Abstract:
A flexible pipe and a method of manufacturing same according to which the pipe is formed by multiple layers of different materials and suitable for use in subsea and land-based applications. (It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure; and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims under 37 CFR §1.72.)

Description:
[0001]    This application is a continuation application of U.S. Ser. No. 09/706,070, filed Nov. 3, 2000, which claims priority of provisional application Serial No. 60/163,908 filed Nov. 5, 1999. 
     
    
     
         [0002]    The present invention relates to a relative low-cost flexible pipe formed by multiple layers of different materials and suitable for use in subsea and land-based applications. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]    [0003]FIG. 1 is a longitudinal sectional view of a flexible pipe according to an embodiment of the present invention.  
         [0004]    [0004]FIG. 2 is a longitudinal sectional view of a flexible pipe according to another embodiment of the present invention.  
         [0005]    FIGS.  3 A- 3 C are longitudinal sectional views of alternative embodiments of a layer of the pipes of the embodiments of FIGS. 1 and 2. 
     
    
     DETAILED DESCRIPTION  
       [0006]    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 tubular member, preferably in the form of a plastic sheath  12  for conveying fluid through its bore. The sheath may be formed in a conventional manner using polymers, or the like.  
         [0007]    A layer  14  is wrapped around the sheath  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 “Flexiok” trademark.  
         [0008]    A wrapped wire assembly  16  extends over the layer  14  and consists of a series of wires  16   a  helically wrapped around the exterior of the layer  14  to form a first tensile layer, and an additional series of wires  16   b  wrapped around the first series of wires  16   a  to form a second tensile layer extending over the first tensile layer. The wires  16   a  and  16   b  have a substantially 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  16   a  and  16   b  are formed by carbon steel with an anodic coating. It is noted that the layer  14  prevents the expansion of the sheath  12  into gaps formed between the wires of the tensile layers  16   a  and  16   b.    
         [0009]    One or more layers of a tape  18  are helically wrapped over the wire assembly  16 . The tape  18  can be formed by plastic or metal and can be reinforced with glass, metal or a stronger plastic. Although not shown in the drawings, it is understood that the tape  18  can also extend between the layer  14  and the wire assembly  16 , and between the series of wires  16   a  and  16   b.    
         [0010]    A protective outer insulative sheath  20  extends over the tape  18  and is preferably extruded over the tape  18  in a conventional manner, with the tape providing a smooth surface for the extrusion. The sheath  20  is optional and is required only when the tape  18  is inadequate to protect the remaining components of the pipe  10 .  
         [0011]    [0011]FIG. 2 depicts a pipe  10 ′ that is similar to the pipe  10  of FIG. 1 and includes some components of FIG. 1 which are given the same reference numerals. In the embodiment of FIG. 2, a wrapped wire assembly  26  extends over the layer  14  and consists of a series of wires  26   a  and  26   b  which are substantially rectangular in cross section. The wires  26   a  are helically wrapped around the exterior of the layer  14  to form a first tensile layer, and the wires  26   b  wrapped around the first series of wires  26   a  to form a second tensile layer extending over the first tensile layer.  
         [0012]    According to an embodiment of the method of the invention, the rectangular profile of the wires  26   a  and  26   b  is achieved by unwinding the coiled wires from a mandrel, or the like, and passing the wires through opposed rollers which flatten the wires to a substantially rectangular cross section.  
         [0013]    According to an alternate method of forming the wires  26   a  and  26   b  an elongated sheet is payed out from a coil and a plurality of spaced cutters are placed in the path of the sheet to slit the sheet in to a plurality of wires. The cutters are spaced in a manner to form a plurality of wires having a rectangular cross section.  
         [0014]    Both of the above methods avoid the high expense of specialized rolling mills in which coils of round carbon steel wire are processed through repeated roll forming and heat treating operations.  
         [0015]    Also, in the embodiment of FIG. 2 it is understood that wrapped tape, identical to the tape layer  18 , can also extend between the layer  14  and the wire assembly  26 , and between the series of wires  26   a  and  26   b.    
         [0016]    Also according to the embodiment of FIG. 2, an inner layer  28  is provided inside the sheath  12 . The layer  28  is preferably formed by a plurality of helically wrapped, corrugated and/or interlocked strips to provide additional collapse and radial compression resistance. If the layer  28  is added, the sheath  12  would be extruded over the outer surface of the layer  24 .  
         [0017]    It is emphasized that both the wire assembly  26  and the layer  28  can be included in the pipe  10  and/or  10 ′, or one can be included without the other.  
         [0018]    FIGS.  3 A- 3 C are alternative embodiments of the layer  14  which can be used with the pipe  10  and/or the pipe  10 ′. Referring to FIG. 3A, a continuous metal strip  30 , preferably of carbon steel, is helically wrapped around the adjacent inner member (not shown). Two adjacent inner windings are shown by the reference numerals  30   a  and  30   b , and three adjacent outer windings are shown by the reference numerals  30   c ,  30   d , and  30   e , respectively. The wrapping of the strip  30  is such that the winding  30   d  overlaps the windings  30   a  and  30   b , the winding  30   c  overlaps the winding  30   a  and its adjacent inner winding (not shown), and the winding  30   e  overlaps the winding  30   b  and its adjacent inner winding (not shown), and so on. The strip  30  is wound in this manner for the length of the pipes  10  or  10 ′, and it is understood that the number of radially spaced windings, and therefore the thickness of the layer thus formed can vary.  
         [0019]    According to the embodiment of FIG. 3B, a continuous metal strip  34 , preferably of carbon steel, is helically wrapped around the adjacent inner member (not shown). The strip  34  is shaped, or formed, in any known manner to form a cross section having a first substantially horizontal inner portion  34   a , and second substantially horizontal portion  34   b  that is spaced radially outwardly from the inner portion  34   a , and a bent portion  34   c  extending between the portions  34   a  and  34   b . The strip  34  is preferably of carbon steel and is helically wrapped around the adjacent inner member (not shown). The wrapping of the strip  34  is such that the portion  34   b  overlaps the inner portion of its adjacent winding, and the portion  34   a  is overlapped by the outer portion of its adjacent winding, to thus achieve an interlocking effect. The strip  34  is wrapped for the length of the pipes  10  or  10 ′, and it is understood that the number of radially spaced windings, and therefore the thickness of the layer thus formed can vary.  
         [0020]    According to the embodiment of FIG. 3C, a continuous metal strip  38 , preferably of carbon steel, is helically wrapped around the adjacent inner member (not shown). The strip  38  is shaped, or formed, in any known manner to form a cross section having a convex portion  38   a  extending from a concave portion  38   b . The wrapping of the strip  38  is such that the convex portion  38   a  overlaps the concave portion of its adjacent winding and the concave portion  38   a  is overlapped by the convex portion of its adjacent winding to thus achieve an interlocking effect. The strip  38  is wrapped for the length of the pipes  10  or  10 ′, and it is understood that the number of radially spaced windings, and therefore the thickness of the layer thus formed can vary.  
       Variations  
       [0021]    1. In each of the above embodiments, additional tensile layers of wires can be provided in addition to the series of wires  16   a  and  16   b  in the pipe  10  and the series of wires  26   a  and  26   b  in the pipe  10 ′.  
         [0022]    2. The carbon steel strip layer  14  can be omitted from each of the above embodiments in which case the first tensile layer  16   a  would be wound directly onto the sheath  12 .  
         [0023]    3. If the carbon steel strip is omitted, as discussed in paragraph  2 , above, an optional wrapped tape, similar to the tape  18  could be provided that extends between the sheath  12  and the first tensile layer  16   a.    
         [0024]    4. The adjacent windings of the strip forming the layer  14  do not have to be interlocked.  
         [0025]    5. In extremely hostile environments, an outer layer similar to the layer  14  can be placed around the sheath  20  for added protection, in each of the embodiments.  
         [0026]    6. In extremely hostile environments, an outer layer similar to the layer  14  can be placed around the sheath  20  for added protection.  
         [0027]    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.  
         [0028]    Since other modifications, changes, and substitutions are intended in the foregoing disclosure, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.