Patent Abstract:
A device for mechanically securing a tubular liner in a pipe having a tubular member and connectors on each end. The connector has a bore with an internal seat that may have grooves and be tapered depending upon the application. The liner extends through the tubular member into the bore. The ends of the liner are radially and plastically deformed into engagement with the seats. An inner ring is positioned inside the liner to retain the end of the liner in engagement with the seat. The inner ring may be held by threads or by radially and plastically deforming it. The connectors are mounted to the tubular member independently of the liner, such as by adhesive. The liner may be replaced by removing the inner rings without affecting the connection between the tubular member and the connectors.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of application Ser. No. 09/657,824, filed Sep. 8, 2000, abandoned. 

   BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates in general to an improved riser pipe for offshore fluid operations, and in particular to an improved apparatus and method for forming composite pipe structures. Still more particularly, the present invention relates to an improved apparatus and method for securing tubular liners inside composite riser pipes for offshore fluid operations. 
   2. Description of the Prior Art 
   Tubular liners for pipes are fairly well known in the prior art. For example, in FIG. 1 of U.S. Pat. No. 4,813,715, a tubular liner 18 is located within a composite drill pipe 10. Each axial end of liner 18 is secured to the ends of drill pipe 10 with a metal connector 30. Another example is illustrated in FIG. 3 of U.S. Pat. No. 5,332,049, wherein a rubber liner 38 is bonded to the interior surface of a composite pipe 34. The ends of liner 38 are secured to pipe 34 with metal connectors 28, 30. In each example, the liners protect the interior surfaces of the composite pipes from pressurized drilling mud and/or other environmental concerns that could damage the non-metallic materials used in the pipes. 
   Prior art liners for composite pipes are typically bonded to the metal end fittings and/or composite tube of the pipe to form seals. However, adhesives for sealing liners to composite tubes are very sensitive to the manufacturing process. As a result, bonded liners may not be sufficiently reliable for oilfield applications. Moreover, when a liner is bonded, it is permanent and not capable of being reused. Bonded liners also require greater care and assembly time in order to cure the adhesive. Furthermore, the material that is used to form the liner can limit the ability of the liner to form a strong, reliable adhesive bond to the composite pipe and metal end fittings. Thus, an improved apparatus and method for joining liners to composite pipes with metal end fittings is needed to overcome the problems and limitations of the prior art. 
   SUMMARY OF THE INVENTION 
   In this invention, the pipe assembly has a tubular member with connectors joined to each end. The connectors serve to connect the pipe assembly to other pipes and are preferably secured to the pipe assembly by adhesive. The connector has a bore with an internal seat. Optionally, the seat may contain axial grooves and may be tapered depending upon the application. The liner inserts through the tubular member, and the ends of the liner are radially deformed against the seats. An inner ring is positioned within the liner to retain the ends of the liner in engagement with the seats. The inner ring may be secured by threads in the bore of the connector in one embodiment. The inner ring may also be radially and plastically deformed into engagement with the seats. In one version of the invention, a flaring tool is used to flare the axial ends of the liner prior to assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric schematic view of a connector constructed in accordance with a first embodiment of the present invention. 
       FIG. 2  is a sectional side view of the connector of  FIG. 1 . 
       FIG. 3  is an isometric view of an inner ring constructed in accordance with the first embodiment of the present invention. 
       FIG. 4  is a sectional side view of the inner ring of  FIG. 3 . 
       FIG. 5  is an isometric view of a flaring tool utilized in the method of assembling the first embodiment of the present invention. 
       FIG. 6  is a schematic sectional side view of the method of the first embodiment of the present invention at an initial stage of assembly. 
       FIG. 7  is a schematic sectional side view of the method of the first embodiment of the present invention at a second stage of assembly. 
       FIG. 8  is a schematic sectional side view of the method of the first embodiment of the present invention at a third stage of assembly. 
       FIG. 9  is an enlarged, schematic, sectional side view of the first embodiment of the present invention after final assembly. 
       FIG. 10  is an isometric schematic view of a connector constructed in accordance with a second embodiment of the present invention. 
       FIG. 11  is a sectional side view of the connector of  FIG. 10 . 
       FIG. 12  is an isometric schematic view of an inner ring constructed in accordance with the second embodiment of the present invention. 
       FIG. 13  is a sectional side view of the inner ring of  FIG. 12 . 
       FIG. 14  is an isometric view of a raming mandrel utilized in the method of assembling the second embodiment of the present invention. 
       FIG. 15  is a sectional side view of the raming mandrel of  FIG. 14 . 
       FIG. 16  is a partially-sectioned, isometric view of the method of the second embodiment of the present invention during assembly. 
       FIG. 17  is an enlarged, schematic, sectional side view of the second embodiment of the present invention after final assembly. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 and 2 , an outer ring or connector  11  for use in a first embodiment of the present invention is shown. Connector  11  is shown schematically as a test or prototype unit. Connector  11  is a hollow, metal, tubular member having an axis  13  and a bore of varying diameter. The rearward portion  15  of the bore is generally cylindrical, and a seat  17  adjoins and is forward of rearward bore portion  15 . Seat  17  is tapered or inclined at approximately 20 degrees relative to axis  13  and diminishes in diameter from right to left. 
   Seat  17  may optionally have a series of internal, axial teeth or grooves  19 . In the preferred embodiment, grooves  19  are circumferential, parallel to one another, and do not form a helical thread. The bore of connector  11  transitions from seat  17  into a generally cylindrical segment  21 , to the right or forward of grooves  19 . A set of threads  25  are formed forward of cylindrical segment  21 . The main body of connector  11  has a set of tapped holes  23  in its right side face that are parallel to axis  13 . Holes  23  are employed for test purposes and not utilized in commercial or production units. Also, in commercial units, the open end of connector  11  is spaced further from threads  25  and a second set of threads (not shown) is located between threads  25  and the open end. The second set of threads enables connector  11  to be connected to other pipe assemblies. 
   As shown in  FIGS. 3 and 4 , an inner ring  31  comprises a separate element from connector  11 . Like connector  11 , inner ring  31  is a hollow, metal, tubular member having an axis  33  and a bore  35 . However, inner ring  31  is smaller in diameter than connector  11  such that inner ring  31  can fit within the bore of connector  11 , as will be described below. Bore  35  and the outer or retaining surface  37  of inner ring  31  are generally cylindrical, but outer surface  37  has a short, 20 degree taper  39  on its left side edge that diminishes in diameter from right to left. Taper  39  is a smooth conical surface in the preferred embodiment. An annular flange  41  is shown extending from the right side edge of inner ring  31 . Flange  41  is used for test fixture purposes and is eliminated in production inner rings  31 . Flange  41  has a set of through-holes  43  that are parallel to axis  33 . Inner ring  31  also has external threads  45  on its outer surface  37 . 
   Referring now to  FIG. 5 , a flaring tool  51  that is utilized in a method of assembling the first embodiment of the present invention is shown. Flaring tool  51  is similar in size and geometry relative to inner ring  31 , except that it is a bull-nosed solid member rather than hollow. Like inner ring  31 , flaring tool  51  has a cylindrical outer surface  53  with a 20 degree taper  55  on its left side edge, and a flange  57  with holes  59 . However, taper  55  has a greater axial dimension than taper  39  on inner ring  31 . 
   In operation, the previously described elements of the first embodiment are used to secure a liner in a pipe having connectors on each end.  FIG. 6  schematically depicts components of a drilling or production riser, which include a fiber and resin composite tubular member  61  that has each end (only one shown) joined to connector  11 . Connector  11  has a bonding surface  63  to which an end of tubular member  61  is adhesively secured axially in an end-to-end interface.  FIG. 6  depicts a test unit, and in the actual production unit, a sleeve portion (not shown) of connector  11  extends rearwardly and receives a forward portion of the end of tubular member  61 . Tubular member  61  is also adhesive bonded between its outer diameter and the inner diameter of rearward extending sleeve portion. 
   A thin wall tubular liner  65  of elastomeric material is located within tubular member  61 . Liner  65  is precisely sized to be closely received by the internal diameter of tubular member  61 . At the initial phase of assembly shown in  FIG. 6 , liner  65  has an axial length that exceeds the axial length of tubular member  61 . Hence, an end portion  67  of liner  65  extends beyond each axial end of tubular member  61  and into the bore of each connector  11 . End portion  67  extends through entry bore portion  15  and seat  17 , but not into cylindrical segment  21  of connector  11 . 
   In the next step of the first embodiment ( FIG. 7 ), flaring tool  51  is inserted into each axial end of the assembly to plastically deform end portions  67  of liner  65  into frusto-conical flares ( FIG. 8 ). The flaring tool  51  is preferably heated to 200–250 degrees F. prior to flaring. The taper  55  on flaring tool  51  engages end portion  67  and defects it outward into the inclined profile of seat  17 . During this operation, outer surface  53  of flaring tool  51  is closely received by cylindrical segment  21  of connector  11  to prevent excessive movement therebetween. If necessary to effect the flares, flaring tool  51  may be temporarily secured to connector  11  by inserting threaded fasteners (not shown) into holes  59 ,  23 . Liner  65  is sufficiently restrained during this operation to prevent incidental movement relative to the overall assembly. After end portions  67  are formed into the permanent flares, flaring tool  51  is removed from connector  11  ( FIG. 8 ) for completion of the assembly. 
   In the final step of the first embodiment ( FIG. 9 ), inner ring  31  is inserted into connector  11  as shown with a sealing O-ring  69  therebetween. Various spacer rings  71  and shims  73  are shown in  FIG. 9  as they form a part of a test fixture. Such are not used in production pipe assemblies. External threads  45  on the outer shoulder of inner ring  31  abut internal threads  25  on the internal shoulder of connector  11 . The taper  39  on inner ring  31  forces the outer surface of the flared end portion  67  into the internal grooves  19  of connector  11 . Grooves  19  serve as retaining surface and provide enhanced grip on liner  65  between connector  11  and inner ring  31 . Threads  45  on inner ring  31  engage internal threads  25  in connector  11  to retain inner ring  31  with connector  11 . Thus, each axial end of liner  65  is securely restrained within the assembly of tubular member  61  and connector  11  to prevent movement therebetween. 
   Liner  65  is replaceable since it is merely flared and not bonded to the assembly. It is replaced by unscrewing each inner ring  31 , then gripping liner  65  and pulling it from tubular member  61 . The bonding between tubular member  61  and connector  11  remains undisturbed during the removal and replacement of liner  65 . 
   Referring now to  FIGS. 10 and 11 , a test prototype of a connector  111  for use in a second embodiment of the present invention is shown. Connector  111  is a hollow, metal, tubular member having an axis  113  and a generally smooth, cylindrical bore portion  115  on a right side. A cylindrical seat  117  adjoins the left side of bore  115 . Seat  117  is slightly smaller in diameter than bore  115  and optionally may have a series of internal, axial teeth or grooves  119 . In the preferred embodiment, grooves  119  are parallel to one another and do not form a helical thread. The main body of connector  111  has a set of tapped holes  121  ( FIG. 10 ) in its right side face that are parallel to axis  113 . Holes  121  are used for test purposes, not in production models. Connector  111  has an internal shoulder  123  located between bore  115  and seat  117 . In the commercial version of connector  111  (not shown), threads are located in the bore of connector  111  for connecting it to other pipe assemblies. 
   As shown in  FIGS. 12 and 13 , an inner ring  131  comprises a second element of the second embodiment of the invention. Like connector  111 , inner ring  131  is a hollow, metal, tubular member having an axis  133  and a generally cylindrical bore  135 . However, inner ring  131  is smaller in diameter and shorter in length than connector  111  such that inner ring  131  can fit wholly within the bores  115 ,  117  of connector  111 , as will be described below. Bore  135  and the outer surface  137  of inner ring  131  are generally cylindrical, except for an outer tapered surface  139  near its midsection that diminishes in diameter from right to left. Taper  139  could be replaced by a cylindrical surface. A series of axial teeth or grooves  141  that are complementary in profile to grooves  119  in connector  111  may optionally be located to the left of taper  139 . Inner ring  131  also has an outer shoulder  143  located between outer surface  137  and taper  139 . Outer shoulder  143  is utilized in the test fixture model of  FIG. 17 , but could be eliminated. 
   Referring now to  FIGS. 14 and 15 , a hardened ramming mandrel  151  that is utilized in a method of assembling the second embodiment of the present invention is shown. Ramming mandrel  151  is essentially toroidal or donut-like in shape. Ramming mandrel  151  has a rounded outer surface  153  with a maximum diameter that is slightly greater than the minimum inner diameter of inner ring  131 . Ramming mandrel  151  also has an axial through hole  155 . A mandrel with an expandable annular collet could be used as an alternative to ramming mandrel  151 . 
   A composite fiber and resin tubular member  161  has opposite ends permanently secured to connector  111 . Connector  111  has a bonding surface  163  that is permanently mounted to an axial end of tubular member  161 .The bonding is preferably by adhesive. In the commercial model (not shown) for a production riser pipe, rather than the test prototype shown in  FIG. 17 , connector  111  has a rearward extending sleeve over which the end of tubular member  161  extends. The bonding surface in the commercial version is thus the outer diameter of this sleeve portion and an inner diameter of tubular member  161  near its end. 
   As shown in  FIG. 17 , an elastomeric liner  165  is inserted into tubular member  161 . Liner  165  has an axial length that exceeds the axial length of tubular member  161 . Hence, the end portions  167  of liner  165  extend beyond each axial end of tubular member  161  and into connector  111 . Liner end portion  167  extends through seat  117 , but not into cylindrical bore  115  of connector  111 . Inner ring  131  is located within connector  111 , and may have an optional O-ring  169  for providing a seal therebetween. Outer shoulder  143  on inner ring  131  abuts inner shoulder  123  in connector  111  in this test fixture version. 
   In the next step of the second embodiment ( FIG. 16 ), ramming mandrel  151  is mounted to the shaft  171  of a press  173  and forced into the bore  135  of inner ring  131  as shown. Connector  111 , inner ring  131 , tubular member  161  and liner  165  are secured from extraneous movement. For ease of understanding, some of these elements are not shown in  FIG. 16 . The oversized diameter of ramming mandrel  151  is readily received on the larger right side of inner ring  131 . However, as the ramming mandrel  151  moves toward the smaller diameter left side of bore  135 , end portion  167  of liner  165  is plastically deformed between and into grooves  119  and  141  of connector  111  and inner ring  131 , respectively. Inner ring  131  is also plastically or permanently deformed radially outward simultaneously. Grooves  119 ,  141  provide enhanced grip on liner  165  between connector  111  and inner ring  131 . The hoop strength of inner ring  131  retains the ends of liner  165  in engagement with the retaining surface of seat  117 . Thus, each axial end of liner  165  is securely restrained within the assembly of tubular member  161  and connectors  111  to prevent movement therebetween. After end portion  167  is deformed, raming mandrel  151  is removed from inner ring  131  ( FIG. 17 ) to complete the assembly. 
   Liner  165  may be replaced by cutting inner ring  131  with a tool and pulling it from connector  111 . Then liner  165  may be gripped and pulled from tubular member  161 . 
   The present invention has several advantages including the ability to effect a reliable engagement between a liner and a composite tubular with metal end connectors. The invention may be utilized in drilling risers, production risers, choke and kill lines, and other applications. The liner may be replaced with other liners without affecting the connection between the tubular member and the connectors. . The liner may be reusable as it may be installed without the use of adhesives. 
   While the present invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, although grooves are shown on the seats, these may be eliminated. If the frictional engagement is sufficient, grooves on the inner ring of the second embodiment may be eliminated.

Technology Classification (CPC): 5