300 metres or greater.

Preferably, the system is installed at a depth of at least 500 metres, more preferably at least 1000 metres, still more preferably 1 500 metres.

It has been found by the inventors that an insulated pipe work system such as the above in which the insulating material is "compliant", i.e.

provides mechanical support to the outer sleeve when the latter is under compression, does not collapse in a simple oval shape. Instead, a part of the external sleeve hinges along three lines to form a ridge or fin running longitudinally along the outside edge. This fin was filled internally with the insulating material, but (more significantly) a significant amount of insulating material remained distributed around the internal flow line. Thus, despite the collapse of the outside pipe there still remained a certain level of insulation.

Suitable design should ensure that this level of insulation is sufficient.

Thus, according to the invention such pipelines can still be used at significant depths despite the significant risk of collapse as this will not cause the insulation layer to become non-functional.

The present invention further provides an insulated pipe work system comprising an outer sleeve, an inner flow pipe and insulating material in the space therebetween, wherein the insulating material provides mechanical support to the outer sleeve when the latter is under compression, the outer sleeve pipe being non-circular at least due to at least one fin projecting therefrom and formed of a fold in the outer sleeve pipe material.

It may be preferable to positively incite such collapse, in order to ensure that it occurs in a controlled manner. The present invention therefore also relates, in a second aspect, to an insulated pipe work system comprising an outer sleeve, an inner flow pipe and insulating materials spaced therebetween, wherein the outer sleeve pipe is circumferentially nonuniform.

Suitable non-uniformities may comprise one or more localised discontinuities in the outer sleeve pipe. Such discontinuities may include folds, ridges, channels, associated series of channels such as a pair on the outside, perhaps associated with a single channel on the inside located between the outer pair, variations in the strength of the material, and so on.

Most of the strength of a double walled pipe system is carried by the inner flow line. Therefore, the outer pipe need not be as strong as the inner pipe and this enables the outer pipe to be made of a more ductile material.

This is probably more suitable to the present invention. The material need not in fact be metallic and could be a suitable plastics material.

A particularly preferred insulation material is alumina-silicate microspheres. These are compliant in that when compacted they provide sufficient mechanical support to the outer sleeve. They are particularly preferred for use in the present invention since, being particulate, they can flow to accommodate changes in shape of the outer sleeve.

Embodiments of the present invention will now be described by way of example, with reference to the accompanying figures, in which; Figure 1 is a cross section through a known double walled pipeline, shown in use in shallow waters; Figure 2 is a cross section through a double walled pipeline of Figure 1, in deep waters; Figure 3 is a cross section through a double walled pipeline according to the present invention, in use at moderately deep waters, according to a first embodiment of the present invention; Figure 4 is a cross section through a double walled pipeline of Figure 3, in use in very deep waters; and Figure 5 is a cross section through a double wailed pipeline according to a second embodiment of the invention.

Figures 1 and 2 have been described already. No further description will be given here.

Figure 3 shows a double walled pipeline comprising an inner pipe 10 and an outer pipe 12, carrying oil or gas 14 within the inner pipe 10. A compliant insulating material 20, in this case alumina-silicate microspheres is compressed into the annulus between the inner and outer pipes 10, 12.

As with Figures 1 and 2, the pipe system is shown resting on the sea bed 18.

Due to the hydrostatic pressure exerted on the pipe system in deep water, particularly above 1000 metres or 1 500 metres, the outer sleeve 1 2 has begun to collapse. The overall pipe system has reduced in volume, principally by an increase in compaction of the insulating material 20. To accommodate this, a fin 22 has formed on the outside of the sleeve pipe 12 as a means of reducing the enclosed volume at constant circumference. The fin is in practice centred on a local discontinuity in the sleeve pipe 12, and takes the form of a three part hinge centred on fold lines 24a, 24b and 24c.

However, it can be seen that despite the narrowing of the overall diameter of the pipeline, there is no single point around the central flow line 10 which is not surrounded by insulating material. This can be contrasted with Figure 2, and shows that according to the present invention the use of a compliant insulation material in deep waters ensures continued insulation performance.

Figure 4 shows the flow line of Figure 3 in still deeper water. It can be seen that further fins have formed at 26 and 28. It is believed that further fins will propagate in preference to a continued extension of the original fin as the insulation material 20a within the original fin 22 will eventually become so compressed as to resist any further growth of fin 22.

Further fins 26, 28 will therefore propagate at alternative discontinuities in the sleeve pipe 1 2. It will be noted that the original fin 22 is shown significantly narrower in Figure 4 as compared to Figure 3.

It will also be noted from Figure 4 that a significant depth of insulation 20 remains present around the entire circumference of the inner flow line 1 0.

Figure 5 shows a second embodiment of the present invention, prior to laying. It corresponds generally to the first embodiment, but with the addition of deliberate discontinuities to the outer sleeve pipe 1 2. These take the form of grooves 26a and 26b on the outer surface, separated by a small angle of about 250. The angle should in general be between 200 and 350.

A further groove 28 is formed on the inner surface of the sleeve pipe 12, roughly midway between the two outer grooves. Thus, this combination of grooves eases the development of a fin as shown in figure 3 and should result in a more predictable behaviour.

The sleeve pipe could of course be prepared with a plurality of such discontinuities spaced about its circumference. It is expected that three or four should be sufficient, but more could be provided if called for. The plurality need not be identical, and may for instance be of different depth so as to collapse at different depths.

The discontinuities need not be grooves and could be replaced with any of the discontinuities referred to above.

The present invention therefore enables a flow line to be provided at significantly greater depth, without suffering from excessive weight. It will of course be appreciated by those skilled in the art that many variations could be made to the above embodiment, without departing from the scope of the present invention.

Claims (11)

1. An insulated pipe work system comprising an outer sleeve, an inner flow pipe and insulating material in the space therebetween, wherein the insulating material provides mechanical support to the outer sleeve when the latter is under compression, the system being installed under water at a depth of 300 metres or greater.
2. An insulated pipework system according to claim 1 wherein the system is installed at a depth of at least 500 metres.
3. An insulated pipework system according to claim 1 wherein the system is installed at a depth of at least 1000 metres.
4. An insulated pipework system according to claim 1 wherein the system is installed at a depth of at least 1 500 metres.
5. An insulated pipe work system comprising an outer sleeve, an inner flow pipe and insulating material in the space therebetween, wherein the insulating material provides mechanical support to the outer sleeve when the latter is under compression, the outer sleeve pipe being non circular at least due to at least one fin projecting therefrom and formed of a fold in the outer sleeve pipe material.
6. An insulated pipe work system comprising an outer sleeve, an inner flow pipe and insulating materials spaced therebetween, wherein the outer sleeve pipe is circumferentially non-uniform.
7. An insulated pipework system according to claim 6 wherein the non uniformities comprise at least one localised discontinuity in the outer sleeve pipe.
8. An insulated pipework system according to claim 7 wherein the at least one discontinuity is one or more of folds, ridges, channels, series of associated channels, and variations in the strength of the material.
9. An insulated pipework system according to claim 8 wherein the series of associated channels comprise at least a pair channels on the outer face of the pipe.
10. An insulated pipework system according to claim 8 wherein the series of associated channels comprise at least a pair channels on the outer face of,the pipe, associated with a single channel on the inner face located between the outer pair.
11. An insulated pipework system according to any preceding claim wherein the outer pipe is of a more ductile material as compared with the inner pipe.
1 2. An insulated pipework system according to any preceding claim wherein the insulation material is alumina-silicate microspheres.
1 3. An insulated pipework system substantially as herein described with reference to and/or as illustrated in the accompanying drawings.
GB9713168A 1997-06-23 1997-06-23 Double walled pipe structure Withdrawn GB2326687A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9713168A GB2326687A (en) 1997-06-23 1997-06-23 Double walled pipe structure

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9713168A GB2326687A (en) 1997-06-23 1997-06-23 Double walled pipe structure

Publications (2)

Publication Number Publication Date
GB9713168D0 GB9713168D0 (en) 1997-08-27
GB2326687A true GB2326687A (en) 1998-12-30

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Family Applications (1)

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GB9713168A Withdrawn GB2326687A (en) 1997-06-23 1997-06-23 Double walled pipe structure

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002025160A1 (en) * 2000-09-25 2002-03-28 Aker Riser Systems As Arrangement for pipelines
US6397895B1 (en) 1999-07-02 2002-06-04 F. Glenn Lively Insulated pipe
US7011115B1 (en) 1999-05-27 2006-03-14 Saipem, S.P.A. Insulated pipe structure and methods of making such structures

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB292514A (en) * 1927-06-20 1929-08-22 Bbc Brown Boveri & Cie Improvements in and relating to pipes containers and the like, particularly for turbines
GB985241A (en) * 1961-10-14 1965-03-03 Hackethal Draht & Kabelwerk Ag Improved insulated piping
US3809149A (en) * 1972-10-04 1974-05-07 D Deutsch Method of supporting a hot oil pipeline through permafrost
GB1442894A (en) * 1973-02-06 1976-07-14 Commissariat Energie Atomique Insulating and sealing arrangement for ducts
GB2028965A (en) * 1978-08-24 1980-03-12 Kabel Metallwerke Ghh Thermally insulated pipe
EP0148717A2 (en) * 1984-01-06 1985-07-17 Jean-Marie Razny Thermally insulated modular element for a fluid line
GB2172547A (en) * 1985-03-19 1986-09-24 Mitsubishi Metal Corp Heat insulating material and heat-insulated conduit
WO1986006148A1 (en) * 1985-04-16 1986-10-23 Alvar Wedin Divisible watertight protective covering for insulation on pipes and similar
GB2200186A (en) * 1986-12-19 1988-07-27 Yamato Kogyo Kk Pipe insulation covers
US4824705A (en) * 1985-09-04 1989-04-25 Skega Ab Insulated pipe
GB2269876A (en) * 1992-08-12 1994-02-23 Terence Jeffrey Corbishley Hydrotherm-thermal insulation for submarine pipelines and equipment
WO1994004865A1 (en) * 1992-08-12 1994-03-03 Terrence Jeffrey Corbishley Improvements in marine and submarine apparatus
GB2271410A (en) * 1992-10-06 1994-04-13 Terence Jeffrey Corbishley Thermal insulation buoyancy and installation of submarine pipelines and equipment
WO1996007846A2 (en) * 1994-08-29 1996-03-14 Sumner Glen R An offshore pipeline with waterproof thermal insulation

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB292514A (en) * 1927-06-20 1929-08-22 Bbc Brown Boveri & Cie Improvements in and relating to pipes containers and the like, particularly for turbines
GB985241A (en) * 1961-10-14 1965-03-03 Hackethal Draht & Kabelwerk Ag Improved insulated piping
US3809149A (en) * 1972-10-04 1974-05-07 D Deutsch Method of supporting a hot oil pipeline through permafrost
GB1442894A (en) * 1973-02-06 1976-07-14 Commissariat Energie Atomique Insulating and sealing arrangement for ducts
GB2028965A (en) * 1978-08-24 1980-03-12 Kabel Metallwerke Ghh Thermally insulated pipe
EP0148717A2 (en) * 1984-01-06 1985-07-17 Jean-Marie Razny Thermally insulated modular element for a fluid line
GB2172547A (en) * 1985-03-19 1986-09-24 Mitsubishi Metal Corp Heat insulating material and heat-insulated conduit
WO1986006148A1 (en) * 1985-04-16 1986-10-23 Alvar Wedin Divisible watertight protective covering for insulation on pipes and similar
US4824705A (en) * 1985-09-04 1989-04-25 Skega Ab Insulated pipe
GB2200186A (en) * 1986-12-19 1988-07-27 Yamato Kogyo Kk Pipe insulation covers
GB2269876A (en) * 1992-08-12 1994-02-23 Terence Jeffrey Corbishley Hydrotherm-thermal insulation for submarine pipelines and equipment
WO1994004865A1 (en) * 1992-08-12 1994-03-03 Terrence Jeffrey Corbishley Improvements in marine and submarine apparatus
GB2271410A (en) * 1992-10-06 1994-04-13 Terence Jeffrey Corbishley Thermal insulation buoyancy and installation of submarine pipelines and equipment
WO1996007846A2 (en) * 1994-08-29 1996-03-14 Sumner Glen R An offshore pipeline with waterproof thermal insulation

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7011115B1 (en) 1999-05-27 2006-03-14 Saipem, S.P.A. Insulated pipe structure and methods of making such structures
US6397895B1 (en) 1999-07-02 2002-06-04 F. Glenn Lively Insulated pipe
WO2002025160A1 (en) * 2000-09-25 2002-03-28 Aker Riser Systems As Arrangement for pipelines

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Publication number Publication date
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