Flexible pipe including a vent passage and method of manufacturing same

[0002] This application is a continuation-in-part of patent application Ser. No. 09/705,309 filed Nov. 3, 2000 now Pat. No. 6,446,672 which, in turn, claims priority of provisional application Ser. No. 60/163,908 filed Nov. 5, 1999.

[0003] This invention relates to a flexible pipe having multiple layers, one of which is formed with a vent passage for venting gases that permeate through the pipe.

[0004] FIG. 1 is a longitudinal sectional view of a flexible pipe according to an embodiment of the present invention.

[0005] FIG. 2 is an end view of the pipe of FIG. 1.

[0006] FIG. 3 is a view similar to FIG. 2 but depicting an alternate embodiment of the invention.

[0007] With reference to FIG. 1, a flexible pipe according to an embodiment of the present invention is shown, in general by the reference numeral 10. The pipe 10 is formed by an inner layer 12, preferably in the form of an extruded plastic sheath, for conveying fluid through its bore. As shown in FIG. 2, the outer surface of the layer 12 is undulated thus forming a series of ridges and valleys for reasons to be described. The layer 12 may be formed in a conventional manner using polymers, or the like.

[0008] A layer 14 extends around the layer 12 and provides resistance to internal pressure, hydrostatic collapse and crush. The layer 14 is formed by helically wrapping a continuous metal strip, preferably formed of carbon steel, with adjacent windings being interlocked, to form a flexible layer that provides significant hoop and axial strength. The layer 14 is marketed by the assignee of the present invention, Wellstream, Inc., under the “Flexlok” trademark. Alternatively, the layer 14 can be of the types disclosed in application Ser. No. 09/706,070 filed concurrently herewith and assigned to the assignee of this application; with the disclosure of the former application being incorporated by reference.

[0009] A seal layer 15, preferably in the form of an extruded plastic sheath, is provided over the layer 14 to increase the resistance to hydrostatic compression, and assist in limiting the moisture that permeates from the bores of the layer 12.

[0010] A layer 16 of wrapped wires extends over the layer 15 and consists of a series of wires 16ahelically wrapped around the exterior of the layer 15 to form a first tensile layer, and an additional series of wires 16bwrapped around the first series of wires 16ato form a second tensile layer extending over the first tensile layer. The wires 16aand 16bmay have a circular cross section, and are wound at a relatively high lay angle to provide significant hoop strength and axial strength. Preferably, at least a portion of the wires 16aand 16bare formed by carbon steel with a plastic or anodic coating. It is noted that the layer 14 prevents the expansion of the layer 12 into gaps formed between the wires of the tensile layers 16aand 16b.

[0011] A layer 18 is formed by helically wrapping tape over the layer 16. The tape forming the layer 18 can be plastic or metal and can be reinforced with glass, metal or a different type of plastic. Although not shown in the drawings, it is understood that the tape layer 18 can also extend between the layer 14 and the layer 16, and between the series of wires 16aand 16b.

[0012] A protective outer layer 20 extends over the tape layer 18 and is preferably in the form of an extruded plastic sheath that extends over the tape layer in a conventional manner, with the tape providing a smooth surface for the extrusion. The layer 20 is optional and is required only when the tape layer is inadequate to protect the remaining components of the pipe 10.

[0013] In operation, when the pipe 10 is put into service the ridges formed by the undulating outer surface of the layer 12, and the corresponding inner surface of the layer 14, form passages 22 for venting any gases that might permeate through the layer 12. These passages extend for the length of the pipe 10 and can discharge into the ambient environment or atmosphere at one of the ends of the pipe.

[0014] According to the embodiment of FIG. 3, a flexible pipe according to an embodiment of the present invention is shown, in general by the reference numeral 30. The pipe 30 is formed by an inner layer 32, preferably in the form of an extruded plastic tubular member, or sheath, for conveying fluid through its bore. The layer 32 may be formed in a conventional manner using polymers, or the like.

[0015] A metal strip layer 34 extends around the layer 32 and provides resistance to internal pressure, hydrostatic collapse and crush. Since the layer 34 is identical to the layer 14 of the embodiment of FIGS. 1 and 2, is will not be described in any further detail.

[0016] A seal layer 36, preferably in the form of an extruded plastic sheath, is provided over the layer 34 to increase the resistance to hydrostatic compression, and assist in limiting the moisture that permeates from the bores of the layer 32.

[0017] A layer 38 extends over the layer 36 and consists of a series of wrapped wires forming two tensile layers. Since the layer 38 is identical to the layer 16 of the embodiment of FIGS. 1 and 2, is will not be described in any further detail.

[0018] A layer 40 is formed by helically wrapping tape over the layer 38. The tape forming the layer 40 can be plastic or metal and can be reinforced with glass, metal or a different type of plastic. Although not shown in the drawing, it is understood that the tape layer 40 can also extend between the layers 32 and 34, between the layers 34 and 36, between the layers 36 and 38, between the layer 38 and 40, and/or between the layers of wrapped wires forming the layer 38.

[0019] A protective outer layer 42 extends over the tape layer 40 and is preferably in the form of an extruded plastic sheath that extends over the tape layer in a conventional manner, with the tape providing a smooth surface for the extrusion. The layer 42 is optional and is required only when the tape layer 40 is inadequate to protect the remaining components of the pipe 40.

[0020] According to the embodiment of FIG. 3, the undulations of the previous embodiment are eliminated and a plurality of relatively small-diameter tubes 44 are embedded in, and angularly spaced around, the layer 32. Although not shown in the drawings due to scale limitations, it is understood that the tubes 44 are provided with relatively small holes or slits, or are fabricated from a material having a relatively high porosity, such as a foam structure, to receive any gases that might permeate through the layer 32 or at least a portion of the layer. The tubes 44 extend for the length of the pipe and thus pass any of the latter gases to one or both ends of the pipe 30 for discharge into the ambient environment or atmosphere. Thus, the embodiment of FIG. 3 enjoys all of the advantages of that of FIGS. 1 and 2

[0021] 1. Additional tensile layers of wires can be provided in addition to the series of wires 16aand 16band the wires forming the layer 38.

[0022] 2. Each layers 16aand 16bcan be formed by one wire rather than by a series of wires, and only one layer (16aor 16b) can be provided.

[0023] 3. The adjacent windings of the strip forming the layers 14 and 34 do not have to be interlocked.

[0024] 4. In the embodiment of FIG. 3, the seal layer 36 can be placed between the seal layers 34 and 38 (as shown and described above), and/or between the layers 38 and 40, and/or between the layers 40 and 42.

[0025] 5. The cross section of the wires 16aand 16b, and the wires forming the layer 38 can be round or rectangular as disclosed in the above cited application.

[0026] 6. In extremely hostile environments, an outer layer similar to the layer 14 and 34 can be placed around the sheaths 20 and 42, respectively for added protection.

[0027] 7. The layers 14 and 34 can be eliminated and the layers 16 and 36 can be applied directly over the tubular members, 12 and 32, respectively.

[0028] 8. The layers 15 and 36 can be eliminated and the layers 16 and 38 can be applied directly over the layers 14, and 34, respectively.

[0029] It is understood that spatial references, such as “under”, “over”, “between”, “outer”, “inner” and “surrounding” are for the purpose of illustration only and do not limit the specific orientation or location of the layers described above.

[0030] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.