Abstract:
A flexible pipe formed by multiple layers of different materials, and one or more vent passages are provided in one of the layers for venting any gases permeating through the pipe.

Description:
[0001]    This application is a continuation-in-part of pending patent application Ser. No. 09/705,309 filed Nov. 3, 2000 which, in turn, claims priority of provisional application Ser. No. 60/163,908 filed Nov. 5, 1999. 
     
    
     
         [0002]    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. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [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 an end view of the pipe of FIG. 1.  
         [0005]    [0005]FIG. 3 is a view similar to FIG. 2 but depicting an alternate embodiment of the invention. 
     
    
     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 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.  
         [0007]    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.  
         [0008]    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 .  
         [0009]    A layer  16  of wrapped wires extends over the layer  15  and consists of a series of wires  16   a  helically wrapped around the exterior of the layer  15  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  may 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  16   a  and  16   b  are 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  16   a  and  16   b.    
         [0010]    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  16   a  and  16   b.    
         [0011]    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 .  
         [0012]    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.  
         [0013]    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.  
         [0014]    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.  
         [0015]    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 .  
         [0016]    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.  
         [0017]    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 .  
         [0018]    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 .  
         [0019]    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  
       VARIATIONS  
       [0020]    1. Additional tensile layers of wires can be provided in addition to the series of wires  16   a  and  16   b  and the wires forming the layer  38 .  
         [0021]    2. Each layers  16   a  and  16   b  can be formed by one wire rather than by a series of wires, and only one layer ( 16   a  or  16   b ) can be provided.  
         [0022]    3. The adjacent windings of the strip forming the layers  14  and  34  do not have to be interlocked.  
         [0023]    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 .  
         [0024]    5. The cross section of the wires  16   a  and  16   b , and the wires forming the layer  38  can be round or rectangular as disclosed in the above cited application.  
         [0025]    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.  
         [0026]    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.  
         [0027]    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.  
         [0028]    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.  
         [0029]    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.