Abstract:
The invention concerns an assembly comprising balanced loading and unloading arm ( 14 ) installed at a first location and having articulated pipeline arms ( 15, 16 ) mounted through one of its end on a base ( 18 ) and provided at the other of its ends with a system connecting ( 28 ) the articulated pipeline arms to coupling means ( 29 ) installed at the second location. It further comprises a cable ( 32 ) linked through one of its ends to the connecting system ( 28 ) and through the other of its ends to means ( 35–39 ) adapted to subject said cable to constant tension, and a connecting winch ( 42 ) whereon is wound a connection cable ( 41 ) for bringing the connecting system ( 28 ) in a position to be connected to the coupling means ( 29 ).

Description:
BACKGROUND OF THE INVENTION  
   The present invention is directed to an articulated arm for loading and unloading products, in particular fluid products such as, for example, liquefied natural gas. 
   More particularly it relates to a balanced loading arm equipped with a hydraulic coupling allowing a transfer to be carried out between two vessels moored side-by-side, between a vessel and a platform or a floating barge moored side-by-side, or also between a jetty on which the loading arm is installed and a vessel moored alongside this jetty. 
   An example of this type of arm is described in the document GB-2 042 466. The connection of the end of this arm to a coupling means provided on the vessel is difficult, even impossible to carry out in difficult sea conditions. Moreover, under these conditions, the risk of impacts between this end and the coupling means is significant. In the majority of cases, these impacts lead to damage to the components constituting the end of the arm or the coupling means. 
   An aim of the invention is to overcome these drawbacks. In particular it aims to allow the connection/disconnection of a loading arm to/from a vessel in difficult sea conditions. 
   SUMMARY OF THE INVENTION 
   To this end, the present invention provides an assembly for loading and unloading products which comprises a balanced loading and unloading arm which is installed at a first site and includes a compass-style duct system, one end of which is mounted on a base and the other end of which is provided with a connection system for connecting the compass-style duct system to a coupling means that is installed at a second site. In particular, the invention comprises a first cable which is secured between the connection system and a means for subjecting the first cable to a constant tension, a connection winch which is attached to the connection system, and a second cable which is wound upon the connection winch and is connectable to the coupling means. In operation, the second cable is wound upon the connection winch to thereby bring the connection system into engagement with the coupling means against the constant tension exerted on the connection system by the first cable and the constant tension means. 
   Thus, the present invention provides an answer to the requirements which have just been mentioned. In fact, the invention allows the connection system to approach the coupling means installed at a site which is moving, such as a vessel, and to make a connection under good conditions. 
   Other characteristics and advantages of the invention will emerge from the following description, given with reference to the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view of a loading/unloading assembly in accordance with an embodiment according to the invention; 
       FIG. 2  is a broken view as seen from the direction of arrow A of  FIG. 1 ; 
       FIG. 3  is an enlarged side elevation view of the connection system of the assembly of  FIG. 1 ; 
       FIG. 4  is a view similar to that of  FIG. 3  and shows a connection system in accordance with a preferred embodiment of the invention; and 
       FIGS. 5 to 8  are side elevation views of the assembly of  FIG. 1 , which show certain stages of the procedure for connecting the loading and unloading arm of this assembly to a coupling means. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a tanker numbered  10  which is moored by means of a mooring rope  11  to a jetty  12  being situated alongside the latter. A fluid loading and unloading assembly  13  according to an embodiment of the invention allows the transfer, in this case of liquefied natural gas, from the tanker  10  to tanks installed on the jetty  12  or close by it and connected to the fluid transfer assembly  13 , or vice versa. 
   To this end, the assembly  13  comprises a loading and unloading arm  14  having a compass-style duct system comprising an internal tube  15  and an external tube  16  and carried by a compass-style support  17  with two branches resting on a common base  18 . 
   This arm  14  is, in this case, balanced by means of a counterweight system comprising two pulleys  19  and  20 , connected to each other by means of a cable  21 , and two counterweights  22  and  23 . The counterweight  22  is mounted on the pulley  20 , whilst the counterweight  23  is mounted on the branch of the compass-style structure  17  supported by the base  18 . 
   A fixed duct runs along the interior of the base  18  and is connected to internal tube  15  by an articulation  24  comprising two 90° bends and two swivel joints, in this case, cryogenic and of the Chiksan® swivel joint type. 
   An articulation  25  comprising two bends and a swivel joint allows the internal tube  15  to be connected to the external tube  16 . 
   The articulation between the branches of the compass-style support  17  and between this compass and the base  18  is realised by means of ball bearings  26  and  27 , surrounding the articulations  24  and  25  respectively. 
   Hydraulic jacks, which cannot be seen in  FIG. 1 , allow the loading and unloading arm  14  to be manoeuvred. 
   A connection system  28  allows the external tube  16  to be connected to a coupling means formed by a manifold  29  situated on the tanker  10 . 
   This connection system  28  comprises a hydraulic coupling  30  connected by bends and swivel joints to the external tube  16 . The conduit section formed by these bends and swivel joints is, moreover, provided with an emergency disconnection system  31 . 
   The loading and unloading assembly  13  as has just been described is well known to a person skilled in the art and will not therefore be described in greater detail here. 
   In accordance with the invention, a cable  32  is connected at one of its ends to a support  33  firmly fixed to the connection system  28 . 
   The other end of this cable  32  is connected to means  34  suitable for subjecting it to a constant tension. 
   These means  34  comprise a double-acting hydraulic jack  35  fixed, in this case, to the jetty  12  by means of a clevis mounting  36 . It extends parallel to the base  18 . 
   The means  34  also comprise two sets of pulleys  37  and  38 , each having two return pulleys around which the cable  32  is wound. 
   The set of pulleys  38  is fixed by its clevis mounting to the piston rod  39  of jack  35 , whilst the clevis mounting of the pulley set  37  is fixed to the base  18 . It is therefore possible to multiply the range of the cable  32  by eight. 
   To apply a constant tension to the cable whatever its speed and its length over which it extends between the base  18  and the support  33 , the jack  35  is fed at a constant hydraulic pressure. 
   A rod  40 , fixed to support  33  and provided with a ring through which the cable  32  passes, moreover, allows the connection system  28  to be maintained in alignment with the cable  32  and a connection cable  41  allowing the connection system  28  to be brought into the position of connection to the manifold  29 . 
   This connection cable  41  is wound on a winch  42 , operating at constant speed, which is also fixed to support  33 . 
   It should be noted, in this respect, that the greater the distance between the points of attachment of the cables  32  and  41  to the connection system  28 , the better the alignment of this system  28  as regards these cables  32  and  41  is. As can be seen in  FIG. 1 , the rod  40  allows this distance to be increased. 
   Given that the cable  32  is attached to the support  33 , the tensile load is not entirely applied to this alignment rod  40 . In fact, only a lateral component is applied to this rod  40  when the connection system  28  is out of alignment. 
   Two tube sections  43  and  44 , one entering the other, allow the connection system  28  to be guided when this arrives close to the flange of manifold  29 . 
   The male section  43  is mounted on the tanker  10  and extends under manifold  29 . Its front end, to which the connection cable  41  is going to be fastened, is situated in front of the flange of manifold  29 . 
   The female section  44  is traversed by the connection cable  41  and fixed to support  33 , under the hydraulic coupling  30 . The free end of this female section  44 , is, on its side, situated in front of the hydraulic coupling  30 . 
   Thus the possibility of impacts between the connector  30  and the flange of manifold  29  is limited. 
   Moreover, each free end of guide tube sections  43  and  44  is formed by a centring cone  45 ,  46 . 
   Furthermore, the internal diameter of female tube section  44  is greater than the external diameter of male tube section  43 , so as to avoid any risk of jamming. 
   Once these two guide tube sections  43  and  44  are engaged in each other, the only movement that is still possible between the hydraulic coupling  30  and the flange of manifold  29  results from the play between these two tubes. This movement is easily compensated for by the guide means which exist on the hydraulic coupling  30 . 
   It should also be noted that a rope, which is not visible in the figures, is used to bring the connection cable  41  to the front end of tube section  43 , at the start of the connection procedure. 
   During this connection procedure, the loading and unloading arm  14  is put in “free wheel” by commoning the chambers of the hydraulic manoeuvring jacks of this arm  14 . Preferably, in order to limit the oscillations of the arm, a flow limiter is used on the hydraulic line extending between the two chambers of each of these jacks. 
   Finally, a hydraulic jack of an emergency disconnection system allows the cable  32  to be detached from support  33  by withdrawing a pin  47  (see  FIG. 3 ) from a pin holder fixed to support  33  and a ring at the end of cable  32 . 
   This jack is not represented in the figures as it is in alignment with pin  47 . 
   The connection procedure is as follows:
     1) An operator firstly uses a remote control panel to raise the connection system  28  above manifold  29  (see  FIG. 5 ). A reduced pressure can be applied to jack  35  to avoid any slackening of cable  32  during this phase. Then the connection cable  41  is unwound from winch  42  and it is brought to the end of guidance section  43  by means of the messenger line in order to fix it to it (see  FIG. 6 ).   2) As shown in this  FIG. 6 , the loading arm  14  is then manoeuvred into an intermediate position between the stored state and the connection state and the “free wheel” mode of this arm is actuated.   3) The cable  32  is then activated by the application of a constant pressure to hydraulic jack  35  (see  FIG. 7 ).   

   This action is impossible if arm  14  is not in “free wheel” mode.
     4) The connection winch  42  is then actuated so as to shorten the length of unwound connection cable  41  and to allow the engagement of guide sections  43  and  44  (see  FIG. 1 ). At the same time, the cable  32  is subjected to a constant tension.   

   Thus, the closer the loading arm  14  is to manifold  29 , the better it follows the movements of vessel  10  which can be seen in  FIG. 5 . The final alignment is effected before the hydraulic coupling  30  reaches the flange of this manifold  29 .
     5) As shown in  FIG. 8 , the hydraulic coupling  30  is then connected to the flange of manifold  29  and a hydraulic limiting valve automatically stops the connection winch  42 .   

   Before the loading and unloading operations can start, the tension applied to cable  32  is reduced to the minimum necessary to keep the cable taut. 
   Moreover, the emergency disconnection systems are armed. 
   The cooling, loading and unloading sequences can then start. 
   The disconnection process follows the same logic, in a reverse sequence. 
   It will be appreciated that, thanks to the loading and unloading assembly  13  according to the invention, it is possible to carry out a connection or disconnection procedure smoothly and in difficult sea conditions. 
   Moreover, it is not necessary to carry out significant modifications to an existing assembly in order to make it conform to the invention. 
   Neither is it necessary to use complex means. 
   Finally, the connection and disconnection procedures do not depend on the dexterity of the operator and can be carried out with relatively large movements. 
   In the case of the embodiment of  FIGS. 1 to 8 , the support  33  and the elements which are fixed to it are arranged under the hydraulic coupling  30 . 
   This support  33  is however, preferably placed alongside hydraulic coupling  30 , as shown in  FIG. 4 . This solution offers the following advantages:
         the male guide section  43  being placed parallel to and alongside manifold  29 , it is possible to provide an access platform to manifold  29  and the free space under the manifold  29  allows maintenance operations to be carried out on the tanker  10 ;   reduced movements of the hydraulic coupling  30 , because the axis of the connection cable  41  is placed at the same level (in the vertical direction) as the axis of this coupling  30 .       

   In another embodiment, the hydraulic jack  35  can be replaced by a winch actuated by a hydraulic transmission fed at a constant hydraulic pressure. 
   Furthermore, the loading and unloading assembly  13  can be of the self-supporting compass-style duct system type and the balancing can be effected with different means. 
   Of course, the invention is in no way limited to the embodiments described and represented, which are given only by way of examples. 
   In particular, it includes all the means constituting technical equivalent of the means described, as well as their combinations. 
   Furthermore, the assembly  13  according to the invention can be used for transferring fluids other than liquefied natural gas. Among these fluids, liquefied petroleum gas and the condensates can be mentioned in particular.