Abstract:
The invention relates to the production of a connector intended for a pipe, including an end piece which is mounted to the end of a pipe. The connector includes a sleeve covering said pipe end in order to crimp same onto the mounting end. According to the invention, the sleeve includes an annular chamber, while the armoring wires have free ends which are folded back against the outer polymer sheath, said sealed annular chamber surrounding the aforementioned pipe end. The annular chamber is then dilated with the injection of a fluid in order to maintain the free ends engaged between the outer polymer sheath and the sleeve.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a 35 U.S.C. §§371 national phase conversion of PCT/FR2008/001250, filed 8 Sep. 2008, which claims priority of French application Ser. No. 07/06,320, filed 10 Sep. 2007, the disclosure of which is incorporated by reference herein. The PCT International Application was published in the French language. 
     BACKGROUND OF THE INVENTION 
     The present invention pertains to a method of mounting a nipple on a flexible tubular pipe end and also, to a connector comprising said tubular pipe end and the nipple mounted according to the method. 
     The flexible tubular pipes concerned are better known as “RTPs” (for Reinforced Thermoplastic Pipes) and they are used for land-based (or “on-shore”) applications for transporting hydrocarbons or water under pressure. They have the advantage of being faster to install and more resistant to corrosion than rigid steel pipes. Their inner diameter is relatively small, lying for example between 50 and 200 mm, and the transported fluid is at a pressure generally lying between 50 and 200 bar and at a temperature which may reach as much as 80° C. 
     The structure of these pipes is relatively simple and inexpensive. They comprise from the inside to the outside an inner polymeric tube made of polymer, an armor generally made of composite materials and an outer polymeric sheath. The inner polymeric tube has a leaktightness function in relation to the fluid transported by the pipe. It is generally made of high-density polyethylene. The function of the outer polymeric sheath, which is in particular made of polyethylene, is to protect the armor. 
     The function of the armor is to take up the mechanical loads, in particular those related to the pressure of the transported fluid. The armor generally consists of at least one pair of crossed plies of helically wound threads. The two overlaid plies constituting each pair of plies are oppositely wound with helix angles that are substantially equal in absolute value, so as to balance the structure in torsion. This helix angle is advantageously of the order of 55°, so as to take up the axial tensile loads and also the radial loads related to the pressure of the fluid. In most cases, the armor comprises only two overlaid layers, namely a pair of crossed plies of armor threads wound at 55°. When the diameter of the pipe and the service pressure are high, it may be necessary and advantageous to add a second pair of crossed plies of armor threads, so that the armor then comprises four overlaid layers. The threads of the armor plies consist for example of fibers of aramid, carbon, glass or polyester. 
     The document FR2828722 describes an exemplary “RTP” pipe in which the armor threads are textile strips strengthened with Kevlar® fibers. The document WO2004/068016 presents another example in which the armor threads consist of glass fibers. 
     The pipes to which the present invention is pertinent are said to be of unbonded type since their various constituent layers are substantially free to slip with respect to one another when the pipe is flexed. 
     One of the drawbacks of these pipes is the cost of their connection. Indeed, in order to be connected these pipes are equipped at their end with a nipple, and the costs of this nipple added to the costs of mounting are relatively significant by comparison with the cost of the bare pipes. 
     A method of mounting a nipple at the end of a flexible tubular pipe so as to produce a connector is for example described in the document FR 2 754 585. The nipple comprises a connection end and, opposite therefrom, a mounting end intended to be fitted into the end of said pipe. Said connector also comprises a sleeve which shrouds the pipe end so as to clamp the tubular pipe end onto said mounting end. Accordingly, the inner diameter of the mounting end is deformed and increased by force by implementing a technique dubbed tube expansion, said technique consisting in forcibly introducing and displacing a tube expander inside and along said mounting end, said tube expander having an outside diameter greater than the initial inside diameter of said mounting end. The effect of this operation is to compress the walls of the end of the pipe inside the sleeve. Thereafter, in order to perfect this mounting, the outer diameter of the sleeve is deformed and reduced by force by implementing a drawing technique. This results in a tightening or clamping of the end of the pipe between on the one hand the mounting end of the nipple and on the other the sleeve, said clamping ensuring the functions of mechanical joining and leaktightness. This solution exhibits the drawback of requiring relatively sizeable and expensive specialized tooling to carry out the tube-expansion and drawing operations. Moreover, it is necessary to provide for a relatively sizeable length of pipe end held tight between the sleeve and the nipple so that, under extreme conditions, the nipple does not become detached from the end of the pipe. Consequently, the cost of the materials used to produce the nipple is correspondingly increased. 
     SUMMARY OF THE INVENTION 
     Hence, a problem that arises and which the present invention is aimed at solving is to devise a method of mounting a nipple on a pipe so as to produce a connector which is not only of an advantageous cost but also which can withstand extreme conditions of use. 
     With the aim of solving this problem, and according to a first aspect, the invention proposes a method of mounting a nipple on a flexible tubular pipe end. The method comprises providing a flexible tubular pipe comprising an inner polymeric tube, an armor around said inner polymeric tube and an outer polymeric sheath around said armor, said armor comprising armor threads wound around said inner polymeric tube. Thereafter a nipple is provided comprising a mounting end intended to be fitted into the end of the pipe. Then a sleeve is provided, which is suitable for shrouding the pipe end so as to clamp the pipe end onto the mounting end. According to the invention, a deformable leaktight annular chamber is formed inside the sleeve. The chamber is intended to surround the pipe end. Then the armor is cropped at the pipe end so as to release free ends of armor threads and to fold back the free ends of armor threads against the outer polymeric sheath before shrouding the pipe end with the sleeve. Finally, a pressurized fluid is injected into the annular chamber to expand the annular chamber and hold the free ends of armor threads gripped between the outer polymeric sheath and the sleeve. 
     Thus, a characteristic of the invention resides both in the mode of preparation of the tubular pipe end and in the mode of clamping of the pipe end onto said mounting end by way of the deformable leaktight annular chamber. Indeed, free ends of armor threads are released at least partially by cropping, so that these free ends of armor threads can thereafter be folded back at 180° against the outer polymeric sheath, and thereafter the pipe end is engaged inside the sleeve and inside the deformable leaktight annular chamber. Then, finally, the annular chamber is expanded, it then extending in an annular space lying between the outer polymeric sheath and the sleeve and hence, it compresses not only the outer polymeric sheath but also the free ends of armor threads. 
     In this way, these free ends of armor threads will be wedged between the outer polymeric sheath and the sleeve which shrouds the pipe end. Consequently, the inner polymeric tube, the armor, the outer polymeric sheath and the folded-back free ends of armor threads will be sandwiched between the outer wall of the mounting end of the nipple and the inner wall of the sleeve, respectively. It will be noted that the mounting end of the nipple and the sleeve being rigid, the expanded leaktight annular chamber tends to substantially squeeze the wall of the pipe. Thus, the outer polymeric sheath and the armor in particular, which according to the prior art were not bonded together and whose relative slippage during movements of the pipe was a cause of detachment of the nipple, are, by virtue of the method which is the subject of the invention, held in a fixed position with respect to one another at the level of the end of the pipe by virtue of the free ends of armor threads folded back at 180° against the outer polymeric sheath. Indeed, the free ends of armor threads emerge from inside the outer polymeric sheath, and they are then curved back against the free edge of this sheath and thereafter applied against the outside surface of this sheath. Folded back in this way, the free end of these armor threads is securely attached to the outer polymeric sheath when the pipe end is clamped between the sleeve and the mounting end of the nipple by virtue of the expansion of the leaktight annular chamber. 
     Thus, cumbersome and expensive specialized tooling may be dispensed with by virtue of the mounting method in accordance with the invention, since it suffices to inject a pressurized fluid inside the deformable leaktight annular chamber of the sleeve, and this may be done with the aid of a simple hand pump. Moreover, the length of the mounting end of the nipple and symmetrically that of the sleeve, can be significantly reduced, since a smaller length of pipe end can be clamped, by comparison with the prior art, while preserving the required resistance to stripping of the nipple and the required leaktightness. 
     The armor advantageously comprises at least one pair of overlaid crossed plies of armor threads wound with a helix angle whose absolute value lies between 52° and 58°, advantageously between 54° and 56° and preferably equal to 55°. This optimum angle substantially equal to 55° affords the pair of crossed plies of armor thread the ability to take up the axial tensile loads and also the radial loads related to the pressure of the fluid. 
     The armor threads can be metallic but composite or woven materials based on high-toughness fibers of the aramid, glass, polyester or carbon type will be preferred. Such threads made of composite materials exhibit, for equal tensile strength, markedly lower weight and flexural stiffness than those of equivalent metal wires. These advantages make it possible to reduce the weight of the pipe and to facilitate its manufacture and its installation. 
     According to a particularly advantageous mode of implementation of the invention, an initially viscous material suitable for setting hard after injection is injected under pressure into said annular chamber. In this way, though the leaktightness of the deformable annular chamber in relation to the injected fluid is absolutely necessary at the precise instant of injection, after solidification, leaktightness is relatively secondary since the material then forms an undeformable rigid mass. Thus, the transformations which could occur on the sleeve after mounting the nipple, and in particular the stresses which could impair the deformable annular chamber, would have no effect on the clamping of the pipe end. Advantageously, a cross-linkable polymer material is injected into the deformable annular chamber, which material is initially relatively viscous but can nonetheless be injected under pressure into the deformable leaktight annular chamber, and which above all cross-links and hardens after injection to become a solid annular element. It will be possible in particular to choose a polymer material of two-component type which makes it possible to obtain rapid hardening of the material and which exhibits significant hardness. The rapidity of hardening is a significant parameter since it conditions the time for which the pressure of the fluid material in the annular chamber will have to be maintained. An epoxy resin will be chosen for example as polymer material. 
     According to a particular embodiment of the invention, an annular strip of deformable material is mounted inside said sleeve to form a deformable leaktight annular chamber. The annular strip exhibits two opposite circular edges and the sleeve an inner cylindrical surface, the two opposite circular edges being secured to the inner cylindrical surface in a leaktight manner. Thus, the deformable leaktight annular chamber is formed by that portion of inner surface of the sleeve which is covered by the annular strip and by the annular strip itself. The latter being deformable, by injecting a fluid under pressure between the inner surface of the sleeve and the annular strip, it tends to deform radially as will be explained in the detailed description which will follow. 
     Advantageously, there is provided a nipple furthermore comprising another mounting end opposite from said one mounting end and there is furthermore also provided another pipe exhibiting another pipe end, said other mounting end being fitted into said other pipe end, while said sleeve shrouds said pipe ends. Thus, such a nipple makes it possible to connect together two pipe ends in a completely symmetric manner and relatively rapidly. Indeed, the preparation of the two pipe ends is completely analogous and identical to the preparation of a single pipe end such as described above. A nipple which exhibits two mutually opposite and substantially symmetric mounting ends is provided simply and the mounting ends are fitted respectively into the pipe ends. Next, the two fitted pipe ends are shrouded with one and the same sleeve equipped with one and the same deformable leaktight annular chamber. And finally, in a manner completely analogous to the previous mode of implementation, a fluid is injected under pressure into the deformable leaktight annular chamber, causing the deformation and the expansion of the deformable leaktight annular chamber and clamps the two pipe ends respectively onto the two mounting ends of the nipple. 
     According to another aspect, the present invention proposes a flexible tubular pipe connector comprising a nipple mounted at the end of a flexible tubular pipe, said pipe comprising an inner polymeric tube, an armor around said inner polymeric tube and an outer polymeric sheath around said armor, said armor comprising armor threads wound around said inner polymeric tube, said nipple comprising a mounting end intended to be fitted into the end of said pipe, said connector furthermore comprising a sleeve suitable for shrouding said pipe end so as to clamp said pipe end onto said mounting end; according to the invention, said sleeve furthermore comprises a deformable leaktight annular chamber situated inside said sleeve, while said armor threads exhibit free ends which extend from said outer polymeric sheath and which are folded back against said outer polymeric sheath, said leaktight annular chamber surrounding said pipe end; and said leaktight annular chamber being expanded by injecting a pressurized fluid into said leaktight annular chamber so as to hold said free ends of armor threads gripped between said outer polymeric sheath and said sleeve. 
     Thus, a characteristic of the invention resides at one and the same time in the mode of preparation of the tubular pipe end and in the mode of clamping of the pipe end onto said mounting end by way of the deformable leaktight annular chamber. In this way, a flexible tubular pipe connector is obtained at an advantageous cost in contradistinction to the pipe connectors obtained according to the prior art. Advantageously, said pressurized fluid is a hardenable material which sets hard in said leaktight annular chamber after having been injected. It thus forms an undeformable annular rigid mass, which compresses the pipe end concentrically between the sleeve and the mounting end. Preferably, said hardenable material is a cross-linkable polymer material. 
     According to an advantageous mode of implementation of the invention, said sleeve exhibits an inner surface, said sleeve comprises an annular strip of deformable material mounted inside said sleeve, and said annular strip and said inner surface of said sleeve form said leaktight annular chamber. Accordingly, said annular strip of deformable material exhibits two opposite circular edges, said two circular edges being held in a leaktight manner against said inner surface, for example by means of a seal or else by welding. Advantageously, said annular strip is made of a copper alloy, particularly one that is malleable, so as to deform under the pressure of the injected fluid and to hug the contours of the outer surface of the outer polymeric sheath against which the free ends of armor threads are folded back. 
     Preferably, said nipple furthermore comprises another mounting end opposite from said one mounting end so as to be able to connect two pipe ends that face one another, said other mounting end being fitted into the other pipe end, while said sleeve shrouds said pipe ends. Thus, one and the same sleeve of a length substantially equivalent to the length of the two aggregate mounting ends makes it possible, by virtue of a deformable leaktight annular chamber extending over the entire length of the sleeve, to clamp the two pipe ends together. 
     Other features and advantages of the invention will emerge on reading the description hereinafter of particular embodiments of the invention, given by way of nonlimiting indication, with reference to the appended drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic axial sectional view of a flexible tubular pipe connector in accordance with the invention, according to a first mode of implementation and in a first position; 
         FIG. 2  is a schematic axial sectional view of the connector illustrated in  FIG. 1  in a second position; and 
         FIG. 3  is a partial schematic axial sectional view of a flexible tubular pipe connector according to a second mode of implementation. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a connector  10  comprising a nipple  12  with axis of symmetry A, linking two ends  14   a  and  14   b  of flexible tubular pipe  16   a ,  16   b . These flexible tubular pipes  16   a ,  16   b  comprise respectively an inner polymeric tube  18   a ,  18   b , around which is wound an armor layer  20   a ,  20   b , of armor threads, this same armor layer  20   a ,  20   b  being covered with an outer polymeric sheath  22   a ,  22   b  for protection. The armor threads are for example made of aramid, and for example of Kevlar®. The nipple  12  exhibits two mounting ends  24   a  and  24   b  which are mutually symmetric with respect to a bush  13 , and respectively fitted into the inner tubes  18   a  and  18   b  as far as the bush  13 . Furthermore, the connector  10  comprises a sleeve  28  which extends concentrically around the mounting ends  24   a  and  24   b  and which is centered with respect to the bush  13 . The sleeve  28  exhibits an inner surface  30 , delimited by two inner annular rims  32   a  and  32   b  opposite one another and situated respectively at the edge of the two ends  34   a  and  34   b  of the sleeve  28 . Furthermore, the sleeve is equipped with an annular strip  36  of copper alloy whose two opposite circular edges are linked in a leaktight manner respectively to the two inner annular rims  32   a  and  32   b . Thus, the annular strip  36  and the sleeve  28  inner surface  30  define a deformable leaktight annular chamber  38 , while the sleeve  28  and the two mounting ends  24   a  and  24   b  define respectively an annular space  39   a ,  39   b  able to receive the ends  14   a ,  14   b  without radial compression in this first position illustrated in  FIG. 1 . Moreover, the sleeve exhibits a filling orifice  40  situated substantially square with the bush  13  the role of which will be explained subsequently in the description. 
     Furthermore, the inner polymeric tube  18   a ,  18   b , respectively of the two ends  14   a  and  14   b , exhibits a free inner edge  42   a ,  42   b  whereas the outer polymeric sheath  22   a ,  22   b  exhibits a free outer edge  44   a ,  44   b ; the two free edges  42   a ,  42   b ;  44   a ,  44   b  then extending substantially edge to edge, while the armor  20   a ,  20   b  exhibits free ends  46   a ,  46   b  of armor threads which extend beyond the gap between free edges  42   a ,  42   b ;  44   a ,  44   b  and which are folded back around the outer polymeric sheath  22   a ,  22   b  over an axial length La, Lb, starting from the free outer edge  44   a ,  44   b . The axial length La, Lb lies substantially between half the inner diameter D of the nipple  12  and two thirds of this inner diameter D. Advantageously, the free ends  46   a ,  46   b  of armor threads are folded back against the outer polymeric sheath  22   a ,  22   b  and are held there by virtue of an adhesive strip wound around the end  14   a ,  14   b  and which imprisons them. Quite obviously, the two ends  14   a  and  14   b  of flexible tubular pipe  16   a ,  16   b  are thus prepared before being fitted respectively onto the two mounting ends  24   a  and  24   b.    
     After having thus installed the ends  14   a ,  14   b  of flexible pipes  16   a ,  16   b , a polymer of epoxy type in the liquid phase is injected under pressure into the deformable leaktight annular chamber  38  by way of the filling orifice  40  and of an appropriate pump. This polymer of epoxy type is in reality thus named loosely speaking. In reality the liquid material contains an epoxy monomer and a cross-linking agent for example of amine type, which has been mixed in a homogeneous manner into the monomer just before injection. 
       FIG. 2  depicts all the elements illustrated in  FIG. 1 , except that the deformable leaktight annular chamber  38  has been lined with the aforesaid polymer material and consequently the deformed annular strip  36 . Only the elements to which the expansion of the deformable leaktight annular chamber  38  is directly pertinent have been referenced here so as not to overload the figure. Thus, the monomer and its cross-linking agent have therefore been injected under pressure through the filling orifice  40  and this has caused an expansion of the deformable leaktight annular chamber  38  and more precisely a deformation of the annular strip  36  of copper alloy in particular at the level of the inner annular rims  32   a  and  32   b  where it has stretched. The annular strip  36 , by virtue of the pressure exerted by the epoxy mixture, has therefore been parted radially from the inner surface  30  so as to extend into the annular spaces  39   a  and  39   b , and compress respectively against the mounting ends  24   a  and  24   b , and free parts  50   a ,  50   b  of the pipe ends  14   a ,  14   b . These free pipe parts  50   a ,  50   b  consist respectively and successively of the inner polymeric tube  18   a ,  18   b , of the armor layer  20   a ,  20   b , of the outer polymeric sheath  22   a ,  22   b  and of the free ends  46   a ,  46   b  of armor threads  20   a ,  20   b , Furthermore, the pressure of the epoxy mixture has been maintained in the deformable leaktight annular chamber  38 , either by virtue of an anti-return valve mounted on the filling orifice  40 , or quite simply by maintaining the pressure of the aforesaid pump, until the mixture sets hard and forms a fully cross-linked and hardened polymer. 
     Said free parts  50   a ,  50   b  of the pipe ends  14   a ,  14   b  are thus clamped between the mounting ends  24   a  and  24   b  and the annular strip  36  of the leaktight annular chamber  38 . The annular strip  36 , by virtue of its ductility, then hugs the anfractuosities and the asperities of the outer sheaths  22   a ,  22   b , of the free ends  46   a ,  46   b  of armor threads  20   a ,  20   b  and of the joint at the level of the bush  13  of the nipple  12 . In this way, the two ends  14   a  and  14   b  of flexible tubular pipe  16   a ,  16   b  are linked together in a leaktight manner and are securely tied together, even should they be stretched in two opposite directions. 
     Reference will now be made to  FIG. 3  to illustrate a second mode of implementation of the invention. In this figure, the elements having the same functions as those of the elements illustrated in the previous figures comprise the same reference, either labeled with a prime sign “′”, or divested of the letter which accompanies it. Thus there is shown a connector  10 ′ comprising a nipple  12 ′ which exhibits a single mounting end  24 . On the other hand, the nipple  12 ′ exhibits a connection end  26  terminating in a fixing flange and it is linked to a single end  14  of flexible tubular pipe  16 . The latter comprises an inner polymeric tube  18 , an armor layer  20  of armor threads, this armor layer  20  being covered with an outer polymeric sheath  22 . The mounting end  24  has been fitted into the inner polymeric tube  18 . 
     Furthermore, the connector  10 ′ comprises a sleeve  28 ′ which extends concentrically around the mounting end  24 . The sleeve  28 ′ is completely analogous to that which is shown in  FIGS. 1 and 2 . The sleeve  28 ′is fixed securely to the connection end  26  by way of fixing means  52  of the screw and nut or equivalent type. 
     Moreover, the inner polymeric tube  18  exhibits a free inner edge  42  whereas the outer polymeric sheath  22  exhibits a free outer edge  44 ; the two free edges  42 ,  44 , then extending substantially edge to edge, while the armor  20  exhibits free ends  46  of armor threads which extend beyond the gap between free edges  42 ,  44  and which are folded back against the outer polymeric sheath  22 . The flexible tubular pipe  16  end  14  is thus prepared before being fitted onto the mounting end  24 . 
     Thereafter, an epoxy mixture of the aforesaid type is injected under pressure into the deformable leaktight annular chamber  38 ′ by way of the filling orifice  40 ′ and of an appropriate pump.  FIG. 3  shows the connector  10 ′ where the deformable leaktight annular chamber  38  has been lined with the polymer material and expanded as is illustrated in  FIG. 2 . 
     The annular strip  36 ′ has therefore been parted radially from the inner surface  30 ′ so as to compress respectively against the mounting end  24 , and the free part  50  of the end  14 . This free part  50  consists respectively and successively of the inner polymeric tube  18 , of the armor layer  20 , of the outer polymeric sheath  22  and of the free ends  46  of armor threads  20 . Furthermore, the pressure of the epoxy mixture has also been maintained in the deformable leaktight annular chamber  38 ′, until the mixture sets hard and forms a fully cross-linked polymer. 
     The free part  50  is thus clamped between the mounting end  24  and the annular strip  36 ′ of the leaktight annular chamber  38 ′. Here again, the annular strip  36 ′, by virtue of its ductility, hugs the asperities of the outer polymeric sheath  22  and of the free ends  46  of armor threads  20  while exerting a strong pressure thereon. 
     The connector  10 ′ thus formed is less expensive than the connectors obtained according to the prior art, since the length of pipe to be clamped, having regard to the effectiveness of the clamping, is shorter and consequently, the length of nipple and of sleeve required ought to be smaller. Additionally, the technique using a deformable leaktight annular chamber is at one and the same time faster to implement and much less expensive than the customary clamping techniques. 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.