KR20220021738A - Lng cargo containment and its construction method - Google Patents

Abstract

Disclosed are a liquefied natural gas cargo hold capable of solving a problem of airtightness and cracking of a joint due to deformation in a membrane weld joint area between dome membranes, and a construction method thereof. According to the present invention, the liquefied natural gas cargo hold comprises a connecting membrane which is coupled to an inner wall membrane of the cargo hold and a liquid dome membrane, respectively, and includes a stretchable part which can be stretched and contracted in response to the longitudinal deformation of the hull, to close the gap between the inner wall membrane and the liquid dome membrane.

Description

Liquefied natural gas cargo hold and its construction method {LNG CARGO CONTAINMENT AND ITS CONSTRUCTION METHOD}

The present invention relates to a liquefied natural gas cargo hold, and more particularly, a liquefied natural gas cargo hold capable of solving the problem of airtightness and cracking of the joint due to deformation in the membrane weld joint area between the inner wall membrane of the cargo hold and the membrane of the liquid dome; It relates to its construction method.

The modern transport of liquefied natural gas (LNG) is carried out in a liquid state in consideration of the maximum load capacity, and long-distance transport from the supply area to the demand area is carried out by ship. A LNG carrier has a hull similar to that of a general cargo carrier in that it must operate stably on the sea, but the cargo hold for LNG, which has to maintain -163 degrees Celsius, must have a material and structure suitable for transporting cryogenic liquids.

Currently, most LNG carriers use austenitic stainless steel (typically SS304L, Fe-18Cr-8Ni) or Invar steel (Fe-36Ni) that retains structural strength and toughness even in contact with cryogenic liquids. there is. Usually, the size of the cargo hold is determined according to the transport capacity, and in consideration of handling safety, ease of loading and unloading, sloshing during operation (sloshing, movement of fluid in a dynamic flow vessel), there are several Separated by dogs.

There are several types of cargo holds for liquefied natural gas transport, and the membrane type in which multiple layers of bulkheads and insulating materials are disposed in a complex manner is the most widely used. It is a method adopted by most ship owners because of its proven stability.

As shown in FIG. 1, the membrane type liquefied natural gas cargo hold has a primary membrane (10) in direct contact with liquefied natural gas on the innermost side, a primary insulation wall (20), 2 It is blocked with multiple layers of secondary membrane (30), secondary insulation (40), and inner hull (H), so it not only maintains the cryogenic temperature of the liquefied natural gas inside, but also the natural leakage during operation. Boil-off gas is also kept to a minimum.

In a typical membrane-type liquefied natural gas cargo hold, the primary membrane 10 is made of stainless steel or Invar steel, as shown in FIG. , the assembly is made by welding.

At this time, while welding the primary membrane 10, which is a rectangular plate, a weld seam in the longitudinal direction is formed, which is caused by various loads from inside and outside the cargo hold (vibration from the power unit during operation, external waves). With respect to hull fluctuation caused by temperature change, hull compression and expansion due to temperature change, weight and pressure change during loading and unloading of cargo, etc.), it has some margin (deformation margin) against deformation in the width direction, but There is almost no margin for deformation.

On the other hand, openings for loading and unloading equipment and various materials are formed in the upper part of the cargo hold, which is generally called a liquefied compartment or 'Liquid Dome'. A membrane having the same shape as that of the above-mentioned primary membrane 10 may be installed in the liquid dome area as well, and the membrane installed in the liquid dome area is the same as the liquid dome membrane 50, but the membrane installed in the liquid dome area is the same as the liquid dome membrane 50, and the remaining A membrane installed in the general area will be referred to as an inner wall membrane 10 .

The liquid dome corresponds to the last operation of the cargo hold production. In order to close the gap (refer to FIG. 2 ) between the liquid dome membrane 50 and the inner wall membrane 10 installed in the liquid dome area, welding between members (eg, butt welding or one side By elongating the membrane member, lap-joint welding or lap-joint welding with a backing plate) can be performed. However, when a load is applied in the longitudinal direction, that is, in the longitudinal direction of the hull, due to the high rigidity in the longitudinal direction by the welding seam of the rectangular membrane by any of the exemplified weld joints, the liquid dome membrane 50 and the inner wall membrane It is self-evident that the largest load will be applied to the welding part of (10) (the part marked with A).

The above-described technical configuration is a background for helping understanding of the present invention, and does not mean a conventional technique widely known in the technical field to which the present invention pertains.

The technical problem to be achieved by the present invention is to provide a liquefied natural gas cargo hold capable of solving the problem of airtightness and cracking of the joint due to deformation in the membrane weld joint region between the inner wall membrane of the cargo hold and the liquid dome membrane, and a construction method thereof.

According to one aspect of the present invention for achieving the above object, it is coupled to the inner wall membrane and the liquid dome membrane of the cargo hold, respectively, and includes a stretchable and contractible part that can be expanded and contracted in response to the longitudinal deformation of the hull, the inner wall membrane and the liquid A liquefied natural gas cargo hold may be provided comprising a connecting membrane that closes the gap between the dome membranes.

The connection membrane may include a first connection plate coupled to the inner wall membrane; a second connection plate coupled to the limud dome membrane; And one side is connected to the first connection plate and the other side is connected to the second connection plate and protrudes in the inner direction of the cargo hold may include a stretchable and contractible by the longitudinal deformation.

The inner wall membrane, the liquid dome membrane, and the connection membrane may be formed of a metal material including stainless steel or Invar steel.

The connecting membrane may further include restraining portions binding the first connecting plate, the second connecting plate, and the stretchable portion to one end at both ends of the connecting membrane, respectively.

The restraining part may be provided by welding and pressing both ends of the first connection plate, the second connection plate, and the stretchable part at both ends of the connection membrane.

The restraining part may have a cross-sectional shape of a single (one) shape.

The inner wall membrane may include a primary membrane that primarily seals the liquefied natural gas.

Separately from the connection membrane, the airtight membrane may further include an airtight membrane coupled to the inner wall membrane and the liquid dome membrane, respectively, to block a gap between the inner wall membrane and the liquid dome membrane.

The airtight membrane may be installed to cover a longitudinal gap between the inner wall membrane and the liquid dome membrane, and the connection membrane may be installed to cover a lateral gap between the inner wall membrane and the liquid dome membrane.

Liquefied natural gas cargo hold according to an aspect of the present invention, the primary membrane sealing the liquefied natural gas and one side of the connecting membrane is coupled; a primary insulating wall provided to be in contact with the connection membrane and the liquid dome membrane to primarily insulate the liquefied natural gas; a secondary membrane provided between the primary insulating wall and the inner wall of the hull to secondaryly seal the liquefied natural gas; and a secondary insulating wall provided between the secondary membrane and the inner wall of the hull to secondaryly insulate the liquefied natural gas.

In addition, according to another aspect of the present invention for achieving the above object, the step of coupling one side of the connecting membrane including the expansion and contraction portion to the inner wall membrane of the cargo hold so as to correspond to the longitudinal deformation of the hull; And there may be provided a construction method of a liquefied natural gas cargo hold comprising the step of coupling the other side of the connecting membrane to the liquid dome membrane.

In a method for constructing a liquefied natural gas cargo hold according to another aspect of the present invention, an airtight membrane is coupled between the inner wall membrane and the liquid dome membrane before the installation operation of the connecting membrane to close the gap between the inner wall membrane and the dome membrane It may include further steps.

The airtight membrane is manufactured in a flat plate shape and is installed to cover the longitudinal gap between the inner wall membrane and the liquid dome membrane, and the connection membrane extends along the lateral direction of the hull and protrudes toward the inside of the cargo hold. It may be installed to cover a lateral gap between the inner wall membrane and the liquid dome membrane, including the expansion and contraction part.

According to an embodiment of the present invention, the connecting membrane connecting the inner wall membrane of the cargo hold and the liquid dome membrane is stretched and contracted by the longitudinal deformation of the hull, thereby preventing airtightness problems and deformation in the weld joint area between the inner wall membrane and the liquid dome membrane. It can solve the joint cracking problem caused by

1 is a cross-sectional view schematically illustrating a structure around a liquid dome of a membrane type cargo hold.
FIG. 2 is a view for explaining a problem in which a load is applied to a weld joint region between an inner wall membrane and a liquid dome membrane due to longitudinal deformation of a hull in a membrane type cargo hold.
3 is a cross-sectional view schematically illustrating a structure around a liquid dome of a cargo hold according to the present invention.
FIG. 4 is a perspective view separately illustrating the connecting membrane shown in FIG. 3 .
FIG. 5 is an enlarged view of an end portion of the connecting membrane shown in FIG. 4 .
6 is a plan view schematically showing the main part of the connecting membrane according to the present invention.
7 is a cross-sectional view taken along lines A and B of FIG. 6 .
8 is a manufacturing process diagram of a connecting membrane according to the present invention.
9 is an operational diagram of a connecting membrane according to the present invention.
10 is a view schematically illustrating that the airtight membrane is coupled between the primary membrane and the liquid dome membrane of the cargo hold according to an embodiment of the present invention.
FIG. 11 is a diagram schematically illustrating that one connecting membrane is coupled between the primary membrane and the liquid dome membrane as a subsequent operation of FIG. 10 .
FIG. 12 is a diagram schematically illustrating that the other connecting membrane is coupled between the primary membrane and the liquid dome membrane as a subsequent operation of FIG. 11 .

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

In the present invention, the use of the terms 'primary' and 'secondary' refers to whether the primary sealing or insulating function or the secondary sealing or insulating function is performed based on the liquefied gas stored in the storage tank. It is used as a classification criterion.

Also, the terms 'upper' or 'above', customarily applied to elements of a storage tank, refer to the direction toward the inside of the storage tank, irrespective of the direction to gravity; Regardless of the direction, it indicates the direction toward the outside of the storage tank.

In the present invention, 'liquefied gas' is liquefied at a low temperature such as LNG, LPG (Liquefied Petroleum Gas), LEG (Liquefied Ethane Gas), liquefied ethylene gas (Liquefied Ethylene Gas), liquefied propylene gas (Liquefied Propylene Gas), etc. It may contain any kind of liquefied gas that can be stored and transported.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings. Like reference numerals in each figure indicate like elements.

3 is a cross-sectional view schematically illustrating a structure around a liquid dome of a cargo hold according to the present invention, FIG. 4 is a perspective view separately illustrating the connecting membrane shown in FIG. 3, and FIG. 5 is an end of the connecting membrane shown in FIG. It is an enlarged view of a part, FIG. 6 is a plan view schematically illustrating a main part of the connecting membrane according to the present invention, and FIG. 7 is a cross-sectional view taken along lines A and B of FIG. 6 .

In addition, FIG. 8 is a manufacturing process diagram of the connecting membrane according to the present invention, FIG. 9 is an operational view of the connecting membrane according to the present invention, and FIG. 10 is between the primary membrane and the liquid dome membrane of the cargo hold according to the embodiment of the present invention. It is a view schematically showing that an airtight membrane is coupled to the As a subsequent operation of FIG. 11 , it is a diagram schematically illustrating that the other connecting membrane is coupled between the primary membrane and the liquid dome membrane.

As shown in these drawings, the liquefied natural gas cargo hold according to the present invention connects between the inner wall membrane 10 and the liquid dome membrane 50 to close the gap between the two membranes 10 and 50 ( 100 , and an airtight membrane 200 that connects the inner wall membrane 10 and the liquid dome membrane 50 separately from the connecting membrane 100 to close a gap between the two membranes 10 and 50 .

The connecting membrane 100 and the airtight membrane 200 are made of the same material as the inner wall membrane 10 of the cargo hold (eg, stainless steel, Invar steel, etc.) or any material having the same quality standard (strength, toughness, fatigue strength, etc.) after welding. of can be applied.

In addition, the connecting membrane 100 and the airtight membrane 200 may be provided with a rectangular plate like the inner wall membrane 100, and the connecting membrane 100 may have a longitudinal direction corresponding to the width direction of the hull, The airtight membrane 200 may have a longitudinal direction corresponding to the longitudinal direction of the hull. That is, the connecting membrane 100 is installed in a direction perpendicular to the longitudinal direction of the inner wall membrane 10 in the longitudinal direction, and the airtight membrane 200 is installed in the same direction as the longitudinal direction of the inner wall membrane 10 . can

Accordingly, in this embodiment, the connecting membrane 100 is installed to cover the lateral gap between the inner wall membrane 10 and the liquid dome membrane 50, and the airtight membrane 200 is the inner wall membrane 20 and the liquid dome membrane ( 50) is installed to cover the longitudinal gap. Here, the 'transverse gap' means the distance between the inner wall membrane 10 and the dome membrane 50 facing each other along the longitudinal direction of the hull, and the 'longitudinal gap' means the inner wall membrane along the transverse direction of the hull. (10) and the dome membrane (50) refers to the distance between the facing each other.

The connecting membrane 100, as shown in FIG. 3, has one side coupled to the inner wall membrane 10 of the cargo hold and the other side coupled to the liquid dome membrane 50, and as shown in FIG. 9, the With respect to longitudinal deformation, it is possible to prevent problems such as airtightness in discontinuities between membranes and joint cracks due to deformation by responding to tensile and compressive conditions without any problems.

Referring to FIG. 4 , the connecting membrane 100 in the present invention corresponds to the transverse spacing between the inner wall membrane 10 of the cargo hold and the liquid dome membrane 50 (discontinuous spacing formed along the transverse direction of the hull). It includes the central portion 110 and the restraint welding portions 120 at both ends exceeding the discontinuous interval.

The central part 110 includes a first connection plate 111 connected to the inner wall membrane 10 of the cargo hold, a second connection plate 112 connected to the liquid dome membrane 50, and a first connection plate 111 . And the second connecting plate 112 includes an expansion and contraction portion 113 that protrudes in the inner direction of the cargo hold and expands and contracts by the longitudinal deformation of the hull.

The first connection plate 111 and the second connection plate 112 may be welded to the inner wall membrane 10 and the liquid dome membrane 50 , respectively.

The stretchable part 113 is formed at a position corresponding to the gap (gap) formed between the inner wall membrane 10 of the cargo hold and the liquid dome membrane 50, and is turned over as shown in (a) of FIG. 7 . By having a U'-shaped cross-sectional shape, it is possible to cope with the longitudinal deformation of the hull by compression or tension action.

For example, when the longitudinal deformation of the hull acts in the right direction in the drawing as shown in FIG. ) can be tensioned and effectively counteract the longitudinal deformation of the hull. Figure 9 (b) shows the opposite to that of Figure 9 (a).

The constraint weld 120 is formed at both ends of the connecting membrane 100, and exceeds the discontinuous gap between the inner wall membrane 10 and the liquid dome membrane 50 formed along the transverse direction of the hull, and another inner wall membrane (10) can be welded. In addition, as will be described later, when the hermetic membrane 200 is installed first in the present embodiment, the constraining welding portion 120 of the connecting membrane 100 may be welded to the hermetic membrane 200 . Welding of the constraint weld 120 and the inner wall membrane 10 or the airtight membrane 200 may be performed by a lap joint welding method.

As shown in FIG. 5 , the constraint welding part 120 includes the first connection plate 111 and the second connection plate 112 and the expansion and contraction part 113 that extend from the central part 110 and are connected to one another. ) includes a constraint 121 that binds together in the shape of a shape.

The stretchable part 113 having a 'U' shape inverted in the central part 110 is merged into one in the restraining part 121, and the two plates, which were arranged parallel to each other with a predetermined space therein, are combined into one, and accordingly, the restraining part ( 121), as shown in FIG.

In addition, as shown in FIG. 5 , the first connecting plate 111 and the second connecting plate 112 disposed at a distance from each other in the central portion 110 may also be joined to each other in the restraining portion 121 , The end portions of the first connection plate 111 , the second connection plate 112 , and the stretchable part 113 are joined by welding to form one restraint part 121 .

As will be described later, the restraining part 121 is, as shown in (e) and (f) of FIG. It may be prepared by pressing and then welding the contacting regions.

Referring to FIG. 7 , the height L1 of the stretchable part 113 in this embodiment may be 5 to 100 mm, and the horizontal length L2 of the first connection plate 111 and the second connection plate 112 is It may be 100 to 200 mm, R1 and R2 may be in the range of 0.2 to 2 times the horizontal length (L2) of the first connection plate 111 and the second connection plate 112.

In addition, referring to FIG. 6 , the length L3 of the constraining welding portion 120 formed at both ends of the connecting membrane 100 is the transverse length L2 of the first connecting plate 111 and the second connecting plate 112 . It may be 0.2 times to 2 times of

Hereinafter, a method of manufacturing the connecting membrane 100 according to the present invention will be briefly described with reference to FIG. 8 .

(A) First, as shown in (a) of FIG. 8, on a jig having a curvature corresponding to 0.7 to 1.0 times the curvature (R1) that the upper end of the stretchable part 113 will have at the center of the plate to be a member Apply bending processing. The bending processing method may vary depending on the thickness of the plate and the curvature size of the stretchable portion 13. In general, cold bending processing is performed, or when the thickness is thin and the curvature is small, warm processing (0.3Tm ~ 0.7Tm, Tm: melting point temperature) may be applied.

(B) Next, as shown in (b) of FIG. 8, the joint curvature (R2: the first connection plate 111 and the second connection plate 112 at a portion corresponding to a certain length on both sides from the center of the plate material) ) and a jig having a curvature corresponding to 0.7 to 1.0 times the curvature of the area in contact with each of the stretching parts 1113) and bending. At this time, the bending amount varies depending on the thickness, curvature (R1, R2) and processing temperature of the plate, but considering the spring-back, the bending amount on the R1 side is at least 180 degrees, and the bending amount on the R2 side is at least 90 degrees or more. should be

(C) After bending is completed, as shown in (c) of FIG. 8, for dimensional correction, the first connection plate ( 111) and the shape and dimensions of the second connection plate 112 in the longitudinal direction are corrected.

(D) Figure 8 (d) shows the state of the member that has undergone the processes (a) to (c).

(E) Next, as shown in (e) of FIG. 8, in order to form the constraining parts 121 on both ends of the member, the side surfaces of the expansion and contraction parts 113 at the end of the member are compressed with a jig. It is mechanically pressed, and accordingly, the cross-sectional shape of the stretchable part 113 is processed from the shape of (a) of FIG. 7 to the shape of (b) of FIG. 7 .

(B) Finally, as shown in (f) of FIG. 8, airtightness is secured at both ends of the member through vertical upward welding. In this embodiment, the welding machine and the welding technique are all possible bonding methods that are airtight.

In the above process, steps (A), (B) and (E), (F) can be performed simultaneously by appropriate equipment and processing conditions.

Hereinafter, a membrane construction method around the liquid dome in the cargo hold according to the present invention will be briefly described with reference to FIGS. 10 to 12 .

(A) First, as shown in FIG. 10, in order to give an airtight effect to the longitudinal gap between the inner wall membrane 10 and the liquid dome membrane 50, a rectangular airtight membrane 200 is applied to the longitudinal gap and lap joint welding At this time, since the liquid dome structure has already been welded to maintain the structural strength with the hull at the upper part (refer to FIG. 3), the lower part only needs to be superimposed for sealing effect between the membranes.

(B) Next, as shown in FIG. 11, the primary membrane 10 of the cargo hold inner wall, the liquid dome membrane 50 under the liquid dome, and the longitudinal gap by applying the connecting membrane 100 to the right transverse gap All areas connected to the airtight membrane 200 covering the lap joint are welded.

(C) Next, as shown in FIG. 12 , the connecting membrane 100 is welded to the left lateral gap in the same manner as in (B) above.

In the present invention, the stretchable part 113 of the connecting membrane 100 can be stretched (compressed and stretched) in response to a change in the spacing in the longitudinal direction of the hull (left and right direction with reference to FIG. 12), and the restraining parts 121 at both ends. ) is welded around the airtight membrane 200 and the three-sided lap joint so that there is no longitudinal deformation. Therefore, the load applied to the central portion 110 is not applied to the vertical upward welding portion applied to the connection membrane 100 for airtightness, that is, the restraining portion 121 .

As described above, according to the present invention, by providing a connection structure capable of responding to structural deformations intensively applied to the discontinuous gap between the inner wall membrane 10 and the liquid dome membrane 50 of the cargo hold and a bonding method thereof, the membranous type A safer and more airtight joint can be formed for discontinuities occurring inside the cargo hold.

In particular, according to the present invention, by the connecting membrane 100 installed between the transverse spacing of the inner wall membrane 10 of the cargo hold and the liquid dome membrane 50, there is no problem in tension and compression conditions due to longitudinal deformation of the hull. It is possible to respond, so it is possible to prevent problems such as airtightness in the discontinuous part of the cargo hold and cracking of joints due to deformation.

The present invention is not limited to the described embodiments, and it is apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. Accordingly, it should be said that such modifications or variations are included in the claims of the present invention.

10: primary membrane
20: primary insulation wall
30: secondary membrane
40: secondary insulation wall
50: liquid dome membrane
100: connecting membrane
110: central part
111: first connection plate
112: second connection plate
113: stretch part
120: constraint weld
121: restraint part
200: airtight membrane
H: hull inner wall

Claims (13)

Liquefied natural gas comprising a connecting membrane coupled to the inner wall membrane and the liquid dome membrane of the cargo hold, respectively, and including an expansion and contraction part capable of expansion and contraction in response to longitudinal deformation of the hull, and blocking the gap between the inner wall membrane and the liquid dome membrane cargo hold. The method according to claim 1,
The connecting membrane is
a first connection plate coupled to the inner wall membrane;
a second connection plate coupled to the limud dome membrane; and
One side is connected to the first connection plate and the other side is connected to the second connection plate, the liquefied natural gas cargo hold comprising a telescopic portion that protrudes in the inner direction of the cargo hold and expands and contracts by the longitudinal deformation. 3. The method according to claim 2,
The inner wall membrane, the liquid dome membrane, and the connecting membrane are liquefied natural gas cargo holds provided with a metallic material including stainless steel or Invar steel. 3. The method according to claim 2,
The connecting membrane is
The liquefied natural gas cargo hold further comprising a restraining portion binding the first connecting plate, the second connecting plate, and the expansion and contraction portions to one end at both ends of the connecting membrane, respectively. 5. The method according to claim 4,
The constraint portion is a liquefied natural gas cargo hold prepared by welding the first connection plate, the second connection plate, and both ends of the expansion and contraction portion at both ends of the connection membrane by welding. 6. The method of claim 5,
The constraint portion is a liquefied natural gas cargo hold having a cross-sectional shape of the one (一) shape. The method according to claim 1,
The inner wall membrane is a liquefied natural gas cargo hold comprising a primary membrane that primarily seals the liquefied natural gas. The method according to claim 1,
The liquefied natural gas cargo hold further comprising an airtight membrane coupled to the inner wall membrane and the liquid dome membrane separately from the connecting membrane to block a gap between the inner wall membrane and the liquid dome membrane. 9. The method of claim 8,
The airtight membrane is installed to cover a longitudinal gap between the inner wall membrane and the liquid dome membrane,
The connecting membrane is a liquefied natural gas cargo hold installed to cover a lateral gap between the inner wall membrane and the liquid dome membrane. The method according to claim 1,
a primary membrane that primarily seals the liquefied natural gas and is coupled to one side of the connecting membrane;
a primary insulating wall provided to be in contact with the connection membrane and the liquid dome membrane to primarily insulate the liquefied natural gas;
a secondary membrane provided between the primary insulating wall and the inner wall of the hull to secondaryly seal the liquefied natural gas; and
A liquefied natural gas cargo hold comprising a secondary insulating wall provided between the secondary membrane and the inner wall of the hull to secondaryly insulate the liquefied natural gas. coupling one side of the connecting membrane including the telescopic portion to the inner wall membrane of the cargo hold so as to be able to cope with the longitudinal deformation of the hull; and
A method of constructing a liquefied natural gas cargo hold comprising the step of coupling the other side of the connecting membrane to the liquid dome membrane. 11. The method of claim 10,
The method for constructing a liquefied natural gas cargo hold further comprising: blocking a gap between the inner wall membrane and the dome membrane by coupling an airtight membrane between the inner wall membrane and the liquid dome membrane before the installation operation of the connecting membrane. 13. The method of claim 12,
The airtight membrane is manufactured in a flat plate shape and installed to cover the longitudinal gap between the inner wall membrane and the liquid dome membrane,
The connecting membrane includes the expansion and contraction part protruding toward the inside of the cargo hold in a form extending along the transverse direction of the hull, the liquefied natural gas cargo hold installed to cover the transverse gap between the inner wall membrane and the liquid dome membrane construction method.

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