Abstract:
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.

Description:
BACKGROUND 
     Flexible pipe can be used for fluid transport in various areas, such as conducting production fluids offshore. For example,  FIGS. 1A-1B  show a flexible pipe  10  similar to that designed by Deepflex, Inc. of Houston, Tex. and disclosed in U.S. Pat. Nos. 6,491,779 and 7,254,933. The pipe  10  can be used in deep sea operations such as disclosed in U.S. Pat. No. 7,073,978. In general, the pipe  10  can have internal diameters of 2, 4, 6, 8, or even up to 16-inches. From inside to outside, the flexible pipe  10  has a number of layers, including a liner layer  11 , pressure reinforcement layers  12 , hoop reinforcement layers  13 , a membrane  14 , tensile reinforcement layers  15 , and an external jacket  16 . 
     The liner layer  11  is composed of extruded thermoplastic, such as HDPE, PA-11, PVDF and XLPE, and the membrane  14  is made of extruded thermoplastic to seal against compressive loads from external seawater pressure. On the outside, the external jacket  16  is made of extruded thermoplastic to provide external protection to the pipe  10 . 
     Internally, wraps helically wound about the pipe  10  form each of the reinforcement layers  12 ,  13 , and  15 . These wraps are made of composite material bonded and stacked together to form composite tapes. As their names imply, the pressure layers  13  are wound for external pressure loads, and the tensile layers  15  are wound for tensile loads. Likewise, the hoop layers  13  are 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&#39;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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a perspective view of a flexible pipe according to the prior art showing the various layers. 
         FIG. 1B  illustrates a cross-sectional view of the flexible pipe of  FIG. 1A . 
         FIG. 2A  illustrates an end view of a flexible pipe according to the present disclosure. 
         FIG. 2B  illustrates a cross-sectional view of the flexible pipe of  FIG. 2A  showing the various layers. 
         FIG. 2C  illustrates an isolated portion of the flexible pipe&#39;s cross-section showing details of the various layers. 
         FIGS. 3A ,  3 B, and  3 C illustrate an end view, a cross-sectional view, and a detailed view of a central ring for the flexible pipe&#39;s ringed layer. 
         FIGS. 4A ,  4 B, and  4 C illustrate an end view, a cross-sectional view, and a detailed view of an end ring for the flexible pipe&#39;s ringed layer. 
         FIG. 5  shows the wall of the flexible pipe as bent. 
         FIG. 6  shows example thicknesses of the flexible pipe&#39;s layers. 
         FIG. 7  shows an end of the flexible pipe connected to an end connector. 
     
    
    
     DETAILED DESCRIPTION 
     A flexible pipe  20  shown in  FIGS. 2A-2C  has a plurality of layers, including from inside to out: a liner layer  30 , a first tensile layer  40 , a ringed layer  50 , a second tensile layer  80 , and an external jacket  90 . The liner layer  30  is 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 pipe  20 . In one example, the liner layer  30  is composed of extruded nylon and Fortron® polyphenylene sulfide (PPS) (a high performance thermoplastic). 
     The ringed layer  50  is composed of a plurality of interlocking rings  60 / 70  discussed in more detail later. The external jacket  90  is composed of a hard plastic material for protection. For example, the jacket  90  can 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 layers  40  and  80  provide tensile strength to the flexible pipe  20  as well as strength against internal/external pressure loads. Both tensile layers  40  and  80  are preferably strong enough to carry longitudinal (tensile) stresses up to 25-kpsi along the axis of the pipe  20 . In the present arrangement and as best shown in  FIG. 2C , each of the tensile layers  40 / 80  can be composed of several layers, including an extruded tube  42 / 82 , a reinforcement layer  44 / 84 , and a surrounding hard shell  46 / 86 . Although two tensile layers  40 / 80  are shown in the present arrangement, other arrangements may have only one tensile layer either inside or outside the ringed layer  50 . In addition, although the tensile layers  40 / 80  are shown having three layers, other arrangements may have more or less layers. 
     In the current arrangement, the extruded tubes  42 / 82  can be composed of a hard plastic material, such as a similar thermoplastic to the liner layer  30 . The reinforcement layers  44 / 84  have fiber or wire woven or wrapped on the extruded tubes  42 / 82  to provide tensile strength to the pipe  20 . These layers  44 / 84  can 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 shells  46 / 86  can be a hard plastic material extruded around the reinforcement layer  44 / 84 . 
     As best shown in  FIG. 2C , the ringed layer  50  is comprised of a series of interconnecting rings, including central rings  60  and an end ring  70  as shown. Each of the central rings  60  interlock end to end to one another in an interlocking arrangement that still allows for bending or tilting between the rings  60  when the pipe  20  is flexed or bent. The end ring  70  interlocks at one end to a central ring  60  and has a terminated end that does not interlock with another ring. 
     The rings  60 / 70  can be composed of metal or composite material. For example, each of the rings  60 / 70  can 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 rings  60 / 70  can 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 pipe  20 . Due to the reinforced strength of these rings  60 / 70 , the flexible pipe  20  can 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 pipe  20  to be used in various applications, such as deep sea oil production. 
     Assembly of the pipe  20  is as follows. The liner layer  30 &#39;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 layer  40  is independently formed as a unit having its three layers  42 / 44 / 46  and having a suitable internal bore diameter and wall thickness and is fit over the liner layer  30 . In another arrangement, the extruded tube  42  of the first tensile layer  40  is independently formed and fit onto the liner layer  30  or is extruded directly onto the liner layer  30 , then the woven layer  44  is formed onto the outside of this extruded tube  42 , and finally the outer shell  46  is extruded over the entire assembly. 
     With the first tensile layer  40  completed, the various rings  60 / 70  are positioned over the first tensile layer  40  in interlocking arrangement. Naturally, the first tensile layer  40 &#39;s outer diameter and the ring  60 / 70 &#39;s internal diameters are configured to fit together. The rings  60 / 70  may be wrapped with tape or the like to hold them together during assembly. Next, the second tensile layer  80  having its three layers  82 / 84 / 86  and having a suitable internal bore diameter and wall thickness is positioned or formed over the rings  60 / 70 . As before, the second tensile layer  80  can be independently formed as a unit and fit over the rings  60 / 70 , or the separate layers  82 / 84 / 86  can be separately positioned or formed on the assembly. Finally, the external jacket  90  is extruded on the outside of the entire assembly to complete the pipe  20 . 
     As discussed above, the ringed layer  50  has several interconnecting central rings  60 —an example of which is shown in more detail in  FIGS. 3A-3C . The central ring  60  has an external diameter D 1 , an internal diameter D 2 , and a length L 1 . For a flexible pipe  20  with an internal bore of about 6-inches, the ring  60 &#39;s external diameter D 1  can be about 8.885-inches, the internal diameter D 2  can be about 8.135-inches, and the length L 1  can be about 4.000-inches. Because these and other values disclosed herein pertain to a flexible pipe  20  with about a 6-inch internal diameter, it is understood that the various values for the pipe&#39;s components will differ for different diameter pipes and for particular implementations. 
     One end of the ring  60  has a circumferential lip  62 , while the other end has a circumferential slot  64 . When rings  60  couple end to end, the circumferential lip  62  interconnects with a circumferential slot  64  on an adjacent central ring  60 . In the exemplary dimensions, the lip  62  defines an overall diameter D 3  of about 8.595-inches, and the slot  64  defines an overall inner diameter D 4  of about 8.575-inches. 
     Because the rings  60  fit together and are intended to tilt relative to one another, the circumferential lip  62  defines an outer profile  63  as shown in  FIG. 3C  for fitting and moving against a complementary inner profile  65  of the circumferential slot  64 . The outer profile  63  extends a length L 2  of about 0.630-inches, while the inner profile  65  extends a length L 3  of about 0.625-inches. In addition, the lip  62  defines an angular slant θ 1  outward of about 2.65-degrees, while the slot  64  defines an angular θ 2  slant inward of about 1.94-degrees. Furthermore, the lip  62 &#39;s outer edge defines a radius R 1  of 0.096-inches, and its inner edge defines a radius R 2  of about 0.096-inches. Likewise, the slots  64 &#39;s inner edge defines radius R 3  of 0.091-inches, and its outer edge defines radius R 4  of 0.096-inches. 
     As shown in  FIGS. 4A-4C , the end ring  70  is very similar to the central ring  60  discussed above. For example, the end ring&#39;s circumferential slot  74  is essentially identical to the central ring  60 &#39;s slot  64  of  FIGS. 3A-3C  having dimensions L 2 , R 3 , R 4 , and θ 2  so it can interconnect with a central ring&#39;s circumferential lip  62 . The ring&#39;s other end  72 , 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 slot  64  of a central ring  60  of  FIGS. 3A-3C  and can have a terminated end and a lipped end with dimensions L 1 , R 2 , R 3 , and θ 1 . 
     The rings  60 / 70  with the associated dimensions discussed above enable the interconnected rings  60 / 70  to 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 pipe  20 ). For example,  FIG. 5  shows a wall of the flexible pipe  20  as bent with each of the central rings  60  tilted at about 1.5-degrees relative to one another. Preferably, gaps G that may occur between the rings  60  where they interconnect are minimal, and sharp edges on the rings  60  are avoided. The other layers  30 / 40 / 80 / 90  being composed of materials such as plastic, fiberglass, composites, etc., readily flex with the bending of the pipe  20 . 
     Various dimensions for the pipe&#39;s layers  30 / 40 / 50 / 80 / 90  have been provided above for illustrative purposes. As shown in  FIG. 6  and in the table below, the layers  30 / 40 / 50 / 80 / 90  in general have wall thicknesses that make up the following example percentages of a flexible pipe&#39;s overall wall thickness in which the pipe has about a 6-inch internal bore: 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 
               
             
             
               
                   
               
               
                 Each Layer&#39;s Percentage of Overall Pipe Wall Thickness 
               
             
          
           
               
                   
                 Wall Thickness 
                 Percentage of Overall 
               
               
                 Layer 
                 (inches) 
                 Pipe Wall Thickness 
               
               
                   
               
               
                 30 - Inner Layer 
                 T 1  = 1.3 
                 31% 
               
               
                 40 - First Tensile layer 
                 T 2  = 0.95 
                 22% 
               
               
                 50 - Ring Layer 
                 T 3  = 0.75 
                 18% 
               
               
                 80 - Second Tensile layer 
                 T 4  = 0.75 
                 18% 
               
               
                 90 - External Jacket 
                 T 5  = 0.46 
                 11% 
               
               
                 All Layers 
                 T 0  = 4.0 
                 100%  
               
               
                   
               
             
          
         
       
     
     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 pipe  20  can 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. 7  shows an end of the flexible pipe  20  connected to one such end connector  200  of the incorporated application. As shown, the end connector  200  has an outer housing  202  and inner components  204 , both of which are essentially the same as those disclosed in the incorporated application. As part of the inner components  204 , locks comprising nuts and sleeves ( 270 / 275  and  290 / 295 ) mechanically grip the pipe  20 &#39;s tensile layers  40 / 80  against an insert  280 . In addition, the insert  280 &#39;s end fits against the terminated end  72  of the end ring  70 . 
     The flexible pipe  20 &#39;s other layers  30 / 90  are handled in similar ways to like layers described in the incorporated application. For example, a tubular insert  250  fits within the inner surface of the liner layer  30 , which also has an inner nut  290  positioned against part of its outer surface. Elsewhere along the pipe  20 , another lock  260  threads into a portion of the connector  200 &#39;s outer housing  202  and grips against the pipe&#39;s external jacket  90 . 
     As disclosed above, the pipe  20  of  FIGS. 2A-2C  has five layers  30 / 40 / 50 / 80 / 90 . However, variations of the disclosed flexible pipe  20  are possible. For example, the flexible pipe  20  can be composed of more or less layers depending on the implementation. In one variation, the flexible pipe  20  may include tensile layer  40 , ringed layer  50 , and tensile layer  80  with either one or both of the liner layer  30  and external jacket  90  not included. In another variation, one of the tensile layers  40  or  80  may not be included in the pipe  20 . Alternatively, one of the tensile layers  40  or  80  may not have multiple layers and may simply include an extruded tube of plastic material. In other words, the flexible pipe  20  can at least include at least one first layer, a ringed layer  50  having interconnected rings (e.g.,  60 / 70 ) disposed about the at least one first layer to provide strength to the pipe  20  against pressure loads, and at least one second layer disposed about the ringed layer  50 , wherein at least one of the first or second layers provides tensile strength to the flexible pipe  20 . 
     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.