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.

Description:
This application claims priority of provisional application Ser. No. 60/163,908 filed Nov. 5, 1999. 
    
    
     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 DRAWING 
     The drawing is a partial longitudinal sectional view of a flexible pipe according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     With reference to the drawing, 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. 
     A layer  14  is wrapped around the sheath  12  and provides resistance to internal pressure. 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. 60/163,908 filed concurrently herewith and assigned to the assignee of this application; with the disclosure of the former application being incorporated by reference. 
     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 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 sheath  12  into gaps formed between the wires of the tensile layers  16   a  and  16   b.    
     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 different type of 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.    
     A protective insulative sheath  20  extends over the tape  18  and can be formed of a foamed, or blown, polymer. 
     A layer  24  is wrapped around the sheath  20  and provides additional resistance to hydrostatic collapse and crush. The layer  24  is preferably formed by a plurality of helically wrapped, corrugated and/or interlocked strips to provide additional collapse and radial compression resistance as also disclosed in the above identified application. 
     An outer protective sheath  26  extends over the layer  24  and is preferably extruded over the layer  24  in a conventional manner. 
     It is understood that the thickness of the layer  24  and the structural strength of the sheath  20  can vary in accordance with the particular application. For example, if the flexible pipe  10  is used to convey fluids in relatively shallow water the layer  24  can be relatively thin and the sheath  20  can be designed to have some collapse resistance, thus providing a cost savings. On the other hand, if the flexible pipe  10  is used to convey fluids in relatively deep water the thickness of the layer  24  can be increased accordingly, and it would not be necessary to design the sheath  20  with any collapse resistance. 
     It is also understood that an additional layer identical to the wrapped wire assembly  16 , or a tape, identical to the tape  18 , can be provided in lieu of, or in additional to, the layer  24 . Also, a tape, identical to the tape  18 , can extend between the sheath  20  and the layer  24  and between the layer  24  and the sheath  26 . 
     VARIATIONS 
     1. Additional tensile layers of wires can be provided in addition to the series of wires  16   a  and  16   b  in the pipe  10 . 
     2. The relatively thicknesses of the sheath  12 , layer  14 , wire assembly  16 , tape  18 , sheath  20 , layer  24 , and sheath  26  are shown only for the purpose of example, it being understood that these thicknesses can be varied withing the scope of the invention. 
     3. The carbon steel strip  14  can be omitted which case the first tensile layer  16   a  would be wound directly onto the inner sheath  12 . 
     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 inner sheath  12  and the first tensile layer  16   a.    
     4. The adjacent windings of the strip forming the layers  14  and  24  do not have to be interlocked. 
     5. The cross section of the wires  16   a  and  16   b  can be rectangular as disclosed in the above cited application. 
     6. In extremely hostile environments, an outer layer similar to the layers  14  and  24  can be placed around the sheath  26  for added protection 
     7. The sheath  20  can be of a plastic that is extruded over the tape  18   
     8. The layer  24  can be identical to the layer  14  as described above. 
     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. 
     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.