Abstract:
A system for transfer of a liquid, such as liquefied natural gas, from a ship such as a liquefied natural gas carrier and a floating or fixed production and/or storage unit. The system has articulated arms and has n degrees of freedom, generally six, provided by rotating joints. At least one of the rotating joints is located on the ship.

Description:
FIELD OF THE INVENTION 
     The invention concerns a system for transfer of a liquid such as liquefied natural gas between a ship such as an LNG carrier vessel and a floating or fixed liquid production or storage unit, of the type with an articulated arm and with n degrees of freedom, generally 6, each ensured by a rotating joint. 
     BACKGROUND 
     A system of this type is known, for example, from the document WO2005/105565. This arm must be capable of being connected to and disconnected from the LNG carrier with complete safety under difficult sea conditions. This system and generally all liquid transfer systems based on inter-articulated rigid pipings have the disadvantage that all the rotating joints are provided on the articulated arm, including three at the end of the arm which consequently has a complex, cumbersome structure with large spatial requirements, and whose rotations are difficult to control particularly while handling the connections/disconnections under conditions of constant movement. 
     SUMMARY OF THE INVENTION 
     The objective of the invention is to compensate for this disadvantage. 
     To realize this objective, the transfer system according to the invention is characterized in that at least one rotating joint is provided on the ship. 
     According to one characteristic of the invention, the transfer system is characterized in that the articulated arm has a support segment connected to fixed piping of the floating or fixed unit, an exterior arm segment and an interior arm segment that have at least three rotating joints, while one to three other rotating joints are provided on the piping attached to the manifold and whose end carries the flange for connection of the articulated arm. 
     According to another characteristic of the invention, the transfer system is characterized in that the articulated arm and the fixed piping of the manifold have suitable elbows and U-shaped parts for ensuring the appropriate orientation of the axes of rotation of the rotating joints. 
     According to yet another characteristic of the invention, the system is characterized in that it has a device for guiding and handling the connection device of the articulated arm, of the type with a cone and trumpet, which is arranged laterally with respect to the connection device. 
     According to yet another characteristic of the invention, the transfer system is characterized in that it has a device for guiding and handling the connection device of the type with cone and trumpet, which is integrated coaxially with respect to the connection means. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING FIGURES 
       The invention will be better understood and other objectives, characteristics, details and advantages thereof will appear more clearly in the course of the following explanatory description with reference to the appended schematic drawings illustrating several embodiments of the invention and in which: 
         FIG. 1  is an elevation of a transfer system according to the invention; 
         FIG. 2  is a side view of this same transfer system, in the direction of arrow II of  FIG. 1 ; 
         FIG. 3  is a kinematic diagram of the transfer system according to the invention; 
         FIG. 4  is a schematic view of another embodiment of the transfer system according to the invention; 
         FIGS. 5 and 6  are respectively an elevation and a side view of yet another embodiment of the invention; 
         FIG. 7  illustrates yet another embodiment of the transfer system according to the invention; and 
         FIG. 8  illustrates the extension of the manifold up to the edge of the ship. 
     
    
    
     DETAILED DESCRIPTION 
     The invention will be described hereafter in an embodiment according to which two rotating joints of the system are provided on the ship. In a similar manner, according to the invention, it is possible to envisage providing three rotating joints or only one on the ship. 
     In these figures, reference  1  designates a ship such as an LNG carrier vessel,  2  designates the manifold of the ship,  3  an articulated transfer arm which at its free end has a device for connection to/disconnection from the manifold, designated by reference  4 , and whose other end is connected to piping  5  of the production or storage unit. This unit can be floating or fixed. The figure shows the transfer system in the process of being connected to the manifold of the ship. 
     Articulated arm  3  essentially has three inter-articulated piping segments, namely first support segment  6  whose free end is connected to piping  5 , second arm segment  7 , called the internal arm, which is connected to segment  6  by first rotating joint  8  and whose other end is connected by second rotating joint  9  to 90° elbow  12 , which is connected at its other end to third rotating joint  11 , which connects this elbow to third arm segment  10 , called the external arm. The free lower end of the external arm is connected by fourth rotating joint  15  to connection device  4 . 
     It should be noted that the axis of rotation of rotating joint  9  is perpendicular to the axis of rotation of joint  8 , that the axis of rotating joint  11  is perpendicular to the axis of joint  9 , and that the axis of joint  15  is perpendicular to that of joint  11 . Schematic  FIG. 3  clearly shows these orientations of the four rotating joints of articulated arm  3 , as well as the relative arrangement of the different elbows and interconnecting pieces. 
     The two missing rotating joints of the transfer device with six degrees of freedom, and therefore of the six rotating joints, are provided on the ship. These two rotating joints are part of connection piping  18 , which is attached to manifold  2  and is formed by two 90° elbows  19 ,  20 . One,  27 , of the two remaining rotating joints designated by reference numerals  26  and  27  has the same axis as manifold  2  with which elbow  19  is connected, and the other,  26 , connects elbows  19  and  20 . The axes of rotating joints  26  and  27  are oriented perpendicularly to one another. 
     The transfer system is equipped with a guiding and handling device, a part of which is mounted on the articulated arm, and another part of which is mounted on connection piping  18 . 
     This guiding device comprises, in a known manner, cone  28 , which is oriented by the pulling force of cable  35 , indicated further below, and is mounted on support  29 , supported by piping element  20 , in such a way as to be laterally offset with respect to flange  21 , and trumpet  31  mounted on connection device  4  while being laterally offset with respect to service coupler  33  of device  4  by support arm  32 . Supports  32  and  29  are located such that the distances between the axis of trumpet  31  and the axis of service coupler  33  and distance between the axis of cone  28  and the axis of flange  21  are identical. The cooperation of the trumpet and the cone ensures that flange surface  21  and the surface of service coupler  33  are parallel. 
     The device moreover comprises winch  34 , which, in the example represented, is mounted on the upper part of exterior arm  10  of articulated arm  3 , and cable  35 , which can be wound on the winch and brought by cable guides  36  through trumpet  31  for attachment, as in the example represented, at the end of cone  28 . Of course, the winch could be arranged at any other appropriate location, for example, on the support arm of the trumpet. 
     In order to ensure correct positioning, the end of support arm  29  of cone  28  is provided with rotational indexing fork  38  intended for cooperating with rotational indexing roller  39  connected to trumpet  31  with an appropriate lateral offset corresponding to the fork  38 /cone  28  offset. It is the cooperation of roller  39  and fork  38  that ensures the proper coaxiality of coupler  33  and flange  21  by rotation about the common axis of cone  28 /trumpet  31 . 
     It should be further noted that articulated arm  3  is balanced by means of counterweight  41  arranged on extension  42  of internal arm  7 . The balancing must be such that the winch line is always taut during the connection/disconnection phases. 
     It should be noted that, for the sake of optimized handling, in the figures, the different elements of the arm have been arranged so that, regardless of the angle of rotation of rotating joints  8 ,  9 ,  11  and  15 , the axis of the trumpet always intersects the axes of rotation of rotating joints  9 ,  11  and  15 . Furthermore, in the realization of such a system, the elements of external arm  10  and of transfer device  4  will be arranged in such a way as to bring the center of gravity of these elements to the level of the axis of trumpet  31  and make them as high as possible. Likewise, on the manifold side, the elements of connection piping  18  have been arranged so that the axis of the cone always intersects the axes of rotation of rotating joints  26  and  27 . Furthermore, in its realization, it will be possible to balance connection piping  18  by means of counterweights or elastic devices (of the spring type, for example). All of these arrangements make it possible to optimize the alignment of the winch line, of the axes of the cone and of the trumpet regardless of the relative position between the ship and the storage or production unit and regardless of their movements. 
     Concerning the functioning of the transfer system according to the invention, it is easily understood that the six rotating joints give the system the necessary six degrees of freedom. The correct positioning of arm  3  on connection flange  21  of the manifold is ensured by guiding device ( 28 ,  31 ,  38 ,  39 ), which allows the transfer system according to the invention also to be used in the open sea despite the dynamic movements generated by the surroundings (swell, current, wind). By arranging some of the rotating joints on the ship, the articulated arm can be less cumbersome and lighter in weight. 
       FIG. 4  illustrates a realization of the transfer device according to the invention according to which three rotating joints corresponding to rotating joints  8 ,  9 , and  11  of  FIGS. 1-3  are on articulated arm  3 , whereas piping  18  attached to the manifold has, in addition to rotating joints  26 ,  27 , a third rotating joint designated by reference numeral  15 ′ since it corresponds functionally to rotating joint  15  of  FIGS. 1-3 . For this purpose, piping  18  has additional U-shaped part  47  and an offset coupler  49 , joint  15 ′ being placed between the offset coupler  49  and the U-shaped part  47  in such a way that it always complies with the advantageous geometric arrangements mentioned above. It should be noted that in the case in which this component were to become available, the arrangement with three rotations could be replaced with a single ball-and-socket with a passage for liquid, which would reduce spatial requirements. 
       FIGS. 5 and 6  illustrate an embodiment of the invention according to which five rotating joints are provided on articulated arm  3 , namely joints  8 ,  9 ,  11 ,  15 , and  26 ′, the latter joint corresponding functionally to joint  26  of  FIGS. 1-3 . Joint  26 ′ is arranged just upstream of connection device  4 . Sixth rotating joint  27  remains on piping  18  of the manifold in accordance with  FIGS. 1-3 . 
       FIG. 7  shows another embodiment whose particularity lies in the fact that the guiding device and the device for connection of articulated arm  3  are integrated in such a way as to produce a coaxial structure. Cone  28  is arranged coaxially in connection flange  21  of piping  18 , which is fixed to the manifold, and trumpet  31  is realized in tubular element  45 , which is arranged coaxially with respect to connection opening  46  of the connection device and along its axis, while, as one moves away from the end, the tube assumes the form of a U, which allows tubular element  45  to open towards the outside in the curved part. Winch  34  is housed in the space delimited by the U-shaped tube, above tubular element  45  of trumpet  31 , so that the cable can pass through the trumpet. The arrangement of the rotating joints is that of  FIGS. 1-3 , with four joints on articulated arm  3  and two on the piping of the manifold, with the exception of joint  15  which is no longer in the straight part of exterior arm segment  10  but rather on the upper branch of the U-shaped part of connection device  4 . This joint is indicated by reference numeral  15 ′. 
     It should also be noted that piping  18  fixed to the manifold could be sufficiently long to offset connection flange  21  toward the location of the edge of the ship and come to rest via support  45  on the structure of the ship to transmit all or part of the forces from the arm to the structure of the ship and relieve the ship&#39;s manifold, as shown in  FIG. 8 . 
     To complete the description, it should be noted that connection device  4  of articulated arm  3  comprises service coupler  33  and emergency disconnection device  43 .