Abstract:
An apparatus, system and method for a retractable LNG cargo transfer bow manifold for tandem marine cargo transfers are described herein. A retractable liquefied natural gas (LNG) cargo transfer system comprises a marine vessel, an LNG cargo transfer bow manifold moveably attached to a main deck of the marl He vessel, wherein the LNG cargo transfer bow manifold is slideable between a forward position proximate a bow of the marine vessel, and an aft position aft of the bow, the LNG cargo transfer bow manifold elevationally coupled to the main deck by a retractable support member, wherein the retractable support member is moveable between an extended position such that the LNG cargo transfer bow manifold is raised above the main deck, and a retracted position such that the LNG cargo transfer bow manifold rests on one of the main deck, below the main deck or a combination thereof.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the invention described herein pertain to the field of marine transfer of liquefied natural gas (“LNG”) between vessels. More particularly, but not by way of limitation, one or more embodiments of the invention enable an apparatus, system and method for a retractable UNO cargo transfer bow manifold for tandem marine cargo transfers. 
         [0003]    2. Description of the Related Art 
         [0004]    Natural gas is often carried in liquefied form onboard special cryogenic tanker ships from the location of its origin to the location of consumption. In this way, natural gas may be transported to areas with a higher demand for natural gas. Since liquefied natural gas (LNG) occupies only about 1/600th of the volume that the same amount of natural gas does in its gaseous state, liquefying the natural gas tor transport facilitates the transportation process and improves the economics of the system. LNG is produced in onshore or offshore liquefaction plants by cooling natural gas below its boiling point (−259° F. at ambient pressures). The LNG may be stored in cryogenic containers either at or slightly above atmospheric pressure. Typically the LNG will be regasified prior to distribution to end users. 
         [0005]    In some instances, a mobile vessel is loaded with LNG cargoes at the natural gas supply source and travels across the ocean to another location for offloading and distribution. Increasingly, an LNG carrier (LNGC) or vessel with regasification facilities is loaded with LNG cargo at a location between the port of origin and the port of consumption using ship-to-ship (STS) transfer of LNG. In one example, a conventional LNGC collects the LNG from the liquefaction plant at the natural gas supply source or other LNG loading location and is used for the long haul or a portion of the transportation route. The conventional LNGC delivers the cargos from the supply source to the STS transfer location. In this example, a regasification vessel receives the cargo from the LNGC and may be used in shuttle service between the STS transfer location and the offloading port. In yet another example, a conventional LNGC berths alongside a floating platform for the regasification of LNG onboard the floating platform, and the floating platform is attached to a riser or jetty. In such scenarios, STS transfer is used to load LNG onto the floating platform. 
         [0006]    In order to implement the STS transfer of LNG, it is often advantageous to use a tandem loading configuration, in which the stem of one of the vessels faces the bow of the other vessel, as illustrated in  FIG. 1 . The actual STS transfer of the LNG may be either from or toward the vessel astern of the other. In  FIG. 1 , loading device  100  is shown on conventional loading deck  110  on conventional receiving vessel  130 . The raised position of loading device  100  is permanent and allows conventional LNG cargo transfer hose(s)  115  or articulated pipeline (arms) to remain in a stable catenary/apex configuration, and also provides for conventional disconnect coupler  120 , Conventional disconnect coupler(s)  120  allows for immediate separation of supply vessel  125  and receiving vessel  130  in the event of an emergency during an STS transfer operation. In such circumstances, the flow of LNG ceases, and the conventional transfer hoses  315  be disconnected from the supply  125  and/or receiving vessel  130  at the conventional disconnect coupling  120 . 
         [0007]    Vessels, including LNGCs and offshore floating platforms, must be capable of withstanding severe weather conditions, such as storms, high wind and hurricanes. During extreme weather conditions, it may not be possible or desirable to move a floating LNG production vessel to a protected location due to moorings, gas risers, and/or pipeline and well controls, and so the vessel may experience heavy loads from large waves beating down on the deck of the vessel. In the case of the transporting LNGC the effects of ocean, wind and wave systems daring significant storm events during a passage, may physically damage a fixed bow loading or fixed bow unloading unit to the extent it is no longer safe to use at the next loading or disport facility. Strong or continuous wave forces on decks can cause damage to the vessel and equipment on board, and the deck may be flooded with green water (a compact mass of water flowing across the deck of the vessel). 
         [0008]    To combat damage during extreme weather conditions, oil bow loading units are typically robust manifold systems capable of weathering stormy seas. However, unlike oil, LNG is cryogenic. For LNG transfer tandem configurations, the transfer systems are not as robust in size and mass and are therefore subject to damage not typically sustained by oil units. Unlike oil loading/offloading devices, these LNG handling systems may include particularly fragile process instrumentation, emergency shutdown systems and/or quick connect/disconnect couplers which are a required design component in order to meet safely standards (e.g., ISO DTR 17177, ISGOTT, SIGTTO STS Transfer Guide). Thus, fixing the LNG loading/offloading device on the bow of the LNGC during travel risks significant damage to the loading and unloading units. 
         [0009]    Conventional LNG bow loading and conventional LNG bow unloading units currently used onboard LNG vessels are not well suited to withstand extreme weather conditions. Therefore, there is a need for a retractable LNG cargo transfer how manifold for tandem marine cargo transfers. 
       SUMMARY 
       [0010]    Embodiments described herein generally relate to an apparatus, system and method for a retractable LNG cargo transfer bow manifold for tandem marine cargo transfers. A retractable LNG cargo transfer bow manifold for tandem marine cargo transfers is described. 
         [0011]    An illustrative embodiment of a retractable liquefied natural gas (LNG) cargo transfer system comprises a marine vessel, an LNG cargo transfer bow manifold moveably attached to a main deck, of the marine vessel, wherein the LNG cargo transfer bow manifold is slideable between a forward position proximate a bow of the marine vessel, and an aft position aft of the how, the LNG cargo transfer bow manifold elevationally coupled to the main deck by a retractable support member, wherein the retractable support member is moveable between an extended position such that the LNG cargo transfer bow manifold is raised above the main deck, and a retracted position such that the LNG cargo transfer bow manifold rests on one of the main deck, below the main deck or a combination thereof, wherein the forward position, together with the extended position, arranges the LNG cargo transfer bow manifold into a cargo transfer position, and wherein the aft position, together with the retracted position, arranges the LNG cargo transfer bow manifold into a stowed position. In some embodiments, the LNG cargo transfer bow manifold further comprises a immoveable cargo transfer conduit fluidly coupling the marine vessel and a second marine vessel when the LNG cargo transfer bow manifold is in the cargo transfer position. In certain embodiments, the LNG cargo transfer bow manifold further comprises detachable piping fluidly coupling the LNG cargo transfer bow manifold to an LNG cargo tank onboard the marine vessel when the LNG cargo transfer bow manifold is in the cargo transfer position. In some embodiments, the cargo transfer conduit and the piping are disconnected from the LNG cargo transfer bow manifold when the LNG cargo transfer bow manifold is in the stowed position. In some embodiments the system further comprises a manifold deck coupled between the retractable support member and the LNG cargo transfer how manifold. In certain embodiments the system further comprises an actuateable barrier, wherein the actuateable barrier closes over the LNG cargo transfer bow manifold in the stowed position. 
         [0012]    An illustrative embodiment of a method for tandem marine liquefied natural gas (LNG) cargo transfers comprises positioning a first marine vessel at a ship to ship (STS) transfer location in tandem with a second marine vessel, sliding m LNG cargo transfer bow manifold onboard the first marine vessel forward along a track to about a bow of the first marine vessel, extending an LNG cargo transfer bow manifold support member to bring the LNG cargo transfer bow manifold above a main deck of the first marine vessel, coupling an LNG transfer conduit to the LNG cargo transfer bow manifold on a first side and to the second marine vessel on a second side at the STS transfer location, connecting LNG piping to the LNG cargo transfer bow manifold on a first coupled side of the LNG piping and an LNG cargo tank onboard the first marine vessel on a second coupled side of the LNG piping at the STS transfer location, transferring LNG between the first marine vessel and the second marine vessel using the LNG cargo transfer bow manifold, and retaining the LNG cargo transfer bow manifold to a protected position onboard the first marine vessel prior to departing the STS transfer location. In some embodiments, returning the LNG cargo transfer bow manifold to a protected position comprises disconnecting the LNG piping from the LNG cargo transfer bow manifold and the LNG cargo tank, sliding the LNG cargo transfer bow manifold aft along a track away from the bow of the first marine vessel, and retracting an LNG cargo transfer bow manifold support member to bring the LNG cargo transfer bow manifold onto the main deck of the first marine vessel. In certain embodiments, extending the LNG cargo transfer bow manifold support member comprises raising the LNG cargo transfer bow manifold over a breakwater. 
         [0013]    An illustrative embodiment of a liquefied natural gas (LNG) cargo transfer system comprises a first LNG carrier vessel comprising a protected location within a hall of the first LNG carrier vessel and below a main deck, an LNG cargo transfer bow manifold slideably coupled to the protected location, wherein the LNG cargo transfer bow manifold is slideable between a protected position at the protected location, and an LNG transfer position forward of a bow of the marine vessel and at least partially outside the hull, an actuateable shield at the bow, wherein the actuateable shield closes the protected location when the LNG cargo transfer bow manifold is in the protected position and opens to allow the LNG cargo transfer bow manifold to slide to the LNG transfer position, and a immoveable LNG transfer conduit fluidly coupling the first LNG carrier vessel and a second LNG carrier vessel when the LNG cargo transfer bow manifold is in the LNG transfer position, and detachable piping fluidly coupling the LNG cargo transfer bow manifold to an LNG cargo tank, onboard the first LNG carrier vessel when the LNG cargo transfer bow manifold is in the LNG transfer position. 
         [0014]    In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. 
       BRIEF DESCRIPTION OF THE DRAWINGS 
       [0015]    Advantages of the present invention, may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings in which: 
         [0016]      FIG. 1  is a perspective view of a tandem LNG transfer configuration of the prior art. 
         [0017]      FIG. 2A  is a perspective view of an illustrative embodiment of a retractable LNG cargo transfer bow manifold in a transfer position. 
         [0018]      FIG. 2B  is a perspective view of a retractable LNG cargo transfer bow manifold of illustrative embodiments in a transfer position and illustrating actuation of the retractable LNG cargo transfer unit aft of the bow. 
         [0019]      FIG. 2C  is a perspective view of a retractable LNG cargo transfer bow manifold of illustrative embodiments actuating downward onto a vessel deck. 
         [0020]      FIG. 2D  is a perspective view of a retractable LNG cargo transfer bow manifold in a protected position of illustrative embodiments. 
         [0021]      FIG. 3  is a perspective view of a breakwater protecting a retractable LNG cargo transfer bow manifold of illustrative embodiments. 
         [0022]      FIG. 4A  is a perspective view of an illustrative embodiment of a retractable LNG cargo transfer bow manifold in a protected position within the hull and alternatively in a transfer position. 
         [0023]      FIG. 4B  is a perspective view of an illustrative embodiment of a retractable LNG cargo transfer bow manifold in a protected position within the hull. 
         [0024]      FIG. 5A  is a perspective view of an illustrative embodiment of a retractable LNG cargo transfer how manifold in an LNG transfer position in front of the bow. 
         [0025]      FIG. 5B  is a perspective view of an illustrative embodiment of a retractable LNG cargo transfer how manifold in a protected position within the hull. 
         [0026]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within, the spirit and scope of the present invention as defined by the appended claims. 
     
    
     DETAILED DESCRIPTION 
       [0027]    A retractable LNG cargo transfer bow manifold for tandem marine cargo transfers will now be described. In the following exemplary description numerous specific details are set forth in order to provide a more thorough understanding of embodiments of the invention, it will be apparent, however, to an artisan of ordinary skill that the present invention may be practiced without incorporating all aspects of the specific details described herein. In other instances, specific features, quantities, or measurements well known to those of ordinary skill in the art have not been described in detail so as not to obscure the invention. Readers should note that although examples of the invention are set forth herein, the claims, and the full scope of any equivalents, are what define the metes and bounds of the invention. 
         [0028]    As used in this specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a hose includes one or more hoses. 
         [0029]    “Coupled” refers to either a direct connection or an Indirect connection (e.g., at least one intervening connection) between one or more objects or components. The phrase “directly attached” means a direct connection between objects or components. 
         [0030]    While for illustration purposes the invention is described in terms of liquefied natural gas, nothing herein is intended to limit the invention to that embodiment. The invention may be equally applicable to other gases which may be transported as cryogenic liquids, for example, ethane, ethylene, ammonia or vinyl chloride. 
         [0031]    A retractable LNG cargo transfer bow manifold, for tandem marine cargo transfers is described herein. Using the apparatus, systems and methods described herein a bow loading and/or unloading manifold may remain protected from shipping seas during severe weather, and/or the shipping of green water may be avoided. Illustrative embodiments may assist in ensuring the LNG transfer system, with its unique and delicate components (process instrumentation, ESD system, etc.) may be available for use and not destroyed by heavy weather sea states. An LNG cargo transfer bow manifold, which may he a loading or unloading manifold on an LNG supply or receiving vessel, may actuate aft from the bow to avoid exposure to waves or weather while the vessel is steaming at sea (or otherwise not in the course of LNG transfer operations), and move forward towards the bow for LNG transfer (loading or unloading) operations. In some embodiments, the LNG cargo transfer bow manifold may retract aft of a vessel bow, down, onto a deck and/or into the hull when the manifold is not in use, for example during travel and/or inclement weather. In some embodiments, a door, shield and/or breakwater may further protect the LNG cargo transfer bow manifold from damage. 
         [0032]    Vessel  200  may be a LNG carrier, regasification vessel, barge or other floating unit or vessel configured to transport cryogenic liquids through navigable waterways, for example an ethane carrier. In embodiments where vessel  200  is a regasification vessel, vessel  200  is equipped with vaporizers onboard to vaporize (regasify) cargoes prior to delivery at a destination. In certain embodiments, vessel  200  may be a floating storage and regasification unit or a floating liquefaction storage and offloading unit. Retractable manifold  210  may be an LNG cargo transfer bow manifold for tandem cargo transfers. In other embodiments, retractable manifold  210  may be an LNG cargo transfer stern manifold for tandem cargo transfers. Vessel  200  and retractable manifold  210  may function in both a loading and unloading capacity. In one example, vessel  200  may employ retractable manifold  210  to receive LNG from a floating liquefaction unit, travel with the obtained cargo to an offloading destination, and then subsequently employ retractable manifold  210  to offload the LNG cargo onto a floating regasification unit by way of a tandem ship-to-ship (STS) cargo transfer. In such an example, retractable manifold  210  be in a transfer position, during receipt of the cargo, placed into and secured in an at-sea, protected position during travel, and then re-positioned into the transfer position during offloading of the cargo. 
         [0033]    Components of loading and unloading manifolds for the tandem STS transfer of LNG and other liquefied gases are well-known to those of skill in the art and are therefore not described in detail herein so as not to obscure the invention. LNG cargo transfer manifolds are based upon industry standards for design, function, size, compatibility with a wide range of terminal facilities, emergency response and mitigation features, for example as described in SIGTTO&#39;s Manifold Recommendations for Liquefied Gas Carriers. STS transfer operations using the tandem configuration may occur in open water, near a jetty or port, or whilst vessel  200  is moored at a jetty or single-point moored. Vessel  200  may be a supply and/or receiving vessel and may be at anchor, single-point moored, moored to a jetty, moored to the other vessel engaged in the transfer operations and/or may be travelling in the same direction as the other vessel (sending or receiving as the case may be) during transfer operations.  FIG. 2A  is an illustrative embodiment of a retractable LNG cargo transfer bow manifold transfer system in a transfer position. In  FIG. 2A , two vessels  200  are both shown in a transfer position; one is a supply vessel supplying LNG and the other is a receiving vessel receiving LNG. For purposes of the example shown in  FIG. 2A , the two vessels  200  are interchangeable, since as shown in  FIG. 2A , both vessels  200  make use of retractable manifold  210  of illustrative embodiments. However, it is not a limitation of the invention that both vessels  200  make use of the invention described herein. In illustrative embodiments, one of the supply vessel, the receiving vessel or both of the supply vessel and the receiving vessel may make use of retractable manifold  210  of illustrative embodiments. The marine vessels  200  of  FIG. 2A  are in a tandem transfer configuration, with bow  220  of first vessel  200  facing stern  290  of second vessel  200 , and the transfer of LNG being between the vessels in either direction. As shown in  FIG. 2A , retractable manifold  210  is in a transfer position on both vessels  200 , extending out over and/or proximate bow  220  and/or stern  290  of the respective vessels  200 . LNG transfer conduit  275  may fluidly connect vessels  200  and allow for the transfer of LNG between vessels  200  when retractable manifolds  210  on vessels  200  are in the transfer position. 
         [0034]      FIGs. 2B-2D  illustrate a retractable LNG cargo transfer bow manifold of an illustrative embodiment. For ease of description and so as not to obscure the invention,  FIGS. 2B-2D  illustrate a retractable LNG cargo transfer bow manifold  210  on bow  220  of vessel  200 , but as those of skill in the art will appreciate and as illustrated in  FIG. 2A , illustrative embodiments may also equally be employed on stern  290 . For purposes of the LNG cargo transfer bow manifold  210  described herein, the supply and receiving vessels  200  will be arranged in a tandem configuration during transfer operations. 
         [0035]      FIG. 2B  shows an illustrative embodiment of retractable manifold  210  in an LNG cargo loading or unloading position at bow  220  of vessel  200 . Retractable manifold  210  may be above bow  220  or extend past bow  220  over the water when in a loading or offloading position, such that quick connect disconnect coupler  270  may be employed on LNG transfer conduit  275 , which LNG transfer conduit  275  may be flexible hoses, rigid piping and/or an articulated arm. Retractable manifold  210  may rest on partial, manifold deck  230 . which is positioned above vessel main deck  215  in  FIG. 2B . Pipe  240  may transfer LNG or another cryogenic liquid to cryogenic cargo tanks  285  onboard vessel  200 , for example in hull  245  of vessel  200 . Pipe  240  may be a flexible hose or articulated pipe and may connect to retractable manifold  210  only during, or in preparation for, loading or unloading operations. Similarly, pipe  240  may be disconnected from retractable manifold  210  when retractable manifold  210  is in a protected position and/or being moved into a protected position. In other embodiments, pipe  240  may have flexibility, the ability to move, pivot or stretch and/or with extra length to accommodate movement, of retractable manifold  210 . 
         [0036]    Manifold deck  230  may include railings  225  or tracks configured to allow retractable manifold  210  to actuate into a cargo transfer position at above, forward of and/or proximate to bow  220  on the one hand, and to a protected position aft of bow  220  on the other hand, as illustrated with aft arrows  250  shown in  FIG. 2B . LNG transfer conduit  275  may be disconnected prior to stowing (moving) the manifold to the at-sea position (i.e., prior to actuation, of retractable manifold  210  away from the transfer position and/or towards a protected position). In some embodiments, a hydraulic or pneumatic system (not shown and well known to those of skill in the art) may be employed to actuate retractable manifold  210 . In one embodiment, prior to arrival of the LNG vessel to the load or disport, the crew manually or in an automated fashion may reposition the LNG cargo bow retractable manifold  210  from the stowed, at-sea position (protected position) to the cargo transfer operational position and proceed to satisfy a series of pre-transfer operational and safety checks. While LNG transfer conduit  275  and/or pipe  240  are connected to retractable manifold  210 , retractable manifold  210  may function, as any bow loading or offloading manifold would function, as is well known to those of skill in the art of LNG STS transfer. After completion of cargo transfer, the LNG transfer conduit  275  and/or pipe  240  may be disconnected, and the crew of vessel  200  may reposition retractable manifold  210  from the cargo transfer operational position to the stowed-at-sea position (protected position) within the protective space dedicated, for this purpose. In the case of an emergency disconnection of the LNG transfer conduits  275  and/or pipe  240 , the disposition of the retractable manifold  210  may be addressed once mitigating action and response to the emergency condition has been satisfied. 
         [0037]    In addition to or instead of actuating aft of bow  220 , retractable manifold  210  may-actuate downwards from manifold deck  230  onto vessel deck  215  and/or manifold deck  230  itself may actuate downwards onto vessel main deck  215 , as illustrated in  FIG. 2C . In some embodiments, retractable manifold  210  and/or manifold deck  230  may first actuate downward towards vessel main deck  215 , and then subsequently actuate aft of bow  220  along vessel main deck  215 , or the ordering of actuation may be reversed. In the former instance, tracks  225  may be located on main deck  215 . In certain embodiments, retractable manifold  210  may actuate aft of how  220  and/or forward towards bow  220  on wheels, a track and/or railing  225 , such as protrusion or indentations on manifold deck  230  and/or main deck  215  on which retractable manifold  210  may slide, roll and/or move into and between appropriate positions. Once situated on vessel main deck  215 , when in the stowed, at-sea position, retractable manifold  210  may be both aft of bow  220  and lowered from partial manifold deck  230  in. a position protected from large waves that may strike bow  220  of vessel  200  during severe weather. As shown in  FIG. 2B and 2C , in some embodiments, the entirety of retractable manifold  210  and/or manifold deck  230  actuates into a protected (stowed) position. 
         [0038]    Supports  235  and/or pillar  280  may support retractable manifold  210  and/or manifold deck  230  when in an operational transfer (raised) position. Supports  235  and/or pillar  280  may retract, telescope, collapse and/or fold onto vessel main deck  215  and/or info hull  245  to allow retractable manifold  210  and/or manifold deck  230  to rest on vessel main deck  215 , as illustrated by lowering arrows  255  in  FIG. 2C . In some embodiments, pillar  280  may be hollow and allow pipe  240  to carry cargo to cargo tanks  285  onboard vessel  200 , for example within hull  245 .  FIG. 2D  illustrates retractable manifold  210  in a protected (stowed, at-sea) position. As shown in  FIG. 2D , retractable manifold  210  is aft of bow  220  and resting on vessel main deck  215 , such that wave  260  may not reach retractable manifold  210  or there is a significantly lower probability (as compared to the transfer position) that wave  260  will reach retractable manifold  210  and potentially cause damage or green water. The location of protected position may be based on the size of vessel  200  and/or the height of reasonably anticipated waves, arid should be a distance from bow  220  reasonably calculated to prevent “crashing” green seas from pummeling retractable manifold  210 . Transfer (loading and/or unloading) operations may not occur while retractable manifold  210  is in a protected position, but rather transfer of cargo may be deferred until the severe weather has passed. 
         [0039]      FIG. 3  illustrates breakwater  300  of an illustrative embodiment protecting retractable manifold  2 . 10  when, retractable manifold  210  is in a stowed position. Breakwater  300  may be removable or may be a permanent addition to bow  220 . Breakwater  300  may be arranged around the periphery of bow  220 , main deck  215  and/or bow manifold  210  and provide additional protection from particularly large or forceful wave  260 . In instances where breakwater  300  is not removable, retractable manifold  210  may actuate above and/or over breakwater  300  when in a loading or offloading position. In some embodiments, breakwater  300  is not necessary. 
         [0040]      FIGs. 4A and 4B  illustrate an alternative embodiment in which retractable manifold  210  retracts not onto vessel, main deck  215 , but into hull  245  when in a protected, at-sea and/or stowed position. As shown in  FIG. 4A , retractable manifold  210  may be in transfer position  400  or hull position  400 ′. Transfer position  400  may be raised above vessel main deck  215  and/or proximate bow  220 . Transfer position.  400  of retractable manifold  210  should be at a sufficient height above vessel main deck  215  and bow  220  bulwarks to allow a clear view of and unrestricted movement of the LNG transfer conduits  275  (shown, in  FIGs. 2A and 2B ). Retractable bow manifold  210  is shown in. protected hull position  400 ′ in  FIG. 4B . As illustrated in  FIG. 4B , barrier  265  may open to allow retractable manifold  210  to actuate between transfer position  400  and hull position  400 ′. Barrier  265  may be a door, moveable wall, hatch or recession in vessel main deck  215  and/or built into vessel main deck  215 . Once retractable manifold  210  Is in protected hull position  400 ′, barrier  265  may close over retractable manifold  210 , protecting retractable manifold  210  from wave  260 . Barrier  265  may be manually, hydraulically or pneumatically actuated. Local and/or remote control may be employed, along with CCTV, closed door sensors and/or interlocks necessary to prevent unauthorized operation and making to sea with the system improperly secured. 
         [0041]      FIGs. 5A and 5B  illustrate a further embodiment of a retractable manifold. As shown in  FIG. 5A , retractable manifold  210  resides below vessel main deck  215 . Retractable manifold  210  may be situated in a position forward of how  220  during loading or offloading operations, for example as illustrated in  FIG. 5A . During severe weather and/or when retractable manifold  210  is not in use, retractable manifold  210  may retract inside (below main deck  215 ) vessel  200  and/or hull  245 , for example as illustrated in  FIG. 5B . Although retractable manifold  210  may actuate forward of bow  220  or aft of how  220  and within vessel  200 , there is no need for retractable manifold  210  to actuate upwards or downwards in the embodiment of  FIGs. 5A and 5B . Shield  500  may be in an open position to allow retractable bow manifold  210  to actuate as shown in  FIG. 5A . or may be in a closed position to protect retractable manifold  210 , as shown in  FIG. 5B . In some embodiments, the entirety of retractable manifold  210  may retract inside vessel  200  when not conducting transfer operations. 
         [0042]    In most cases, due to the cargo tank  285  containment design of LNG vessels, the STS transfer of LNG should take place in a fairly benign metocean environment or the LNG vessel may be subject to sloshing cargo impacts on the walls of the cargo containment system. These impacts can and have been known to cause cargo containment failures. In all cases of when LNG vessel  200  is steaming between, load and disport locations, the cargo system along with all other aspects of vessel  200  are maintained in a manner which is commonly characterized as in compliance with, the practices of good seamanship. In instances of LNG vessel  200  steaming “at sea” the retractable manifold  210  may be stowed away into the protected location to prevent, in the case of severe weather where LNG vessel  200  is likely to ship green seas and/or push bow  220  underwater due to excessive wave height, damage to the system, components including cryogenic valves, piping, insulation, process instrumentation, insulation and safety systems which do not exist on tankers with conventional loading or offloading units. 
         [0043]    Thus, a retractable LNG cargo transfer bow manifold for tandem marine cargo transfers has been described herein. Illustrative embodiments provide a cargo transfer bow manifold onboard a marine vessel that is retractable into a protected position while the vessel is underway and/or not conducting transfer operations. When in the protected position, the LNG cargo transfer bow manifold may be less susceptible to damage from severe weather and/or damage from large waves. The retractable bow manifold may be moved from the protected position into a transfer position in preparation for transfer operations and may remain in the transfer position during transfer operations. 
         [0044]    Further modifications and alternative embodiments of various aspects of the invention may be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims. In addition, it is to be understood that features described herein independently may, in certain embodiments, be combined.