Fixing device of membrane-type liquefied gas insulation system

Abstract

The present invention relates to a fixing device for fixing a barrier-intersection structure in a membrane-type liquefied gas insulation system comprising an insulation layer installed on the inner wall of a hull, a secondary barrier installed on the upper part of the insulation layer, a primary barrier installed spaced apart from the upper part of the secondary barrier, and a barrier-intersection structure disposed between the secondary barrier and the primary barrier, the fixing device comprising: a base anchor plate installed on the upper surface of the insulation layer; a socket portion fixed on the base anchor plate; and a stud having a lower end fastened to the socket portion and formed to protrude in a vertical direction. The present invention provides a fixing device for a membrane-type liquefied gas insulation system, comprising a fixing member that is fitted into a stud and restrains and fixes the barrier structure in the vertical direction, wherein the secondary barrier is composed of a plurality of membrane sheets connected by overlapping welding, and a vertex or a portion of the corner edge of the membrane sheet is welded on the base anchor plate, wherein a diagonal portion or a cut portion is formed at the vertex or corner edge portion of the membrane sheet to avoid interference with the socket portion and the stud. The fixing device of the membrane-type liquefied gas insulation system according to the present invention has the effect of minimizing membrane penetration and improving the structural stability of the insulation system, as the protruding part does not directly penetrate the secondary barrier and the sealing work of the secondary barrier can be performed without interference with the protruding part, and the welding of the membrane sheet constituting the secondary barrier and the fixing of the structure between barriers can be performed at one point.

Description

Technology Field

[0001] The present invention relates to a fixing device for a membrane-type liquefied gas insulation system, and more specifically, to a fixing device for fixing a structure disposed between a primary and a secondary barrier in a membrane-type liquefied gas insulation system. Background Technology

[0002] Natural gas is transported in a gaseous state through onshore or offshore gas pipelines, or transported to distant consumption sites in the form of liquefied natural gas (LNG) while stored on LNG carriers (LNGCs). LNG is obtained by cooling natural gas to cryogenic temperatures (approximately -163°C), and since its volume is reduced to approximately 1 / 600 of that of natural gas in its gaseous state, it is highly suitable for long-distance transportation by sea.

[0003] Ships used to transport or store LNG, such as LNG carriers that carry LNG across the sea and unload it at onshore locations, are equipped with storage tanks (commonly referred to as 'cargo tanks') specially designed to withstand the cryogenic temperatures of LNG.

[0004] LNG storage tanks can be classified into independent type and membrane type depending on whether the load of the cargo acts directly on the insulation material. Typically, membrane-type storage tanks are constructed with a double barrier structure in which a secondary insulation layer, a secondary barrier, a primary insulation layer, and a primary barrier are sequentially stacked on the inner wall of the hull; representative examples include GTT’s NO 96 type and MARK III type.

[0005] The NO 96 type storage tank has a structure in which the primary and secondary insulation layers are composed of insulation boxes filled with insulating materials such as perlite powder or glass wool inside plywood boxes, and a barrier is formed by installing an invar steel (36% nickel steel) membrane with a thickness of 0.5 to 0.7 mm on the top of the insulation boxes forming each layer.

[0006] These NO 96 type storage tanks have the advantage that the primary and secondary barriers have almost the same liquid tightness and strength, so the cargo can be safely supported by the secondary barrier alone for a considerable period of time in the event of a leak in the primary barrier, the insulation layer composed of insulation boxes can have high compressive strength and rigidity, and the welding automation rate is high.

[0007] The MARK III type storage tank is composed of an insulation panel in which a wooden plywood board is bonded to the upper or lower surface of a polyurethane foam (PUF) layer, and a stainless steel (SUS) membrane approximately 1.2 mm thick is installed on the upper part of the primary insulation layer to form a primary barrier, and a composite material called Triplex is used on the upper part of the secondary insulation layer to form a secondary barrier.

[0008] These MARK III type storage tanks are advantageous in terms of BOR (Boil Off Rate) because the insulation panels based on polyurethane foam insulation have excellent thermal insulation effects. However, since the insulation panels have flexible properties and are susceptible to thermal deformation or hull deformation, it is not easy to apply an Invar steel membrane on top of them. Therefore, a primary barrier is formed using a stainless steel membrane with corrugated sections to absorb thermal shrinkage deformation.

[0009] In addition, due to the structural characteristics of stainless steel membranes having corrugated sections, it is difficult to install a metal membrane between the primary and secondary insulation layers. Therefore, in current MARK III type storage tanks, a composite material called Triplex is used instead of metal to form the secondary barrier, but this has the disadvantage of being vulnerable to watertightness compared to an insulation system where both the primary and secondary barriers are made of metal.

[0010] An insulation system in which the insulation layer is composed of an insulation box, as in the aforementioned NO 96 type storage tank, is called a box type insulation system, and to distinguish it from this, an insulation system in which the insulation layer is composed of an insulation panel, as in the MARK III type storage tank, is called a panel type insulation system.

[0011] Meanwhile, in membrane-type storage tanks, the primary insulation layer installed between the primary and secondary barriers is required to be fixed to the upper part of the secondary insulation layer. In the NO 96 type storage tank, the primary insulation box is fixed to the inner wall of the hull and secured by being fastened to a coupler formed to penetrate the secondary barrier, while in the MARK III type storage tank, the primary insulation panel is fixed to the upper part of the secondary barrier by bonding.

[0012] In cases where the insulation layer fixing device penetrates the secondary barrier, such as in the NO 96 type storage tank, there is a disadvantage that additional welding work is required to seal the penetration of the membrane, and there is also a risk that the seal may be damaged if stress is concentrated at the weld and fatigue failure occurs.

[0013] In addition, in cases where the insulation layer is fixed to the secondary barrier by an adhesive method, such as in a MARK III type storage tank, the secondary barrier follows the behavior of the insulation layer, which can lead to localized stress concentration on the membrane and a decrease in structural stability. The problem to be solved

[0014] Generally, membrane-type storage tanks for storing cryogenic liquefied gases such as LNG are designed to consist of two airtight barriers to protect the hull from cryogenic cargo. Therefore, the insulation system is separated by the two barriers, and a device to fix the membranes constituting each barrier and the adjacent insulation system is required for installation.

[0015] The objective of the present invention is to provide a fixing device for a membrane-type liquefied gas insulation system that can be installed more easily and solves the problems of the aforementioned conventional methods when fixing a structure placed between two barriers installed in a liquefied gas storage tank.

[0016] More specifically, the technical objective of the present invention is to provide a fixing device for a membrane-type liquefied gas insulation system that has excellent structural stability as a structure capable of minimizing membrane penetrations, excellent installation efficiency as the shape and fastening method are simplified, and easy maintenance / repair after installation. means of solving the problem

[0017] According to one aspect of the present invention for achieving the above objective, in a membrane-type liquefied gas insulation system comprising an insulation layer installed on the inner wall of a hull, a secondary barrier installed on the upper part of the insulation layer, a primary barrier installed spaced apart from the upper part of the secondary barrier, and a barrier-interval structure disposed between the secondary barrier and the primary barrier, a fixing device for fixing the barrier-interval structure comprises: a base anchor plate installed on the upper surface of the insulation layer; a socket portion fixed on the base anchor plate; and a stud having a lower end fastened to the socket portion and formed to protrude in a vertical direction. A fixing device for a membrane-type liquefied gas insulation system may be provided, comprising a fixing member that is fitted into the stud and restrains and fixes the barrier structure in the vertical direction, wherein the secondary barrier is composed of a plurality of membrane sheets connected by overlapping welding, and a vertex or a portion of the corner edge of the membrane sheet is welded on the base anchor plate, wherein a diagonal portion or a cut portion is formed at the vertex or corner edge portion of the membrane sheet to avoid interference with the socket portion and the stud.

[0018] The above socket portion may be fixed to the upper part of the base anchor plate by welding and provided in a form that does not penetrate the base anchor plate.

[0019] The above fixing device is installed at least one along the length direction of the membrane sheet at the four corner portions of the membrane sheet and at the corner portions of the membrane sheet, and the membrane sheet has a diagonal portion cut at the corner portions, and a 'V'-shaped cut portion may be formed at the corner portions of the membrane sheet at a position corresponding to the fixing device.

[0020] The base anchor plate of the fixing device installed at the vertex portion of the membrane sheet may have a cross-shaped cross section, and the base anchor plate of the fixing device installed at the corner portion of the membrane sheet may have a straight cross section.

[0021] A thermal protection member is installed between the base plates that are spaced apart from each other, and a plurality of the base plates and the thermal protection member form a grid-shaped line on the upper part of the insulation layer, and the membrane sheet can be overlap welded with the edge of an adjacent membrane sheet while its edge is positioned on the grid-shaped line.

[0022] A stepped groove may be formed on the upper surface of the insulation layer so that the base plate and the thermal protection member can be seated thereon. Effects of the invention

[0024] According to the present invention, the protruding part of the fixing device for fixing a structure installed between a primary barrier and a secondary barrier does not directly penetrate the secondary barrier, and the sealing work of the secondary barrier can be performed without interference with the protruding part of the fixing device. Furthermore, since the welding of the membrane sheet constituting the secondary barrier and the fixing of the structure between barriers can be performed at a single point where the fixing device is installed, the membrane penetration is minimized and the structural stability of the insulation system is improved.

[0025] In addition, according to the present invention, the shape and fastening method of the fixing device are simplified, and additional sealing work on the protrusions of the fixing device is eliminated, thereby improving the efficiency of the installation work and facilitating maintenance and repair even after installation.

[0026] The effects of the present invention are not limited to those described above, and other unmentioned effects will be clearly understood from the description below. Brief explanation of the drawing

[0027] FIG. 1 is a schematic diagram showing the structure of a membrane-type liquefied gas insulation system according to the present invention. FIG. 2 is a perspective view showing the installation structure of a fixing device according to the present invention. FIG. 3 is a perspective view showing a state in which a secondary barrier is installed in the periphery of a fixing device according to the present invention. FIG. 4 is an exploded perspective view of a fixing device according to the present invention. FIG. 5 is a cross-sectional view showing the installation structure of a fixing device according to the present invention. Specific details for implementing the invention

[0028] In order to fully understand the present invention, the operational advantages of the present invention, and the objectives achieved by the implementation of the present invention, reference must be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

[0029] The liquefied gas insulation system of the present invention may include all insulation systems installed in storage tanks that store various types of liquefied gases that can be liquefied at low temperatures for storage / transport, such as LNG, the most representative liquefied gas, as well as LPG (Liquefied petroleum gas), LEG (Liquefied ethylene gas), liquefied ethylene gas, and liquefied propylene gas.

[0030] In the present invention, the terms 'primary' and 'secondary' are used as a criterion for distinguishing whether the LNG stored in the storage tank performs the function of primarily sealing or insulating the LNG, or performs the function of secondarily sealing or insulating the LNG.

[0031] Furthermore, the terms 'upper' or 'top,' conventionally applied to elements of a tank, refer to the direction toward the interior of the tank regardless of the direction of gravity, and likewise, the terms 'lower' or 'bottom' refer to the direction toward the exterior of the tank regardless of the direction of gravity.

[0032] The present invention will be described in detail below by explaining preferred embodiments of the invention with reference to the attached drawings. Identical reference numerals in each drawing indicate identical components.

[0034] FIG. 1 is a schematic diagram showing the structure of a membrane-type liquefied gas insulation system according to the present invention. FIG. 2 is a perspective view showing the installation structure of a fixing device according to the present invention, and FIG. 3 is a perspective view showing a state in which a secondary barrier is installed in the periphery of the fixing device according to the present invention. FIG. 4 is an exploded perspective view of the fixing device according to the present invention, and FIG. 5 is a cross-sectional view showing the installation structure of the fixing device according to the present invention.

[0035] Referring to FIG. 1, the membrane-type liquefied gas insulation system according to the present invention may include an insulation layer (10) installed on the inner wall of the hull and a secondary barrier (20) installed on the upper side of the insulation layer (10). Although omitted in the drawing, a primary barrier may be installed at a position spaced above the secondary barrier (20), and a barrier-inter-barrier structure may be arranged between the secondary barrier (20) and the primary barrier.

[0036] The insulation layer (10) serves as the primary insulation function in the insulation system of the present invention, namely, preventing heat intrusion from the outside of the storage tank, and may be composed of a plurality of insulation panels (11) having a protective plate (11b) attached to the upper or lower surface, or both upper and lower surfaces, of an insulation material (11a) made of polyurethane foam or reinforced polyurethane foam (R-PUF). Here, the protective plate (11b) is intended to protect the insulation material (11a) and provide mechanical rigidity, and may be made of a composite material such as plywood or fiber reinforced plastic (FRP).

[0037] The secondary barrier (20) is designed to secondarily seal the cryogenic liquefied gas contained inside the storage tank, and is designed to allow the liquid sealing and support of the liquefied gas for a considerable period of time in the event of leakage of the primary barrier. The primary barrier and the secondary barrier (20) may be composed of a metal material with high low-temperature brittleness to respond to stress changes caused by the cryogenic temperature of the liquefied gas, and, for example, low-temperature steel such as stainless steel, Invar steel, or aluminum alloy may be used.

[0038] Meanwhile, between the second barrier (20) and the first barrier (not shown), a barrier structure (not shown) may be placed for the purpose of separating the two barriers or functioning as a first insulation layer.

[0039] When the barrier structure functions as a simple spacing layer, it may be formed as a layer having a predetermined thickness of a material that can be used at cryogenic temperatures and can serve as a load-bearing structural material (e.g., a composite material such as plywood or fiber-reinforced plastic, or high-density reinforced polyurethane foam), and when the barrier structure functions as a primary insulation layer, it may be formed as a layer with a structure similar to the insulation panel (11) described above.

[0040] The structure between the barriers needs to be fixed on a structure placed at the bottom, whether it functions as a simple spacing layer or as a primary insulation layer. As mentioned above, the technical problem of the present invention is to provide a fixing device for a membrane-type liquefied gas insulation system that has improved effects in terms of securing structural stability, installation efficiency, and maintenance / repair, as a device for fixing a structure placed between a primary barrier and a secondary barrier (20).

[0041] To achieve the above technical objectives, the present invention aims to provide a new type of fixing device for a membrane-type liquefied gas insulation system designed by considering four conditions: ① the fixing device does not interfere with the welding of the membrane sheet, ② the fixing device does not penetrate the lower barrier, ③ installation is simple due to the simplification of the shape, and ④ maintenance / repair is easy after installation.

[0042] The structure of the fixing device (100) of the membrane-type liquefied gas insulation system according to the present invention will be examined in detail below with reference to FIGS. 2 to 5.

[0043] Referring to FIGS. 2 to 5, the fixing device (100) of the membrane-type liquefied gas insulation system according to the present invention may include a base anchor plate (110) installed on the upper surface of the insulation layer (10), a socket portion (120) fixed on the base anchor plate (110), a stud (130) formed with a lower end fastened to the socket portion (120) and protruding in a vertical direction, and a washer (140) and a fixing nut (150) sequentially fastened on the stud (130).

[0044] The base anchor plate (110) is seated in a groove formed on the upper surface of the insulation layer (10) and can be fixed by a mechanical fastening method using a member such as a screw, rivet, or staple.

[0045] Depending on the installation location, the base anchor plate (110) may have a cross shape as shown in (a) of FIG. 2 or a straight shape as shown in (b) of FIG. 2. Referring again to FIG. 1, in order to form a welding line of a membrane sheet (21) that is provided in a roughly square plate shape, a line consisting of a base anchor plate (110) and a thermal protector (200) is provided in a grid shape on the entire insulation layer (10) composed of a plurality of insulation panels (11). Accordingly, the cross-shaped base anchor plate (110) is placed at the intersection of the grid shape, that is, at the vertex position of the membrane sheet (21), and the straight-shaped base anchor plate (110) is placed at the straight part of the grid shape, that is, at the corner side position of the membrane sheet (21). A straight base anchor plate (110) can be installed at least one along the length direction of the membrane sheet (21) at the corner edge portion of the membrane sheet (21).

[0046] A cross or straight groove may be formed on the upper surface of the insulation layer (10), more specifically on the upper protective plate (11b) of the insulation panel (11), so that the base anchor plate (110) can be seated. At this time, the groove may be provided in a form that extends from the edge end of the insulation panel (11) to the opposite edge end, and a thermal protection member (200) is placed in the remaining space excluding the space where the base anchor plate (110) is seated, thereby preventing damage to the insulation layer (10) by fire during welding of the membrane sheet (21).

[0047] The socket portion (120) can be fixed to the base anchor plate (110) by welding, and it is preferable that the socket portion (120) having a protruding structure be provided in a form that does not penetrate the base anchor plate (110).

[0048] The lower end of the stud (130) can be fastened to the socket portion (120) by a screw connection method, and for this purpose, corresponding screw threads can be formed on the outer surface of the stud (130) and the inner surface of the socket portion (120).

[0049] A washer (140) is fitted onto a stud (130), and a washer (140) having a predetermined area restrains and fixes a structure placed on the upper part of a secondary barrier (20) in the vertical direction. At this time, a fixing nut (150) fastened to the upper part of the stud (130) presses the washer (140) downward, thereby allowing the structure to be firmly fixed. The washer (140) also serves the function of dispersing the pressure acting between the fixed structure and the fixing nut (150).

[0050] Meanwhile, referring to FIG. 3, a structure is shown in which a secondary barrier (20) is installed on the upper part of the insulation layer (10). The secondary barrier (20) may be formed by connecting a plurality of membrane sheets (21), and the edge portions of adjacent membrane sheets (21) may be overlap-welded to form a seal of the secondary barrier (20).

[0051] In addition, the membrane sheet (21) may have a diagonal section (S) formed diagonally at the vertex portion to avoid interference with the protrusions (120, 130) of the fixing device (100) installed on the upper part of the insulation layer (10), and a cut section (C) processed into a 'V' shape at the corner portion.

[0052] First, referring to FIG. 3(a), the membrane sheet (21) can be welded to the base anchor plate (110) of the fixing device (100) at the apex of the diagonal portion (S). At this time, four membrane sheets (21) are arranged so that parts of the diagonal portion (S) overlap each other, and the membrane sheet (21) installed later can be welded not only to the base anchor plate (110) but also partially overlap welded with the previously installed membrane sheet (21).

[0053] Referring to FIG. 3(b), two membrane sheets (21) are arranged to overlap each other based on a fixing device (100). The membrane sheet (21) installed first is welded to a base plate (110) located below a corner edge including a cut portion (C), and the membrane sheet (21) installed later is welded overlappingly to the edge of the membrane sheet (21) installed before the corner edge excluding the cut portion (C), and the cut portion (C) can be welded to the base plate (110).

[0054] In parts where the base anchor plate (110) is not located in Figures 3 (a) and (b), adjacent membrane sheets (21) can form a seal through overlap welding, and a heat protection member (200) is placed in the corresponding part to prevent damage from fire.

[0056] According to the present invention as described above, the protruding part (120, 130) of the fixing device (100) for fixing a structure installed between a first barrier (not shown) and a second barrier (20) does not directly penetrate the second barrier (20), and the sealing operation of the second barrier (20) can be performed without interference with the protruding part (120, 130) of the fixing device (100). Since the welding of the membrane sheet (21) constituting the second barrier (20) and the fixing of the structure (not shown) between barriers can be performed at a single point where the fixing device (100) is installed, the membrane penetration part is minimized and the structural stability of the insulation system is improved.

[0057] In addition, according to the present invention, the shape and fastening method of the fixing device (100) are simplified, and additional sealing work on the protrusions (120, 130) of the fixing device (100) is unnecessary, so the efficiency of the installation work is improved and maintenance and repair are easy even after installation.

[0058] It is obvious to those skilled in the art that the present invention is not limited to the described embodiments and can be modified and varied in various ways without departing from the spirit and scope of the invention. Accordingly, such modifications or variations should be deemed to fall within the scope of the claims of the present invention. Explanation of the symbols

[0059] 10: Insulation layer 11: Insulation panel 20: Second Barrier 21: Membrane sheet S: Diagonal line C: Cutting section 100: Fixture 110: Base Anchor Plate 120: Socket part 130: Stud 140: Washer 150: Fixing nut

Claims

Claim 1 A fixing device for fixing the barrier-intersection structure in a membrane-type liquefied gas insulation system comprising an insulation layer installed on the inner wall of a hull, a secondary barrier installed on the upper part of the insulation layer, a primary barrier installed spaced apart from the upper part of the secondary barrier, and a barrier-intersection structure disposed between the secondary barrier and the primary barrier, wherein the fixing device comprises: a base anchor plate installed on the upper surface of the insulation layer; a socket portion fixed by welding on the base anchor plate and provided in a form that does not penetrate the base anchor plate; a stud having a lower end fastened to the socket portion and formed to protrude in a vertical direction; and a washer having a predetermined area that is fitted into the stud and restrains and fixes the barrier-intersection structure disposed on the upper part of the secondary barrier in the vertical direction. A fixing device for fixing a barrier structure of a membrane-type liquefied gas insulation system, comprising a fixing nut fastened to the upper end of the stud so as to firmly fix the barrier structure by pressing the washer downward, wherein the secondary barrier is composed of a plurality of membrane sheets connected by overlapping welding, and a vertex or a part of the corner edge of the membrane sheet is welded on the base anchor plate, wherein a diagonal section or a cut section is formed at the vertex or corner edge of the membrane sheet to avoid interference with the socket section and the stud. Claim 2 delete Claim 3 A fixing device for fixing a barrier structure of a membrane-type liquefied gas insulation system, wherein, in claim 1, the fixing device is installed at least one along the longitudinal direction of the membrane sheet at the four vertex portions of the membrane sheet and at the corner portions of the membrane sheet, the membrane sheet has a diagonal portion cut at the vertex portions, and a 'V'-shaped cut portion is formed at the corner portions of the membrane sheet at a position corresponding to the fixing device. Claim 4 A fixing device for fixing a barrier structure of a membrane-type liquefied gas insulation system, characterized in that, in claim 3, the base anchor plate of the fixing device installed at the vertex portion of the membrane sheet has a cross-shaped cross section, and the base anchor plate of the fixing device installed at the corner portion of the membrane sheet has a straight cross section. Claim 5 A fixing device for fixing a barrier structure of a membrane-type liquefied gas insulation system, wherein, in claim 4, a thermal protection member is installed between the base anchor plates that are spaced apart from each other, a plurality of the base anchor plates and the thermal protection member form a grid-shaped line overall on the upper part of the insulation layer, and the membrane sheet is overlap-welded with the edge of an adjacent membrane sheet while the edge is positioned on the grid-shaped line. Claim 6 A fixing device for fixing a barrier structure of a membrane-type liquefied gas insulation system, characterized in that, in claim 5, a stepped groove is formed on the upper surface of the insulation layer so that the base anchor plate and the thermal protection member can be seated thereon.

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