Patent Abstract:
In one aspect, the present disclosure relates to a tubular assembly with gap control. Embodiments disclosed herein relate to one or more embodiments of and methods for controlling gaps between helically wrapped layers in a pipe structure. A tubular assembly includes a fluid barrier, a first layer, and a second layer comprising a plurality of non-interlocking helical wraps and disposed on an outer surface of the first layer, in which the first layer is disposed between the fluid barrier and the second layer and configured to at least partially displace into a space created between adjacent non-interlocking helical wraps of the second layer.

Full Description:
BACKGROUND OF THE DISCLOSURE 
       [0001]    1. Field of the Disclosure 
         [0002]    The present disclosure relates to flexible composite pipe for conducting petroleum or other fluids offshore or on land and a method of controlling gaps within the same. 
         [0003]    2. Description of the Related Art 
         [0004]    A composite flexible pipe may be formed, in part, from composite tape stacks of laminated tape strips. The composite tape stacks may be helically wound onto a pipe to provide structure and support. Gaps may form between adjacent wrappings of the tape stacks, which may allow for blow through of a fluid barrier or layer that may be beneath the wrappings. However, advantageously, the gaps may provide flexibility to the wrapped layers so that there may be relative movement or spacing between adjacent layers, thereby allowing the pipe to bend and/or flex. Therefore, control over the gaps may be desired so as to prevent blow through of a fluid barrier, but allow flexibility in the pipe. 
         [0005]    In traditional steel pipes, which may be flexible pipes, interlocking layers or wrappings may be employed to control the blow through and provide gap control. This is particularly prevalent in high-pressure applications, where pressure armor may be employed to provide resistance to internal and external pressure and mechanical crushing loads. The pressure armor may include interlocked metallic hoop strength layers and gaps may be controlled by only allowing a maximum separation between adjacent wraps to be the full extension of interlocked wraps. Furthermore, an internal pressure sheath material may be able to span the gap under a high internal pressure loading, thereby allowing some flexibility to the pipe, but also preventing blow through of the internal pressure sheath. 
         [0006]    However, in the design of some flexible pipes, which may employ composite materials for reinforcement layers, and, particularly, flexible fiber reinforced pipe, there may be no interlocking layers. As such, gap control may be difficult to achieve effectively. 
       SUMMARY OF INVENTION 
       [0007]    In one aspect, the present disclosure relates to a tubular assembly with gap control. Embodiments disclosed herein relate to one or more embodiments of and methods for controlling gaps between helically wrapped layers in a pipe structure. A tubular assembly includes a fluid barrier, a first layer, and a second layer comprising a plurality of non-interlocking helical wraps and disposed on an outer surface of the first layer, in which the first layer is disposed between the fluid barrier and the second layer and configured to at least partially displace into a space created between adjacent non-interlocking helical wraps of the second layer. The helically wrapped layers may include composite tape stacks. 
         [0008]    In another aspect, the present disclosure relates to a method to control gaps between adjacent non-interlocking helical wraps disposed on a tubular member. The method includes installing a control layer between a curved outer surface of the tubular member and the non-interlocking helical wraps, in which the control layer is configured to at least partially displace between the adjacent non-interlocking helical wraps from underneath the wraps. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]    Features of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings. 
           [0010]      FIG. 1  shows an isometric view of a composite flexible pipe in accordance with one or more embodiments of the present disclosure. 
           [0011]      FIG. 2  is a cross-sectional view of a composite flexible pipe in accordance with one or more embodiments of the present disclosure. 
           [0012]      FIG. 3  is a cross-sectional view of a composite flexible pipe in accordance with one or more embodiments of the present disclosure. 
           [0013]      FIG. 4A  is a top view,  FIG. 4B  is a cross-sectional view, and  FIG. 4C  is a blown up cross-sectional view of a gap control layer in accordance with one or more embodiments of the present disclosure. 
           [0014]      FIG. 5  is a cross-section view of a portion of a composite flexible pipe in accordance with one or more embodiments of the present disclosure. 
           [0015]      FIG. 6  is a cross-section view of a portion of a composite flexible pipe in accordance with one or more embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    A control layer and method of controlling gaps of a non-interlocking helically wrapped layer of a flexible pipe in accordance with one or more embodiments will be described herein with reference to the accompanying drawings. 
         [0017]    Referring to  FIG. 1 , an isometric view of a composite fiber reinforced flexible pipe  100  is shown. A fluid barrier (or liner or internal pressure sheath)  102  may be wrapped with a hoop reinforcement layer  104 , tensile layers  106  and  108 , and may be sealed, covered, and/or protected by a jacket (or outer sheath)  110 . Further, an anti-extrusion layer may be included between the fluid barrier  102  and the hoop reinforcement layer  104 . The anti-extrusion layer may include multiple layers and/or wrappings  120  and  122  of an anti-extrusion material, such as fiber reinforced tape, polymers, and/or any other pressure resistant material known in the art. Further, those skilled in the art will appreciate that composite flexible pipe  100  may be made of different and/or additional layers including perforated cores, collapse resistant hoop layers, anti-wear layers, lubricating layers, tensile layers, membranes, burst resistant hoop layers, perforated jackets, and/or any other additional layers, or combinations thereof, without deviating from the scope of the present disclosure. 
         [0018]    In certain embodiments, hoop reinforcement layer  104  may be made from laminated tape stacks such as that disclosed in U.S. Pat. No. 6,491,779, filed on Apr. 24, 2000, entitled “Method of Forming a Composite Tubular Assembly,” U.S. Pat. No. 6,804,942, filed on Sep. 27, 2002, entitled “Composite Tubular Assembly and Method of Forming Same,” U.S. Pat. No. 7,254,933, filed on May 6, 2005, entitled “Anti-collapse System and Method of Manufacture,” and U.S. Patent Application Publication No. 2008/0145583, filed on Dec. 18, 2006, entitled “Free Venting Pipe and Method of Manufacture,” all of which are hereby incorporated by reference in their entireties. 
         [0019]    Hoop reinforcement layer  104  may be wound at any “lay angle” relative to the longitudinal axis of fluid barrier  102 , in which higher lay angles may provide relatively high hoop strength and lower lay angles may provide relatively high axial strength. However, in accordance with one or more embodiments of the present disclosure, hoop reinforcement layer  104  may be wound at a relatively high lay angle relative to the longitudinal axis of the pipe, for example 60° to 89°, to provide internal pressure resistance against burst and/or external pressure resistance against collapse or crushing due to external loads. As noted, hoop reinforcement layer  104  may be made from stacks of tape, which may include fibers of glass fiber, aramid, carbon, and/or any other fiber used in composite structural materials. 
         [0020]    Further, those skilled in the art will appreciate that the hoop reinforcement layer  104  may be made from steel wire which may be helically wound at a high lay angle to provide hoop strength. The steel wire may be rectangular or any other shape that may allow for a high lay angle. Additionally, although only one hoop strength layer  104  is shown in  FIG. 2 , those skilled in the art will appreciate that multiple layers or wrappings of hoop reinforcement to provide additional burst, collapse, or crushing resistance may be applied to a pipe without deviating from the scope of the present disclosure. Furthermore, superimposed hoop strength layers may be counter-wound, such that, for example, one layer may be wound clockwise and a next layer may be wound counter-clockwise, so as to provide and/or improve torsion balance within the pipe. 
         [0021]    Hoop reinforcement layers  104  may have gaps  128  formed between adjacent wrappings of the layer. Gap  128  may result from imperfect installation, particularly if 100% coverage of a liner or other previously applied layer is desired and/or attempted to be achieved. Alternatively, gaps  128  may be intentionally produced, so as to allow for flexibility within pipe  100 . 
         [0022]    Further, as shown in  FIG. 1 , anti-extrusion layers  120  and  122  may be applied to a pipe structure to prevent fluid barrier  102  from entering gaps  128  and to prevent blow-through of fluid barrier  102 . Multiple layers may be applied so that stronger blow through resistance is achieved. As the blow through resistance (i.e., layers  120  and  122 , and any additional layers) is increased, gap  128  may be increased in size, thereby allowing more flexibility. However, a larger gap  128  may increase the likelihood of blow-through of fluid barrier  102 . 
         [0023]    Further, although only two anti-extrusion layers between fluid barrier  102  and hoop reinforcement layer  104  are shown in  FIG. 1 , those skilled in the art will appreciate alternative structures may be used without deviating from the scope of the present disclosure. For example, additional anti-extrusion layers, in accordance with one or more embodiments of the present disclosure, or other anti-extrusion layers and/or lubricating layers, may be applied between two hoop strength layers and/or between any superimposed, adjacent, and/or sequentially wrapped layers. For example, an anti-extrusion layer such as that disclosed in U.S. Patent Application Publication No. 2008/0145583 may be applied, or a lubricating layer and/or anti-wear layer described in American Petroleum Institute Specifications 17J and 17B, which are hereby incorporated in their entireties, may be applied. Further, more than one layer may be wrapped and/or applied between consecutive pipe structure layers, thereby providing a stronger anti-extrusion layer. 
         [0024]    During the manufacture and operation of pipe  100 , control of gaps  128  between adjacent wrappings of a helically wrapped layer may be desired. Gaps  128  may allow for appropriate spacing between adjacent wrappings so that the pipe may flex and/or bend, without damaging the pipe structure. As noted above, a composite flexible pipe may be made without interlocking adjacent wraps, and therefore an alternative gap control system and/or method may be necessary. 
         [0025]    Referring again to  FIG. 1 , anti-extrusion layers  120  and  122  may provide gap control. A first layer  120  may be helically wrapped around fluid barrier  102 . A second layer  122  may be helically wrapped around the first layer  120 , but second layer  122  may be wrapped with an offset from first layer  120 , such that the gaps between adjacent wraps of first layer  120  may be covered by second layer  122 . Further, second layer  122  may, at least partially, be made of a material that may allow for at least part of second layer  122  to displace between adjacent wraps of hoop layer  104  which may be wrapped over second layer  122 . 
         [0026]    The displaced material of second layer  122  may form a filler  124 , which may be displaced bedding material (as described below). As shown in  FIG. 1 , filler  124  may fill gaps  128  that form between adjacent wrappings of hoop layer  104 . Accordingly, filler  124  may form as a counter-wound raised surface of second layer  122 , as shown in  FIG. 1 . Filler  124  may provide gap control between the wrappings of hoop layer  104 . 
         [0027]    As shown in  FIG. 1 , the first and second anti-extrusion layers  120  and  122  may be made of rectangular cross section tape that may be helically wound around fluid barrier  102 . Anti-extrusion layers  120  and  122  may be reinforced with uniaxial or woven fibers that may provide tensile and/or lateral strength and may be twisted and/or woven (see  FIGS. 4A-4C ). Furthermore, cross fibers may be woven perpendicular to the uniaxial fibers to provide additional strength and/or support. 
         [0028]    The reinforcement fibers of anti-extrusion layers  120  and  122  may be made from glass fiber, aramid, carbon, metallic fibers, and/or any other fibrous materials known in the art. The reinforcement fibers may be short fibers or long chopped fibers embedded in a polymer matrix, so as to provide appropriate reinforcement to the anti-extrusion layers. 
         [0029]    Moreover, although shown as two wrappings of a tape, anti-extrusion layers  120  and  122  may be a single anti-extrusion layer, such as a single tape wrapping, a sleeve, or an extruded layer or may be more than two wrappings, sleeves, and/or layers or combinations thereof without deviating from the scope of the present disclosure. 
         [0030]    Furthermore, second layer  122  may include a low modulus bedding material, allowing for a low stress concentration in second layer  122  at the edge of gaps  128  in hoop layer  104 . Fillers  124  of anti-extrusion layer  122  may form because of the bedding material, and/or bedding layer, of anti-extrusion layer  122 . The bedding material may be a polymeric material, and, more particularly, may be an elastomeric material, for example, elastomers and other materials used in bonded flexible pipe. Furthermore, the bedding material, used to form the fillers, may include a foam material to allow for greater displacement and/or expansion. 
         [0031]    Alternatively, in accordance with one or more embodiments of the present disclosure the elastomeric material, which may cover any reinforcement fibers, may be made of a swellable material, such as that disclosed in U.S. Patent Application Publication No. 2008/0093086, filed on Oct. 19, 2007, entitled “Swellable Packer Construction for Continuous or Segmented Tubing,” which is hereby incorporated by reference in its entirety. The swellable material may swell in the presence of water or other moisture, thereby expanding and displacing between adjacent wraps in layer  104  and forming fillers  124 . During manufacture, after a swellable anti-extrusion layer may be applied, and a hoop layer may be wrapped over the anti-extrusion layer, the pipe may be conveyed through a fluid bath and/or high humidity zone, thereby swelling the anti-extrusion layer  122  and forming fillers  124 . 
         [0032]    Alternatively, in accordance with one or more embodiments of the present disclosure, the fillers may be created by interaction between the surface of the anti-extrusion layer and a layer that may be helically wrapped thereupon. Referring to  FIG. 2 , a cross-sectional view of a pipe section in accordance with one or more embodiments of the present disclosure will be discussed. Anti-extrusion layers, first layer  220  and second layer  222 , may be wrapped around a fluid barrier  202 . Further, hoop strength wrappings  204  may form a hoop strength layer of a pipe helically wrapped over the anti-extrusion layers  220  and  222 . The top anti-extrusion layer  222  may be made of a material which may allow it to displace into gaps  228  between adjacent wrappings  204  of the hoop strength layer, such as elastomers used in the manufacturing of bonded flexible pipe. Accordingly, fillers  224  may form and may provide gap control between wrappings  204  of the hoop strength layer. Filler  224  may form as a ridge or nub and fill (or displace) between wrappings  204 , thereby preventing adjacent wrappings  204  from impacting or getting too close, thereby preventing too much rigidity in the pipe and preventing high alternating stress in the hoop strength layer when the pipe is subject to repetitive bending. Further, as filler  224  may form in each gap  228  between each wrapping  204 , it may also prevent adjacent wraps  204  from separating too much, and therefore may provide blow-through prevention. Accordingly, gaps  228  may be controlled. 
         [0033]    In one or more embodiments of the present disclosure, wrappings  204  of a hoop strength layer may be wound on the underlying anti-extrusion layer  222  with an interference fit (see  FIG. 5 ). Accordingly, the inner wrapping diameter of wrappings  204  may be smaller than an outer diameter of anti-extrusion layer  222 . For example, the interference fit between the two layers  204  and  222  may be 0.010 to 0.030 inches, such that the outer diameter of anti-extrusion layer  222  may be 0.010 to 0.030 inches larger than an inner diameter of wrapping  204 . Accordingly, wrappings  204  may impact and/or press into anti-extrusion layer  222  by an amount in that range. Those skilled in the art will appreciate that other interference fits outside of that range may be used without deviating from the scope of the present invention and the stated range is merely provided as an example. Furthermore, the amount of interference may depend, at least partially, on the thickness of the anti-extrusion layer. 
         [0034]    As noted above, and discussed below, anti-extrusion layer  222  may have a bedding surface as an outer surface, which may be the contact surface between anti-extrusion layer  222  and wrappings  204 . Accordingly, due to the interference fit, wrappings  204  may squeeze and/or press into the bedding surface. As a result, the material of the bedding surface may displace into gaps  228  formed between adjacent wrappings  204 . The displacement may occur as a result of the wrappings  204  pressing into the bedding material, and displacing the pressed material into gaps  228  between adjacent wrappings  204 , thereby forming fillers  224 . Fillers  224  may, therefore, control the gaps between adjacent wrappings  204 . 
         [0035]    To control gaps  228 , fillers  224  may prevent wrappings  204  from moving axially relative to the fluid barrier and may maintain gaps  228  between adjacent wrappings  204 . Wrappings  204  may, therefore, be held in approximately the same position in which they were installed, even during spooling, subsequent manufacturing operations, installation, and/or service. 
         [0036]    As anti-extrusion layer  222  may be made with a reinforced elastomer that may allow for the formation of fillers  224 , wrappings  204  may be applied with minimal force, even with the interference fit, and thereby prevent damage to the fluid barrier during manufacture. Therefore, excessive force, collapse and/or shrinking of the fluid barrier and high pre-stress in the hoop strength layer may be avoided. 
         [0037]    Now referring to  FIG. 3 , a cross-sectional view of a pipe section in accordance with one or more embodiments of the present disclosure will be discussed. A single anti-extrusion layer  326  may be wrapped around a fluid barrier  302 . Accordingly, anti-extrusion layer  326  may be a single layer which may allow for displacement between adjacent wrappings  304 . Fillers  324  may form between adjacent wrappings  304  in gaps  328 , and thereby provide gap control, as discussed above. Further anti-extrusion layer  326  may be a reinforced structure, where the reinforcement may be provided by fibers  330  within anti-extrusion layer  326 . 
         [0038]    Further, as shown in  FIG. 3 , pressure (arrows of  FIG. 3 ) may be applied from beneath fluid barrier  302 . Under normal conditions, without a gap control mechanism in accordance with one or more embodiments of the present disclosure, the pressure may tend to push fluid barrier  302  radially outward and into gaps  328 . Further, as a pipe is manufactured, stored, transported, installed, and/or used in service, the pipe may be wound, bent, and/or manipulated, thereby allowing gaps  328  to fluctuate in size. For example, the wrappings  304  may shift and/or slide relative to each other and relative to a surface of the fluid barrier  302 . As such, the gaps  328  may increase in size between some wrappings  304 , and decrease in size between other wrappings  304 . Accordingly, the amount of free space that may be in a particular gap  328  may become large, and when pressure may be applied through the pipe, the radial pressure within fluid barrier  302  may become large enough, and gap  328  may be weak enough (due to its large width), so that blow through of the fluid barrier may occur. Further, if gaps  328  are removed by shifting and/or moving of wraps  304 , regions or sections of the pipe may lose flexibility and/or cause damage to a pipe if forced to bend. 
         [0039]    Therefore, according to one or more embodiments of the present disclosure, an anti-extrusion layer  326  may be applied between fluid barrier  302  and wrappings  304 . Anti-extrusion layer  326  may displace between adjacent wrappings  304 , thereby preventing relative movement and/or sliding of the wraps. Accordingly, gap  328  may be controlled and maintained at a desired width so as to prevent increases in the size of gap  328 , thereby preventing blow through of fluid barrier  302 . Further, gap  328  may be controlled so that the size of gap  328  may not decrease in size, thereby maintaining flexibility within the pipe. 
         [0040]    Now referring to  FIG. 4A , a top view of a gap control layer in accordance with one or more embodiments of the present disclosure will be described. Gap control layer  426  may be a reinforced tape. However, as noted above, the gap control layer may alternatively be a sleeve or extruded layer, with or without reinforcements. Fibers  435  and  436  may be threaded through gap control layer  426  to provide reinforcement and structure. The threading may be parallel to the direction of the tape, or may be perpendicular thereto, or may be a combination thereof, or may be oriented at any angle between. Accordingly, a matrix structure may be formed, with cross-weaving of reinforcement fibers  435  and  436 . 
         [0041]      FIG. 4B  shows an end-on cross-sectional view of gap control layer  426 . As shown in  FIG. 4B , elastomeric layers  440  and  441  may contain parallel fibers  450  which may be supported and reinforced by woven fibers  435  and  436  and cross-knitting  460  and  461 . 
         [0042]      FIG. 4C  shows a blown-up detail of the end-on view shown in  FIG. 4B . Fibers  450  may be contained and aligned with cross-knitting  460  and  461 . Cross-knitting  460  may provide a top support and cross-knitting  460  may provide a bottom support to the fibers  450  and to gap control layer  426  or may be woven within gap control layer  426 . 
         [0043]    Although shown as reinforcement fibers, fibers  450  may be individual fibers, woven bundles, and/or other fibrous structures. Similarly, cross-knitting  460  and  461 , and woven fibers  435  and  436 , may be single fibers, bundles, woven bundles, and/or any other fiber and/or fiber structure that may provide support and/or reinforcement to gap control layer  426 . Furthermore, although fibers  450  are shown in  FIG. 4B  as a particular orientation, fibers  450  may be in a different orientation, such as perpendicular to that shown in  FIG. 4B , or may be in a matrix form, such that  FIG. 4B  may represent a side cross-sectional view as well. Accordingly, variations in fibers  450 , cross-knitting  460  and  461 , and/or woven fibers  435  and  436  may be applied and/or employed without deviating from the scope of the present disclosure. 
         [0044]    Gap control layer  426  may be 0.05 inches thick, thereby allowing only a very slight increase in the size of the pipe, but allowing for an effective control over the gaps between adjacent wrappings. However, this thickness is for example only and those skilled in the art will appreciate that the thickness of gap control layer  426  may vary in thickness without deviating from the scope of the present disclosure. 
         [0045]    Displacement of the gap control layer between adjacent wrappings of a superimposed layer will be discussed with reference to  FIG. 5 . Specifically, the anti-extrusion layer may include a lower anti-extrusion surface  541 , an upper anti-extrusion surface  540 , and reinforcement fiber bundles  550 . Reinforcement fiber bundles  550  may be further supported by cross-knitting  560  and  561  and woven fibers  535  and  536 . Hoop strength wraps  504  may be helically wound around the anti-extrusion layer. Gaps  528  may form between adjacent wraps  504 . Prior to installation of wraps  504 , upper anti-extrusion surface  540  may be represented by dashed line  555 . However, after installation of wraps  504 , upper anti-extrusion surface  540  may deform. The deformation of upper anti-extrusion surface  540  is shown by a decrease in thickness below each wrapping  504  and an increase in thickness in gaps  528  between each set of adjacent wrappings  504 . Accordingly, filler  524  may form as a gap controller, preventing wraps  504  from shifting or moving relative to the other wraps  504  or relative to a fluid barrier upon which the anti-extrusion layer may be applied. Alternatively, deformation of upper anti-extrusion surface  540  may be caused by application of a force and/or pressure  570  from beneath the lower anti-extrusion layer  541 . 
         [0046]    Accordingly, in accordance with one or more embodiments of the present disclosure the deformation of upper anti-extrusion surface  540  may occur during factory acceptance hydrostatic pressure testing of the pipe. For example, when internal pressure  570  may be applied to the pipe, the liner  541  may be forced radially outward (upward in  FIG. 5 ) toward hoop strength wraps  504 , thus squeezing filler  524  from beneath hoop strength wraps  504  into gaps  528 . 
         [0047]    Now, referring to  FIG. 6 , a cross section view of a portion of a composite flexible pipe in accordance with one or more embodiments of the present disclosure is shown. Particularly,  FIG. 6  shows a cross section of a free venting pipe. For example, a free venting pipe as disclosed in U.S. Patent Application Publication No. 2008/0145583 may incorporate aspects of the present disclosure. 
         [0048]    Specifically, with reference to  FIG. 6 , anti-extrusion layers  680  and  681 , in accordance with one or more embodiments as described above, may be applied during manufacture of a free venting pipe. A free venting pipe may include a perforated core  602 , an internal hoop layer  605 , an inner anti-extrusion layer  680 , a membrane  685 , an outer anti-extrusion layer  681 , and an external hoop layer  606 . Internal hoop layer  605  may provide collapse resistance, and external hoop layer  606  may provide internal pressure resistance. Additional layers such as those discussed above, including anti-wear layers, tensile layers, and jackets, may be provided without deviating from the scope of the present disclosure. 
         [0049]    In a pipe as shown in  FIG. 6 , gaps  688  and  698  may be present between adjacent wraps of hoop layers  605  and  606 , respectively. Anti-extrusion layers  680  and  681  may be applied between the hoop layers  605  and  606  and membrane  685 . In accordance with embodiments of the present disclosure, gaps  688  and  698  may be controlled by fillers  684  and  694 , respectively. 
         [0050]    Accordingly, anti-extrusion layers may be applied between reinforcement layers and membrane layers, to thereby control gaps in the reinforcement layers. Therefore, gap control may be achieved in an internal reinforcement layer, in addition to achieving gap control in an external reinforcement layer. As such, there may be two or more anti-extrusion layers with filler for gap control, and, particularly, on either side of a membrane. 
         [0051]    Further, in accordance with one or more embodiments of the present disclosure, an anti-extrusion layer with bedding may be applied externally to a hoop strength reinforcement layer. The anti-extrusion layer control may potentially be improved if application of the anti-extrusion layer is made both internally and externally to a hoop strength layer, thereby allowing gap control from both sides of the hoop strength layer. Alternatively, an anti-extrusion layer with bedding may only be applied to the external surface of the hoop strength layer. For example, referring again to  FIG. 3 , anti-extrusion layer  326  may be applied above hoop strength wraps  304 , instead of, or in addition to being applied between hoop strength wraps  304  and fluid barrier  302 . The anti-extrusion layer may be applied with sufficient tension so that fillers  324  may form between wraps  304  and into gaps  328 . 
         [0052]    Advantageously, gap control in accordance with one or more embodiments of the present disclosure may provide minimum requirements to prevent blow through. According to the American Petroleum Institute Specification 17J, Table 6, “the maximum allowable reduction in wall thickness (of the internal pressure sheath) below the minimum design value due to creep in(to) the supporting structural layers shall be 30% under all load combinations.” Although this requirement is for conventional flexible pipe, the requirement also applies to flexible fiber reinforced pipe, and is a requirement to prevent blow through of a fluid barrier, internal pressure sheath, or liner. Gap control in accordance with one or more embodiments of present disclosure may provide fillers which may prevent slip between adjacent wrappings of a hoop strength layer while maintaining a minimum of less than 30% thickness reduction. 
         [0053]    Moreover, reinforcement layers may be wound at any lay angle relative to the fluid barrier, where a high lay angle may provide hoop strength and low lay angles may provide axial strength. In some embodiments of flexible fiber reinforced pipe, the innermost structural reinforcement layer may be applied at an approximately 40° to 60° lay angle to the pipe axis. Thus, when the pipe bends, any gaps that may exist between adjacent wrappings may not open significantly. However, in accordance with one or more embodiments of the present disclosure, hoop reinforcement layers (i.e.,  104 ,  204 ,  304 , and  504  of  FIGS. 1 ,  2 ,  3 , and  5 , respectively) may be wound at a relatively high lay angle relative to the longitudinal axis of the pipe (i.e., 60° to 89°) to provide internal pressure resistance against burst and/or external pressure resistance against collapse. Therefore, one or more embodiments of the present disclosure may allow for a higher lay angle, thereby allowing hoop strength reinforcement instead of axial strength reinforcement. 
         [0054]    Moreover, one or more embodiments of the present disclosure may provide control over the gaps between adjacent wrappings of a structural layer so as to prevent blow through of a fluid barrier or other layer beneath the gap control layer. Accordingly, fewer wrappings and/or applications of anti-extrusion layers may be allowed, thereby increasing the efficiency with which flexible pipes may be made. Further, fewer wrappings and/or applications may reduce the pipe diameter, reducing costs and weight. 
         [0055]    Moreover, one or more embodiments of the present disclosure may allow a first reinforcement layer above a fluid barrier to be applied at a high lay angle, thus providing more hoop than axial strength. Accordingly, the innermost structural support layer may be a hoop strength layer, and therefore may provide burst and/or collapse resistance. Further, embodiments described herein may require less material than traditional flexible pipe, as a hoop strength layer may be applied at a smaller diameter. Further, the reinforcement may also prove a relatively “soft” layer onto which a hoop resistant layer may be applied. 
         [0056]    Moreover, one or more embodiments of the present disclosure may provide reinforcement to a fluid barrier so as to prevent blow through. In accordance with one or more embodiments of the present disclosure, the gap control layer, which may be an anti-extrusion layer, may be applied as a single tape layer, sleeve, or extrusion, or may be applied as multiple tape layers, sleeves, and/or extrusions, or combinations thereof. Accordingly, the efficiency with which gap control may be applied may be improved. 
         [0057]    Moreover, gap control provided by one or more embodiments of the present disclosure may be used with pipes employing internal carcass designs, free venting designs, standard annulus designs, and/or any other pipe designs where gap control may be desired, including non-interlocking steel pipe layers. Additionally, gap control layers in accordance with one or more embodiments described herein may be provided between any two consecutively wrapped layers of a pipe. 
         [0058]    While the disclosure has been presented with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope of the invention should be limited only by the attached claims.

Technology Classification (CPC): 5