Abstract:
An apparatus for transferring a fluid product between a fluid transport vessel and a storage vessel includes a tubular arrangement for conveying the fluid between the two vessels. The tubular arrangement includes a flexible transfer pipe hanging freely between ends in its transferring position and connected to a manifold of the transport vessel. Each of the ends of the transfer pipe has a pivoted connection with a vertical pin to avoid torsional stresses in the transfer pipe. The invention is useful to transferring liquefied natural gas.

Description:
FIELD OF THE INVENTION 
   The invention concerns a system for transferring a fluid product, particularly liquefied natural gas, between a vessel for transport of the fluid and a storage station such as a storage vessel, of the type which has a tubular arrangement for conveying the fluid between the transport vessel and the storage station, one end of which is connected to the latter and the other end of which can be connected to a manifold device of the transport vessel. 
   BACKGROUND 
   Known transfer systems of this type have the major disadvantage of having a very complex structure but without the ability to function under severe environmental conditions involving extensive relative movement between the transport vessel and the storage station, particularly when this station is a storage vessel. 
   SUMMARY OF THE INVENTION 
   The present invention aims to mitigate these disadvantages and proposes a transfer system with a relatively simple structure which is suitable even for difficult environmental conditions, while allowing the transfer of liquefied natural gas. 
   In order to realize this aim, the transfer system according to the invention has a flexible transfer conduit freely suspended between its ends in its transfer position, connected to a manifold device of the transport vessel, and each of its ends has a rotating connection with a vertical axis to prevent torsional stresses in and buckling of the conduit. 
   According to another characteristic of the invention, the flexible conduit is formed by a hose such as a cryogenic hose, suitable for the transfer of a liquefied natural gas. 
   According to another characteristic of the invention, the transfer conduit is a sequence of elements articulated one to another. 
   According to another characteristic of the invention, the flexible transfer conduit is suspended in the form of a chain. 

   
     BRIEF DESCRIPTION OF DRAWING FIGURES 
     The invention will be better understood and other aims, characteristics, details and advantages thereof will appear more clearly in the following explanatory description in reference to the appended figures given only as examples and illustrating an embodiment of the invention. 
       FIG. 1  is an elevation of a fluid transport system in its position for transfer of a fluid between a transport vessel and a storage vessel; 
       FIG. 2  is an enlarged view of the storage system indicated by  3  in  FIG. 1 ; 
       FIG. 3  is a top view of the transfer system according to  FIG. 2 ; 
       FIG. 4  is a view similar to  FIG. 3  but on a larger scale, showing the two vessels in an unaligned position. 
       FIG. 5  is a top view on a larger scale of the front part of the vessel and of the manifold device; 
       FIG. 6  is an elevation on a larger scale of the front part of a transport vessel provided with the manifold device in its position in which it is connected to the transfer conduit; 
       FIG. 7  is a view showing the exposed manifold device according to  FIG. 6  and its support structure in the rest state; 
       FIGS. 8 and 9  show another embodiment of the manifold device according to the invention respectively in its position in which it is connected to the transfer conduit and in its rest position. 
   

   DETAILED DESCRIPTION 
   In the figures, reference numbers  1 ,  2  and  3  respectively designate a vessel for transport of a product such as liquefied natural gas, a vessel for storage of this product and a system for transferring this product between the two vessels  1  and  2 , in accordance with the invention. The number  4  indicates the water level. 
   In the example represented, the transfer system according to the invention essentially comprises two flexible fluid transfer conduits  5  which, in the rest state of the system, are wound on wheel  6  mounted on top of support structure  7  in the form of a turret mounted at one end of storage vessel  2 . In the operating state, that is, in its position for transfer of a product between the two vessels, each conduit, advantageously formed by a cryogenic hose, is unwound from its storage wheel  6  and connected to manifold device  9  supported by common support structure  10  arranged at the front of transport vessel  1 . Thus, each hose  5  extends freely in the form of a chain between its ends. It is also observed that transport vessel  1  is anchored to the storage vessel by any appropriate means, for example, by cable  10 . In the example represented, storage vessel  2  is anchored and connected to the bottom at  11 . 
   As shown in  FIG. 4 , the two storage wheels  6  for hose  5  are mounted to pivot over an angle □ on their support tower about a vertical axis in order to make possible the relative movement of transport vessel  1  and the storage vessel to prevent torsional stress to the hoses. This pivoting is ensured by a rotating shaft with a vertical axis indicated by  8 . The two support turrets  7  can advantageously be arranged symmetrically with respect to the longitudinal axis X-X of the storage vessel. The longitudinal axis of the transport vessel is designated Y-Y. 
   The free end of cryogenic hose  5 , designated by general reference  13 , is formed by an endpiece bearing quick connector  14 , with emergency disconnection device  15  arranged a certain axial distance from connector  14 . Endpiece  13  moreover bears a centering rod called pin  17  which is laterally offset from the axis of the endpiece but which extends parallel to it approximately in the vertical plane formed by the catenary of the hose. 
   Provided for each cable  5 , on the front of transport vessel  1 , is manifold device  9  mounted on support structure  10  at a certain height, which bears two catwalks  22  and  23 . The two catwalks are offset from the axis of the vessel, with a slight overlap, the front catwalk  23  being arranged above rear catwalk  22 . The two catwalks are provided in order to allow operators to observe and/or maneuver the two manifold devices  9 . 
   Each device  9  comprises curved tubular portion  25  in the form of an arc of a circle somewhat less than an angle of 180°. The rear end of portion  25  is attached by rotating connection  26  with a vertical axis to vertical pipeline portion  28  of the fixed pipeline of the vessel. 
   Curved portion  25  of the connection device, which is thus mounted to pivot, bears manifold flange  30  at its free end for the sealed attachment of connector  14  of the hose, as well as flared piece  32 , which is laterally offset from the axis of the connector by a distance that makes possible, during connection of the hose to device  9 , the reception of pin  17  of the connecting endpiece of the hose. The flared piece is oriented parallel to the axis of connector  30 . Portion  25  of connecting device  9  of the vessel also bears winch  34 , on which is wound cable  35 . This cable will be unwound during connection of hose  5  to manifold device  9 , passing through flared piece  32  and attaching to the end of pin  17 . The connection is then completed by winding the cable on winch  34 . 
   As seen clearly in the figures, in order to make possible the connection of hoses  5  to manifold devices  9  of the transport vessel, an approximately semicircular cut  37  is made in upper catwalk  23  from its rear edge  38 , overlapping front edge  39  of lower catwalk  22 , around the pivot axis of curved portions  25  of manifold devices  9 , coaxially thereto. 
   Thus, each manifold device  9  can pivot between its rest position, in which its connector  30  is above lower catwalk  29  ( FIG. 7 ) and its operating position, that is, its connection position represented in  FIG. 6 , in which connector  30  passes through cut  37  so that it can be connected to hose  5 . It is observed that the angle of arc of curved portion  25  of each connection device  19  is less than 180° with a difference allowing an appropriate inclination of the axis of manifold flange  30  for easy connection to the hose. 
   According to an important feature of the invention, and due to rotating connection  26  with vertical axis of each manifold device  9  of the vessel and to the vertical pivot axis of storage wheels  6 , each cryogenic hose  5  suspended in catenary form comprises, at each end, a rotating connection with vertical axis ensuring that the hose always extends approximately in the vertical plane independently of the angle of misalignment a of the two vessels  1  and  2 . This ensures great freedom of relative pitch and yaw between the vessels. Due to the rotating connections with vertical axis, the torsion and bending from the vertical plane of the hose catenary (buckling) in the hose are negligible. They are therefore only exposed to the very slight relative rolling between the vessels. For the safety of the hose, only one measurement or verification of the distance between the two ends of the hose is necessary. 
   The operation of the transfer system according to the invention follows from the figures and the description of the structure just given. It is sufficient to recall that for a transfer of liquefied natural gas between transport vessel  1  and storage vessel  2 , at least one of cables  35  of the corresponding manifold device  9  will be unwound from its winch  34 , and hose  5  will be unwound from its storage wheel  6 , the end of cable  35  is attached to the end of pin  17  on endpiece  13  of the hose, cable  35  is wound on winch  34  until the pin engages in flared piece  32  of manifold device  9 , which, of course, has been made to pivot from its storage position represented in  FIG. 7  to its connection position according to  FIG. 6 . 
   It should also be noted that the hoses never cross the mooring cable, which is very important, particularly in case of emergency disconnection. Thus, the hoses cannot be damaged by falling on the cable. During disconnection, the hoses are wound on their storage wheel. 
   Of course, various modifications can be made to the system as described and represented in the figures.  FIGS. 8 and 9  illustrate an embodiment variant, wherein the winch and the flared piece now bearing reference numbers  34 ′ and  32 ′, are provided on endpiece  13  of each hose, while the pin, now bearing reference number  17 ′, is carried by manifold device  9 . It would also be possible to consider other ways to implement the means for storing the hoses in their rest position. In any embodiment considered, it is only important for a rotating connection with vertical axis to be provided at each end of the hose so that the hose is not subjected to torsional stresses and buckling. These stresses are absorbed by the connections.