The invention provides a secondary barrier system for a hull or a hold, and a barrier system comprising a primary and secondary barrier.

It is known to transport or store media in a ship or vessel at temperatures below ambient temperature, for example liquefied natural gas (LNG), liquid ethylene, liquid petroleum gas (LPG), or liquid nitrogen. It is common to transport such media by ship and there is an increasing interest in storing such media in floating offshore storage units. A hold of such a ship or storage unit may be insulated from a hull thereof, or a wall of the hold or hull, using an array of insulating panels which cover largely the entire surface area of the hull. It is desirable to seal the insulating panels, and the hull or the wall, from the hold so as to prevent any liquid in the hold from leaking through to the insulating panels and the hull/wall. Liquid in such areas would reduce the efficiency and lifespan of the insulating panels, and may damage the hull. Thus, whilst there is a primary barrier that stores the media in the hull/hold, there is a need for a secondary barrier between the primary barrier and the hull/hold.

Prior attempts to provide such a secondary barrier have included providing insulation panels attached to the hull and a membrane provided on the interior surface of the insulation panel. The membrane acts to seal the insulation panels from the interior of the hold. One such example is the NO 96 system produced by Gastransport et Technigaz (GTT). In this system, the membrane is formed by a plurality of strakes which are joined to the insulating panels indirectly via separate components in the form of tongues. The tongues are retained in position by engaging in slots formed in the insulation panels. The tongues are necessary in the GTT system to allow the strakes to thermally expand and contract relative to the insulating panels. However, this is a complex system that requires the strakes to be indirectly attached to the insulating panels via the tongues and requires substantial modification of the insulating panels in order to have the tongues and strakes attached thereto. Further, in the GTT system, the primary barrier is substantially similar to the secondary barrier and is supported by the secondary barrier.

The present invention aims to provide a simpler solution.

In a first aspect, the invention provides a secondary barrier system for a hull or a hold of a ship or a vessel, the secondary barrier system comprising: a membrane; and a membrane support layer attachable to the hull or hold for supporting the membrane relative to the hull or hold, the membrane comprising: a plurality of panels covering at least a portion of the membrane support layer and sealed to one another such that liquids may not pass through the membrane, characterised in that: the plurality of panels comprises at least one corrugated panel comprising at least one corrugation therein; the membrane is directly attached to the membrane support layer by at least one attachment; and the at least one attachment and the at least one corrugation are arranged such that, as the membrane undergoes thermal expansion and contraction, the membrane slides relative to the membrane support layer so as to relieve the stress in the membrane induced by the thermal expansion and contraction.

Because the membrane is attached directly to the membrane support layer, the attachment of the membrane is simpler than in the prior art systems. The direct attachment is advantageous as it is a simple and strong way of attaching the membrane to the membrane support layer. However, without further modification the direct attachment of the membrane to the membrane support layer would cause stress to occur when the membrane undergoes thermal expansion or contraction. Thus, the inventors have devised a system where at least one corrugation allows the membrane to slide relative to the membrane support membrane. Further, the inventors have devised a system that includes attachments that, whilst directly attaching the membrane to the membrane support layer (e.g. not requiring an intermediate element, such as a tongue), are arranged to allow the membrane to slide relative to the membrane support layer. The corrugation and the attachments work in combination to relieve stress in the membrane, which otherwise would be there given the direct attachment of the membrane to the membrane support layer due to thermal expansion/contraction of the membrane.

The membrane may be liquid-tight. The membrane may also be gas-tight, i.e. the plurality of panels (and possibly the other components of the membrane, see below) may be sealed to one another such that gases may not pass through the membrane.

Additionally/alternatively, the hull/hold may also be gas tight.

A gas-monitoring system may be placed between the membrane and the wall of the hull/hold. The gas-monitoring system may detect if any gas is leaking through the membrane.

The membrane support layer may be attached/attachable to an inside surface a wall of the hull or hold.

The plurality of panels may be attached and sealed to one another by welds.

The ship or vessel may be for transport or storage of media at temperatures below ambient temperature, such as liquefied natural gas (LNG), liquid ethylene, liquid petroleum gas (LPG), or liquid nitrogen.

By "directly" attached, it is meant that the membrane is attached to the membrane support layer using an attachment means that attaches the membrane to the support layer without any intermediate features. Looked at another way, it is meant that the panel(s) of the membrane are attached to the membrane support layer using an attachment means that attaches the panel(s) to the support layer without any intermediate features. For instance, in the GTT NO 96 system, the attachment is not direct because the membrane is attached to the membrane support layer via a tongue. The direct attachment of the current invention is a simple attachment, such as a screw, that is applied directly to the membrane and membrane support layer.

As mentioned above, the at least one attachment and the at least one corrugation are arranged such that, as the membrane undergoes thermal expansion and contraction, the membrane slides relative to the membrane support layer so as to relieve the stress in the membrane induced by the thermal expansion and contraction. Thus, the inventors have devised a system where the attachment(s) and the corrugation(s) work in synergy to relieve a stress in the membrane that otherwise would have been there due to the direct attachment. This may be achieved by selecting the location of the attachment(s), the orientation of attachment(s), the orientation of the corrugation(s), the size of the

corrugation(s), etc. Thus, the geometry of the membrane may be selected so as to minimise the global stress of the membrane.

By "relieving" stress, it is meant that stress is reduced in comparison to what the stress otherwise would have been without the attachments and corrugation(s) of the present invention, i.e. that stress is prevented from building up to the level it otherwise would have been. There may of course be some stress left in the membrane, as it may be difficult or impossible to completely remove stress due to thermal expansion/contraction whilst having the membrane directly attached to the membrane support layer.

By "attaching" the membrane to the membrane support layer, it is meant that the membrane is held or retained relative to the membrane support layer. The membrane may be held or retained relative to the membrane support layer in a direction perpendicular to the general plane of the membrane (or membrane support layer) at a given point; the membrane may be able to slide relative to the membrane support layer in the direction of the general plane of the membrane (or membrane support layer) at a given point.

Not every location of the membrane may slide relative to the membrane support layer. There may be location(s) that, due to the global geometry/arrangement of the membrane, remain stationary relative to the membrane support layer during thermal expansion/contraction.

The membrane may be made from a material that comprises Invar. The panels may be made from Invar. Invar may be Invar M93. Invar M93 is an alloy comprising mainly Nickel and Iron. It has an extremely low coefficient of thermal expansion (approximately 1 .5 x 10 ^"6 /cm). It is therefore particularly useful in the present invention, as it further reduces the stress on the membrane. Preferably, at least substantially, all of the components that make up the membrane are made from Invar, e.g. the panels, the corner pieces, the support member plate, and/or the support member, etc. mentioned below. The panels may be generally planar, and may be rectangular in shape. The panel may be described as a strake.

The plurality of panels may comprise at least one non-corrugated panel. The inventors have found that in order to reduce global stress of the system, it is not necessary for very panel to comprise a corrugation. Thus, some, or preferably even a majority, of the panels may not include a corrugation. For instance, for every one corrugated panel there may be at least 2, 3, 4, 5, 6, 7 or 8 non-corrugated panels. For every one corrugated panel, there may be less than 8, 7, 6, 5, 4 or 3 non-corrugated panels. For every one corrugated panel there may be between 2 to 8, preferably 4 to 6 non-corrugated panels.

Adjacent corrugated panels may run parallel with each other. There may be at least

2, 3, 4, 5, 6, 7 or 8 (or less than 8, 7, 6, 5, 4 or 3, or between 2 to 8 or between 4 to 6) non- corrugated panels between adjacent parallel corrugated panels, the non-corrugated panels running parallel with the corrugated panels. The non-corrugated panels may be planar. It is advantageous to use non-corrugated panels where possible since they are cheaper to produce.

There may be a plurality of corrugated panels.

The/each corrugated panel may comprise a corrugation extending in a linear direction. This may be the only corrugation in the corrugated panel. The corrugation may extend substantially the entire length of the panel. The corrugation may be located approximately in the mid-point of the width of the panel. The corrugated panel may have a non-corrugated end portion, preferably at both ends of the length of the corrugated panel. This non-corrugated end portion may be advantageous as it can straightforwardly be overlapped with an adjacent panel. Alternatively, the corrugation may run all the way to one or both ends of the corrugated panels (for instance, when the corrugation is to be continuous over a corrugated corner piece, see below).

The plurality of corrugated panels may be arranged such that at least one panel is orientated such that its corrugation extends in a first direction and at least one panel is arranged such that is corrugation extends in a second direction, the first direction being perpendicular to the second direction. The inventors have found that orientating the corrugations perpendicular to one another reduces the global stress of the membrane during thermal expansion/contraction. Preferably, all the corrugated panels are either orientated in the first direction or the second direction.

When the membrane is in situ in the hull/hold, the first direction may be a longitudinal direction of the hull/hold and the second direction may be a transverse direction of the hull/hold. The longitudinal direction may be the direction in the length of the hull/hold and the transverse direction may be in the direction of the width of the hull/hold. However, these terms may also be merely relative terms, and so could be used the other way round. The inventors have also found a particularly desirable arrangement for the positioning and lengths of the corrugated panels. This is a grid-like system, with the corrugated panels extending in the first and second directions. Adjacent parallel corrugated panels may be spaced apart by one or more non-corrugated panels, which may preferably extend in the same direction as the adjacent parallel corrugated panels. The corrugated panels extending in the first direction may be placed both collinearly and may be arranged parallel to other corrugated panel(s). Likewise, the corrugated panels extending in the second direction may be placed both collinearly and may be arranged parallel to other corrugated panel(s). A collinear set of corrugated panels may be joined together end to end, and may also be interrupted, between adjacent corrugated panels, by a corrugated panel extending in the other direction. These interruptions are set out in more detail in the paragraphs below. The inventors have found that it can be advantageous to have some interrupted sets of corrugated panels and some non-interrupted corrugated panels running parallel to one another. The non-interrupted corrugated panel may preferably be

substantially the same length as the total length of the interrupted set of corrugated panels.

The non-interrupted corrugated panel may be longer than the corrugated panels that are interrupted. Alternatively/additionally, the non-interrupted corrugation may be comprised of a plurality of corrugated components (e.g. panels and corner pieces) that are shaped and arranged such that they are connected together such that the corrugation is continuous (even if the panels are not continuous).

Thus, an end of a first corrugated panel, extending in the first direction, may be joined to a side-portion of a second corrugated panel, extending in the second direction. An end of a third corrugated panel, extending in the second direction, may be joined to a first side-portion of the first corrugated panel. An end portion of a fourth corrugated panel, extending in the second direction, may be joined to a second side-portion of the first corrugated panel opposite the first side-portion. The second corrugated panel may be longer than each of the third and fourth corrugated panels. The third and fourth corrugated panels may extend co-linearly.

The first side portion may be one of the length-wise edges of the panel, and the second side portion may be the other length-wise edge of the panel.

In this arrangement, the third and fourth panels may be described as the set of interrupted panels mentioned above, interrupted by the first corrugated panel. The second panel may be the non-interrupted corrugated panel mentioned above. There may be one or more further corrugated panels arranged collinearly with the third and fourth panels and there may be one or more respective further corrugated panels extending in the first direction attaching the respective ends of these corrugated panels. Preferably, the second corrugated panel is of substantially the same length as the interrupted set of corrugated panels. The second corrugated panel may extend across substantially the entirety of the hull/hold.

There may also be at least one additional corrugated panel extending collinearly with the first corrugated panel, and attached to an opposite side portion of the second panel. In this way, it can be seen that the second panel has interrupted a set of corrugated panels extending collinearly in the first direction.

In this way, it can be seen that the invention may comprise a, preferably

perpendicular, network or grid of interrupted and non-interrupted corrugations, formed of plurality of perpendicularly, parallel and collinearly extending corrugated panels. The precise arrangement can be selected so as to reduce the global stress of the membrane, which may depend on the geometry of the hull/hold in question.

The hull/hold typically has (at least partially) vertically extending wall(s) and (at least partially) horizontally extending wall(s), such as a floor and/or ceiling. In order for the membrane to provide the necessary protection against leaks, the membrane should be able to conform to the general shape of the hull/hold (which is typically also followed by the membrane support layer). The membrane may (completely) cover the inner surface of the floor of the membrane support layer/hull/hold, and preferably also covers the at least some of the side walls. It may or may not cover the ceiling. Preferably, the membrane only extends part-way up the side walls.

Thus, the membrane support layer may comprise a corner joining two or more substantially planar sections, and the membrane may comprise at least one corner piece shaped to sit in the corner of the of the membrane support layer, the at least one corner piece being sealed to at least one of the plurality of panels on each of the planar sections.

When the corner piece is shaped to sit in a corner of the membrane support layer that joins only two planar sections of the membrane support layer (e.g. a (partially) vertical section and a (purely) horizontal section or a partially vertical section and a purely vertical section), the corner portion may comprise two planar portions connected to one another at substantially the same angle as the two planar sections of the membrane support layer extend relative to each other.

When the corner piece is shaped to sit in a corner of the membrane support layer that joins only three planar sections of the membrane support layer (e.g. a first (partially) vertical section, a second (partially) vertical section and a purely horizontal section), the corner portion may comprise three planar portions connected to one another at substantially at the same angle as the three planar sections of the membrane support layer extend relative to each other. By "partially" vertical, it is meant an angle between horizontal and vertical, such as between 0° and 90°, between 10° and 80°, or between 20° and 70°, or between 30° and 60°, or between 40° and 50° to the horizontal.

Thus, the geometry of the corner piece of the membrane may be substantially the same as the geometry of the corner of the membrane support layer in which it sits, e.g. the planar portions of the corner piece of the membrane may extend relative to each other at the same angle as the planar portions of the membrane support layer that form the corner.

The corner piece may be corrugated or non-corrugated. A non-corrugated corner piece may be attached to non-corrugated panels. A corrugated corner piece may be attached to corrugated panels. The corrugated corner piece may have a corrugation substantially similar to that of the corrugation of the corrugated panel(s). The corrugation may run across the corner piece (preferably at a midpoint of the corner piece) and join the corrugation of one corrugated panel to the corrugation of another corrugated panel in another plane. The corrugated corner piece can thus effectively allow a corrugation in one plane to be continuous (i.e. not interrupted) with a corrugation in another plane.

The at least one attachment may be configured such that, as the membrane undergoes thermal expansion and contraction, the membrane may slide relative to the membrane support layer in the direction of the general plane of the membrane at the location of the at least some of the attachments. Thus, whilst the attachment directly attaches the membrane to the membrane support layer, the attachment allows for relative movement of the membrane at the location of the attachment in the general plane of the membrane at that location. This helps to relieve the stress at the attachment locations. There may be a plurality of such attachments.

The attachment may be configured to allow the sliding to be in both dimensions of the general plane of the membrane (at the location of the attachment).

Additionally or alternatively, the attachment may be configured to allow the sliding in only one dimension of the general plane of the membrane.

When the membrane is viewed as a whole, due to the presence of the corrugations, some locations on the membrane may move in two dimensions of the general plane of the membrane, some locations on the membrane may move in only one dimension of the general plane of the membrane, and some locations may not move in the general plane of the membrane due to thermal expansion/contraction. The inventors have realised this and, depending on the desired attachment location, have devised attachments that allow for the necessary movement.

The at least one attachment may comprise: a groove in the membrane support layer; a sunken portion in one of the panels, said sunken portion being located within said groove; and a sunken portion retainer for retaining the sunken portion within the groove. The groove, the sunken portion and the sunken portion retainer may be shaped such that the sunken portion can slide within the groove when the membrane undergoes thermal expansion and/or contraction. This sliding may be both in the first and second directions.

An adjacent panel may overlap the groove, the sunken portion and the sunken portion retainer and may be attached and sealed to the panel with the sunken portion. In this way, the adjacent panel is also retained relative to the membrane support layer via the attachment.

The sunken retainer portion may act to push or press the panel(s) downwards toward the membrane support layer.

As is explained in more detail below, the sunken portion may be located at an edge of the panel.

Regarding the attachment in more detail, the attachment is located generally where two adjacent panels meet. The attachment is located generally at an edge of one of the panels, preferably the longer edge of the panel. Preferably there is (only) one attachment between the membrane and the membrane support for each location where two panels are joined to each other.

A possible form of an attachment is now described.

A first panel may comprise a sunken portion. The sunken portion may extend along the length of the edge of the first panel, preferably along a majority of the length but not necessarily along the entirety of the edge.

The membrane support layer may comprise a groove. The groove may be in the top panel of the membrane support layer or in the box. The groove may be for the attachment of the membrane to the membrane support layer. The groove may have a uniform depth across its width (the width of the groove being perpendicular to the direction in which the groove extends and to the direction of the depth of the groove). However, preferably, the groove comprises a deeper section and a shallower section. These two sections may extend from opposite sides of the groove, and may meet each other at a step toward the middle of the width of the groove. These two sections may have substantially the same widths, but preferably the deeper section is (slightly) wider than the shallower section. For instance, the deeper section may have a width of 10-30mm and the shallower section may have a width of 10-20mm. The deeper section may be deeper than the shallower section by an amount substantially equal to (or slightly larger than) the thickness of the material used to form the membrane.

The groove may extend in the same direction as the sunken portion. The sunken portion may interact with the groove. This interaction may allow the sunken portion to slide in the within the groove in a direction both parallel to the direction of the groove and perpendicular to the direction of the groove (and within the general plane of the membrane support layer) when the membrane expands and contracts due to thermal effects.

This interaction is explained in more detail below.

The sunken portion may be step-shaped. The sunken portion may comprise a sunken planar portion orientated parallel with the remainder of the first panel. The sunken planar portion may be connected to the remainder of the first panel via a step, which extends substantially perpendicularly to the remainder of the first panel.

The sunken planar portion may have a length substantially equal to the length of the first panel, but may be shorter than the length of the first panel (i.e. it need not extend over the entirety of the length of the edge of the first panel); however, it may extend over a majority of the length of the panel. The sunken planar portion may have a width that is less than the width of deeper portion of the groove, preferably the width of the sunken planar portion is up to 1 mm, 2mm, 3mm, 4mm, 5mm or 10mm (or at least 1 mm, 2mm, 3mm, 4mm, 5mm or 10mm) smaller than the width of the deeper portion of the groove. This allows the sunken planar portion to slide in the direction of the width of the groove when the membrane expands and contracts due to thermal effects.

The depth of the sunken planar portion (e.g. the length of the step) is approximately equal to the depth of the deeper portion of the groove. This allows the first panel to sit flush against the membrane support layer whilst allowing the sunken planar portion to sit flush against the bottom of the deeper portion of the groove.

The distance between neighbouring grooves in the membrane support may be substantially equal to the distance between the sunken portions of the panels. Neighbouring sunken portions in the membrane may be on the same panel(s) (e.g. opposite side of the same panels) and/or on different panels (e.g. on neighbouring panels).

The membrane may be retained relative to the membrane support layer via the sunken portion retainer, which may be a wedge. The sunken portion retainer may retain the sunken portion of the first panel in the groove. The sunken portion retainer may be placed in the groove. The sunken portion retainer may have a length substantially equal to the length of the groove. The sunken portion retainer may have has a width less than the width of the groove but greater than the width of the shallower portion of the groove. The sunken portion retainer may have a thickness that is substantially equal to, or less than, the depth of the shallower portion of the groove. The sunken portion retainer may be fixed to groove, e.g. to the bottom of the shallower portion of the groove, for example by means of a screw or a plurality of screws. The sunken portion retainer may be fixed to the shallower portion of the groove such that there is a clearance between the sunken portion retainer and the edge of the deeper groove portion. The clearance may be such that the sunken portion (e.g. the step) can pass between the sunken portion retainer and the edge of the deeper groove portion, and is such that the first panel can slide in the direction of the width of the groove (e.g. perpendicular to the direction in which the groove extends) when the membrane expands and contracts due to thermal effects. The clearance may be up to 1 mm, 2mm, 3mm, 4mm, 5mm or 10mm (or at least 1 mm, 2mm, 3mm, 4mm, 5mm or 10mm).

Placed over the sunken portion retainer and the edge of the first panel is a second neighbouring panel. Specifically, it may be an edge of the second panel that overlaps the sunken portion retainer and the first panel. The second panel may overlap the first panel. The second panel may be fixed and sealed to the first panel, such as by a weld.

The second panel may comprise a raised portion. The raised portion may extend in the along the length of the edge of the second panel, preferably along the entirety of the length of the second panel. The raised portion may overlap the first panel. The raised general plane of the portion may be orientated parallel with the general plane of the remainder of the second panel.

The raised portion may have a length substantially equal to the length of the second panel. The raised portion may be raised by an amount substantially equal to the thickness of the first panel, and possibly the thickness of the second panel (the thicknesses of these panels may be equal. Indeed the thickness of all of the panels may be substantially equal); however, there may also be some degree of variation in the thickness. This allows the second panel to sit flush against the membrane support layer whilst allowing the raised portion to sit flush against the first panel.

The membrane support layer, e.g. the top panel of the membrane support layer, may comprise a groove for housing a weld protection strip. The weld protection strip may be made from a material that can protection the top panel from the heat of welding when welding is performed at a location above the weld protection strip. The groove for housing a weld protection strip and the strip may be located at locations where welds are to be placed to secure panels of the membrane to each other, e.g. where neighbouring panels meet or overlap. Such locations are typically adjacent the grooves for the attachment discussed above. Thus the groove for housing a weld protection strip and the strip may be placed adjacent the groove for the attachment, and may extend parallel to groove for the attachment. Each groove for the attachment may have a groove for housing a weld protection strip adjacent to it.

The depth of the groove for housing a weld protection strip may be substantially equal to the thickness of the strip (preferably the depth is less than 5mm, preferably less than 2mm, preferable less than 1 mm, preferably less than the depth of groove 1042). The width of the groove for housing a weld protection strip may be substantially equal to the width of the strip (preferably the width is 10-100mm, preferably 30-80 mm, preferably 50-70 mm). The length of the groove for housing a weld protection strip may be substantially equal to the length of the strip, preferably the length extends across the entirety of panel.

Between the first panel and the membrane support layer at a location beneath the overlap and the weld is the weld protection strip, which is comprised of thermal protection material. This strip is placed in the groove for the thermal protection material in the membrane support layer. The thermal protection material protects the membrane support layer from the heat of the weld.

As can be appreciated from the above discussion, attachment allows thermal expansion and contraction of the membrane both along the length of the groove and in the direction of the width of the groove, whilst also allowing the membrane to be attached to the membrane support.

Each attachment may be located between different adjacent panels. Each attachment may be substantially similar, with one panel having a sunken portion retained in a groove by a sunken portion retainer, said panel being overlapped by an adjacent panel. The panels may be transverse panels, or longitudinal panels, or partially vertical panels, or vertical panels. The panels may be corrugated or non-corrugated.

There may be one attachment located at the location where each pair of adjacent panels meets. These adjacent pairs may be transverse panels, or longitudinal panels or both.

As should be understood, whilst the attachment has been discussed above primarily for the attachment at a location between two adjacent panels, the attachment may be placed at any location where a first membrane component meets a second membrane component. In this case, the first membrane component comprises a sunken portion retained, but still slidable, within a groove of the membrane support layer and the second membrane component overlaps the sunken portion and is fixed and sealed to the first membrane component. Any combination of membrane components may be used for the first and/or second membrane components here, such as corner portions, end caps, corrugated panels, non-corrugated panels, support plates, etc. The membrane components may comprise any of the features described in relation to the attachment herein.

In one example of the system, the corrugated panels may not have any sunken portions. For example the longitudinal corrugated panels and/or the transverse corrugated panels may not have any sunken portions.

As should be understood from the above, when a panel does not have a sunken portion on its edge, the edge of the panel without a sunken portion may instead overlap an adjacent panel that does have a sunken portion. This is the case for the length edges (at least), but may also be the case for the width edges of the panels. Thus, when the corrugated panels do not comprise any sunken portions, they overlap the adjacent panels, preferably non-corrugated panels. The corrugated panels may overlap adjacent panels along edges of the adjacent panels that have a sunken portion.

A given panel may comprise two edges with sunken portions, one edge or no edges with sunken portions. When a panel has two edges with sunken portions, this panel may be overlapped by two adjacent panels. When the panel has one sunken portion, it may overlap one adjacent panel (e.g. via a raised portion) and may be overlapped by another adjacent panel. When a panel has no sunken portion, it may overlap two adjacent panels (e.g. via two raised portions).

As can be appreciated from the above, a first exemplary panel (which may be corrugated, but which is preferably non-corrugated) may comprise two sunken portions that extend along the majority of the length of the panel, preferably on opposite length edges of the panel. It should be noted that the sunken portions may not extend along the entire length of the panel. At one end (preferably only one end, but possibly both ends) of the panel, the panel may comprise a raised portion for overlapping another portion of the membrane, such as a neighbouring panel or corner portion or support plate. The raised portion preferably extends along the entirety of the width of the panel, so that when it is welded to the panel that it overlaps, the membrane can be completely sealed.

A second exemplary panel (which may be corrugated, but which is preferably non- corrugated) may comprise only one sunken portion that extends along the majority of the length of the panel, preferably along one of the length edges of the panel. It should be noted that the sunken portion may not extend along the entire length of the panel. Along the other length side of the panel may be the raised portion. The raised portion may extend along the entirety of the length of the panel, so that when it is welded to the panel that it overlaps, the membrane can be completely sealed. At one end (preferably only one end, but possible both ends) of the panel, the panel may comprise a raised portion for overlapping another portion of the membrane, such as a neighbouring panel or corner portion or support plate. This raised portion may extend along the entirety of the width of the panel, so that when it is welded to the panel that it overlaps, the membrane can be completely sealed.

Some of the panels may have substantially identical lengths and widths to each other, some may have substantially identical lengths but different widths, some may have substantially identical widths but different lengths and some may have different lengths and widths.

It may be desirable to taper a corrugation to a flat end, for example where a corrugation is to be interrupted. In order to do this, an end cap may be provided. The end cap may be attached to an end of a given corrugated panel. The end cap may comprise a corrugation which may be attached to the corrugation of the corrugated panel to which the end cap is attached to form a continuous corrugation between the corrugated panel and the end cap. The corrugation of the end cap may then taper to a flat end. The end cap portions are preferably around 100-500mm, preferably 300mm, in length. The width of the end cap portion may be substantially equal to the width of the corrugated panel to which it is attached. The radius of the taper of corrugation in the end cap may be between.

Where a corrugation is interrupted or stopped (such as where the end of a corrugated panel in one direction meets a corrugation running in a perpendicular direction or meets a non-corrugated membrane component), the corrugated panel may be connected and sealed to the adjacent membrane component. This can be achieved via the end cap.

The corrugated panel whose corrugation is to be interrupted or terminated may comprise a central portion and an end cap attached to the central portion. The end cap may be attached to the central portion by an overlap and/or an underlap. The overlap and/or underlap may be welded to both the central portion and the end cap. The overlap and/or underlap may be around 10-100mm in width and may have a length similar to (though possibly larger or smaller than) the width of the corrugated panel. The overlap may have a smaller or larger length than the underlap; the overlap may have smaller or larger width than the underlap. The overlap and/or underlap may be strip of material, such as Invar. The overlap and/or underlap may also comprise a corrugated portion shaped similarly to the corrugation of the corrugated panel and end cap. Adjacent to the overlap and/or the underlap the end portion may meet the central portion in an end-on fashion.

The very end of the corrugated panel (e.g. the end portion of flat portion of end cap) may overlap or underlap with the membrane component that is interrupting or terminating the corrugation.

Where a corrugation is not to be interrupted, the corrugated panel may not comprise the end cap. Rather, it may be attached to another corrugated component effectively forming a continuous corrugation between said components. Such a component may be another corrugated panel or a corrugated corner portion. Similarly to the end cap, an overlap and/or underlap can be used to attach these adjacent components together.

As an aside, in this specification, the terms "inner" and "outer" are used in relation to the hull/hold. The inner direction is that closer to the centre of the hull/hold and the outer direction is that further from the centre of the hull/hold.

The membrane support layer may comprise a plurality of boxes (preferably made of wood). At least some of the boxes may comprise one or more grooves for receiving the sunken portion of a panel and/or for receiving the heat-resistant strip, discussed above. Wood is used because it is strong, cheap and quite well insulating. Further, it is easy to screw into. Preferably the wood is plywood. The boxes may be filled with an insulating material such as polyurethane foam. The membrane support layer may be configured to thermally isolate the hold/hull from the inside of the membrane support layer. The membrane support layer may be thermally insulating. The membrane support layer may comprise thermally insulating material, such as polyurethane foam.

The membrane support layer may comprise insulation panels, preferably made from polyurethane foam.

The membrane support layer may comprise top panels (preferably made from wood) on its inner surface. The top panels may be plywood panels. The top panels may be attached to the inner side of the insulation panels or be the inner panel of the box.

The boxes may be used at the corners of the secondary barriers. These boxes may be placed end-to-end and may extend generally horizontally.

The membrane support layer may also comprise one or more insulation stack. The insulation stack may be located between the boxes. The top surface of the insulation stack may comprise one or more grooves for the sunken portion, discussed above.

The insulation stack(s) may comprise gaps and/or there may be gaps between adjacent insulation stacks. These gaps may allow for passage of any leaking fluid (e.g. gas) through the membrane.

The stack may comprise an insulating panel, preferably a plurality of insulating panels, preferably only two insulating panels. A plurality of stacks may be used to construct the membrane support layer. The insulating stack may comprise a cold insulating panel and a warm insulating panel. The warm insulating panel may be mounted to the hull/hold wall and the cold insulating panel may be mounted to the inner side of the warm insulating panel. On the inner surface of the cold insulating panel, a top panel (preferably made of wood, preferably plywood) may be mounted. The cold and warm insulating panels may have substantially the same dimensions as each other, e.g. around 100-300mm (preferably 200mm) thick, 500-1500mm (preferably 1000mm) in length and 500-1500mm (preferably 1000mm) in breadth. However, the cold panel may preferably have a slightly smaller length and/or width than the warm panel. This allows for larger gaps between adjacent cold panels in comparison to between adjacent warm panels. The insulating panels, and hence the stack, may be approximately square in plan.

The hull/hold wall may comprise a plurality of connecting stubs that may pass through holes in the stack and/or box. The connecting stubs may be used to attach the stack(s) and box(es) to the hull/hold wall. The connecting stubs may be threaded and may secure the insulating panels to the hull/hold wall via washers and/or nuts. The holes in the cold insulating stack and/or box may be filled with a bung so as to insulate the holes and connecting stubs. On the inner surface of the cold insulating panel, the top panel may be attached. This may be attached using the connecting stubs. The top panel is preferably plywood. The top panel may to protect the surface of the insulating panel(s) and to provide structural support to the insulating panel(s), such as providing contraction control. Further the top panel may allow the attachment of the membrane to the membrane support via the attachments, as discussed above.

The top panel may have substantially the same length and breadth as the insulating panel(s). However, it may have a substantially smaller thickness, such as less than 50mm, preferably less than 20mm. The top panel may be substantially square.

The top panel of stack may comprise at least one groove for the attachment of the membrane to the top panel. This groove has been described above. Preferably each panel may comprise two such grooves (preferably only two) that are substantially parallel with each other. The number of such grooves (or the presence of such grooves at all) can be determined and selected by the designer of the secondary barrier system so as to allow for the desired level of attachment and security between the membrane and the membrane support, which may vary from system to system.

Preferably the groove(s) may extend across the entirety of the panel(s).

The top panel of the stack also comprises a groove for housing the weld protection strip. This groove and the strip have been described above.

The length of the groove may be substantially equal to the length of the strip, preferably the length extends across the entirety of top panel. Adjacent stacks may be arranged such that their respective grooves form a continuous groove, effectively increasing the length of the groove over multiple stacks.

Around the perimeter of the cold insulating panel, a flexible and porous frame may be placed. This may be made of Rockwool. This may act to maintain integrity of the insulating panel and provide flexibility of the insulation layer and provide gas evacuation channels in case of a leak. The flexible frame may effectively fill the gaps between adjacent insulation panels and allow for fluid (e.g. gas) to pass through the membrane support layer in case of a leak.

Around the perimeter of the warm insulating panel, a flexible frame may be placed.

This may be made of Rockwool. This may act to maintain integrity of the insulating panel and provide flexibility of the insulation layer and provide gas evacuation channels in case of a leak.

Preferably, the insulating panels may comprise or are made from polyurethane foam. Additionally or alternatively, there may be another insulating stack present in the membrane support layer. This stack is largely identical to the stack described above except that no grooves or weld protection strips are present, as they are not needed when no membrane is to be attached to the stack.

Regarding the box in more detail, the box may generally be closed, hollow box made of panels. The box may be at least partially filled with an insulating material, such as polyurethane foam.

The box may comprise a plurality of portions. These portions may each be in the form of an at least substantially closed box. These portions may comprise a cold box portion and a warm box portion. The warm box portion may be mounted to the hull/hold wall and the cold box portion may be mounted to the inner side of the warm box portion. The cold and warm box portions may have substantially the same dimensions as each other , e.g. around 100-300mm( preferably 200mm) thick, 500-1500mm (preferably 1000mm) in length and 100-500mm (preferably around 300mm) in breadth. However, the cold box may preferably have a slightly smaller length and/or width than the warm box. This allows for larger gaps between adjacent cold boxes and panels in comparison to between adjacent warm boxes and panels. The warm and cold box portions may be approximately rectangular in plan, and cuboidal in shape.

The thickness of the box is substantially equal to the thickness of the stack(s). The thickness of the cold box portion may be substantially equal to the thickness of the cold insulating panel. The thickness of the warm box portion may be substantially equal to the thickness of the warm insulating panel.

The warm box portion may take the form of a closed, hollow box. The warm box portion may be formed of panels, preferably of wood. The warm box portion may be filled with an insulating material, such as polyurethane foam.

The cold box portion may take the form of a closed, hollow box. The cold box portion may be formed of panels, preferably of wood. The cold box portion may be filled with an insulating material, such as polyurethane foam. The top panel of the cold box portion may also the top panel of the box as a whole.

Each box (or box portion) may be divided into cells. Each cell may take the form of a closed hollow portion of the box (or box portion) filled with the insulating material.

As mentioned above, the hull/hold wall may comprise a plurality of connecting stubs.

These may pass through holes in the box, such as holes in the warm and cold box portions, and possibly holes in the insulating materials. The connecting stubs may be threaded and may secure the box to the hull/hold wall via washers and/or nuts.

The top of the box may comprise at least one groove for the attachment of the membrane to the box. This groove has been described above. Preferably each box may comprise only one groove. The number of grooves (or the presence of grooves at all) can be determined and selected by the designer of the secondary barrier system so as to allow for the desired level of attachment and security between the membrane and the membrane support, which may vary from system to system.

Preferably the groove(s) may extend across the entirety of the box(es).

The top of the box may comprise a groove for housing the weld protection strip. This groove and the strip have been described above.

Preferably the groove(s) extend in a direction parallel to the length direction of the box.

The length of the groove may be substantially equal to the length of the strip, preferably the length extends across the entirety of top panel.

Adjacent stacks may be arranged such that their respective groove(s) form a continuous groove, effectively increasing the length of the groove over multiple boxes and/or stacks.

The secondary barrier system may comprise at least one support member for supporting a primary barrier. The support member(s) may be arranged to transfer the load of the primary barrier to the hull or hold, without substantially any of said load being transferred through the remainder of the secondary barrier system (i.e. the membrane and the membrane support layer). The load may be the weight of the primary barrier (and its contents) and/or vertical/horizontal reaction forces associated with movement of the vessel/ship.

At least one of the at least one the support members may be attachable to the hull or hold. Said support member may extend through the membrane support layer and the membrane. Said support member may be sealed to the membrane adjacent the support member. Said support member may be arranged such that the load of the primary barrier may be substantially transferred to the hull or hold via the support member and not via the remainder of the secondary barrier.

Additionally/alternatively, at least of the at least one support members may be supported by a support member support. The support member support may be attachable to the hull or hold and may support the support member. Said support member and said support member support may be arranged such that the load of the primary barrier may be substantially transferred to the hull or hold via the support member and support member support, and not via the remainder of the secondary barrier.

The support member support may support a support member plate on which said support member sits, or to which said support member is attached, or with which said support member is integrally formed.

This plate, or the support member in general, may form part of, or may be sealed to, the membrane. The support member may comprise an insulating material to prevent heat flowing through the support member. This insulating material may be polyurethane foam and/or a glass fibre reinforced epoxy. It may be necessary to have an insulating material that is capable of bearing loads (such as the glass fibre reinforced epoxy), as it is desirable for only the insulating material to contact the primary barrier, in order to maximise thermal insulation. Thus, the portion of the support member that contacts the primary barrier may be an insulating material capable of bearing the load of the primary barrier, such as glass fibre reinforced epoxy. The support member may comprise a metal (preferably comprising or consisting of NV9Ni), which provides for the transmission of the load from the primary barrier to the hull/hold. The support member may be hollow or may be a frame (i.e. the metal portion may be hollow or may be a frame), and the inside of the hollow portion or the frame may be filled with an insulating material such as polyurethane foam.

The support member may comprise a support member plate that is arranged to be sealed to the membrane adjacent the support member, the support member plate being orientated such that it is substantially in the general plane of the membrane in the location of the support member. The plate may be made of Invar. The membrane may overlap with, and may be welded to, the support plate. The support plate may be either an integral part of the support member or sealed thereto. This helps to ensure that the secondary barrier is leak-tight.

The support member, the support member plate and/or the support member support may comprise (or consist of) a material suitable for bearing loads, such as NV9Ni.

There may be a plurality of support members. There may be at least one or a plurality of support members connectable to a floor of the hull/hold. There may be at least one or a plurality of support members connectable to at least one, two, three, four, or each, side wall of the hull/hold. There may be at least one or a plurality of support members connectable to a ceiling of the hull/hold.

Advantageously, the components that may make up the membrane (e.g. the panels, the corner pieces, the support plate, etc.) may each be made of one piece. This is possible because of the simple design of the present membrane. This simplifies the construction of the membrane and reduces the risk of leaks.

The membrane may be less than 5 mm thick, preferably less than 2 mm thick, and preferably less than or equal to around 1 mm thick. The panel(s) and/or corner piece(s) and/or any other piece that makes up the membrane may be less than 5 mm thick, preferably less than 2 mm thick, and preferably less than or equal to around 1 mm thick. The membrane may have a substantially constant thickness; however, the thickness may vary slightly, since the thickness of some of the components may differ. For instance, some of the panels may be around 1 mm thick (preferably the panels which have either lowered portion(s), raised portion(s) and/or corrugation(s)) and other panels may be around 0.7mm thick (preferably the panels which have no lower, raised or corrugated portion(s)).

In a second aspect, the invention provides a barrier system comprising: the secondary barrier system, as discussed above, and the primary barrier, wherein: the primary barrier is supported by the at least one support member; and the primary barrier is a tank.

The tank may be a steel tank. The tank may be an independent tank. The tank may be a gravity tank. The tank may be capable of carrying LNG. The tank may be of a design meeting regulations for carrying LNG, such as the DNV Rules for Classification of Ships. Preferably, the tank may be of a design fitting DNV Rules for Classification of Ships 2016, Part 5: Chapter 7: Liquefied Gas Tankers, Section 20: Design with independent prismatic tanks of type-A and type-B.

The use of a tank as a primary barrier is advantageous over the known systems, such as the GTT NO 96 system. In the prior art, the primary barrier is also made of a specially constructed membrane and insulating panel layer (i.e. the primary barrier is essentially similar to the secondary barrier, and sits inside the secondary barrier). However, using a tank for the primary barrier is simpler and cheaper. Further, because there are recognised industry-standard specifications (such as the DNV Rules for Classification of Ships) available for tanks, the user will know that the primary barrier meets the specifications without needing to conduct any assessment or checks.

Further, in the prior art, the primary barrier is typically supported by the secondary barrier. The present system avoids this by supporting the primary barrier using at least one support member. In this way, the load of the primary barrier (which may include the cargo, such as LNG) may be transferred directly to the hull. Thus, the secondary barrier of the present system may not be subjected to substantial loads, which may reduce wear of the secondary barrier, and hence lengthen its lifespan.

The components of the secondary barrier system may be arranged such that the membrane is substantially symmetric (e.g. as symmetric as possible given the geometry of the hull/hold). The inventors have found that, in order to reduce global stress of the membrane, the membrane should be arranged symmetrically. This means that the components that make up the membrane may be arranged in such a way that the membrane is as symmetric as possible. The membrane may be symmetric about at least one line, preferably two lines. Thus, the corrugated panel(s), the non-corrugated panel(s), the corner piece(s) and/or the support member(s) may be arranged substantially

symmetrically, or at least as symmetrically as the geometry of the hull/hold allows.

This symmetry may only be present when looking at the membrane or secondary barrier system as a whole (e.g. at a large, zoomed-out scale). At smaller scales (e.g. when smaller details of the membrane or secondary barrier are considered), the membrane or secondary barrier may not have such symmetry.

The second aspect may comprise any of the features of the first aspect of the invention described above.

In a third aspect, the invention provides a barrier system for a hull or a hold of a ship or a vessel, the barrier system comprising: a primary barrier and a secondary barrier, the secondary barrier comprising a membrane and a membrane support layer attachable to the hull or hold for supporting the membrane relative to the hull or hold, and characterised by: the secondary barrier comprises at least one support member for supporting the primary barrier arranged such that the load of the primary barrier is at least substantially transferred to the hull or hold via the support member and not via the remainder of secondary barrier.

The load may be the weight of the primary barrier and/or vertical/horizontal reaction forces associated with movement of the vessel/ship.

The support member may comprise an insulating material to prevent heat flowing through the support member. This insulating material may be polyurethane foam and/or a glass fibre reinforced epoxy. It may be necessary to have an insulating material that is capable of bearing loads (such as the glass fibre reinforced epoxy), as it is desirable for only the insulating material to contact the primary barrier, in order to maximise thermal insulation. Thus, the portion of the support member that contacts the primary barrier may be an insulating material capable of bearing the load of the primary barrier, such as glass fibre reinforced epoxy. The support member may comprise a metal (preferably comprising or consisting of NV9Ni), which provides for the transmission of the load from the primary barrier to the hull/hold. The support member may be hollow or may be a frame (i.e. the metal portion may be hollow or may be a frame), and inside the hollow portion or the frame may be filled with an insulating material such as polyurethane foam.

At least one of the at least one the support members may be attachable to the hull or hold. Said support member may extend through the membrane support layer and the membrane. Said support member may be sealed to the membrane adjacent the support member. Said support member may be arranged such that the load of the primary barrier may be substantially transferred to the hull or hold via the support member and not via the remainder of the secondary barrier.

Additionally/alternatively, at least of the at least one support members may be supported by a support member support. The support member support may be attachable to the hull or hold and may support the support member. Said support member and said support member support may be arranged such that the load of the primary barrier may be substantially transferred to the hull or hold via the support member and support member support, and not via the remainder of the secondary barrier. The support member support may support a support member plate on which said support member sits, or to which said support member is attached, or with which said support member is integrally formed.

This plate, or the support member in general, may form part of, or may be sealed to, the membrane.

The support member may comprise a support member plate that is arranged to be sealed to the membrane adjacent the support member, the support member plate being orientated such that it is substantially in the general plane of the membrane in the location of the support member. The plate may be made of Invar. The membrane may overlap with, and may be welded to, the support plate. The support plate may be either an integral part of the support member or sealed thereto. This helps to ensure that the secondary barrier is leak-tight.

The support member may extend from the hull/hold wall through the secondary barrier and into an internal space of the hull/hold where the primary tank is located.

There may be a plurality of support members. There may be at least one or a plurality of support members connectable to a floor of the hull/hold. There may be at least one or a plurality of support members connectable to at least one, two, three, four, or each, side wall of the hull/hold. There may be at least one or a plurality of support members connectable to a ceiling of the hull/hold.

The primary barrier may be a tank. The tank may be a steel tank. The tank may be an independent tank. The tank may be a gravity tank. The tank may be capable of carrying LNG. The tank may be of a design meeting regulations for carrying LNG, such as the DNV Rules for Classification of Ships. Preferably, the tank may be of a design fitting DNV Rules for Classification of Ships 2016, Part 5: Chapter 7: Liquefied Gas Tankers, Section 20:

Design with independent prismatic tanks of type-A and type-B.

As mentioned above, the use of a tank as a primary barrier is advantageous over the known systems, such as the GTT NO 96 system. In the prior art, the primary barrier is also made of a specially constructed membrane and insulating panel layer that supports the membrane (i.e. the primary barrier is essentially similar to the secondary barrier, and sits inside the secondary barrier). However, using a tank for the primary barrier is simpler and cheaper. Further, because there are recognised industry-standard specifications (such as the DNV Rules for Classification of Ships) available for tanks, the user will know that the primary barrier meets the specifications without needing to conduct any assessment or checks.

Further, in the prior art, the primary barrier is typically supported by the secondary barrier. The present system avoids this by supporting the primary barrier using at least one support member. In this way, the load of the primary barrier (which may include the cargo, such as LNG) may be transferred directly to the hull. Thus, the secondary barrier of the present system may not be subjected to substantial loads, which may reduce wear of the secondary barrier, and hence lengthen its lifespan.

The third aspect may comprise any of the features of the first and/or second aspects of the invention described above.

It should be readily understood that the barrier system may comprise any of the features described above in relation to the primary barrier, the secondary barrier and/or the hull/hold.

Preferred embodiments will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 shows a plan, side and end view of a membrane according to an

embodiment of the present invention;

Figure 2 shows details of the membrane according to an embodiment of the present invention;

Figure 3 shows details of a membrane support layer according to an embodiment of the present invention;

Figure 4 shows details of an insulating panel of the membrane support layer according to an embodiment of the present invention;

Figure 5 shows details of another insulating panel of the membrane support layer according to an embodiment of the present invention;

Figure 6 shows details of a box of the membrane support layer according to an embodiment of the present invention;

Figure 7 shows a cross-section of an interrupted transverse corrugation in the membrane according to an embodiment of the present invention;

Figure 8 shows a cross-section of a non-interrupted transverse corrugation in the membrane according to an embodiment of the present invention;

Figure 9 shows details of a portion of the membrane according to an embodiment of the present invention;

Figure 10 shows a cross-section of an interrupted longitudinal corrugation according to an embodiment of the present invention;

Figure 1 1 shows details of a portion of the membrane according to an embodiment of the present invention;

Figure 12 shows a cross-section of a secondary barrier comprising a support member according to an embodiment of the present invention and shows details of the attachments directly fixing the membrane to membrane support layer;

Figure 13 shows details of the attachments used to secure the membrane to the membrane support layer Figures 14, 15 and 16 show possible panels of the membrane according to embodiments of the present invention;

Figure 17 an end piece of a corrugated panel according to an embodiment of the present invention; and

Figure 18 shows an exemplary primary barrier for use with the present system.

Figure 1 a shows the side view of a longitudinally extending side wall portion of a membrane 1 of a secondary barrier. The membrane comprises a plurality of corrugated panels extending in a partially vertical direction 3 and in a substantially vertical direction 2. The corrugated panels extending in a partially vertical direction 3 extend perpendicularly to the longitudinal direction. The corrugated panels extending in a substantially vertical direction 2 extend perpendicularly to the longitudinal direction. Between the corrugated panels there are a four non-corrugated panels 4. The non-corrugated panels 4 extend perpendicularly to the longitudinal direction. The panels 2, 3 and 4 are generally

rectangular-shaped and their ends are attached to corner pieces 5, 6. Corner pieces 5 connect the vertical panels with the partially vertical panels and corner pieces 6 connect the partially vertical panels with horizontal panels (as can be seen in Figure 1 c). At each end of the longitudinal wall portion, the longitudinal wall portion is connected to a transverse end wall of the membrane 1 via corner portions 7, 8, 9, 10, 58.

The membrane also comprises another plurality of corrugated panels extending in a partially vertical direction 56. These panels 56 extend perpendicularly to the longitudinal direction. Between the corrugated panels there are non-corrugated panels 57. These panels 57 extend perpendicularly to the longitudinal direction. The panels 56, 57 are rectangular-shaped and their lower ends are attached to corner pieces 55, 55'. Corner piece 55 connects the vertical panels 4 with the partially vertical panels 57 (as can be seen in Figure 1 a). Corner piece 55' connects the vertical panel corrugated 2 with the partially vertical corrugated panel 56 (as can be seen in Figure 1 a). The upper edges of panels 56, 57 may extend through the membrane support layer 101 and may be attached to the hull/hold as discussed below with reference to Figures 7 and 8.

Figure 1 b shows the plan view of a floor of the membrane 1. The floor comprises a plurality of interrupted transverse corrugations 1 1 running parallel with each other. These interrupted transverse corrugations 1 1 comprise collinear transverse corrugated panels 12 that are interrupted by longitudinal corrugations 13 running parallel with each other and which are made of collinear longitudinal corrugated panels 14. The floor also comprises non-interrupted transverse corrugations 15 which extend across the floor between two opposite corner pieces 6. The non-interrupted transverse corrugations 15 interrupt the longitudinal corrugations 13 and are parallel with interrupted corrugations 1 1. Thus, the ends of the longitudinal corrugated panels 14 are attached to opposite side portions of the non-interrupted transverse corrugated panels 15 and the ends of transverse corrugated panels 12 are attached to opposite side portions of the longitudinal corrugated panels 14.

In the embodiment shown, four non-corrugated transverse panels 16 separate adjacent transverse corrugations 1 1 , 15. The non-corrugated transverse panels 16 are also rectangular and their ends are attached to corner portions 6, longitudinal corrugated panels 14 and/or support member plates 51.

There are preferably two longitudinal corrugations 13 spaced by distance di, which may be less than around 2, 3, 4 or 5 m. As shown in Figure 1 , there are twenty two transverse corrugations 1 1 , 15, which may be substantially evenly spaced by distance d ₂ , which may be up to 1 , 2, 3 or 4 m. However, a different number of transverse corrugations 1 1 , 15 could of course be used, depending on the specific shape and size of hull or hold.

The support members 50 are located substantially at the midpoint (d ₃ ) between adjacent transverse corrugations 1 1 , 15 and the midpoint (d ₄ ) between either adjacent longitudinal corrugations 13 or a longitudinal corrugation 13 and a corner piece 6. The support member plate 51 may have a width approximately equal to the width of two of the non-corrugated panels 16. The support members/plates 51 may therefore be considered to run in longitudinal and transverse lines, these longitudinal lines being separated by distance d ₅ (preferably up to 2, 3, 4 or 5 m) and d ₆ (preferably up to 4, 6, 8 or 10 m) and the transverse lines being separated by distance d ₂ .

Figure 1 c shows the end view of a transverse end wall of the membrane 1 . The end wall comprise a plurality of rectangular transverse non-corrugated panels 17 whose ends are attached to vertically extending corrugated panels 18 and/or corner pieces 7, 8, 9, 10, 58. These panels 17 extend perpendicularly to the longitudinal direction. Further, there are non- corrugated corner pieces 65 connecting the vertically orientated non-corrugated panels 17 with partially vertical non-corrugated panels 67 and corrugated portion corner pieces 65' connecting vertically orientated corrugated panels 18 with corrugated partially vertical panels 66. Panels 17 extend perpendicularly to the longitudinal direction.

The opposite side wall is substantially identical to that shown in Figure 1 a and the opposite end wall is substantially identical to that shown in Figure 1 c.

As can be appreciated from Figure 1 , each partially vertical corrugated panel 56 is connected to a respective vertical corrugated panel 2 in the side wall which is connected to a respective partially vertical corrugated panel 3 which is connected to a respective transverse corrugation 1 1 , 15 via corrugated corner portions 5', 6', 55'. Thus, these corrugated components form a continuous transverse corrugation. These transverse corrugations extend perpendicular to the longitudinal direction extend in an end-to-end fashion and are preferably not interrupted by the corner portions 5' 6' 55'. Likewise, each partially vertical non-corrugated panel 57 is connected to a vertical non-corrugated panel 4 which is connected to a respective partially vertical non-corrugated panel 4 which is connected to a respective transverse non-corrugated panel 16 via corner portions 5, 6, 55. Thus, the non-corrugated panels also extend in an end-to-end fashion.

Likewise, each partially vertical corrugated panel 66 at the end wall is connected to a vertical corrugated panel 18 which is connected to a respective longitudinal corrugation 13 in the floor of the membrane 1 via an end corner portion 19', 65'. Thus, these corrugated components form a continuous longitudinal corrugation 13. These longitudinal corrugations 13 extend perpendicular to the transverse direction extend in an end-to-end fashion and are preferably not interrupted by the corner portions 19', 65'.

Further, as can be appreciated from Figure 1 , the membrane 1 is substantially symmetrical. Looking at Figure 1 b, one plane of symmetry is in the longitudinal direction at the midpoint of the width of the membrane. This symmetry may only be present when looking at the membrane 1 as a whole (e.g. at a large, zoomed-out scale). At smaller scales (e.g. when smaller details of the membrane 1 , such as the grooves and raised and lowered portions etc. are considered), the membrane 1 may not have such a general symmetry.

The membrane 1 may be in the form of a trough- or bath-like shape formed by the floor, the side walls and the end walls. The height of the membrane, d ₇ , may be up to 3, 4, 5, 6 or 7m. The exact shape and height of the membrane may of course vary from ship to ship, depending on class and requirements. Each support member plate 51 is supported by a support member plate support 54 (or simply support member support 54). The support member plate support 54 extends between the hull/hold wall 106 and the membrane 1 . The support member plate support 54 may (or may not) form part of the support member 50, which are described below. The support member plate support 54 may comprise one or more at least partially vertically-extending plates.

One or more (or each) of the support members 50 and/or support member plates 51 are arranged to support a primary barrier (e.g. a tank) in the vertical direction (i.e. this or these support member(s) 50 and/or support member plate(s) 51 may support the weight of the primary barrier). One or more (or each) of the support members 50 and/or support member plates 51 are arranged to support a primary barrier (e.g. a tank) in the horizontal direction (i.e. this or these support member(s) 50 and/or support member plate(s) 51 may prevent horizontal motion of the primary barrier). The member(s) 50 and/or plate(s) 51 that support the primary barrier in the vertical direction may be the same or different to the member(s) 50 and/or plate(s) 51 that support the primary barrier in the horizontal direction.

The support member(s) 50 may be integrally formed with respective support member plate(s) 51. For support member(s) 50 and/or support member plate(s) 51 that vertically support the primary barrier, the (respective) support member plate(s) 51 may be supported by support member plate support(s) 54. These support(s) 54 may take the form of one or more at least partially vertically orientated members, on which the/each support member plate 51 may sit.

For support member(s) 50 and/or support member plate(s) 51 that horizontally support the primary barrier, the (respective) support member plate(s) 51 may be supported by support member plate support(s) 54. These support(s) 54 may take the form of one or more at least partially vertically orientated members, on which the/each support member plate 51 may sit. These support(s) 54 may comprise one or more at least partially vertically orientated members that extend through the membrane/secondary barrier, and

prevent/inhibit horizontal movement of the primary barrier.

Figure 2a shows a cut-away view of the hull/hold of a vessel in which the membrane 1 and the membrane support layer 101 can be seen. The support members 50 shown in Figure 2a sit on support member plate 51

Figure 2b, shows a close-up view of detail B of Figure 2a. Thus, Figure 2b, shows five different corner pieces 6, 6', 7, 8, 19, each shaped so as to fit a respective corner of the membrane support layer 101 . The first corner pieces 6, 6' attach the horizontal panels 15, 16 with the partially vertical panels 3, 4.

In particular, non-corrugated corner piece 6 connects respective ends of non- corrugated panels 16 and non-corrugated panels 4. The non-corrugated corner piece 6 comprises two planar sections 6a connected by a corner portion 6b, which preferably has a radius of curvature of around 30 mm (see Figure 2d), and may have an angle of around 120°. The planar sections preferably extend at least around 240 mm from the corner portion (see Figure 2d).

At one longitudinal end, the corner piece 6 is connected to a corrugated corner piece 6' that attaches to an end of a horizontal transverse corrugate panel 15 and a partially vertical corrugated panel 3. At the other longitudinal end, the corner piece 6 connects to corner piece 7.

Corner piece 7 is a 3D corner piece in that it connects three different walls together: the end wall, the side wall and the floor. Likewise, corner pieces 9 and 58 may be thought of as 3D corner pieces. The other corner pieces 5, 5', 6, 6', 8, 10, 19, 19', 55, 55', 65, 65' may be thought of as 2D corner pieces. Corner piece 7 comprises three panels each extending in the respective direction of the floor, the end wall and the side wall, and each connected together by appropriate corner portions.

Corner piece 8 connects the side wall with the end wall and is similar to corner piece 6 in construction, except that the corner angle may be around 90°. Likewise corner piece 19 connects the floor with the end wall and is similar to corner piece 6 in construction, except that the corner angle may be around 90°. There may also be a corrugated corner piece (not shown) connecting the longitudinal corrugations 13 with the vertical corrugations 18. Again, the construction of this piece may be similar to corrugated corner piece 6'.

The corner pieces 6, 6', 7, 8, 19 may be attached to one another by overlaps, underlaps and by welding, as is explained in more detail below.

Figure 2c shows a close-up view of detail A in Figure 2a. A cross-section of the secondary barrier can be seen showing the membrane 1 and the membrane support layer 101 . The membrane support layer comprises insulating panels 102 and 103 stacked on top of one another and attached to the hull/hold. Panel 102 is a cold insulating panel and panel 103 is a warm insulating panel. More details of these panels are discussed in Figure 6. The support layer 101 also comprises a plurality of boxes 121 , preferably made of wood, preferably plywood. The boxes 121 are attached to the corner of the hull/hold and are used to form the corners of the support layer 101 . The corner piece 5, 5', 6, 6', 7, 8, 9, 10, 19, 19', 55, 55', 65, 65' are attached to the boxes 121 . As can be seen in Figure 2c, a transverse horizontal corrugated panel 12 is attached to a corrugated corner piece 6' which in turn is attached to a partially vertical corrugated panel 3 which in turn is attached to a corrugated corner piece 5' which in turn is attached to a vertical corrugated panel 2. Similarly, non- corrugated corner pieces 6 and 5 attach non-corrugated panels 16, 4 to each other.

Figure 2e shows the end wall of the secondary barrier system. Top panel 104, which is placed on the inner surface of respective cold insulation panels 102 as explained below, can be seen lining the hull/hold at a height above the membrane 1. As discussed in relation to Figure 1 c, a plurality of horizontal non-corrugated panels extend between vertical corrugated panels 18 and corner pieces 7, 8, 9, 10 to form the end wall of the membrane 1 . The upper edge of the end wall of the membrane 1 may be formed by another corner piece 65 that is attached to the upper-most horizontal panels 17. The corner pieces 19 includes non-corrugated portions 19 that connected non-corrugated panels of the floor and the wall, and corrugated pieces 19' that connect the vertical corrugated panels 18 with the

longitudinal corrugated panels 14.

As can be seen, substantially the entire inner surface of the hull/hold is lined with insulation. Thus, the ceiling, side walls, end walls and floor of the hull/hold are lined with insulation, such as the insulating panels 102, 103 and the insulation-filled support member 50 and the insulation-filled boxes 121 and corner portions 105.

Figure 2f shows a cross section of the end wall of the secondary barrier system taken through E-E of Figure 2e. Highlighted in detail F (see Figure 13b below for more details) is the attachment mechanism by which the panels 17 are attached to one another and to the membrane support layer 101 . Figure 3a shows a cut-away view of the secondary barrier with the membrane 1 removed. Thus, the membrane support layer 101 can be seen. The membrane support layer is made from boxes 121 (preferably wooden boxes) and insulating panels 102, 103 covered with top panels 104 (preferably wooden panels) on their inner surfaces. The wood is preferably plywood. The membrane support layer comprises two forms of insulation stack. A plurality of first insulation stacks 201 are used beneath the membrane 1 , and a plurality of second insulation stacks 202 are used at locations where there is no membrane 1 . First insulation stack 201 and second insulation stack 202 are described in detail in Figures 4 and 5.

Figure 3b shows a close up view of detail BA of Figure 3a. Here, the corner between the side wall, the end wall and the floor of the membrane support layer 101 is shown. The corner itself is constructed by a plurality of the boxes 121 . The corner between the side wall and the floor is formed by two boxes 121 , each arranged such that an inner-most planar surface of each box 121 is orientated in the plane of the side wall and the floor respectively. The corner between the side wall and the end wall is formed by two boxes 121 , each arranged such that an inner-most planar surface of each box 121 is orientated in the plane of the side wall and the end wall respectively. The corner between the end wall and the floor is formed by two boxes 121 , each arranged such that an inner-most planar surface of each box 121 is orientated in the plane of the end wall and the floor respectively. Adjacent the boxes 121 , again in the general plane of the floor, end wall and sidewall respectively, is a plurality of top panels 104. Together, the top panels 104 and the inner-most surface of the boxes 121 form the inner surface of the membrane support layer 101.

Figure 3c shows a close up view of detail BB of Figure 3b. This shows a cross- section of the membrane support layer 101 at a corner between the floor and the longitudinal side wall. By comparing Figures 3c and 2c, it can be seen that the transverse-extending panels of the side wall and the floor generally overlie top panels 104 whereas the corner pieces generally overlie boxes 121 . As can be seen, on the outer surface of the top panels 104, insulating panels 102, 103 are attached. The outer surface of these panels 102, 103 is attached to the hull/hold.

Further, between the boxes 121 of the corner of the membrane support layer 101 , the membrane support layer 101 comprises a corner portion 105. The corner portion 105 is an insulating corner piece preferably made from insulating material such as polyurethane foam and possibly also wood. It is shaped so as to fit closely between the two boxes 121 at the corner and the hull/hold.

Figure 3d shows a view of the end wall of the membrane support layer 101 , and shows a cross-section view of the floor, ceiling and side walls of the membrane support layer 101 . As can be seen, boxes 121 are used at the bottom corner of the secondary barrier and at the upper-most extremity of the membrane 1 . These boxes 121 are placed end-to-end and extend generally horizontally. Between the boxes, insulation stacks 201 are provided. The top surface of the insulation stacks 201 can be seen in Figure 3d as comprising horizontally-extending grooves 1042 for fixing the membrane 1 to the membrane support layer 101 . This is explained in more detail in Figure 4. Above the upper-most extremity of the membrane, insulation stacks 202 are provided. The top surface of the insulation stacks 202. These insulation stacks do not comprise any such grooves 1042 as there is no need for any grooves since the membrane is not attached to stacks 202. This is explained in more detail in Figure 5.

Figure 4 gives details of the first type of insulating stack 201. Figure 4a gives a plan view of the stack 201 , Figure 4b gives an exploded view of the stack 201 , Figure 4c gives a cross-section view through AI-AI of the stack 201 and Figure 4d gives an enlarged view of detail AJ of the stack 201.

The stack 201 comprises insulating panels 102, 103 and is used to construct the membrane support layer 101 . The insulating stack 201 comprises a cold insulating panel 102 and a warm insulating panel 103. The warm insulating panel 103 is mounted to the hull/hold wall 106 and the cold insulating panel 102 is mounted to the inner side of the warm insulating panel 103. On the inner surface of the cold insulating panel, a top panel 104 (preferably made of wood, preferably plywood) is mounted. The cold and warm insulating panels 102, 103 have substantially the same dimensions as each other, e.g. around 100- 300mm( preferably 200mm) thick, 500-1500mm (preferably 1000mm) in length and 500- 1500mm (preferably 1000mm) in breadth. The insulating panels 102, 103 are approximately square in plan.

The hull/hold wall 106 comprises a plurality of connecting stubs 1061 that pass through holes in the warm and cold insulating panels 102, 103. The connecting stubs 1061 may be threaded and may secure the insulating panels 102, 103 to the hull/hold wall 106 via washers 1021 , 1031 and nuts 1022, 1033. The holes in the cold insulating panel 102 may be filled with a bung 1023 so as to insulate the holes and connecting stubs 1061.

On the inner surface of the cold insulating panel, the top panel 104 is attached. This may be attached using the connecting stubs 1061 . The top panel 104 is preferably plywood, and acts to protect the surface of the insulating panel 102, 103 and to provide structural support to the insulating panel, such as providing contraction control. Further the top panel 104 allows the attachment of the membrane 1 to the membrane support 101 via the attachments 60 as described below.

The top panel 104 has substantially the same length and breadth as the insulating panels 102, 103. However, it has a substantially smaller thickness, such as less than 50mm, preferably less than 20mm. The top panel 104 is substantially square. The top panel 104 of stack 201 comprises at least one groove 1042 for the attachment of the membrane 1 to the top panel 104. Preferably each panel 104 may comprise two grooves 1042 that are substantially parallel. The number of grooves 1042 (or the presence of grooves 1042 at all) can be determined and selected by the designer of the secondary barrier system so as to allow for the desired level of attachment and security between the membrane 1 and the membrane support 101 , which may vary from system to system. The function of the grooves 1042 are described in more detail in Figures 9, 1 1 and 13.

The groove 1042 may have a uniform depth across its width (the width of the groove 1042 being perpendicular to the direction in which the groove extends and to the direction of the depth of the groove). However, preferably, the groove comprises a deeper section 1042' and a shallower section 1042". The depth of the groove 1042 may substantially be around 1 -10mm, preferably around 5mm.

These two sections 1042', 1042" may extend from opposite sides of the groove 1042. These two sections 1042', 1042" may have substantially the same widths, but preferably the deeper section 1042' is (slightly) wider than the shallower section 1042". For instance, the deeper section may have a width of 10-30mm and the shallower section may have a width of 10-20mm. The deeper section 1042' may be deeper than the shallower section 1042" by an amount substantially equal to the thickness of the material used to form the membrane 1 (as is explained in more detail below).

Preferably the groove 1042 extends across the entirety of the panel 104.

The top panel 104 of the stack also comprises a groove 1041 for housing a weld protection strip 1043. The weld protection strip 1043 may be made from a material that can protection the top panel 104 from the heat of welding when welding is performed at a location above the weld protection strip 1043. The groove 1041 and the strip 1043 may be located at locations where welds are to be placed to secure panels of the membrane 1 to each other, e.g. where panels meet or overlap. Such locations are typically adjacent the grooves 1042 (for reasons that are clear from Figures 9, 1 1 and 13). Thus the groove 1041 and the strip 1043 may be placed adjacent the groove 1042, and may extend parallel to groove 1042. Each groove 1042 may have a groove 1041 adjacent to it.

The depth of the groove 1041 may be substantially equal to the thickness of the strip 1043 (preferably the depth is less than 5mm, preferably less than 2mm, preferable less than 1 mm, preferably less than the depth of groove 1042). The width of the groove 1041 may be substantially equal to the width of the strip 1043 (preferably the width is 10-100mm, preferably 30-80 mm, preferably 50-70 mm). The length of the groove 1041 may be substantially equal to the length of the strip 1043, preferably the length extends across the entirety of panel 104. Around the perimeter of the cold insulating panel 102, a flexible frame 1024 may be placed. This may be made of Rockwool and may act to seal adjacent stacks 201 and boxes 121 to one another.

Around the perimeter of the warm insulating panel 103, a flexible frame 1034 may be placed. This may be made of Rockwool and may act to seal adjacent stacks 201 and boxes 121 to one another.

Preferably, the insulating panels 102, 103 comprise or are made from polyurethane foam.

Figures 5a to 5c show second insulating stack 202. This stack 202 is largely identical to stack 201 , except that no grooves 1041 or 1043 or strips 1043 are present, as they are not needed when no membrane 1 is to be attached to the stack 202.

Figures 6a to 6e show details of the box 121. Figure 6a gives an exploded view of the box 121 , Figure 6b gives a plan view of the box 121 , Figure 6b gives a side view of the box 121 , Figure 6d gives an end view of the box and Figure 6e gives an enlarged view of detail W of the box 121.

The box 121 comprises two portions 122, 123. The box 121 comprises a cold box portion 122 and a warm box portion 123. The warm box portion 123 is mounted to the hull/hold wall 106 and the cold box portion 122 is mounted to the inner side of the warm box portion 123. The cold and warm box portions 122, 123 have substantially the same dimensions as each other , e.g. around 100-300mm( preferably 200mm) thick, 500-1500mm (preferably 1000mm) in length and 100-500mm (preferably around 300mm) in breadth. The warm and cold box portions 122, 123 are approximately rectangular in plan, and cuboidal in shape. The thickness of the box 121 is substantially equal to the thickness of the stacks 201 , 202. The thickness of the cold box portion 122 is substantially equal to the thickness of the cold insulating panel 102. The thickness of the warn box portion 123 is substantially equal to the thickness of the warm insulating panel 103.

The warm box portion 123 takes the form of a closed, hollow box. The box portion 123 is formed of panels, preferably of wood. The box portion 123 is filled with an insulating material 1231 , such as polyurethane foam.

The cold box portion 122 takes the form of a closed, hollow box. The box portion 122 is formed of panels, preferably of wood. The box portion 122 is filled with an insulating material 1221 , such as polyurethane foam. The top panel 1222 of the cold box portion 122 is also the top panel 1222 of the box 121 as a whole.

Each box portion 122, 123 may be divided into cells 1229, 1239. Each cell 1229, 1239 takes the form of a closed hollow portion of the box portions 122, 123, filled with the insulating material 1221 , 1231 . The hull/hold wall 106 comprises a plurality of connecting stubs 1061 that pass through holes in the warm and cold box portions 122, 123 and insulating materials 1221 , 1231. The connecting stubs 1061 may be threaded and may secure the box portions 122, 123 to the hull/hold wall 106 via washers 1224, 1232 and nuts 1225, 1233.

The top 1222 of box 121 comprises at least one groove 1227 for the attachment of the membrane 1 to the box 121 . Preferably each box 121 may comprise only one groove 1227. The number of grooves 1227 (or the presence of grooves 1227 at all) can be determined and selected by the designer of the secondary barrier system so as to allow for the desired level of attachment and security between the membrane 1 and the membrane support 101 , which may vary from system to system. The function of the grooves 1227 are described in more detail in Figures 9, 1 1 and 13.

The groove 1227 may have a uniform depth across its width (the width of the groove 1227 being perpendicular to the direction in which the groove extends and to the direction of the depth of the groove 1227). However, preferably, the groove comprises a deeper section 1227' and a shallower section 1227". The depth of the groove 1227 may substantially be around 1 -10mm, preferably around 5mm. The shape and depth of the groove 1227 may be substantially similar to that of groove 1042.

These two sections 1227', 1227" may extend from opposite sides of the groove 1227. These two sections 1227', 1227" may have substantially the same widths, but preferably the deeper section 1227' is (slightly) wider than the shallower section 1227". For instance, the deeper section may have a width of 10-30mm and the shallower section may have a width of 10-20mm. The deeper section 1227' may be deeper than the shallower section 1227" by an amount substantially equal to the thickness of the material used to form the membrane 1 (as is explained in more detail below).

Preferably the groove 1227 extends across the entirety of the box 121.

The top 1222 of the box 121 also comprises a groove 1228 for housing a weld protection strip 1223. The weld protection strip 1223 may be made from a material that can protection the top panel 1222 from the heat of welding when welding is performed at a location above the weld protection strip 1223. The groove 1228 and the strip 1223 may be located at locations where welds are to be placed to secure panels of the membrane 1 to each other, e.g. where panels meet or overlap. Such locations are typically adjacent the grooves 1227 (for reasons that are clear from Figures 9, 1 1 and 13). Thus the groove 1228 and the strip 1223 may be placed adjacent the groove 1227, and may extend parallel to groove 1227. Each groove 1227 may have a groove 1228 adjacent to it.

The groove 1227 and/or the groove 1228 and/or the strip 1223 may have

substantially similar shapes and dimensions to the groove 1042 and/or the groove 1041 and/or the strip 1043 respectively. The depth of the groove 1228 may be substantially equal to the thickness of the strip 1223 (preferably the depth is less than 5mm, preferably less than 2mm, preferable less than 1 mm, preferably less than the depth of groove 1227). The width of the groove 1228 may be substantially equal to the width of the strip 1223 (preferably the width is 10-100mm, preferably 30-80 mm, preferably 50-70 mm). The length of the groove 1228 may be substantially equal to the length of the strip 1223, preferably the length extends across the entirety of length of the box 121

Preferably the groove 1227 and/or the groove 1228 extend in a direction parallel to the length direction of the box. Figure 7a shows a transverse cross-section of the membrane 1 and the membrane support layer 101 taken through the midpoint of an interrupted transverse corrugation 1 1. As mentioned above, the interrupted transverse corrugation 1 1 is interrupted in the floor region by longitudinal corrugations 13.

Figure 5b shows a close up view of detail I of Figure 5a. This shows that the membrane 1 is attached to the hull/hold wall 106 at the upper-most edge of the membrane 1 . This attachment is preferably achieved by a weld 22. The membrane 1 extends through the membrane support layer 101 in the location of the weld, from the hull/hold wall 106 through to the inner side of the membrane support layer 101. This preferably occurs at a downward angle intermediate the horizontal and the vertical, such as around 30° to the vertical. In order to achieve this, the insulating panels 102, 103 and/or boxes 121 of the membrane support layer 101 are shaped to allow the membrane 1 to pass through the membrane support layer 101 to the hull/hold wall 106. In order for the membrane 1 to extend through the membrane support layer 101 , the uppermost portion of the membrane 1 (i.e. the uppermost portion of the vertical panels 2, 4) may be curved. Preferably, however, there may be an upper corner piece 55, 55' connecting to another partially vertical panel 56, 57 (as can be seen Figure 1 ), which extends through the membrane and is attached to the hull/hold.

The corner piece 55 may be a non-corrugated corner piece when the corner piece connects two non-corrugated panels 57, 4. However, similarly to the other corner pieces discussed above, the corner piece 55' may be a corrugated corner piece when the corner piece connects two corrugated panels 2, 56, so as to provide a continuous, non-interrupted corrugation.

Figure 7c shows a close up view of detail K of Figure 7a (further details of which are given in Figure 1 1 ). This shows a cross-section of an interruption of the interrupted corrugation 1 1. As can be seen, respective ends of two transverse corrugated panels 12 overlap 20 with a longitudinal corrugated panel 14. These panels are welded together.

Figure 7d shows a close up view of detail J of Figure 7a. This shows a cross-section of the corrugated corner piece 6' that joins a horizontal transverse corrugated panel 12 with a partially vertical corrugated panel 3. As can be seen, the corrugation is continuous, i.e. not interrupted, here. Respective ends of the corrugated panels 3, 12 overlap 20 with the corner piece 6'. The panels and the corner piece are welded together. The radius of curvature of the corner piece may be around 10 mm. Further details of the connection between the panels 3, 12 and the corner piece 6' are given below in relation to Figure 10c.

Figure 7e shows a close up view of detail L of Figure 7a. This shows a cross-section of the corrugated corner piece 5' that joins a vertical corrugated panel 2 with a partially vertical corrugated panel 3. As can be seen, the corrugation is continuous, i.e. not interrupted, here. Respective ends of the corrugated panels 2, 3 overlap 20 with the corner piece 5'. The panels and the corner piece are welded together. The radius of curvature of the corner piece may be around 30 mm. Further details of the connection between the panels 2, 3 and the corner piece 5' are given below in relation to Figure 9c.

As can be appreciated from Figure 7, the transverse corrugation that extends both horizontally and vertically from one side of the membrane 1 to the other may only be interrupted in the horizontal/floor portion of the membrane 1. The transverse corrugation may be continuous over the corner pieces and the side walls.

Figure 8a shows a transverse cross-section of the membrane 1 and the membrane support layer 101 taken through the midpoint of a non-interrupted transverse corrugation 15. As mentioned above, the non-interrupted transverse corrugation 15 is not interrupted in the floor region by any longitudinal corrugations 13.

Figure 8b shows a close up view of detail O of Figure 8a. This shows that the membrane 1 is attached to the hull/hold wall 106 at the upper-most edge of the membrane 1 . This attachment is preferably achieved by a weld as shown in Figure 7b. The membrane 1 extends through the membrane support layer 101 in the location of the weld through to the inner side of the membrane support layer 101 . This preferably occurs at a downward angle intermediate the horizontal and the vertical, such as around 30° to the vertical. In order to achieve this, the insulating panels 102, 103 and/or wooden boxes 121 of the membrane support layer 101 are shaped to allow the membrane 1 to pass through the membrane support layer 101 to the hull/hold wall 106. In order for the membrane 1 to extend through the membrane support layer 101 , the uppermost portion of the membrane 1 (i.e. the uppermost portion of the vertical panels 2, 4) may be curved. Preferably, however, there may be an upper corner piece 55, 55' connecting to another partially vertical panel 55, 56, which extends through the membrane 101 and is attached to the hull/hold.

The corner piece 55 may be a non-corrugated corner piece when the corner piece connects two non-corrugated panels 57, 4. However, similarly to the other corner pieces discussed above, the corner piece 55' may be a corrugated corner piece when the corner piece connects two corrugated panels 2, 56, so as to provide a continuous, non-interrupted corrugation.

Figure 8c shows a close up view of detail N of Figure 8a. This shows a cross-section of the corrugated corner piece 6' that joins a horizontal transverse non-interrupted corrugated panel 15 with a partially vertical corrugated panel 3. As can be seen, the corrugation is continuous, i.e. not interrupted, here. Respective ends of the corrugated panels 3, 15 overlap 20 with the corner piece 6'. The panels and the corner piece are welded together. The radius of curvature of the corner piece may be around 10 mm.

Further details of the connection between the panels 3, 15 and the corner piece 6' are given below in relation to Figure 10c.

Figure 8d shows a close up view of detail M of Figure 8a. This shows a cross- section of the corrugated corner piece 5' that joins a vertical corrugated panel 2 with a partially vertical corrugated panel 3. As can be seen, the corrugation is continuous, i.e. not interrupted, here. Respective ends of the corrugated panels 2, 3 overlap 20 with the corner piece 5'. The panels and the corner piece are welded together. The radius of curvature of the corner piece may be around 30 mm. Further details of the connection between the panels 2, 3 and the corner piece 5' are given below in relation to Figure 9c.

As can be appreciated from the Figure 8 embodiment, the non-interrupted

corrugation extends substantially continuously both horizontally and vertically from one side of the membrane 1 to the other, despite being constructed from separate components 15, 6', 3, 5', 2, 55', 56.

Figure 9a shows a plan view of the detail P of the membrane 1 highlighted in Figure 1 b. It shows how transverse corrugated panels 12, transverse non-corrugated panels 16, longitudinal panels 14 and support member plates 51 interact to form the membrane 1.

Regarding an exemplary transverse corrugated panel 2, 3, 12, 15, 56, the length of the panel may be between 0.5m and 10m, or between 1 and 10m, and the precise length will depend on its use, e.g. if it is to be an interrupted panel 12 or a non-interrupted panel. The corrugated panel 2, 3, 12, 15, 56 is generally planar and rectangular in shape and comprises a corrugation 41 that extends in the direction of the length of the rectangle substantially over the entire length L of the panel 2, 3, 12, 15, 56. The corrugation 41 is located at the midpoint of the width of the panel.

The panel 2, 3, 12, 15, 56 comprises a central portion 42, which preferably makes up the majority of the panel 2, 3, 12, 15, 56 and two end cap portions 43. The end cap portions 43 each comprise a tapered corrugation 44, which tapers the corrugation 41 to a flat end 45. The end cap portions 43 are preferably around 100-500mm, preferably 200mm, in length. The radius of the taper of corrugation 44 in the end cap may be around 100mm. Figure 9b shows an enlarged view of detail Q showing in more detail how the transverse corrugated panel 1 1 is connected and sealed to the longitudinal corrugated panel 14. As can be seen, the end cap 43 is attached to the central portion 42 by an overlap 46 and an underlap 46', which are welded to both the central portion 42 and the end cap 43. The overlap/underlap 46 may be around 10-100mm in width and may have a length similar to (though possibly larger or smaller than) the width of the transverse corrugated panel 12. The overlap 46 may have a smaller or larger length than the underlap 46'; the overlap 46 may have smaller or larger width than the underlap 46'. In between the overlap 46 and the underlap 46' the end portion 43 meets the central portion 42 in an end-on fashion. The overlap 46 and underlap 46' extend in the longitudinal direction.

The very end of the transverse corrugated panel 12 (e.g. the end portion of flat portion 45 of end cap 43) may overlap or underlap 20 with the longitudinal corrugated panel. The very end of the transverse non-corrugated panels 16 may overlap or underlap 20 with the longitudinal corrugated panel 13. Further, the transversely-extending edges of the transverse corrugated panel 12 may overlap or underlap 20 with the transversely-extend edges of the adjacent transverse non-corrugated panels 16. This is explained in more detail in Figures 9d and 9e.

Figure 9c shows the corrugated corner piece 5', 6', 55'. When the corrugated panels 2, 3, 12, 15, 56 attach to the corrugated corner piece 5', 6', 55', the relevant end piece 43 of the panel 2, 3, 12, 15, 56 may be omitted. Thus, it is the central portion 42 of the panel 2, 3, 12, 15, 56 that attaches to the corner piece 5', 6', 55'. In this way the corrugation need not be tapered and can effectively be continuous, so as not to be interrupted by the corner piece 5', 6', 55'. The central portion 42 may be attached to the corner piece 5', 6', 55' using the overlap and underlap as described above for the end piece 43. The corner piece may have two planar sections extending at an angle a (preferably between 100-130°, such as around 1 15° as shown in Figure 9c) relative to one another, and separated by a corner section. The corner section may have a radius of curvature of around 30 mm and the two planar sections may extend approximately 150 mm from the corner section.

Figure 9d shows a cross-section view of the membrane 1 taken through line AG-AG shown in Figure 9b. Figure 9e shows an exploded view of Figure 9d. Whilst shown for transverse corrugated panel 12, a similar system is used for where any corrugation is interrupted in the membrane 1 or where any corrugated panel meets another corrugated panel extending perpendicularly or a corner piece.

Starting from the left-hand side, the corrugated transverse panel 12 overlaps 20 with the non-corrugated panel 16. These panels 12 and 16 are welded together to seal the membrane 1 . Weld protection 1043 in groove 1041 protects the membrane support 101 from heat during the welding process. The non-corrugated panel 16 is attached to the membrane support 101 via groove 1042 and sunken portion retainer 48. This attachment 60 is discussed in more detail in Figure 13.

Overlapping both the panels 16 and 12 is overlap 46'. As mentioned above, this is a strip of material used to attach the end piece 43 to the central portion 42 of the corrugated panel 12. Underlapping corrugated panel 12 is the underlap 46'. As mentioned above, this is a strip of material used to attach the end piece 43 to the central portion 42 of the corrugated panel 12. It has a shorter length than the overlap 46. The non-corrugated panel 16 is attached to the membrane support 101 via groove 1042 and sunken portion retainer 48, as is discussed in more detail in Figure 13. The overlap 46 and underlap 46' are welded to the corrugated panel 12 (i.e. to both the central portion 42 and the end piece 43), so as to form a seal, and also possibly the non-corrugated panels.

Since the underlap 46' and the non-corrugated panels 16 are attached to the membrane support 101 , and since the corrugated panel 12 is attached to the non-corrugated panels 16, the entire membrane 1 is attached to the membrane support 101 , in a slidable expandable manner as discussed below in relation to Figure 13.

Figure 10a shows a longitudinal cross-section of the membrane 1 and the membrane support layer 101 taken through the midpoint of a longitudinal corrugation 13. As mentioned above, the longitudinal corrugation 13 is interrupted in the floor region by non-interrupted transverse corrugations 15.

Figure 10b shows a close up view of detail R of Figure 10a. This shows a cross- section of an interruption of the interrupted longitudinal corrugation 13. As can be seen, respective ends of two longitudinal corrugated panels 14 overlap 20 with a transverse corrugated panel 15. These panels are welded together.

Figure 10c shows a close up view of detail S of Figure 10a. This shows a cross- section of the corrugated corner piece 19' that joins a horizontal longitudinal corrugated panel 14 with a corrugated panel 18 of the end wall. As can be seen, the corrugation is continuous, i.e. not interrupted, here. Respective ends of the corrugated panels 14, 18 overlap 20 with the corner piece 19'. The panels and the corner piece are welded together. The radius of curvature of the corner piece may be around 10 mm. Further details of the connection between the panels 14, 18 and the corner piece 19' are given below in relation to Figure 1 1 c.

Figure 10d shows a close up view of detail T of Figure 10a. This shows that the membrane 1 is attached to the hull/hold wall 106 at the upper-most edge of the membrane 1 . This attachment is preferably achieved by a weld. The membrane 1 extends through the membrane support layer 101 in the location of the weld through to the inner side of the membrane support layer 101. This preferably occurs at a downward angle intermediate the horizontal and the vertical, such as around 30° to the vertical. In order to achieve this, the insulating panels 102, 103 and/or wooden boxes 121 of the membrane support layer 101 are shaped to allow the membrane 1 to pass through the membrane support layer 101 to the hull/hold wall 106. In order for the membrane 1 to extend through the membrane support layer 101 , the uppermost portion of the membrane 1 (i.e. the uppermost portion of the vertical panels 2, 4) may be curved. Preferably, however, there may be an upper corner piece 65, 65' connecting to a partially vertical panel 66, 67, which extend through the membrane 101 and is attached to the hull/hold.

The corner piece 65 may be a non-corrugated corner piece when the corner piece connects two non-corrugated panels 67, 17. However, similarly to the other corner pieces discussed above, the corner piece 65' may be a corrugated corner piece when the corner piece connects two corrugated panels 66, 18, so as to provide a continuous, non-interrupted corrugation.

As can be appreciated from the Figure 10 embodiment, the longitudinal corrugation that extends both horizontally and vertically from one end of the membrane 1 to the other may only be interrupted in the horizontal/floor portion of the membrane 1. The longitudinal corrugation may be continuous over the corner pieces and the end walls.

Figure 1 1 a shows a plan view of the detail U of the membrane 1 highlighted in Figure 1 b. It shows how longitudinal corrugated panels 14, transverse non-corrugated panels 16, transverse corrugated panels 12 and support member plates 51 interact to form the membrane 1 .

Regarding an exemplary transverse longitudinal panel 14, 18, 66, the length of the panel may be between 0.5m and 10m, or between 1 and 10m, and the precise length will depend on its use, e.g. if it is to be an interrupted panel 12 or a non-interrupted panel. The corrugated panel 14, 18, 66 is generally planar and rectangular in shape and comprises a corrugation 41 that extends in the direction of the length of the rectangle substantially over the entire length L of the panel 14, 18, 66. The corrugation 41 is located at the midpoint of the width of the panel.

The panel 14, 18, 66 comprises a central portion 42, which preferably makes up the majority of the panel 14, 18, 66 and two end cap portions 43. The end cap portions 43 each comprise a tapered corrugation 44, which tapers the corrugation 41 to a flat end 45. The end cap portions 43 are preferably around 100-500mm, preferably 200mm, in length. The radius of the taper of corrugation 44 in the end cap may be around 100mm.

Figure 1 1 b shows an enlarged view of detail V showing in more detail how the longitudinal corrugated panel 14 is connected and sealed to the transverse corrugated panel 15. As can be seen, the end cap 43 is attached to the central portion 42 by an overlap 46 and an underlap 46', which are welded to both the central portion 42 and the end cap 43. The overlap/underlap 46 may be around 10-100mm in width and may have a length similar to (though possibly larger or smaller than) the width of the transverse corrugated panel 12. The overlap 46 may have smaller or larger length than the underlap 46'; the overlap 46 may have smaller or larger width than the underlap 46'. In between the overlap 46 and the underlap 46' the end portion 43 meets the central portion 42 in an end-on fashion. The overlap 46 and underlap 46' extend in the transverse direction.

The very end of the longitudinal corrugated panel 12 (e.g. the end portion of flat portion 45 of end cap 43) may overlap or underlap 20 with the transverse corrugated panel 15. The very end of the transverse non-corrugated panels 16 may overlap or underlap 20 with the longitudinal corrugated panel 14. Further, the transversely-extending edges of the transverse corrugated panel 15 may overlap or underlap 20 with the transversely-extend edges of the adjacent transverse non-corrugated panels 16. This is explained in more detail in Figures 1 1 d and 1 1 e.

Figure 1 1 c shows the corrugated corner piece 19', 65' shows the corrugated corner piece 19', 65'. When the corrugated panels 14, 18, 66 attach to the corrugated corner piece 19', 65', the relevant end piece 43 of the panel 14, 18, 66 may be omitted. Thus, it is the central portion 42 of the panel 14, 18, 66 that attaches to the corner piece 19', 65'. In this way the corrugation need not be tapered and can effectively be continuous, so as not to be interrupted by the corner piece 19', 65'. The central portion 42 may be attached to the corner piece 19', 65' using the overlap and underlap as described above for the end piece 43. The corner piece may have two planar sections extending at an angle a (preferably around 90°) relative to one another, and separated by a corner section. Alternatively, and as is shown in Figure 1 1 c, the corner piece may have three planar sections each extending at an angle relative to each other such that the total angle of the corner piece is around 90°. For instance, there may be two corner sections separating three planar portions, each corner section having an angle of 135°. The or each corner section may have a radius of curvature of around 30 mm. The or each planar section may extend approximately 100mm from the corner section.

Figure 1 1 d shows a cross-section view of the membrane 1 taken through line AH-AH shown in Figure 1 1 a. Figure 1 1 e shows an exploded view of Figure 1 1 d. Whilst shown for longitudinal corrugated panel 14, a similar system is used for where any corrugation is interrupted in the membrane 1 or where any corrugated panel meets another corrugated panel extending perpendicularly or a corner piece.

Starting from the left-hand side, the corrugated longitudinal panel 14 overlaps 20 with the non-corrugated panel 16. These panels 14 and 16 are welded together to seal the membrane 1 . Since the grooves 1041 run transversely, the panel 16 is not shown as attached to the grooves 1041 in Figure 1 1 d, as is shown in Figure 9d. Overlapping both the panels 16 and 14 is overlap 46'. As mentioned above, this is a strip of material used to attach the end piece 43 to the central portion 42 of the corrugated panel 12. Underlapping corrugated panel 12 is the underlap 46'. As mentioned above, this is a strip of material used to attach the end piece 43 to the central portion 42 of the corrugated panel 14. It has a shorter length than the overlap 46. The non-corrugated panel 16 is attached to the membrane support 101 via groove 1042 and sunken portion retainer 48, as is discussed in more detail in Figure 13. The overlap 46 and underlap 46' are welded to the corrugated panel 14 (i.e. to both the central portion 42 and the end piece 43), so as to form a seal, and also possibly the non-corrugated panels.

Since the underlap 46' and the non-corrugated panels 16 are attached to the membrane support 101 , and since the corrugated panel 14 is attached to the non-corrugated panels 16, the entire membrane 1 is attached to the membrane support 101 , in a slidable expandable manner as discussed below in relation to Figure 13.

Figure 12a shows a transverse cross-section of the membrane 1 and the membrane support layer 101 taken through non-corrugated panels 4, 16, 57 and support members 50 for supporting the primary barrier.

Each support member 50 is attached to the hull/hold and extends through the membrane support layer 101 and the membrane 1. The support member 50 is sealed to the membrane 1 adjacent the support member by a support member plate 51.

The support member 50 comprises an insulating material to prevent heat flowing through the support member. This insulating material may be polyurethane foam and/or a glass fibre reinforced epoxy. The support member 50 may also comprise a metal frame/structure so as to provide strength to the support member 50.

The support member plate 51 is arranged to be sealed to the membrane 1 adjacent the support member. The support member plate 51 is orientated such that it is substantially in the general plane of the membrane 1 in the location of the support member. The plate may be made of Invar.

As can be seen from Figure 12b, which shows a close-up view of detail G in Figure 12a, the membrane 1 overlaps 52 with, and may be welded 53 to, the support plate 51. The overlap 52 may preferably be at least, or around, 3mm. The support plate 51 may be either an integral part of the support member 50 or a separate piece sealed thereto.

There is a plurality of support members 50. The support members 50 are arranged on the floor of the hull/hold and/or on the ceiling and/or on the walls of the hull/hold. The support members 50 are generally evenly distributed in a grid-like pattern so as to provide even support to the primary barrier and so as to maintain the general symmetry of the secondary barrier. Figure 12c shows a close-up view of detail F in Figure 12a. It shows how the membrane 1 is attached directly to the membrane support layer 101 by an attachment 60. Each attachment 60 comprises a sunken portion retainer, in the form of a wedge 48 that is screwed into the groove 1227, such that it is attached to shallow portion 1227" of the groove 1227. The sunken portion retainer 48 is of substantially uniform thickness such that there is a gap 1227"' between the sunken portion retainer 48 and the deeper portion 1227' of the groove 1227. This allows a sunken portion 130 of the membrane 1 (in this case corner portion 6) to extend into the gap 1227"', and thus be held against movement perpendicular to the plane of the membrane 1. However, the membrane 1 may slide in the plane of the membrane 1 whilst being held by the attachment 60. Adjacent the attachment 60, another portion of the membrane (such as panel 16) is attached to the portion 6 that is fixed to the membrane support 101. This is achieved by a weld 53, which can also seal the portions of the membrane 1 to each other. Weld protection 1223 is provided beneath the weld 53 location. At the location of detail F at least, the panel 6 is not attached to the sunken portion retainer 48, and is only held to the membrane support 101 via the weld 53.

The portion 16 of the membrane 1 that is welded to the portion 6 of the membrane 1 that is fixed to the membrane support 1 via attachment 60 comprises a raised portion 140. The raised portion 140 allows the portion 16 to overlap 20 the portion 6 whilst allowing the remainder of the membrane 1 to stay flush against the membrane support 101.

As should be understood, such an attachment 60 (i.e. of a first membrane

component comprising a sunken portion retained, but still slidable, within a groove of the membrane support layer and another membrane component overlapping the sunken portion and fixed and sealed to the first membrane component) may use any combination of the membrane components, such as corner portions, end caps, corrugated panels, non- corrugated panels, support plates, etc., discussed herein.

Regarding Figure 12d, this shows a close-up view of detail H in Figure 12a. This shows the corner section of the membrane support layer 101 . This comprises insulating panels 102, 103 attached to the floor of the hull/hold, a first box 121 located adjacent the corner of the membrane support layer 101 and attached to floor of the hull/hold, a corner portion 105 is located at the corner of the hull/hold and a second box 121 is located adjacent the corner of the membrane support layer 101 and is attached to a side wall of the hull/hold. The boxes 121 and the corner portion 105 are preferably filled with an insulating material such as polyurethane foam.

Figure 13a shows a cross-section viewed from the transverse direction of the membrane 1 . The cross-section shows two neighbouring transverse corrugated panels 12, 15 and the non-corrugated transverse panels 16 in between them. An exploded view of Figure 13a is shown in Figure 13c. Starting from the left-hand side of Figure 13a, there is a transverse corrugated panel 12, 15. This overlaps 20 and is welded to a first non-corrugated transverse panel 161 . Overlapping 20 and welded to the first non-corrugated transverse panel 161 is a second non-corrugated panel 162. Overlapping 20 and welded to the second non-corrugated transverse panel 162 is a third non-corrugated panel 163. Overlapping 20 and welded to the third non-corrugated transverse panel 163 is a second non-corrugated panel 164.

Overlapping 20 and welded to the fourth non-corrugated transverse panel 164 is another transverse corrugated panel 12, 15.

The membrane 1 is attached to the membrane support via a plurality of fixings 60, one of which (detail AK) is shown in more detail in Figure 13b. There is (only) one fixing 60 between the membrane 1 and the membrane support 101 for each location where two panels 12, 15, 16, etc. are joined to each other.

Regarding Figure 13b, the first non-corrugated transverse panel 161 comprises a sunken portion 130. The sunken portion 130 extends in the transverse direction along the length of the edge of the first non-corrugated transverse panel 161 . The sunken portion 130 interacts with a groove 1042, which also extends parallel with the sunken portion 130. This allows the sunken portion 130 to slide in the transverse direction within the groove 1042 when the membrane expands and contracts due to thermal effects.

The sunken portion 130 is step-shaped. The sunken portion 130 comprises a sunken planar portion 132 orientated parallel with the remainder of the first non-corrugated panel 161 . The sunken planar portion 132 is connected to the remainder of the first non- corrugated panel 161 via a step 131 , which extends substantially perpendicularly to the remainder of the first non-corrugated panel 161 .

The sunken planar portion 132 has a length substantially equal to the length of the first non-corrugated panel 161 . The sunken planar portion 132 has a width that is less than the width of deeper portion of the groove 1042', preferably the width of the sunken planar portion 132 is up to 1 mm, 2mm, 3mm, 4mm, 5mm or 10mm (or at least 1 mm, 2mm, 3mm, 4mm, 5mm or 10mm) smaller than the width of the deeper portion of the groove 1042'. This allows the sunken planar portion 132 to slide in the longitudinal direction within the deeper portion of the groove 1042' when the membrane expands and contracts due to thermal effects.

The depth of the sunken planar portion (e.g. the length of the step 131 ) is

approximately equal to the depth of the deeper portion of the groove 1042'. This allows the first non-corrugated panel 161 to sit flush against the membrane support 101 whilst allowing the sunken planar portion 132 to sit flush against the bottom of the deeper portion of the groove 1042'. The distance between neighbouring grooves 1042 in the membrane support 101 is substantially equal to the distance between the sunken portions 130 of the non-corrugated panel(s) 16.

Placed in the groove 1042 is a sunken portion retainer 48. The sunken portion retainer 48 has a length substantially equal to the length of the groove 1042. The sunken portion retainer 48 has a width less than the width of the groove 1042 but greater than the width of the shallower portion of the groove 1042". The sunken portion retainer 48 has a thickness that is substantially equal to the depth of the shallower portion of the groove 1042". The sunken portion retainer 48 is fixed to the bottom of the shallower portion of the groove 1042", for example by means of a screw or a plurality of screws. The sunken portion retainer 48 is fixed to the shallower portion of the groove 1042" such that there is a clearance 49 between the sunken portion retainer 48 and the edge of the deeper groove portion 1042'. The clearance 49 is such that the sunken portion 130 (e.g. the step 131 ) can pass between the sunken portion retainer 48 and the edge of the deeper groove portion 1042', and is such that the first non-corrugated panel 161 can slide in the longitudinal direction when the membrane 1 expands and contracts due to thermal effects. The clearance 49 may be up to 1 mm, 2mm, 3mm, 4mm, 5mm or 10mm (or at least 1 mm, 2mm, 3mm, 4mm, 5mm or 10mm).

Placed over the sunken portion retainer 48 and the edge of the first non-corrugated panel 161 is a second non-corrugated panel 162. The second non-corrugated panel 162 overlaps 20 the first non-corrugated panel 161 . The second non-corrugated panel 162 is welded 53 to the first non-corrugated panel 161 .

The second non-corrugated transverse panel 162 comprises a raised portion 140. The raised portion 140 extends in the transverse direction along the length of the edge of the second non-corrugated transverse panel 162. The raised portion 140 overlaps 20 the first non-corrugated panel 161 . The raised portion 140 is orientated parallel with the remainder of the second non-corrugated panel 162.

The raised portion 140 has a length substantially equal to the length of the second non-corrugated panel 162. The raised portion 140 is raised by an amount substantially equal to the thickness of the first non-corrugated panel 161 , and possibly the thickness of the second non-corrugated panel 162 (the thicknesses of these panels may be equal). This allows the second non-corrugated panel 162 to sit flush against the membrane support 101 whilst allowing the raised portion 140 to sit flush against the first non-corrugated panel.

Between the first non-corrugated panel 161 and the membrane support 101 at a location beneath the overlap 20 and the weld 53 is thermal protection material 1043 placed in the groove 1041 in the membrane support 101 . The thermal protection material 1043 protects the membrane support 101 from the heat of the weld. As can be appreciated from the above discussion, fixing 60 allows thermal expansion and contraction of the membrane 1 both in the longitudinal and transverse directions whilst allowing the membrane 1 to be attached to the membrane support 101 .

Each fixing 60 between different adjacent panels 12, 15, 16, etc. is substantially similar, with one panel having a sunken portion retained in a groove by a sunken portion retainer, said panel being overlapped by an adjacent panel.

Regarding Figure 13c, the corrugated panels 12, 15 do not have any sunken portions, rather they overlap the adjacent non-corrugated panels 161 , 164. The first non- corrugated panel 161 comprises (only) two sunken portions 130 and does not comprise a raised portion. The second non-corrugated panel 162 comprises (only) one raised portion 140 (overlapping the sunken portion 130 of the first non-corrugated panel 161 ) and (only) one sunken portion 130. The third non-corrugated panel 163 is substantially identical to the second non-corrugated panel 162. Thus, the third non-corrugated panel 163 comprises (only) one raised portion 140 (overlapping the sunken portion 130 of the second non- corrugated panel 162) and (only) one sunken portion 130. The fourth non-corrugated panel 164 is substantially identical to the second non-corrugated panel 162. Thus, the fourth non- corrugated panel 164 comprises (only) one raised portion 140 (overlapping the sunken portion 130 of the third non-corrugated panel 163) and (only) only sunken portion 130 (which is overlapped by the corrugated panel 12, 15).

Of course, other configurations are possible.

Figure 14a shows the first non-corrugated panel 161 in more detail. This shows the two sunken portions 130 that extend along the majority of the length of the panel 161. It should be noted that the sunken portions 130 need not extend along the entire length of the panel 161 . At (only) one end of the panel 161 , the panel 161 comprises a raised portion 140 for overlapping another panel, such as a longitudinal corrugated panel 14 or support plate 51 . This raised portion 140 does extend along the entirety of the width of the panel 161 , so that when it is welded to the panel that it overlaps, the membrane 1 can be completely sealed.

Figure 14b shows a cross-section of Figure 14a taken through line X-X.

Figure 14c shows an enlarged view of detail Y of Figure 14b. Here, the sunken portion 130 can be seen.

Figure 15a shows the second or third non-corrugated panel 162, 163 in more detail. The (only one) sunken portion 130 extends along the majority of the length of the panel 162, 163. It should be noted that the sunken portion 130 need not extend along the entire length of the panel 161 . Along the other length side of the panel 162, 163 is the raised portion 140. This raised portion 140 does extend along the entirety of the length of the panel 161 , so that when it is welded to the panel that it overlaps, the membrane 1 can be completely sealed. At (only) one end of the panel 162, 163, the panel 162, 163 comprises a raised portion 140 for overlapping another panel, such as a longitudinal corrugated panel 14 or support plate 51 . This raised portion 140 does extend along the entirety of the width of the panel 161 , so that when it is welded to the panel that it overlaps, the membrane 1 can be completely sealed.

Figure 15b shows a cross-section of Figure 15a taken through line 7.-7..

Figure 15c shows an enlarged view of detail AA of Figure 15b. Here, the raised portion 140 can be seen.

Figure 16a shows the fourth non-corrugated panel 164 in more detail. The (only one) sunken portion 130 extends along the majority of the length of the panel 164. It should be noted that the sunken portion 130 need not extend along the entire length of the panel 164. Along the other length side of the panel 164 is the raised portion 140. This raised portion 140 does extend along the entirety of the length of the panel 164, so that when it is welded to the panel that it overlaps, the membrane 1 can be completely sealed.

At (only) one end of the panel 164, the panel 164 comprises a raised portion 140 for overlapping another panel, such as a longitudinal corrugated panel 14 or support plate 51 . This raised portion 140 does extend along the entirety of the width of the panel 164, so that when it is welded to the panel that it overlaps, the membrane 1 can be completely sealed.

Figure 16b shows a cross-section of Figure 16a taken through line AB-AB.

Figure 16c shows a cross-section of Figure 16a taken through line AC-AC.

Figure 16d shows an enlarged view of detail AD of Figure 16c. Here, the raised portion 140 can be seen.

Panels 161 , 162, 163 and 164 may have substantially the same lengths, or may have different lengths. Panels 161 and 164 may have substantially similar widths. Panels 162 and 163 may have substantially similar widths. Panels 162 and 163 may have smaller widths than panels 161 and 164.

Figure 17a shows in more detail the end cap 43 discussed above. The end cap 43 comprises a corrugation 44 which tapers to a flat end 45. The end cap portions 43 are preferably around 100-500mm, preferably 300mm, in length. The width of the end cap portion 43 is the substantially equal to the width of the corrugated panel (e.g. 12, 14 15, etc.) to which it is attached. The radius R of the taper of corrugation 44 in the end cap may be between 10-100mm, preferably around 50-70mm.

Figure 17b shows a cross-section view of the end cap 43 through line AE-AE of Figure 17a.

Figure 17c shows a cross-section view of the end cap 43 through line AF-AF of

Figure 17a. Figure 18 shows an example of a primary barrier 200 that may be used along with the secondary barrier described above in a barrier system. The primary barrier 200 may be located within the secondary barrier and may be supported by the at least one support member 50 and/or support member plate 51 of the secondary barrier. The primary barrier 200 is a tank. The primary barrier 200 may be sized and shaped so as to fit within the secondary barrier. The primary barrier 200 may be similarly shaped to the secondary barrier, e.g. it may have a similar shape, but may be smaller in dimensions. The tank 200 may be self-supporting, such that it may only be supported in a number of locations by the support members 50, and not continuously over its area, in contrast to the GTT primary barrier.