SUPPORT SYSTEMS FOR CONTAINERS ON-BOARD A MARINE VESSEL CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U. S. Provisional Application 60/459,204, filed March 31,2003.

FIELD OF THE INVENTION [0002] This invention relates to support systems for vertical cylindrical containers on-board marine vessels and in storage facilities and, more particularly, to support systems for vertical cylindrical containers in cryogenic temperature service.

BACKGROUND OF THE INVENTION [0003] Various terms are defined in the following specification. For convenience, a Glossary of terms is provided herein, immediately preceding the claims.

[0004] United States Patent Number 6,085, 528 (the"PLNG Patent"), entitled"Improved System for Processing, Storing, and Transporting Liquefied Natural Gas", and having corresponding International Publication Number WO 98/59085, describes containers and transportation vessels for storage and marine transportation of pressurized liquefied natural gas (PLNG) at a pressure in the broad range of about 1035 kPa (150 psia) to about 7590 kPa (1100 psia) and at a temperature in the broad range of about-123°C (-190°F) to about-62°C (-80°F). These containers can be cylindrical in shape.

Further, containers described in the PLNG Patent are constructed from ultra-high strength, low alloy steels containing less than 9 wt% nickel and having tensile strengths greater than 830 MPa (120 ksi) and DBTTs lower than about-73°C (-100°F), i. e. , from HSLT Steels. DBTT, or Ductile-to-Brittle Transition Temperature, is a measure of toughness, as defined in the Glossary. The PLNG Patent is hereby incorporated herein by reference.

Containers as described and claimed in the PLNG Patent will be referred to herein as HSLT PLNG Containers.

[0005] Containers that are used in cryogenic temperature service on-board <BR> <BR> marine vessels (e. g. , ships, barges, etc. ) require support systems capable of appropriately supporting and stabilizing the loaded containers when subjected to motion in the marine environment. In particular, containers as described in the aforementioned PLNG Patent, which discusses containers used in pressurized, cryogenic temperature service, require support systems and methods capable of minimizing fatigue cracking that would tend to occur due to the combined effects of: (i) thermal and pressure cycling of the cryogenic temperature fluid cargo of the containers, (ii) global ship motions, i. e., roll, <BR> <BR> heave, and pitch motions, and (iii) global hull deflections, i. e. , relative motions between support connections.

[0006] Typical support designs for vertical cylindrical containers use fillet welds to attach a support skirt to a cylindrical container. For reference, referring to FIG. 1A and FIG. 1 D, a typical fillet weld 111 is shown connecting a support skirt 112 to wall 113 of a cylindrical container (e. g. , cylindrical container 110 as shown in FIG. 1A). With supports of this type on-board a marine vessel, accelerations imparted to the cylindrical container due to motions of the marine vessel manifest themselves as cyclic stresses, and cyclic stresses at geometric discontinuities, such as fillet welds, can increase the chance of fatigue cracking through the walls of the cylindrical container.

These cracks can be difficult to detect, particularly in the immediate area of the fillet weld and, therefore, may grow to unacceptable sizes prior to detection. The use of high strength steels in a cylindrical container design tends to exacerbate the problem with cracking and crack propagation, since high strength steels have higher design stresses when compared with typical steels in equivalent service.

[0007] Conventional land-based supports systems typically consist of a bottom support skirt only. This arrangement is inadequate for cylindrical containers installed on ocean-going vessels. Inertial forces due to ship motions induce large stresses and deflections, which make a bottom-support-only system insufficient. Furthermore, the skirt poses an additional problem at the connection between the skirt and the ship inner bottom concerning stress concentrations and thermal conductions. At this connection, a skirt with circular cross section must mate up with a surface typically reinforced with longitudinal and transverse girders. This criss-cross pattern of reinforcement is optimal for ship structure stiffening, but high peak stress concentrations occur at the skirt/ship inner bottom connection due to the dissimilar stiffness patterns of circular and rectilinear arrangements. In addition, ship steel typically cannot handle the low temperatures of the cryogenic cargo, and thermal barriers must be designed and installed to protect the integrity of the ship structure. Additional storage tank background concerning mostly spherical tanks can be found in US 3,677, 021 to Bognaes et al., Patent Abstracts of Japan, vol. 0070, no. 74 (M-203) of JP 58 000699 to Nippon Kokan KK, US 4,181, 235 to Baysinger, US 4,104, 887 to Kvamsdal, US 4,133, 094 to Stafford, US 4,141, 465 to Tonnessen, US 3,841, 269 to Urruela, and US 4,672, 906 to Asai.

[0008] Currently available supports are typically not suitable for cylindrical containers used for transporting PLNG or other pressurized, cryogenic temperature fluids. It would be advantageous to have improved support systems and methods for supporting cylindrical containers used for transporting PLNG and other cryogenic temperature fluids.

[0009] Therefore, an object of this invention is to provide systems and methods for supporting cylindrical containers used for transporting PLNG and other cryogenic temperature fluids, which systems provide, for the containers being supported, a substantially lower risk of fatigue cracking than is provided by current fillet weld support systems. Other objects of this invention will be made apparent by the following description of the invention.

SUMMARY OF THE INVENTION [0010] Consistent with the above-stated objects, support systems are provided for supporting cylindrical containers in a containment structure, such as a marine vessel or a storage facility. The following summary will describe several bottom support systems and several top support systems, which may be used individually or in pairs as appropriate. For a particular application, any bottom support system may be used in conjunction with any top support system, thus providing a support system designer with flexibility. Each arrangement must be individually verified for each particular application.

Since heat loss is an important issue in cryogenic fluid containment, an innovative thermal break system is also provided.

[0011] In one embodiment of this invention, a bottom support system for supporting a cylindrical container with a top head and a bottom head in a containment structure comprises a bottom support adapted to support said cylindrical container, said bottom support having a base portion and a base- support portion attached to said base portion. The base-support portion of the bottom support preferably has a top edge and a bottom edge, the bottom edge being either in contact with the containment structure or in contact with an intermediate material or materials that is/are in contact with the containment structure. The base portion of the bottom support preferably has a radius of curvature that is substantially equal to or greater than the radius of curvature of the bottom head of the cylindrical container and is preferably attached to the base-support portion. An advantage of the present invention is that fillet welds are not used to connect the bottom support directly to the container. Avoiding such fillet welds is preferable for many reasons, including without limitation: (i) a structural discontinuity is avoided, (ii) weld flaw detection capability is improved over the standard fillet weld design, (iii) imposition of a heat-affected-zone (HAZ) directly onto the container during welding, which HAZ would tend to cause embrittling of steel in the container, is avoided, and (iv) residual stresses on the container due to welding are avoided. Therefore, a support system according to this invention for supporting a cylindrical container preferably comprises a bottom support adapted to support said cylindrical container without being welded or otherwise attached to said cylindrical container, said bottom support having a base portion and a base-support portion attached to said base portion.

[0012] In another embodiment, an integrated bottom support system is provided for the bottom support of containers used in fluid delivery ships and terminal fluid storage barges. Specifically, such a support system according to this invention is structurally integrated with the bottom head (s) of the container (s) being supported. The integration is accomplished in such a way that stresses from the container (s), including gravity-induced, inertial-induced, and vibration-induced stresses, are transmitted directly to the support system.

Additionally, the support system is structurally connected to the underlying ship (or barge) structure, such that stresses in the support system are further carried into the hull inner-bottom structure.

[0013] In another embodiment, a bottom support is arranged in a cruciform or web pattern. This arrangement reduces stresses at the bottom [0014] support/ship interface and allows use of two-sided full penetration welds. In order to minimize heat loss of cargo and prevent sub cooling of ship steel, a thermal break system is provided that may be utilized in conjunction with each bottom support system. The thermal break system avoids direct connection between the bottom support and the ship structure through a system of footings and grooves, which are placed in compression. An insulating material such as wood or ceramic is placed between the feet and the grooves to minimize heat loss.

[0015] In another embodiment, a top support system is provided that comprises a truss connecting the container top and the ship structure through pinned connections. The pinned connections permit vertical movement of the container due to pressure and thermal expansion and dilation, but prevent lateral movement due to overturning moments.

[0016] In an alternative embodiment, a top support system comprises a load bracket affixed to the ship structure and several load collars affixed to the nozzle on the top head of a container. Two or more load surfaces are attached to the load collars ; the load surfaces slide within the load bracket permitting vertical movement of the container due to pressure and thermal expansion and dilation, but preventing lateral movement due to overturning moments.

[0017] In another embodiment of this invention, a top support system comprises a load bracket affixed to the marine vessel structure and a load frame affixed to the top head of a container. The load frame comprises a support ring with several reinforcing load collars and a load surface. The load bracket slides within the load frame against the load surface permitting vertical movement of the container due to pressure and thermal expansion and dilation, but preventing lateral movement due to overturning moments.

DESCRIPTION OF THE DRAWINGS [0018] The advantages of the present invention will be better understood by referring to the following detailed description and the attached drawings in which: [0019] FIG. 1A (PRIOR ART) is a sketch showing a cylindrical container supported by a standard fillet weld support system, which container could otherwise be supported by a support system according to this invention; [0020] FIG. 1 B (PRIOR ART) is an enlarged view of the hemispherical- shaped top head of the cylindrical container shown in FIG. 1A ; [0021] FIG. 1 C (PRIOR ART) is an enlarged view of the hemispherical- shaped bottom head of the cylindrical container shown in FIG. 1A; [0022] FIG. 1 D (PRIOR ART) is an enlarged view of the fillet weld of the standard fillet weld support system shown in FIG. 1A; [0023] FIG. 2A illustrates an embodiment of a bottom support of a support system according to this invention, said bottom support having a base- support portion comprising a skirt and cup; [0024] FIG. 2B is a cross-sectional view showing an embodiment of how the connection is made between the skirted base-support portion and the substantially hemispherical-shaped base portion of a bottom support according to this invention, such as the bottom support shown in FIG. 2A; [0025] FIG. 2C is a cross sectional view of a preferred orientation of a container bottom head relative to the base portion of a bottom support according to this invention, such as the bottom support shown in FIG. 2A; [0026] FIG. 3A is a sketch showing a cutaway view of a container being supported by one embodiment of a system according to this invention comprising an integrated bottom support; [0027] FIG. 3B is a sketch showing the individual parts of FIG. 3A; [0028] FIG. 3C is a sketch of the container shown in FIG. 3A; [0029] FIG. 3D is an enlarged view of a portion of FIG. 3A, showing various joints; [0030] FIG. 4 illustrates an embodiment of a bottom support of a support system according to this invention, said bottom support having a base- support portion comprising webs; [0031] FIG. 5A illustrates an exploded view of an embodiment of slots for securing a bottom support, such as the skirt of the bottom support shown in FIG. 2A or the webs of the bottom support shown in FIG. 4; [0032] FIG. 5B illustrates an embodiment of slots for securing a bottom support, such as the skirt of the bottom support shown in FIG. 2A or the webs of the bottom support shown in FIG. 4; [0033] FIG. 6A illustrates one embodiment of a top support of a support system according to this invention comprising a pinned truss system; [0034] FIG. 6B illustrates one embodiment of components of a pad eye attachment suitable for use in a top support of a support system according to this invention; [0035] FIG. 6C illustrates an embodiment of a pad eye comprised of the components shown in FIG. 6B; [0036] FIG. 7 is a sketch showing a container being supported by one embodiment of a top support system according to this invention comprising a load collar system; and [0037] FIG. 8 is a sketch showing of a container being supported by one embodiment of a top support system according to this invention comprising a load frame system.

[0038] While the invention will be described in connection with its preferred embodiments, it will be understood that the invention is not limited thereto.

On the contrary, the invention is intended to cover all alternatives, modifications, and equivalents, which may be included within the spirit and scope of the present disclosure, as, defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION [0039] The present invention relates to support systems for cylindrical containers in a containment structure, such as a marine vessel or a storage facility. Support systems of this invention are described in greater detail herein as used on a marine vessel; however, this is not intended to limit the scope of this invention.

[0040] In one embodiment, support systems according to this invention comprise a bottom support system. The bottom support system comprises a base portion and a base-support portion and is adapted to support a cylindrical container and its load. Preferably, the base portion has a radius of curvature that is substantially equal to or greater than the radius of curvature of the bottom head of the container to be supported. In one embodiment of this invention, both the bottom head of the container and the base portion of the bottom support are substantially hemispherical-shaped. A layer of compliant material is preferably placed between the outer surface of the bottom head of the container and the inner surface of the base portion of the bottom support to substantially prevent fretting of the bottom head of the container or of the base portion of the bottom support. The layer of compliant material may also serve to assist in insulating cryogenic temperature fluids in the container from the environment, including without limitation from the hull of the marine vessel, depending on the arrangement of ship insulation. The curvatures of the base portion of the bottom support and of the bottom head of the container are likely to be out of round by some degree, due to manufacturing limitations and operating conditions of the system. The layer of compliant material acts to limit the tendency for bottom head/base portion contact at the interface, and to distribute the contact pressure across a greater surface area, than it would be distributed without the layer of compliant material. For example, without limiting this invention, the compliant layer may be (i) one or more layers of a single material such as wood, (ii) a plurality of layers of different materials, such as wood with a coating of a waxy, opaque material, such as polytetrafluoroethylene, sold under the trademark TEFLON, or (iii) an engineered layer such as steel wool or wire mesh.

[0041] For reference purposes, FIG. 1A illustrates a representative cylindrical container 110 suitable for being supported by a conventional support system. Container 110 comprises a hemispherical-shaped top head 114, a cylindrical body 116, and a hemispherical-shaped bottom head 115.

Typical nozzles, piping, and instrumentation peripherals, as are familiar to those skilled in the art, are not shown. FIG. 1 B is an enlarged view 114'of top head 114 shown in FIG. 1A; and FIG. 1C is an enlarged view 115'of bottom head 115 shown in FIG. 1A. The hemispherical shape of the top and bottom heads 114 and 115 is not a limitation to this invention, as containers having semi-elliptical top and/or bottom heads or other shaped top and bottom heads may also be supported by support systems according to this invention.

[0042] Referring to FIG. 2A, in one embodiment of this invention, bottom support 10 with a skirted base-support portion comprises base portion 12 having lip portion 11 and being attached to first edge 14 of skirt 16. Second edge 18 of skirt 16 is adapted to be attached preferably to the inner bottom of a marine vessel (not shown in FIG. 2A) for holding and/or transporting the cylindrical container to be supported. The base portion 12/skirt 16 combination of skirted bottom support 10 acts to transfer the load carried by the container to the inner bottom of the marine vessel. Base portion 12 can be attached to first edge 14 of skirt 16 in any conventional manner, for example, without thereby limiting this invention, by welding. The hemispherical shape of base portion 12 is not intended as a limitation to this invention, as the shape of base portion 12 in support systems according to this invention can be adapted to support containers having semi-elliptical shaped bottom heads or other shaped bottom heads.

[0043] Referring now to FIG. 2B, in another embodiment, lip portion 11'of base portion 12'extends beyond the radius of skirt 16', providing a reduction in peak contact stresses. Referring again to FIG. 2A, similarly, second edge 18 of skirt 16 can be attached to the inner bottom of a marine vessel in any conventional manner, for example, without thereby limiting this invention, by welding. Additional structure (not shown in FIG. 2A), e. g. , footings, can be placed at the intersection of second edge 18 and the inner bottom of the marine vessel to assist in evenly distributing the load. An advantage to the embodiment of skirted bottom support 10 illustrated in FIG. 2A is that a skirt <BR> <BR> support is utilized in such a manner that the skirt, e. g. , skirt 16, is not welded to the container. Instead, skirt 16 is attached to base portion 12 of skirted bottom support 10, which supports the container and its load. The stress concentration of a fillet weld attaching a support skirt to a container is avoided, thus reducing stress concentration points for crack propagation in the container while improving crack detection capability. Access ways and auxiliary piping that connect to or pass through bottom support 10, as will be familiar to those skilled in the art, are not shown in the FiGs.

[0044] The desired dimensions, including wall thickness, of base portion 12 of skirted bottom support 10 depends on the service and loads to be borne by bottom support 10. In a preferred embodiment of this invention, base portion 12 of bottom support 10 does not extend all the way to the edge of the bottom head of the container being supported. As illustrated by FIG. 2C, in one embodiment of this invention the base portion 12"of a bottom support extends at an angle 141 below the plane containing edge 37 of container bottom head 115". Thus, not all of container bottom head 115"is in contact with the base portion 12". In one embodiment, angle 141 is between 20 and 30 degrees. Thus, the diameter of skirt 16"of a bottom support according to this invention is typically less than the diameter of the container being supported, e. g. , container 110 of FIG. 1A.

[0045] In another embodiment of a support system according to this invention, referring now to FIG. 3C, a system is provided for supporting a substantially cylindrical-shaped container 62, comprising container shell 70, including top head 71, and a container bottom head 74, on-board a marine vessel. Referring now to FIG. 3A, in one embodiment said system comprises a connector 78, support skirt 76, and vessel inner bottom 80 of said marine vessel. Referring now to FIG. 3B, said container bottom head 74 comprises top edge 82 and substantially hemispherical-shaped bottom portion 84. Said support skirt 76 is substantially cylindrical-shaped and has a skirt open top side 86, a skirt top edge 87, and a skirt bottom side 88. Said connector 78 comprises (i) connector top edge 92 that is attached to said container shell lower edge 73; (ii) a substantially cylindrical-shaped connector skirt 96 having a skirt edge 95 that is attached to said skirt top edge 87; and (iii) a substantially inwardly-oriented attachment portion 98 having an attachment edge 97 that is attached to said top edge 82 of said container bottom head 74. Said container bottom head 74 is located within said skirt open top side 86. Said skirt bottom side 88 is preferably attached to said vessel inner bottom 80 using a thermal break design such as described herein. The advantage of the integrated bottom support is that fillet welds may be completely avoided and full penetration butt welds may be exclusively utilized.

Full penetration butt welds provide a higher level of mechanical integrity with regard to fatigue issues and have higher inspectability than traditional fillet welded skirts.

[0046] Throughout the remainder of this description, unless otherwise specified, any reference to container 62 is meant to be a reference to a HSLT PLNG Container. Referring now to FIG. 3A through FIG. 3C, a support system according to this invention is integrated with the bottom head, e. g., container bottom head 74, of the container to be supported, e. g. , container 62. Since the support for container 62 is integrated into container bottom head 74, the support can sustain bending moments, allowing containers, such as container 62, to be installed into marine vessels without the need for temporary top supports. Preferably, given appropriate stress and fatigue analyses, any associated top support design load may be reduced in magnitude. This will allow for use of a lighter top support structure that can be integrated into the top deck of the marine vessel in such as way as to achieve efficiency of construction and low cost, as will be familiar to those skilled in the art.

[0047] To attach support skirt 76 to container 62, in one embodiment of this invention a connector 78 is preferably forged of a suitable alternative <BR> <BR> steel, i. e. , a steel that is not a HSLT Steel, and machined and integrated with container 62 as the junction of container shell 70, container bottom head 74, and support skirt 76. For example, referring now to FIG. 3D, a cut-away view of connector 78, it can be seen that connector top edge 92 is attached to container shell lower edge 73 at joint 321, attachment edge 97 is attached to top edge 82 of said container bottom 74 at joint 371, and skirt edge 95 is attached to skirt top edge 87 at joint 351. In one embodiment, all of container bottom head 74 and/or top head 71 is/are fabricated from the suitable alternative steel, rather than being partially fabricated from HSLT Steel.

Depending on material strength and weight, material relative costs, labor costs, and welding speed, etc. , as will be familiar to those skilled in the art, both container heads may be fabricated from the suitable alternative steel.

For example, said suitable alternative steel might be a high-nickel-content carbon steel alloy or any other steel having adequate strength and toughness for the application.

[0048] When a support system as illustrated in FIG. 3A through FIG. 3D is used in marine vessels transporting PLNG in one or more HSLT PLNG Containers, any concerns about long-term reliability and fatigue of PLNG vent piping (not shown in the FIGs) at the top of the HSLT PLNG Containers, which could potentially be caused by deflections expected at the tops of the HSLT PLNG Containers, can be effectively eliminated by top supports that react a portion of the container loads, as will be familiar to those skilled in the art. The bottom support system according to this invention would allow said top supports to be designed with minimal size and weight and to be constructed efficiently in a shipyard automated fabrication environment.

[0049] FIG. 4 illustrates one embodiment of a bottom support according to this invention having a webbed base-support portion. Web bottom support 20 comprises webs 26. Container bottom head 22 is attached to first edge 24 of webs 26. While FIG. 4 is not intended to limit this invention, embodiments of this invention such as the embodiment shown in FIG. 4 comprise preferably four webs 26. The load exerted by a container supported by web bottom support 20 is passed through webs 26 to the inner bottom of the marine vessel. Bottom head 22 can be attached to first edge 24 of webs 26 in any conventional manner, for example, without limiting this invention, by welding.

In order to substantially prevent buckling, orthogonal webs 26 are preferably augmented by flanges 21, at their outer vertical edges and are further augmented by stiffeners 23. Brackets 32 at the rim 36 of bottom head 22 help to prevent buckling and to distribute contact pressure between the bottom head 22 of the container being supported and webs 26. The hemispherical shape of bottom head 22 as shown in FIG. 4 is not intended as a limitation to this invention, as the shape of bottom head 22 can be semi- elliptical shaped or another shape.

[0050] The bottom support illustrated in FIG. 4 may also include a cruciform 35. In one embodiment, cruciform 35 is integrated with bottom head 22 and preferably aligned with webs 26, as shown. In another embodiment, not illustrated in the FIGs, a cruciform, such as cruciform 35, in integrated within the bottom head 22 of a container which rests on a cup or base support that is integrated with webs 26.

[0051] An advantage of the embodiment of web bottom support 20 illustrated in FIG. 4 is that bottom support 20 is designed to be situated in a marine vessel in such a manner that webs 26 line up with the marine vessel structure beneath the inner bottom floor and, thus, generally no additional supporting structure to distribute the container load is required. In situations in which additional supporting structure may be desirable, those skilled in the art have the skills and knowledge needed to design and construct such additional supporting structure. Another advantage is that the welds connecting webs 26 to container bottom head 22 may be a two-sided full penetration weld as opposed to the fillet welds used in traditional skirt arrangements. A two-sided full penetration weld will provide a higher mechanical integrity concerning fatigue issues and is more inspectable than a fillet weld.

[0052] FIG. 5A and FIG. 5B are cross sectional views of two particular, non-limiting embodiments of brackets useful in a support system according to <BR> <BR> this invention. Referring to FIG. 5A, a footing, e. g. , footing 29, is attached to at least one support 260 at support edge 250 and two or more brackets 28 are provided, at least one of said brackets 28 being provided with an upper flange 288. Support 260 may be, for example without limiting this invention, a web 26 as shown in FIG. 4 or a skirt 76 as shown in FIG. 3A. Support 260 is positioned within brackets 28 such that upper flange 288 restricts vertical movement of footing 29, and thus, of support 260. Thereby, bracket 28 is adapted to prevent vertical movement of support 260. Referring now to FIG.

5B, insulating material 311 placed under footing 29', between footing 29'and brackets 28', between support 260'and brackets 28', and between support 260'and upper flange 288'; and insulating material 31 placed around otherwise exposed surfaces of brackets 28'and upper flange 288', both reduce thermal heat leak from the inner-bottom of the marine vessel or other containment structure (neither of which is shown in the FIGs) to the bottom support by primarily eliminating metal to metal contact. Insulating material 311 comprises any suitable insulating material, preferably an insulating material capable of bearing the load imposed upon it. For example, without thereby limiting this invention, insulating material 311 can comprise concrete, ceramic, wood, or cellular structural material comprised of rigid cellulated slabs, blocks, lumps, or the like sold under the trademark FOAMGLAS.

Insulating material 31 comprises any suitable insulating material. For example without thereby limiting this invention, insulating material 31 can comprise polystyrene, polyurethane, or PERLITE. Preferably, in the design of a bottom support according to this invention, slippage is allowed to ensure that thermal expansion and contraction can occur; however designs which restrict this movement by welding, chocking or bolting the bottom support to the inner-bottom of a marine vessel are within the scope of this invention. In addition, the types of footing arrangements shown in FIG. 5A and FIG. 5B can be used to secure bottom support systems described herein, including the traditional fillet welded skirt FIG. 1, cup and skirt support FIG. 2, integrated bottom support FIG. 3, and webbed bottom support FIG. 4, and with other bottom support systems that may be or become available, as will be familiar to those skilled in the art.

[0053] In bottom supports according to this invention, some type of compliant layer (not shown in the FIGs) is preferably provided for the primary purpose of preventing fretting of the container bottom head 115 (FIG. 1A), and of base portion 12 of support 10 (FIG. 2A) or of container bottom head 22 of support 20 (FIG. 4). The purpose of such a compliant layer is to minimize bottom head/base portion contact and the resulting localized stresses. In one embodiment of this invention, the compliant layer is silicon rubber, which for certain grades may typically be used at temperatures as low as about-115°C (-175°F). Other suitable compliant layer materials, without limiting this invention, may be (i) one or more layers of a single material such as wood, (ii) a plurality of layers of different materials, such as wood with a coating of a waxy, opaque material, such as polytetrafluoroethylene, sold under the trademark TEFLON, or (iii) an engineered layer such as steel wool or wire mesh.

[0054] A top support according to this invention is adapted to provide rotational and translational stability to the container being supported. In one embodiment of this invention, one or more support arms, or keys, connect the top head of the container being supported to the marine vessel. Referring now to FIG. 6A, in a preferred embodiment of this invention, one or more support arms 51 connect the top head 114"of a container, such as container 110 illustrated in FIG. 1A, to the structure of a marine vessel at pivot location 58 via connection to nozzle 52. Each support arm 51 preferably is installed in such a manner that it may move in the vertical plane containing it to <BR> <BR> accommodate vertical thermal shrinkage of the container, e. g. , by connection of support arm 51 at pivot locations 53 and 58. This vertical range of motion can be obtained, for example, by using a pinned connection at pivot locations 53 and 58, or by other means as will be familiar to those skilled in the art.

The connection of support arms 51 to nozzle 52 or top head 114"and to the marine vessel structure is preferably designed to resist overturning moments and rotation about the vertical axis of the container.

[0055] In one embodiment of this invention, the connection at pivot locations 53 and 58 is via pad eye attachments. Referring now to FIG. 6B, one or more pad eye attachments 67 and 69 for use in this invention are illustrated. Each of pad eye attachments 67 is adapted to be connected to nozzle connector section 55 at pivot location 53 (see FIG. 6A). Referring again to FIG. 6B, pin 66 is adapted to be inserted through pad eyes 68 of pad eye attachments 67 and 69 and is adapted to rotate therethrough. Pin 66 my be covered by a bushing or other insulation material (not shown in the FIGs).

Mated pad eye attachments 67 and 69 are adapted to be attached to a support arm, e. g. , support arm 51 as shown in FIG. 6A. Referring now to FIG. 6C, pin 66'is inserted through pad eyes 68'of pad eye attachments 67' and 69'and is adapted to rotate therethrough. Pin 66'is secured in any appropriate manner, as will be familiar to one skilled in the art. In one embodiment of this invention, support arms 51 are made of tubulars that are connected and trussed together to provide strength. The connections of support arms 51 to the marine vessel structure preferably allow for movement caused by contraction of the container during cool-down and compensate for relative motion between the top and bottom supports. This can be accomplished by a pinned connection, similar to pad eye attachments 67 and 69, with pin 66 at the point of intersection of the support arms 51 to the structure to the marine vessel (not shown in the FIGs). Pinned connections 53 and 58 (as shown in FIG. 6A) may be outfitted with a insulative bushing made of ROULON or a similar material to minimize heat conduction from the ship structure into the container.

[0056] Referring again to FIG. 6A, the nozzle connector section 55, i. e., the section of nozzle 52 in the vicinity of where support arms 51 attach to nozzle 52, is preferably reinforced to withstand imposed stresses. In the embodiment shown in FIG. 6A, cone 60 connects nozzle 52 to container top head 114"via welded container top portion interface 57 between cone 60 and container top head 114"and welded nozzle interface 56 between cone 60 and nozzle 52. Cone 60 is advantageous in that if nozzle 52 was connected <BR> <BR> directly to the container being supported, e. g. , at the top of top head 114" (via welding for steel containers, for example), accelerations from marine vessel motions may result in excessive stresses. The wall thickness of cone 60 is preferably substantially equal to the wall thickness of nozzle 52 at nozzle interface 56, and is preferably substantially equal to the thickness of container top head 114"at container top portion interface 57. The conical geometry of top head 114"is not intended to limit this invention; other top head designs may be used with this invention including hemispherical and semi-elliptical.

[0057] In general, materials suitable for low temperature operating conditions to which the components will be subjected is preferably used for constructing components of the top support of a support system according to this invention. For example, a 3-1/2 wt percent nickel or a stainless steel may be used, but is not required. By using suitable insulation materials and, thus, providing a thermal break, conventional carbon steels may be used for construction of the support arms (e. g., tubular) of the top support of a support system of this invention. Pad eye attachments and associated connecting pins are preferably constructed of materials suitable for low temperature operating conditions to which these components will be subjected.

[0058] The design parameters preferably taken into account for support systems according to this invention include global ship motion parameters of roll, pitch, and heave for a given ship, for 30 years in north Atlantic sea states.

[0059] Referring now to FIG. 7, in another embodiment of this invention, a container having top head 271 may be supported using a load bracket 225 affixed to top deck 290 of a marine vessel (not shown in the FIG.). Access nozzle 222 of top head 271 is fitted with a plurality of reinforcing load collars, e. g. , 227a and 227b, having load bearing surfaces 228a and 228b. Load collars 227a and 227b slide within load bracket 225 against load bearing surfaces 228a and 228b providing free vertical movement to accommodate thermal and pressure expansions and dilations, while preventing lateral movement and overturning moments. Load bearing surfaces 228a and 228b may be layered with a thermal layer of insulating material (not shown in the FIG.) to reduce heat leak. Insulation 226 may be placed between load bracket 225 and top deck 290. Access nozzle 222 may include vapor pipe 221.

[0060] In an alternative embodiment of a support system according to this invention, referring now to FIG. 8, a top support system is provided for supporting a substantially cylindrical-shaped container comprising top head 171 on-board a marine vessel. In this embodiment, top head 171 may include access port 122 and vapor outlet 123 to allow venting of vapor from <BR> <BR> cargo 121 of, e. g. , a liquefied gas. Top head 171 is supported at the top by a top support system comprising load frame 125 and load bracket 124. Load frame 125 comprises load frame ring 125a, which may be constructed of steel plates reinforced with two or more collars, such as collars 150a and 150b.

Load frame ring 125a as illustrated in FIG. 8 is shown for purposes of example only and should not be interpreted as limiting the scope of this invention. A skilled engineer designing a load frame 125 for a particular application may design load frame ring 125a to be the appropriate size, <BR> <BR> shape, etc. , as needed to suit the application. Load frame ring 125a is fitted with two or more load bearing surfaces, such as load bearing surfaces 127a and 127b. Load frame 125 may be welded to top head 171 and joint 135 is preferably a two-sided full penetration weld. Preferably, the thicknesses of the load frame 125 and top head 171 are optimized to share stresses efficiently. Load bracket 124 is preferably affixed to top deck 190 of a marine vessel (not shown in FIG. 8) and provides external surface 147. Preferably, load frame 125 slides on external surface 147 of load bracket 124 permitting vertical motion while preventing lateral motion. Load bracket 124 may include insulation (not shown in FIG. 8), for example, a ROULON or other TEFLON pad may be mounted to the load bearing surface of load bracket 124 and act as a thermal break protecting the vessel's steel. Thermal break materials may include, without limitation, any of the insulating materials described herein.

[0061] A support system according to this invention may be used for the support of HSLT PLNG Containers within a cold box, i. e. , at cryogenic temperatures, in a marine vessel, as will be familiar to those skilled in the art.

A support system according to this invention provides an integral structural support system for a cryogenic pressure container (s) fabricated of HSLT steel and that are subject to motions that induce large and cyclic loads and moments on that support. A support system according to this invention transfers these loads, not to a foundation on the ground, but to a steel double bottom structure within the ship.

[0062] As will be familiar to those skilled in the art, fracture mechanics and non-destructive evaluation of limiting flaw size are preferably used for the design of welds connecting container shells to support systems as discussed herein. Additionally, as will be familiar to those skilled in the art, ship motions analyses are preferably used to determine the inertia loads acting on containers that must be carried by support systems and structural and stress analyses are preferably used for design of containers, support systems and for the ship structure. As an example, 0. 5g lateral load and 1.5g vertical load may be applied to the center of gravity of the container and the reaction forces may be calculated at the top and bottom supports. These reaction forces may be used to compute the stresses in the supports. The stresses may then be used to select appropriate materials and design appropriate sizes and thicknesses of components as will be familiar to those skilled in the art. As an example, the welded connections between components may use such welding techniques as shielded metal arc welding, or other such welding process as will be familiar to those skilled in the art.

[0063] Advantages of this invention include, but are not limited to: (a) lower support system fabrication cost, (b) lower cost for installing containers in the marine vessel, (c) higher mechanical integrity of the support systems by eliminating the use of fillet welds on the container and minimizing the stress concentrations at the ship-bottom support interface, (d) minimizing container deflections through the use of top supports, and (e) minimizing heat leaks with a system of thermal break arrangements.

[0064] Although this invention is well suited for supporting HSLT steel and other steel containers containing pressurized, cryogenic temperature fluids on-board a marine vessel, it is not limited thereto; rather, this invention, including modifications hereof not specifically described herein, is suitable for supporting other containers containing other fluids or substances on-board marine vessels or at storage sites. For example, a support system according to this invention may be used to support composite containers as described in U. S. Patent No. 6,460, 721, having a corresponding International Publication No. of WO 00/57102 and entitled"Systems and Methods for Producing and Storing Pressurized Liquefied Natural Gas". Additionally, while the present invention has been described in terms of one or more preferred embodiments, it is to be understood that other modifications may be made without departing from the scope of the invention, which is set forth in the claims below.

GLOSSARY OF TERMS [0065] cylindrical container: a substantially cylindrical-shaped container; [0066] cryogenic temperature: any temperature of about-40°C (-40°F) or colder ; [0067] DBTT (Ductile-to-Brittle Transition Temperature): delineates the two fracture regimes in structural steels ; at temperatures below the DBTT, failure tends to occur by low energy cleavage (brittle) fracture, while at temperatures above the DBTT, failure tends to occur by high energy ductile fracture; [0068] HSLT PLNG Containers: containers as described and claimed in the PLNG Patent; [0069] HSLT Steels : ultra-high strength, low alloy steels containing less than 9 wt% nickel and having tensile strengths greater than 830 MPa (120 ksi) and DBTTs lower than about-73°C (-100°F) ; [0070] PLNG: pressurized liquefied natural gas; [0071] PLNG Patent: United States Patent Number 6,085, 528; [0072] vertical cylindrical container: a substantially cylindrical-shaped container that is positioned substantially vertically;