Flexible pipe

A flexible pipe for fluid transport especially in offshore application has a first extruded tube having nylon and a first layer having aromatic polyamide disposed about the first tube. A plurality of rings composed of stainless steel are disposed about the first layer. Each of the rings has first ends with circumferential lips and second ends with circumferential grooves interconnecting together. These lips and grooves permit adjacent ones of the rings to tilt relative to one another by about 1.5-degrees for every 4-inches of flexible pipe. A second extruded tube having fiberglass is disposed about the plurality of rings, and an exterior jacket having nylon is disposed about the second tube.

BACKGROUND

Flexible pipe can be used for fluid transport in various areas, such as conducting production fluids offshore. For example,FIGS. 1A-1Bshow a flexible pipe10similar to that designed by Deepflex, Inc. of Houston, Tex. and disclosed in U.S. Pat. Nos. 6,491,779 and 7,254,933. The pipe10can be used in deep sea operations such as disclosed in U.S. Pat. No. 7,073,978. In general, the pipe10can have internal diameters of 2, 4, 6, 8, or even up to 16-inches. From inside to outside, the flexible pipe10has a number of layers, including a liner layer11, pressure reinforcement layers12, hoop reinforcement layers13, a membrane14, tensile reinforcement layers15, and an external jacket16.

The liner layer11is composed of extruded thermoplastic, such as HDPE, PA-11, PVDF and XLPE, and the membrane14is made of extruded thermoplastic to seal against compressive loads from external seawater pressure. On the outside, the external jacket16is made of extruded thermoplastic to provide external protection to the pipe10.

Internally, wraps helically wound about the pipe10form each of the reinforcement layers12,13, and15. These wraps are made of composite material bonded and stacked together to form composite tapes. As their names imply, the pressure layers13are wound for external pressure loads, and the tensile layers15are wound for tensile loads. Likewise, the hoop layers13are wound for compressive loads.

Because flexible pipes can be used in conditions having high internal and/or external pressures, any rupture in one of the layers such as the pipe's inner layer can allow pressurized fluid to leak through to other surrounding layers. If those surrounding layers have gaps in them such as formed by wrapped tapes, then nothing essentially keeps the pressurized leak from reaching even more layers of the pipe.

DETAILED DESCRIPTION

A flexible pipe20shown inFIGS. 2A-2Chas a plurality of layers, including from inside to out: a liner layer30, a first tensile layer40, a ringed layer50, a second tensile layer80, and an external jacket90. The liner layer30is an extruded tube made of a plastic material, such as a composite thermoplastic or the like. Choice of the particular material depends on the intended use of the pipe20. In one example, the liner layer30is composed of extruded nylon and Fortron® polyphenylene sulfide (PPS) (a high performance thermoplastic).

The ringed layer50is composed of a plurality of interlocking rings60/70discussed in more detail later. The external jacket90is composed of a hard plastic material for protection. For example, the jacket90can be composed of a nylon material, such as Ultramid® polyamide (nylon) from BASF Corporation for resistance to abrasion, corrosion, and high temperature (ULTRAMID is a registered trademark of BASF Aktiengesellschaft Corporation of Germany), although other materials can be used.

As their names imply, the tensile layers40and80provide tensile strength to the flexible pipe20as well as strength against internal/external pressure loads. Both tensile layers40and80are preferably strong enough to carry longitudinal (tensile) stresses up to 25-kpsi along the axis of the pipe20. In the present arrangement and as best shown inFIG. 2C, each of the tensile layers40/80can be composed of several layers, including an extruded tube42/82, a reinforcement layer44/84, and a surrounding hard shell46/86. Although two tensile layers40/80are shown in the present arrangement, other arrangements may have only one tensile layer either inside or outside the ringed layer50. In addition, although the tensile layers40/80are shown having three layers, other arrangements may have more or less layers.

In the current arrangement, the extruded tubes42/82can be composed of a hard plastic material, such as a similar thermoplastic to the liner layer30. The reinforcement layers44/84have fiber or wire woven or wrapped on the extruded tubes42/82to provide tensile strength to the pipe20. These layers44/84can be composed of a heat-resistant and strong synthetic fiber, such as an aromatic polyamide (“aramid”) (one type of which is Kevlar®), or can be composed of metal wire. (KEVLAR is a registered trademark of E. I. du Pont de Nemours and Company. The surrounding shells46/86can be a hard plastic material extruded around the reinforcement layer44/84.

As best shown inFIG. 2C, the ringed layer50is comprised of a series of interconnecting rings, including central rings60and an end ring70as shown. Each of the central rings60interlock end to end to one another in an interlocking arrangement that still allows for bending or tilting between the rings60when the pipe20is flexed or bent. The end ring70interlocks at one end to a central ring60and has a terminated end that does not interlock with another ring.

The rings60/70can be composed of metal or composite material. For example, each of the rings60/70can be cast of 17-4 stainless steel with electroless nickel/fluoropolymer coating (e.g., Xylan®—a registered trademark of Whitford Corporation of West Chester, Pa.) for rust prevention. Alternatively, the rings60/70can be composed of a composite material, such as carbon-fiber or glass reinforced plastic, fiber thermoplastic, or thermoplastic formulated with metal powder, although other materials are also possible depending on the desired use of the flexible pipe20. Due to the reinforced strength of these rings60/70, the flexible pipe20can preferably withstand inside and outside pressures better than a flexible pipe composed entirely of extruded or wrapped layers, yet still provide the flexibility needed for the pipe20to be used in various applications, such as deep sea oil production.

Assembly of the pipe20is as follows. The liner layer30's extruded plastic tube is formed with the desired internal bore diameter and wall thickness for the particular implementation. In one arrangement, the first tensile layer40is independently formed as a unit having its three layers42/44/46and having a suitable internal bore diameter and wall thickness and is fit over the liner layer30. In another arrangement, the extruded tube42of the first tensile layer40is independently formed and fit onto the liner layer30or is extruded directly onto the liner layer30, then the woven layer44is formed onto the outside of this extruded tube42, and finally the outer shell46is extruded over the entire assembly.

With the first tensile layer40completed, the various rings60/70are positioned over the first tensile layer40in interlocking arrangement. Naturally, the first tensile layer40's outer diameter and the ring60/70's internal diameters are configured to fit together. The rings60/70may be wrapped with tape or the like to hold them together during assembly. Next, the second tensile layer80having its three layers82/84/86and having a suitable internal bore diameter and wall thickness is positioned or formed over the rings60/70. As before, the second tensile layer80can be independently formed as a unit and fit over the rings60/70, or the separate layers82/84/86can be separately positioned or formed on the assembly. Finally, the external jacket90is extruded on the outside of the entire assembly to complete the pipe20.

As discussed above, the ringed layer50has several interconnecting central rings60—an example of which is shown in more detail inFIGS. 3A-3C. The central ring60has an external diameter D1, an internal diameter D2, and a length L1. For a flexible pipe20with an internal bore of about 6-inches, the ring60's external diameter D1can be about 8.885-inches, the internal diameter D2can be about 8.135-inches, and the length L1can be about 4.000-inches. Because these and other values disclosed herein pertain to a flexible pipe20with about a 6-inch internal diameter, it is understood that the various values for the pipe's components will differ for different diameter pipes and for particular implementations.

One end of the ring60has a circumferential lip62, while the other end has a circumferential slot64. When rings60couple end to end, the circumferential lip62interconnects with a circumferential slot64on an adjacent central ring60. In the exemplary dimensions, the lip62defines an overall diameter D3of about 8.595-inches, and the slot64defines an overall inner diameter D4of about 8.575-inches.

Because the rings60fit together and are intended to tilt relative to one another, the circumferential lip62defines an outer profile63as shown inFIG. 3Cfor fitting and moving against a complementary inner profile65of the circumferential slot64. The outer profile63extends a length L2of about 0.630-inches, while the inner profile65extends a length L3of about 0.625-inches. In addition, the lip62defines an angular slant θ1outward of about 2.65-degrees, while the slot64defines an angular θ2slant inward of about 1.94-degrees. Furthermore, the lip62's outer edge defines a radius R1of 0.096-inches, and its inner edge defines a radius R2of about 0.096-inches. Likewise, the slots64's inner edge defines radius R3of 0.091-inches, and its outer edge defines radius R4of 0.096-inches.

As shown inFIGS. 4A-4C, the end ring70is very similar to the central ring60discussed above. For example, the end ring's circumferential slot74is essentially identical to the central ring60's slot64ofFIGS. 3A-3Chaving dimensions L2, R3, R4, and θ2so it can interconnect with a central ring's circumferential lip62. The ring's other end72, however, is terminated and has no slot or lip. Although not shown, an opposite end ring for the flexible pipe can similarly be made for fitting on an opposing slot64of a central ring60ofFIGS. 3A-3Cand can have a terminated end and a lipped end with dimensions L1, R2, R3, and θ1.

The rings60/70with the associated dimensions discussed above enable the interconnected rings60/70to be bent or tilted relative to one another by about 1.5 degrees for every 4-inches (i.e., about 1.5-degrees for every length of ring in the flexible pipe20). For example,FIG. 5shows a wall of the flexible pipe20as bent with each of the central rings60tilted at about 1.5-degrees relative to one another. Preferably, gaps G that may occur between the rings60where they interconnect are minimal, and sharp edges on the rings60are avoided. The other layers30/40/80/90being composed of materials such as plastic, fiberglass, composites, etc., readily flex with the bending of the pipe20.

Various dimensions for the pipe's layers30/40/50/80/90have been provided above for illustrative purposes. As shown inFIG. 6and in the table below, the layers30/40/50/80/90in general have wall thicknesses that make up the following example percentages of a flexible pipe's overall wall thickness in which the pipe has about a 6-inch internal bore:

The above dimensions are provided merely for illustrative purposes. It will be appreciated that the various thickness of the layers will depend on the needs of a particular implementation, including, for example, pressure levels, tensile strength, length of the pipe, intended use of the pipe, materials selected, etc.

The flexible pipe20can be used with end connectors such as disclosed in co-pending U.S. application Ser. No. 11/961,709 entitled “End Connector for Flexible Pipe,” which is incorporated herein by reference in its entirety.FIG. 7shows an end of the flexible pipe20connected to one such end connector200of the incorporated application. As shown, the end connector200has an outer housing202and inner components204, both of which are essentially the same as those disclosed in the incorporated application. As part of the inner components204, locks comprising nuts and sleeves (270/275and290/295) mechanically grip the pipe20's tensile layers40/80against an insert280. In addition, the insert280's end fits against the terminated end72of the end ring70.

The flexible pipe20's other layers30/90are handled in similar ways to like layers described in the incorporated application. For example, a tubular insert250fits within the inner surface of the liner layer30, which also has an inner nut290positioned against part of its outer surface. Elsewhere along the pipe20, another lock260threads into a portion of the connector200's outer housing202and grips against the pipe's external jacket90.

As disclosed above, the pipe20ofFIGS. 2A-2Chas five layers30/40/50/80/90. However, variations of the disclosed flexible pipe20are possible. For example, the flexible pipe20can be composed of more or less layers depending on the implementation. In one variation, the flexible pipe20may include tensile layer40, ringed layer50, and tensile layer80with either one or both of the liner layer30and external jacket90not included. In another variation, one of the tensile layers40or80may not be included in the pipe20. Alternatively, one of the tensile layers40or80may not have multiple layers and may simply include an extruded tube of plastic material. In other words, the flexible pipe20can at least include at least one first layer, a ringed layer50having interconnected rings (e.g.,60/70) disposed about the at least one first layer to provide strength to the pipe20against pressure loads, and at least one second layer disposed about the ringed layer50, wherein at least one of the first or second layers provides tensile strength to the flexible pipe20.

The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.