WO1997025561B1

WO1997025561B1 - Subsea flexible pipe

Info

Publication number: WO1997025561B1
Application number: PCT/IB1996/001475
Authority: WO
Filing date: 1996-12-31
Publication date: 1997-12-11

Abstract

A flexible pipe (11) for subsea installation has a fluid impervious tube (13) surrounded by a structure pipe (21). The structure pipe (21) is a cylindrical monolithic member. It has at least two rows of slots (23) extending along the length of the wall. The slots (23) are evenly spaced apart, parallel and located on a helix (31). Each of the slots are in a row, which is also located on a helix (25), but extending in a different direction from the slot helix (31). Solid bands (27) extend between the rows of slots (23). Arc members (33) are located between each of the slots, the arc members (33) joining the bands (27). The structure pipe (21) surrounds a fluid impervious tube (13) which is corrugated.

Claims

AMENDED CLAIMS

I received by the International Bureau on 29 October 1997 (29 10 97), original claims 1 -20 replaced by amended claims 1-19 (4 pages)] 1 A flexible pipe (1 1) having an axis (30), a cylindrical structure pipe (21 ) and sealing means to contain the transporting fluid inside the structure pipe (21), the improvement characterized by the structure pipe (21) having at least two rows of slots (23), each of the slots extending circumferentially less than 180 degrees, defining at least two bands (27) extending along the length of the structure pipe, the bands being free of slots to provide tensile strength

2 The flexible pipe (11) according to claim 1 wherein each of the rows of slots (23) has a centerline (25) which intersects the slots and extends helically along the structure pipe (21 )

3 The flexible pipe (11) according to claim 1 wherein the rows and the bands (27) extend along helical lines which incline at an angle which is the same, and the slots (23) of one of the rows have arc members (33) spaced between them which are substantially along helical lines (31) which incline in an opposite direction to and at a substantially larger angle than the rows of slots and the bands.

4 The flexible pipe (11) according to claim 1 wherein the structure pipe (21) has a transition zone (43) near at least one end of the structure pipe (21) in which the lengths of the slots (23) gradually decrease toward said end.

5 The flexible pipe (11) according to claim 1 wherein the sealing means is a fluid impervious tube (13)

6 The flexible pipe (11) according to claim 5 wherein the tube (13) comprises a cylindrical conduit having corrugated undulations (15) to enhance flexibility

7. The flexible pipe (11) according to claim 5 wherein the tube (13) comprises a cylindrical conduit having corrugated undulations (15) to enhance flexibility, the tube having an outer diameter which during assembling is less than an inner diameter of the structure pipe (21), and

9 which is plastically deformed into contact with the inner diameter of the structure tube with internal pressure.

8. The flexible pipe (11) according to claim 1 wherein the pipe (11) has an axis (30), the slots (23) are evenly spaced apart from each other to define arc members (33) between each of the slots, each of the slots having a length determined by two ends (23a, 23b) which are circumferentially apart from each other, the arc members being parallel to each other and oriented relative to the axis (30) on an arc member helix (31), each of the slots having a centerpoint (23c) equidistant between its ends, the centerpoints within the same row being located on a row helix (25) which is in the opposite direction to arc member helix (31) and substantially transverse to the lengths of the slots, the row helix of each of the rows being at a row helix angle which is the same as the other rows; and each of the bands (27) joins the arc members and has a centerline which is on a band helix (29) which is at a band helix angle that is the same as the row helix angle.

9. The flexible pipe (11) according to claim 8 wherein at least a central portion of the slots (23) within each of the rows has the same length as the slots within the other of the rows.

10. The flexible pipe (11) according to claim 8 wherein at least a central portion of the slots (23) within each of the rows has the same length as the slots within the other of the rows; and wherein the structure pipe (21) has a transition zone (43) joining the central portion near at least one end of the support pipe in which the lengths of the slots gradually decrease toward said end.

11. The flexible pipe (11) according to claim 8 wherein the arc member helix (31 ) is at a much larger helix angle than the row helix (25) angle and the band helix (29) angle and inclines in an opposite direction.

12. The flexible pipe (11) according to claim 8 wherein the sealing means is a fluid impervious tube (13) comprising a cylindrical conduit having corrugated undulations (15) to enhance flexibility.

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13. The flexible pipe (11) according to claim 8 wherein the tube (13) comprises a cylindrical conduit having corrugated undulations (15) to enhance flexibility, the tube having an outer diameter which during assembling of the flexible pipe is less than an inner diameter of the structure pipe (21), and which is plastically deformed into contact with the inner diameter of the structure pipe with internal fluid pressure.

14. The flexible pipe (11) according to claim 1, wherein the structure pipe (21) is of a monolithic single piece construction.

15. The flexible pipe (11) according to claim 1, wherein the slots (23) enhance elastic flexing beyond the elastic flexing of the same size and material solid pipe; and wherein the sealing means is a fluid impervious tube ( 3) having corrugated undulations (15) to enhance elastic flexibility beyond the elastic flexing of the non corrugated tube with the same wall thickness and material.

16. The flexible pipe (11) according to claim 15, wherein the structure pipe (21) is of a monolithic single piece construction and the fluid impervious tube (13) is inserted within the structure pipe (21).

17. The flexible pipe (11) according to claim 15 wherein the inner fluid impervious tube (13) has an outer diameter which during installation is less than an inner diameter of the structure pipe (21) by an amount sufficient to provide an annular clearance between the fluid impervious tube (13) and the structure pipe (21), and which is expanded into contact with the inner diameter of the structure pipe (21 ) with internal fluid pressure.

18. A method of manufacturing a flexible pipe (11), comprising: providing a metal monolithic construction fluid pervious structure pipe (21) made flexible by placing slots (23) in the structure pipe, which has an inner diameter; providing a metal fluid impervious tube (13) which has an outer diameter that is a selected amount less than the inner diameter of the structure pipe (21); then

11 inserting the metal fluid tube (13) into the structure pipe (21); then applying an internal fluid pressure to the inner fluid tube (13) at a sufficient level to permanently expand the outer diameter of the fluid tube (13) into zero clearance with the inner diameter of the structure pipe (21 ) .

19. The method according to claim 18, wherein the metal impervious tube (13) has corrugations (15).

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