JP2021081035A - Low-temperature liquid reservoir, manufacturing method therefor, and method for constructing lateral cold resistance relaxation layer - Google Patents

Abstract

To improve workability upon constructing a lateral cold resistance relaxation layer for protecting a low-temperature liquid reservoir.SOLUTION: In a lateral cold resistance relaxation layer 10, a fixing layer 15 contains at least a part of a reinforcing sheet 14 inside, and is fastened to a heat insulating layer 13. The fixing layer 15 can fix the reinforcing sheet 14 in a state of following the surface shape of the heat insulating layer 13. That is, the reinforcing sheet 14 can be laminated on the heat insulating layer 13 without being limited by the surface shape of the heat insulating layer 13. Consequently, when the reinforcing sheet 14 is laminated on the heat insulating layer 13, the step of cutting the surface of the heat insulating layer 13 to make it flat and the step of fixing it with an adhesive can be omitted, so that it is possible to improve workability.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a low-temperature liquid storage tank in which a low-temperature liquid of 0 ° C. or lower is stored, a method of manufacturing the same, and a method of constructing a side cold resistance relaxation layer that protects the liquid barrier of the low-temperature liquid storage tank from a cold impact.

As a conventional low-temperature liquid storage tank, an inner tank for storing low-temperature liquid inside and an outer tank for covering the inner tank from the outside are provided, and a mesh structure is reinforced on a side cooling heat resistance relaxation layer formed on the inner surface of the outer tank. Those provided with a sheet are known (see, for example, Patent Document 1).

Patent No. 3044605 (paragraphs [0002], [0006], [0010], FIGS. 4, 6)

In the conventional low-temperature liquid storage tank described above, the side cooling heat resistance relaxation layer is configured to have a reinforcing sheet on the surface of the heat insulating layer via an adhesive layer. In this configuration, large-scale equipment is required to prevent the reinforcing sheet from floating from the surface of the heat insulating layer, and a process of cutting and flattening the surface of the heat insulating layer before applying the adhesive is required. It was. In particular, in the latter case, the construction of the side cooling heat resistance relaxation layer is performed manually by a worker riding on a gondola suspended on the inner surface of the outer tank. Such a cutting process and the work of removing dust by cutting required enormous man-hours and costs. Further, there is a problem that not only the working environment is deteriorated by dust, but also there is a risk of dust explosion. Therefore, it has been required to improve workability in the construction of the side cooling heat resistance relaxation layer.

In the invention of claim 1 made to solve the above problems, a cold insulation layer is arranged between an inner tank in which a low temperature liquid of 0 ° C. or lower is stored and an outer tank covering the outside thereof, and the outer tank is provided. While the outer surface of the tank is covered with a concrete liquid barrier, the inner surface of the outer tank contains hard urethane foam as the cold insulation layer in order to suppress leakage of the low temperature liquid and alleviate the thermal impact. It is a low-temperature liquid storage tank coated with a side cooling heat resistance relaxing layer having a heat insulating layer, and the side cooling heat resistance relaxing layer is coated with a fixed layer made of hard urethane foam on the inner surface of the heat insulating layer. At least a part of the mesh-structured reinforcing sheet arranged on the surface of the heat insulating layer is a low-temperature liquid storage tank contained in the fixed layer.

The invention of claim 2 includes a plurality of temporary fixing tools that hold the reinforcing sheet in a shape that matches the undulations of the inner surface of the heat insulating layer, and the temporary fixing tools are arranged in the undulating recesses of the heat insulating layer. The low temperature liquid storage tank according to claim 1.

The invention of claim 3 is the low temperature liquid storage tank according to claim 2, wherein the temporary fixing tool is made of resin.

The invention according to claim 4 is any one of claims 1 to 3, wherein the inner surface surface of the heat insulating layer and the fixed layer are chemically and / or physically linked to each other by being in direct contact with each other. The low temperature liquid storage tank described in the item.

The invention of claim 5 is the low temperature liquid storage tank according to any one of claims 1 to 4, wherein the thickness of the fixed layer is 5 to 30 mm.

The invention according to claim 6 is the low temperature liquid storage tank according to any one of claims 1 to 5, wherein the mesh size of the reinforcing sheet is 1.5 to 4 mm.

In the invention of claim 7, a cold insulation layer is arranged between an inner tank in which a low-temperature liquid of 0 ° C. or lower is stored and an outer tank covering the outside thereof, and the outer surface of the outer tank is made of concrete. On the inner surface of the outer tank of the low temperature liquid storage tank covered with a liquid bank, a side having a heat insulating layer containing a hard urethane foam as the cold insulating layer in order to suppress leakage of the low temperature liquid and mitigate a thermal impact. This is a construction method for coating a partial cooling heat resistance relaxation layer, in which the first step of applying a urethane foam raw material to the inner surface of the outer tank and foaming and curing to form a heat insulating layer, and the inner surface of the heat insulating layer. In the second step of stacking the reinforcing sheets having a mesh structure and temporarily fixing them with a plurality of temporary fixing tools, the same or different urethane foam raw material as the heat insulating layer is applied from the inside of the reinforcing sheets, and the reinforcing sheets are foamed and cured. The third step of forming a fixed layer containing at least a part of the above is performed, and the side cooling heat resistance relaxation layer containing the heat insulating layer, the reinforcing sheet, and the fixed layer is formed on the inner surface of the outer tank. This is a method of constructing a side cooling resistance relaxation layer to be coated on concrete.

The invention of claim 8 is a method of manufacturing a low-temperature liquid storage tank for manufacturing a low-temperature liquid storage tank by using the method of constructing the side cooling heat resistance relaxation layer according to claim 7.

According to the disclosure of claims 1, 7 and 8, since the fixed layer contains at least a part of the reinforcing sheet inside and is fixed to the heat insulating layer, the fixed layer has the reinforcing sheet in the surface shape of the heat insulating layer. It can be fixed to the heat insulating layer in a state of being along the line. Here, as a principle of spray construction, since liquid particles are laminated while being foamed, the shape derived from the particles and, in some cases, the spraying pattern emerges on the surface, and it is difficult to avoid unevenness on the surface. In addition, a step due to the shape of a step or groove on the surface of the outer tank may occur. Even if the surface of the heat insulating layer has irregularities or steps as described above, according to the configuration of the present disclosure, the reinforcing sheet can be laminated on the heat insulating layer without being limited in its shape. As a result, when laminating the reinforcing sheets, the step of cutting or polishing the surface of the heat insulating layer to make it flat and the conventional step of fixing the reinforcing sheet to the heat insulating layer with an adhesive can be omitted, and workability can be improved. Can be improved. Further, by including at least a part of the reinforcing sheet inside the fixed layer, the fixed layer and the reinforcing sheet are connected by an anchor effect, and the fixed layer is prevented from peeling off at the interface of the reinforcing sheet.

Further, according to claims 2 and 7, before the fixing layer is applied, the reinforcing sheet is temporarily fixed in a shape that matches the undulations of the heat insulating layer in advance, so that between the reinforcing sheet and the heat insulating layer. The fixed layer can be applied in a state in which the occurrence of floating is suppressed. As a result, the side cooling heat resistance relaxation layer can be formed in a state where the reinforcing sheet is arranged near the surface of the heat insulating layer. In particular, by arranging the temporary fixing tool in the concave-convex concave portion formed on the surface of the heat-insulating layer, the reinforcing sheet can be effectively arranged in the vicinity of the surface of the heat-insulating layer (disclosure of claim 2). By making the temporary fixing tool for temporarily fixing the reinforcing sheet to the heat insulating layer not made of metal but made of resin as in claim 3, it is possible to make it difficult to transfer the cold heat of the low temperature liquid to the heat insulating layer. ..

Here, in the conventional configuration, for example, a rubber-based adhesive such as chloroprene or a plastic-based adhesive such as polyurethane or epoxy is applied between the reinforcing sheet and the heat insulating layer. Separately, the raw materials and equipment for adhesives were also required. In the present disclosure, the fixing layer serves as an adhesive for fixing the reinforcing sheet to the heat insulating layer. Further, in the present disclosure, since the fixed layer and the heat insulating layer are made of the same raw material and can be constructed with the same equipment, the construction period can be shortened. Moreover, since the fixed layer is made of the same urethane foam material as the heat-insulating layer, the affinity is higher than when the adhesive is applied to the heat-insulating layer, and the fixation is stable.

Specifically, the surface of the heat insulating layer (skin layer) and the fixed layer are in direct contact with each other to form a chemical and / or physical bond with each other (disclosure of claim 4). As a chemical bond, urethane bond and van der Waals force (bond) can be mentioned, and as a physical bond, an anchor effect can be mentioned. Thereby, the fixation between the fixed layer and the heat insulating layer can be stabilized. In the urethane bond, an unreacted urethane foam raw material (for example, polyol, polyisocyanate, etc.) remaining in the skin layer of the heat insulating layer reacts with the urethane foam raw material when the fixed layer is sprayed to form a chemical bond. Will be done. In the van der Waals bond, a chemical bond is formed by attracting the highly polar urethane components (urethane bonds) of the heat insulating layer and the fixed layer to each other by van der Waals force. The anchor effect is that the urethane foam raw material when the fixed layer is sprayed enters into the fine irregularities formed in the skin layer of the heat insulating layer, particularly the recesses, and foams and hardens to form a physical bond. By these bonds, the fixed layer can be stably fixed to the heat insulating layer.

Further, it can be easily visually determined whether or not the reinforcing sheet is embedded in the fixed layer (specifically, near the surface of the heat insulating layer). Further, since the reinforcing sheet is embedded in the fixed layer, the possibility of peeling from the heat insulating layer can be reduced as compared with the case where the reinforcing sheet is fixed to the heat insulating layer by an adhesive.

Since the fixing layer includes at least a part of the reinforcing sheet and is arranged on the surface of the side cooling heat resistance relaxing layer, the reinforcing sheet is not arranged on the surface of the side cooling heat resistance relaxing layer, and the appearance is improved. Moreover, the heat insulating performance can be improved because there is no adhesive between the fixed layer and the heat insulating layer.

Here, from the viewpoint of the permeability (transparency) of the urethane foam raw material to the reinforcing sheet, the mesh size of the reinforcing sheet is preferably 1.5 to 4 mm as disclosed in claim 6.

Further, the thickness of the fixed layer needs to be embedded in the fixed layer, and is preferably 10 mm or more. Further, if the thickness is too large, it becomes difficult for the reinforcing sheet to exert a binding force on the surface of the fixed layer. Therefore, the surface of the fixed layer is rapidly shrunk due to the thermal impact of the low-temperature liquid, and cracks are likely to occur. Therefore, 30 mm or less is preferable (disclosure of claim 5).

Breaking front view of the low temperature liquid storage tank according to the embodiment of the present invention Enlarged sectional view of the tank part Cross-sectional view of the side cooling resistance relaxation layer Sectional view of the reinforcing sheet temporarily fixed to the heat insulating layer The figure which shows the construction state of the side cooling resistance relaxation layer to the inner side surface of an outer tank. The figure which shows the flow of the construction method of the side cooling heat resistance relaxation layer Table showing the results of Confirmation Experiment 2

Hereinafter, one embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, the low-temperature liquid storage tank 100 of the present embodiment has a hollow cylindrical tank portion 40 having an inner tank 20 and an outer tank 30, and a cylindrical liquid barrier surrounding the tank portion 40. It consists of 50. The tank portion 40 stores the liquefied natural gas L inside the inner tank 20. The capacity of the low-temperature liquid storage tank 100 is generally 140,000 to 230,000 kL, and in the low-temperature liquid storage tank 100 of 230,000 kL, the diameter of the liquid barrier 50 is about 90 m, and the height thereof is about 40 m. It becomes.

The inner tank 20 and the outer tank 30 are provided with ceiling portions 21 and 31, respectively, and have a structure in which the inside thereof is shielded from the outside. The ceiling portions 21 and 31 have a dome shape with a bulging central portion, and are a space filled with vaporized liquefied natural gas L. Both the inner tank 20 and the outer tank 30 are made of metal, and for example, iron or steel is preferable from the viewpoint of low temperature toughness. In particular, since the inner tank 20 is constantly exposed to extremely low temperatures, an alloy such as nickel containing iron as a main component, which has excellent low temperature toughness, is preferable.

The liquid barrier 50 is installed to prevent the diffusion of the liquefied natural gas L when a leakage accident of the liquefied natural gas L occurs. In the present embodiment, the inner surface of the liquid barrier 50 is the outer surface of the outer tank 30. It is piled up on. The liquid barrier 50 is made of prestressed concrete that is hard to crack.

In the tank portion 40, in the space K formed between the inner tank 20 and the outer tank 30, a cold insulation layer 60 for keeping the liquefied natural gas L at about −160 ° C. and reducing the vaporization of the liquefied natural gas L is provided. It is equipped. The cold insulation layer 60 is composed of a ceiling cold insulation layer 61, a side cold insulation layer 62, and a bottom cold insulation layer 63.

Specifically, of the inner tank 20 and the outer tank 30, the space K formed in the ceiling portions 21 and 31 is filled with granular pearlite or the like having heat insulating performance as the ceiling portion cooling layer 61. Of the inner tank 20 and the outer tank 30, the space K formed in the side portions 22 and 32 is coated with the side cold resistance relaxation layer 10 as the side cold insulation layer 62 on the inner side surface 30S of the outer tank 30. At the same time, between the side cooling heat resistance relaxation layer 10 and the inner tank 20, granular pearlite or the like is filled in the same manner as the ceiling cooling layer 61. Further, in the space K formed in the bottoms 23 and 33 of the inner tank 20 and the outer tank 30, pearlite concrete, lightweight aerated concrete, etc. having load-bearing performance and heat insulating performance are arranged as the bottom cold insulation layer 63. ing. The side cold resistance relaxation layer 10 is formed to prevent the cold impact of the leaked liquefied natural gas L from being rapidly transmitted to the liquid barrier 50. Here, the side cold insulation layer 62 corresponds to the "cold insulation layer" of the present disclosure.

As shown in FIG. 2, the side cooling resistance relaxing layer 10 includes the side cooling resistance relaxing layer 10S that covers the entire inner side surface 30S of the outer tank 30, and the peripheral portion of the inner bottom surface 30T of the outer tank 30 on the entire circumference. It is composed of an annular bottom surface cooling resistance relaxation layer 10T that covers the entire surface. The outer edge of the bottom surface cooling resistance relaxation layer 10T is continuous with the lower end of the side surface cooling resistance relaxation layer 10S, the inner edge is bent upward, and the end surface abuts against the end surface of the bottom cooling layer 63 covering the inner bottom surface 30T. Has been done. Even if the liquefied natural gas L flows into the outer tank 30, the sudden transfer of cold heat (cold heat impact) is suppressed, and the cold heat impact reaches the surface of the liquid barrier 50 inside the outer tank 30. It can be relaxed. Here, when the cold impact of the liquefied natural gas L is slowly transmitted to the liquid barrier 50 over 24 hours or more, the liquid barrier 50 is not rapidly cooled but is gradually cooled. As a result, the liquid barrier 50 is not exposed to the thermal shock, and it is possible to prevent the occurrence of problems such as cracks on the surface thereof.

FIG. 3 shows the cross-sectional structure of the side cooling resistance relaxation layer 10 of the present embodiment. In the side cooling heat resistance relaxation layer 10, a bottom blowing layer 12, a heat insulating layer 13 (13A, 13B), a reinforcing sheet 14, and a fixing layer 15 are laminated on the inner surface (inner side surface 30S and inner bottom surface 30T) of the outer tank 30. Become.

The underblow layer 12, the heat insulating layer 13, and the fixed layer 15 are all made of hard urethane foam formed by foaming and curing a urethane foam raw material. Rigid urethane foam has a relatively thin thickness and has excellent heat insulating performance. Therefore, it is possible to alleviate a sudden temperature change (cold heat impact) due to the cold heat of the liquefied natural gas L and prevent the liquid barrier 50 from being subjected to a cold heat shock.

The lower blowing layer 12 is a layer directly laminated on the inner surface of the outer tank 30, and is a layer that plays a role of a primer for ensuring the adhesiveness of the heat insulating layer 13. The thickness is preferably 0.1 to 5 mm.

The heat shield layer 13 is laminated on the underblow layer 12 and protects the liquid barrier 50 by suppressing and mitigating the rapid transfer of cold heat of the liquefied natural gas L. Therefore, it is preferable that the heat insulating layer 13 has excellent heat insulating performance and compressive strength, and is thin from the viewpoint of efficient use of space. Specifically, those having a density of 40 to 90 kg / m ³ , a thermal conductivity of 0.040 W / mK or less, and a compression strength of 360 kPa or more are preferable. The thickness of the heat insulating layer 13 is preferably 40 mm or more and 60 mm or less. By setting this thickness, it is possible to suppress a local temperature drop in the outer tank 30. In the present embodiment, the heat insulating layer 13 is composed of two layers (13A and 13B), but may be composed of one layer or three or more layers. The skin layer of the heat insulating layer 13 is a high-density urethane layer, and since the ratio of the urethane resin is increased as compared with the core portion, the thermal conductivity is increased and the heat insulating performance is lowered. Therefore, it is preferable that the number of layers constituting the heat insulating layer 13 is small, and it is more preferable that the heat insulating layer 13 is composed of one layer or two layers.

The compressive strength required for the heat shield layer 13 is 40 m (230,000) for the height of the liquid barrier according to "9.5.2.2 Load calculation" in the LNG above-ground storage tank guideline of the Japan Gas Association. Assuming a kL low-temperature liquid storage tank), the safety factor is calculated as 2.0 from "8.4.4 Cold resistance mitigation material", which is about 360 KPa. Therefore, the compressive strength required for the heat insulating layer 13 is 360 KPa or more.

The heat shield layer 13 of the present embodiment has a density of 65 kg / m ³ , a thermal conductivity of 0.022 W / mK, and a compression strength of 520 KPa. The measurement method and the method for preparing a sample for measurement will be described later.

The fixed layer 15 constitutes the outermost surface of the side cooling resistance relaxation layer 10. The fixing layer 15 includes at least a part of a reinforcing sheet 14 having a mesh structure, which will be described later, and is laminated on the heat insulating layer 13. Specifically, the fixing layer 15 is formed by applying a urethane foam raw material from the inside (surface side) of the temporarily fixed reinforcing sheet 14. A part of the applied urethane foam raw material passes through the mesh holes of the reinforcing sheet 14 and comes into direct contact with the surface of the heat insulating layer 13 to be laminated and fixed to the heat insulating layer 13. At that time, at least a part of the reinforcing sheet 14 is embedded inside the fixed layer 15 by the urethane foam raw material.

Since the fixed layer 15 of the present embodiment is composed of the same urethane foam raw material as the heat insulating layer 13, the characteristics such as density and compressive strength are the same as those of the heat insulating layer 13 described above. Here, the density is measured according to JIS K 7222: 2005 / ISO 845: 1988, and the thermal conductivity is measured according to JIS A 1412-: 1999 / ISO 8301: 1999, and the compression strength is measured. Measured in accordance with JIS K 7220: 2006 / ISO 844: 2004.

Specifically, the measurement sample shown below was prepared based on JIS A9526: 2015 and measured. The measurement sample is made by spraying an underblow layer 12 of about 3 mm onto an aluminum plate having a thickness of 900 mm square × 5 mm using a urethane foam raw material for the heat shield layer 13, and then laminating two heat shield layers of about 25 mm. Then, a heat insulating layer 13 having a thickness of about 50 mm was produced. Since the fixed layer 15 is made of the same urethane foam raw material as the heat insulating layer 13, no measurement sample is prepared or measured.

The density was measured by cutting a sample for measurement into a 100 mm square × 30 mm thickness (without a skin layer on the entire surface) so as to include the skin layer of the first heat shield layer 13A in the thickness direction. The thermal conductivity was measured by cutting a measurement sample into a 200 mm square × 25 mm thickness (without a skin layer on the entire surface) so as to include the skin layer of the first heat shield layer 13A in the thickness direction. The compression strength was measured by cutting out the measurement sample into a 50 mm square × 30 mm thickness (without a skin layer on the entire surface) so as to include the skin layer of the first heat insulating layer 13A in the thickness direction.

The reinforcing sheet 14 is laminated near the surface of the heat insulating layer 13 so that at least a part thereof is included in the fixed layer 15. The reinforcing sheet 14 has a mesh structure, and in the present embodiment, it is a glass mesh. The reinforcing sheet 14 may be a mesh structure of carbon fiber or nylon reinforcing material in addition to glass.

The reinforcing sheet 14 prevents the heat insulating layer 13 from locally shrinking due to the cold impact of the liquefied natural gas L to generate cracks. In the present embodiment, since the reinforcing sheet 14 is arranged near the surface of the heat insulating layer 13 with at least a part enclosed in the fixed layer 15, even if a cold impact of liquefied natural gas L is applied to the heat insulating layer 13. The reinforcing sheet 14 suppresses the occurrence of cracks. From the viewpoint of the permeability of the urethane foam raw material, the size of the mesh holes of the reinforcing sheet 14 is preferably 1.5 to 4 mm.

The fixing layer 15 includes at least a part of the reinforcing sheet 14 having a mesh structure and is laminated on the heat insulating layer 13. Here, the reinforcing sheet 14 does not protrude from the surface of the fixed layer 15 toward the inner tank 20, and is arranged inside the surface of the fixed layer 15. Therefore, the thickness of the fixed layer 15 is preferably 5 mm or more, more preferably 10 mm or more. On the other hand, if the thickness is too large (for example, 30 mm or more), the binding force of the reinforcing sheet 14 does not reach the surface of the fixed layer 15, and the fixed layer 15 itself may be cracked due to a thermal impact. The cracks generated in the fixed layer 15 are stopped by the reinforcing sheet 14 embedded in the fixed layer 15, and the heat insulating layer 13 can be protected. However, from an economical point of view, in order to have the function of including the reinforcing sheet 14 inside the fixed layer 15, the thickness thereof is preferably 30 mm or less. The thickness of the fixed layer 15 of the present embodiment is 10 mm. If the thickness is 10 mm, the binding force of the reinforcing sheet 14 with respect to the fixed layer 15 extends to the surface thereof, and it is possible to prevent cracks from entering the fixed layer 15 itself.

Further, as shown in FIG. 4, the reinforcing sheet 14 is fixed to the heat insulating layer 13 with a temporary fixing tool 16. In this embodiment, a tacker is used as the temporary fixing tool 16. Here, the material of the tucker needle (staple) is not particularly limited, but it is more preferable to use a resin needle having a lower thermal conductivity than a metal needle. The temporary fixing tool 16 holds the reinforcing sheet 14 in a shape that matches the undulations of the heat insulating layer 13 and fixes (temporarily fixes) the reinforcing sheet 14. The temporary fixing tool 16 fixes the reinforcing sheet 14 stacked on the heat insulating layer 13 with the undulating recesses of the heat insulating layer 13. By fixing with the recess, the reinforcing sheet 14 can be made to follow by the undulations of the heat insulating layer 13, and it is possible to suppress the occurrence of floating (gap) between the reinforcing sheet 14 and the heat insulating layer 13. The reinforcing sheet 14 does not have to completely follow the undulations of the heat insulating layer 13, and there may be a gap between the reinforcing sheet 14 and the heat insulating layer 13. This gap is filled by the fixed layer 15 when the fixed layers 15 are laminated.

Next, the construction method of the side cooling heat resistance relaxation layer 10 will be described with reference to FIGS. 5 and 6. The construction of the side cooling resistance relaxation layer 10 is arranged on the side portions 22 and 32 of the inner tank 20 and the outer tank 30 in the space K with the inner tank 20, the outer tank 30 and the liquid barrier 50 almost completed. This is done before the granular pearlite as the side cold insulation layer 62 is filled. Therefore, as shown in FIG. 6, an operator enters the narrow space K between the side portion 22 of the inner tank 20 and the side portion 32 of the outer tank 30 to perform the construction. At this time, since the bottom cooling resistance relaxation layer 11 is arranged on the outer tub 30 and the inner tub 20 is arranged on the bottom, it usually goes in and out from an entrance provided on the ceiling (not shown). The width of the side portion 22 of the inner tank 20 and the side portion 32 of the outer tank 30 is 1000 mm to 2000 mm, and the height is about 45 m.

Of the side cooling resistance relaxation layer 10, the construction of the side cooling resistance relaxation layer 10S provided on the inner side surface 30S of the outer tank 30 was attached to a trolley beam installed on a ceiling (not shown) as shown in FIG. The construction is carried out by the worker who got into the gondola 70. The gondola 70 is suspended in the annular space K so as to be able to move up and down and horizontally move along the inner side surface 30S of the outer tank 30.

The construction of the side cooling resistance relaxation layer 10 is performed for each of a plurality of construction regions W in which the inner side surface 30S and the inner bottom surface 30T of the outer tank 30 are vertically divided at predetermined intervals. In the construction of the side cooling resistance relaxation layer 10S, the workers M, N or O who got into the gondola 70 perform the construction area W in order from the upper end portion or the lower end portion. When the construction of a certain construction area W is completed, the work is horizontally moved to the adjacent construction area W, and the construction is repeated from the upper end portion or the lower end portion in the same manner. When the construction area W is constructed in order from the upper end portion or the lower end portion, the region that cannot be constructed from the gondola 70 is horizontally moved to the adjacent construction region W without being constructed. Of the above-mentioned side surface cooling resistance relaxation layer 10S, the area that cannot be constructed from the gondola 70 and the bottom surface cooling resistance relaxation layer 10T are performed by the operator O after the construction of the side cooling resistance relaxation layer 10S is completed, as shown in FIG. .. Alternatively, each time M or N gets off the gondola 70, the construction may be continued.

FIG. 6 shows the flow of construction of the side cooling heat resistance relaxation layer 10. As shown in the figure, in the construction of the side cooling heat resistance relaxation layer 10, the first step S1 is first performed by the worker M. After that, the second step S2 is performed by the worker N so as to chase after the worker M. Further, after that, the third step S3 is performed by the worker O so as to chase the worker N.

In the first step S1, the urethane foam raw material is sprayed onto the inner surface of the outer tank 30 by a spray method and foam-cured to form the heat insulating layer 13. At this time, before forming the heat insulating layer 13, the lower blowing layer 12 is formed by the same spray method.

Specifically, in the first step S1, the worker M sprays the spray gun 90 carried toward the inner surface of the outer tank 30 to form the lower blowing layer 12, and then sprays it again to form the heat insulating layer 13. It is formed to have a predetermined thickness. In the present embodiment, the spraying is performed in two steps to form two heat insulating layers 13A and 13B. This is because even if an attempt is made to form a predetermined thickness by spraying once, the foamed curing of the sprayed urethane foam raw material progresses to some extent, and the urethane foam material hangs down before exhibiting its shape-retaining power, so that the predetermined thickness becomes uniform. This is because it becomes difficult to secure it. In this case, after the first spraying is completed, the second spraying is performed after the curing progresses and the surface tack (stickiness) disappears. The thicknesses of the first heat insulating layer 13A and the second heat insulating layer 13B are formed to be substantially the same.

In the present embodiment, the bottom blown layer 12 is formed by applying the same urethane foam raw material as the heat insulating layer 13. Due to the presence of the lower blowing layer 12, the adhesiveness of the first heat insulating layer 13A to the inner side surface 30S of the outer tank 30 can be improved. Also in this case, after the bottom blowing layer 12 has been sprayed, the spraying is performed after the curing has progressed and the surface tack has disappeared. When the heat insulating layer 13 is formed directly on the inner surface of the outer tank 30 without providing the lower blowing layer 12, heat is taken from the portion of the outer tank 30 made of metal and having high thermal conductivity, which is adhered to the inner surface. There is a risk that the degree of foaming will be insufficient, the adhesive strength between the outer tank 30 and the heat insulating layer 13 will decrease, and the heat insulating layer 13 will come off from the outer tank 30.

In the second step S2, the reinforcing sheet 14 is temporarily fixed to the surface of the heat insulating layer 13 by a tacker. Worker N unwinds the roll-shaped reinforcing sheet 14 loaded on the gondola 70 to the required length, addresses it to the surface of the heat insulating layer 13, and maintains the shape of the reinforcing sheet 14 according to the unevenness of the heat insulating layer 13. In the state, fix it with a tacker. At that time, if the reinforcing sheet 14 is temporarily fixed at the concave and convex recesses of the heat insulating layer 13, the reinforcing sheet 14 can be made to follow the unevenness of the heat insulating layer 13. Here, the reinforcing sheet 14 addressed to the heat insulating layer 13 is temporarily fixed so as to overlap the adjacent construction area W. The overlap between the adjacent reinforcing sheets 14 is not particularly limited, but may be about 50 mm.

In the third step S3, spray spraying is performed on the reinforcing sheet 14 temporarily fixed to the heat insulating layer 13 to form a fixed layer 15 having a predetermined thickness. At this time, the urethane foam raw material is sprayed from the inside (inner tank 20 side) of the reinforcing sheet 14 temporarily fixed to the surface of the heat insulating layer 13. For example, the operator O can easily allow the urethane foam raw material to enter the mesh holes by spraying the spray gun 90 perpendicularly to the mesh holes of the reinforcing sheet 14 from a distance of 20 to 70 cm. In this way, the reinforcing sheet 14 is enclosed in the fixed layer 15 and fixed to the heat insulating layer 13. As a result, the reinforcing sheet 14 temporarily fixed to the heat insulating layer 13 by the tacker in the second step S2 can be arranged near the surface of the heat insulating layer 13 via the fixing layer 15.

At this time, if the foaming and curing speed of the urethane foam raw material is too fast, the passability deteriorates, and the fixing layer 15 is formed before the urethane foam raw material sufficiently passes through the mesh holes of the reinforcing sheet 14. In this case, a gap is likely to occur between the heat insulating layer 13 and the fixed layer 15 (reinforcing sheet 14), the fixing layer 15 and the heat insulating layer 13 are insufficiently adhered, and the fixed layer 15 is completely peeled off from the heat insulating layer 13. There is a risk that it will end up. On the other hand, if the rate of foaming and curing of the urethane foam raw material is too slow, workability deteriorates due to dripping, and it becomes difficult to control the uniformity of thickness.

The urethane foam raw material is composed of a solution A composed of a component other than isocyanate such as a polyol and a solution B composed of isocyanate. The speed at which the urethane foam raw material foams and cures can be evaluated by the time (cream time) at which the raw material begins to swell after mixing and stirring the liquid A and the liquid B. From the viewpoint of permeability and workability, the liquid A can be evaluated. It is preferable that the cream time is 0.1 to 1 second when the liquid B is sprayed with a sprayer in a state where the temperature of the liquid B is adjusted to 40 ° C.

Here, in the adhesion of the fixed layer 15 to the heat insulating layer 13, the surface (skin layer) of the heat insulating layer 13 and the fixed layer 15 are in direct contact with each other to form a chemical and / or physical bond with each other. It will be stable. Specifically, in the skin layer of the heat insulating layer 13, active hydrogen groups derived from isocyanate groups, polyols and the like remain in an unreacted state. By applying a urethane foam raw material for laminating the fixing layer 15 on the heat insulating layer 13, a urethane bond which is a chemical bond with unreacted isocyanate groups and active hydrogen groups existing in the heat insulating layer 13 is formed. it is conceivable that. Therefore, the fixing layer 15 can be stably fixed to the heat insulating layer 13.

Further, the highly polar urethane components (urethane bonds) constituting the heat insulating layer 13 and the fixed layer 15 are attracted to each other by Van der Waals force to form a chemical bond. This also stabilizes the adhesion between the fixing layer 15 and the heat insulating layer 13.

As a physical bond, an anchor effect can be mentioned, and the urethane foam raw material when the fixing layer 15 is sprayed enters into a particularly concave portion of minute irregularities formed in the skin layer of the heat insulating layer 13, and foams and hardens. It is formed. This also stabilizes the adhesion between the fixing layer 15 and the heat insulating layer 13.

The configuration of the side cooling resistance relaxation layer 10 of the present embodiment and the construction method thereof have been described above. Next, the action and effect of the side cooling heat resistance relaxation layer 10 and the construction method thereof will be described.

In the side cooling resistance relaxation layer 10 of the present embodiment, the fixing layer 15 is fixed to the heat insulating layer 13 by embedding at least a part of the reinforcing sheet 14 inside. Therefore, the fixing layer 15 can fix the reinforcing sheet 14 in a state of following the surface shape of the heat insulating layer 13. Here, as a principle of spray construction, since liquid particles are laminated while being foamed, the shape derived from the particles and, in some cases, the spraying pattern emerges on the surface, and it is difficult to avoid unevenness on the surface. In addition, a step due to the shape of a step or groove on the surface of the outer tank 30 may occur. Even if the surface of the heat insulating layer 13 has irregularities or steps as described above, according to the configuration of the present embodiment, the reinforcing sheet 14 can be laminated on the heat insulating layer 13 without being limited by the surface shape. it can. As a result, it is possible to omit the conventional steps of cutting or polishing the surface of the heat insulating layer 13 to make it flat or fixing the reinforcing sheet 14 with an adhesive before laminating the reinforcing sheet 14 on the heat insulating layer 13. Workability can be improved.

Specifically, as described above, when the reinforcing sheet 14 is attached to the surface of the heat insulating layer 13 with an adhesive, the reinforcing sheet 14 may be lifted from the surface of the heat insulating layer 13 due to the rigidity of the reinforcing sheet 14. Therefore, in order to fix the reinforcing sheet 14 to the heat insulating layer 13, a step of cutting and flattening the surface of the heat insulating layer 13 is required. In this cutting process, not only the working environment is deteriorated by the dust of cutting chips generated at the time of cutting, but also there is a risk of dust explosion. On the other hand, in the present embodiment, since the cutting step is not required, the workability can be improved without causing such a problem.

Moreover, since the cutting step is for the purpose of flattening, it is necessary to perform the cutting step after the foam hardening of the heat insulating layer 13 has progressed to develop sufficient strength. If cutting or processing such as a grander is performed before sufficient strength is developed, there is a risk that the material will not be cut flat or will be torn. On the other hand, in the present embodiment, after the curing of the first step S1 has progressed and the surface tack has disappeared, the next second step is performed, and after the second step is completed, the next third step is performed. Do. Therefore, the above-mentioned problems do not occur, and workability can be improved.

Further, the fixing layer 15 plays a role as an adhesive to the heat insulating layer 13 of the reinforcing sheet 14 by incorporating at least a part of the reinforcing sheet 14 inside. In the conventional configuration, as described above, an adhesive such as rubber or plastic is applied between the reinforcing sheet and the heat insulating layer. Therefore, the adhesive is procured separately from the urethane foam raw material. And equipment was required, and there was a risk that management would become complicated. In the present embodiment, the fixed layer 15 can be constructed with the same raw materials and the same equipment as the heat insulating layer 13 and the underblow layer 12, and the management can be simplified and the construction period can be shortened. Moreover, since the fixing layer 15 is the same raw material as the heat insulating layer 13, the affinity is higher than that when the adhesive is applied to the heat insulating layer 13, and the fixing is stable.

Specifically, when the heat insulating layer 13 and the fixed layer 15 are in direct contact with each other, they are urethane-bonded to each other and chemically bonded to each other, or physically bonded by the anchor effect. As a result, the fixing layer 15 and the heat insulating layer 13 are stably adhered to each other. Further, since the urethane components (urethane bonds) constituting the heat insulating layer 13 and the fixed layer 15 are attracted to each other by van der Waals force, the fixed layer 15 can be stably fixed to the heat insulating layer 13.

Moreover, in the conventional configuration, since the adhesive layer is provided between the heat insulating layer 13 and the reinforcing sheet 14, it is not easy to visually check the adhesiveness. In the present embodiment, the fixing layer 15 corresponding to the adhesive is on the outermost surface, and it can be easily visually determined whether or not the reinforcing sheet 14 is included. Therefore, it is possible to easily inspect whether or not the fixed layer 15 (reinforcing sheet 14) is in close contact with the heat insulating layer 13. Further, since the heat insulating layer 13 and the fixed layer 15 are chemically and / or physically bonded, the possibility that the fixed layer 15 is peeled off from the heat insulating layer 13 can be reduced, and at least a part of the reinforcing sheet 14 is a fixed layer. Since it is embedded in 15, the possibility of peeling from the heat insulating layer 13 can be reduced.

Further, the fixed layer 15 is superior in heat insulating performance as compared with the adhesive, and the heat insulating performance of the side cooling heat resistance relaxation layer 10 can be improved.

Further, in the present embodiment, in the second step S2, the reinforcing sheet 14 is temporarily fixed in a state of following the undulations of the heat insulating layer 13 in advance. Therefore, in the third step S3, when the fixed layer 15 is applied, it is possible to suppress the occurrence of floating between the fixed layer 15 and the heat insulating layer 13. Moreover, since the reinforcing sheet 14 is embedded in the fixed layer 15, the reinforcing sheet 14 is not arranged on the outermost surface of the side cooling resistance relaxation layer 10, so that the appearance is improved. Further, the heat insulating performance can be improved as compared with the case where the reinforcing sheet 14 is fixed to the heat insulating layer 13 with an adhesive. Here, if the reinforcing sheet 14 is slackened or distorted diagonally, the reinforcing sheet 14 may be cut and rearranged so as to be straight. At that time, the reinforcing sheets 14 are arranged so as to overlap each other by a predetermined width or more so that a portion where the reinforcing sheet 14 is not arranged does not occur.

[Confirmation experiment 1]
Regarding the side cooling heat resistance relaxation layer 10 of the above embodiment, the fixing layer 15 made of hard urethane foam containing the reinforcing sheet 14 is fixed to the heat insulating layer 13 made of hard urethane foam to prevent heat when receiving a cold impact. It was confirmed by experiments that the occurrence of cracks in the layer 13 could be suppressed. In this experiment, a side cooling heat resistance relaxation layer 10 was formed in the metal mold, liquid nitrogen was poured from above, and it was confirmed whether or not the heat insulating layer 13 was cracked. The temperature of liquid nitrogen is -196 ° C, which is a harsher condition than the liquefied natural gas L at about −160 ° C. In addition, since nitrogen is an inert gas and there is no risk of fire, etc., it was used as an alternative solution for experiments.

Specifically, a dismantleable metal mold having an inner dimension of 1600 mm length × 700 mm width × 100 thickness and whose upper side is open is prepared. The metal mold is erected (the bottom surface is in the length direction and the thickness direction), the bottom surface of the metal mold (the side opposite to the open surface) is regarded as the outer tank 30, and the urethane foam material for the heat insulating layer 13 is sprayed on the bottom surface of about 3 mm. After forming the blowing layer 12, a heat insulating layer 13 having a thickness of 50 mm (the thickness of each layer is 25 mm in a two-layer structure) was formed. A reinforcing sheet 14 is temporarily fixed on the reinforcing sheet 14 with a tacker (resin needle), and a urethane foam raw material is sprayed on the reinforcing sheet 14 to form a fixed layer 15 having a thickness of 10 mm (one-layer structure) for testing. A piece was made. At this time, the same urethane foam raw material was used for the heat insulating layer 13 and the fixed layer 15. As the reinforcing sheet 14, a glass mesh having a mesh hole size of 2.5 mm was used.

Then, the prepared test piece is tilted down (the bottom surface is in the length direction and the width direction), and liquid nitrogen is poured from above (the fixed layer 15 side), so that the liquid level of the liquid nitrogen is 20 to 30 mm above the fixed layer 15. I tried to be. Then, the liquid nitrogen was added as needed so that the liquid level height of the liquid nitrogen was 20 to 30 mm, and 2 hours were allowed to elapse. After 2 hours, liquid nitrogen was removed from the metal mold, and the presence or absence of cracks was visually confirmed. When cracks were generated, a dye diluted with a solvent was dropped from the surface of the cracks with a dropper and left for about 1 hour to color the cracks. Then, the metal mold was disassembled, the test piece was taken out, the test piece was cut, and the cut cross section was visually inspected to confirm the presence or absence of cracks in the heat insulating layer 13. For reference, a reference sample (conventional configuration) in which a reinforcing sheet was fixed to the surface of a heat insulating layer (50 mm thick (two-layer structure with a thickness of each layer of 25 mm)) with an adhesive was prepared.

As a result, the heat insulating layer 13 of the side cooling heat resistance relaxing layer 10 provided with the fixed layer 15 having a thickness of 10 mm (one-layer structure) and the heat insulating layer of the conventional side cooling heat resistance relaxing layer having a reinforcing sheet on the surface of the heat insulating layer. There were no cracks. From this experiment, by fixing the fixing layer 15 made of hard urethane foam containing at least a part of the reinforcing sheet 14 to the heat insulating layer 13 made of hard urethane foam, the hard urethane of the heat insulating layer 13 is subjected to a cold impact. It was confirmed that the occurrence of foam cracks could be suppressed. It was confirmed that the side cold resistance relaxation layer of the present disclosure cushions the cold impact in the same manner as the side cold resistance relaxation layer having a reinforcing sheet on the surface of the conventional heat shield layer.

[Confirmation experiment 2]
As the confirmation experiment 2, the size of the mesh hole of the reinforcing sheet 14 in the confirmation experiment 1 was changed to prepare a test piece, and the same experiment was performed. The mesh hole sizes were 1.0 mm, 1.5 mm, 3.1 mm, 4.0 mm, 6.0 mm, and 8.0 mm in addition to 2.5 mm (confirmation experiment 1). The result is shown in FIG. Here, the handleability is the ease of handling (workability) at the time of manufacturing the test piece, and is the presence or absence of defects such as the end portion being easily loosened and the mesh hole being distorted due to the tension during construction. If there were no such problems, it was marked with "○", and if there were any problems, it was marked with "x". As for the impregnation property, it was confirmed whether or not the urethane foam raw material passed through the mesh holes when the urethane foam raw material was applied. When the urethane foam raw material passed through the mesh holes, it was marked with "○", and when it did not pass, it was marked with "x". When both the handling property and the impregnation property were "○", the judgment was "○", and when either one was "x", the judgment was "x". From the table shown in FIG. 7, it was confirmed that the mesh hole of the reinforcing sheet 14 is preferably 1.5 mm to 4.0 mm.

[Confirmation experiment 3]
Regarding the urethane foam raw material forming the fixed layer 15 in the side cooling resistance relaxation layer 10 of the above embodiment, a plurality of urethane foam raw materials having different foaming and curing speeds (cream time) are prepared, and the heat insulating layer 13 of each urethane foam raw material is prepared. An experiment was conducted to confirm the permeability and workability of the reinforcing sheet 14 temporarily fixed to the surface. In this experiment, when the urethane foam raw material forming the fixed layer 15 was spray-sprayed on the reinforcing sheet 14 temporarily fixed to the heat insulating layer 13, the permeability and workability were visually evaluated. The test piece was prepared in the same manner as in Confirmation Experiment 1.

The cream time of foaming by hand mixing was measured by the following procedure. First, liquid A (components other than isocyanate such as polyol) and liquid B (isocyanate), which are urethane foam raw materials, were weighed and the temperature was adjusted to 10 ° C. for each. Next, the liquid B was put into the container of the liquid A, stirred with the stirring blade adjusted to 3600 rpm for 3 seconds, and then the stirring blade was removed from the container. Then, the time when the liquid level began to rise was measured using a stopwatch. Here, in the construction with the spray foaming machine, the temperatures of the liquid A and the liquid B are high, the reaction is too fast, and it is difficult to measure the difference in cream time. Therefore, by setting the temperatures of the liquid A and the liquid B low and foaming by hand mixing, it is possible to clearly measure the difference in cream time.

As a result, in the case of a urethane foam raw material having a cream time of 1 to 3 seconds in hand mixing, the foaming and curing speed of the urethane foam raw material is too fast, and when construction is performed with a spray foaming machine, the mesh holes of the reinforcing sheet 14 are formed. The fixed layer 15 was formed without sufficiently passing through. In addition, in the case of a urethane foam raw material with a cream time of more than 10 seconds in hand mixing, when the urethane foam raw material is applied with a spray foaming machine, the foaming and curing speed of the urethane foam raw material is too slow, causing dripping and deterioration of workability. have done. From this experiment, when the cream time of foaming by hand mixing is 4 to 10 seconds when the temperature of the urethane foam raw material is 10 ° C., the permeability and workability to the reinforcing sheet 14 can be obtained by applying with a spray foaming machine. Was confirmed to be good. At the time of construction of the side cooling resistance relaxation layer 10 of the above embodiment, the temperature of the liquid A and the liquid B is adjusted to 40 ° C. A urethane foam raw material having a cream time of foaming by hand mixing at 10 ° C. of 4 to 10 seconds has a cream time of 0.1 to 1 second when foamed by a spray foamer at 40 ° C.

[Other Embodiments]
(1) In the above embodiment, the liquefied natural gas L is stored in the low temperature liquid storage tank 100, but other low temperature liquid such as liquefied propane gas may be used.

(2) In the above embodiment, the tank portion 40 includes ceiling portions 21 and 31, but may have a structure in which a lid is provided and the upper portion is open.

(3) In the above embodiment, the fixed layer 15 is one layer, but a plurality of layers may be laminated.

(4) In the above embodiment, the fixing layer 15 includes the reinforcing sheet 14 and is fixed to the heat insulating layer 13. However, the reinforcing sheet 14 is superposed on the heat insulating layer 13, and a conventional rubber-based or plastic-based material is used on the reinforcing sheet 14. Such an adhesive may be applied. In this case as well, the reinforcing sheet 14 may be temporarily fixed to the heat insulating layer 13 with the temporary fixing tool 16 in advance.

(5) In the above embodiment, in the temporary fixing tool 16, the reinforcing sheet 14 overlapped with the heat insulating layer 13 is fixed by the undulating recesses of the heat insulating layer 13, but in addition to the undulating recesses of the heat insulating layer 13, It may be further fixed by the convex portion. As a result, the reinforcing sheet 14 can be made to follow the undulations of the heat insulating layer 13, and it is possible to suppress the occurrence of floating between the reinforcing sheet 14 and the heat insulating layer 13.

(6) In the above embodiment, the roll-shaped reinforcing sheet 14 is used, but it may be cut out into a predetermined shape and used. In particular, the work can be effectively performed in a place where there are steps or grooves on the surface of the outer tank 30. At that time, in order to eliminate the place where the reinforcing sheets 14 are not arranged, the reinforcing sheets 14 are arranged so as to overlap each other.

10 Side cold resistance relaxation layer 13 Heat insulation layer 14 Reinforcing sheet 15 Fixed layer 20 Inner tank 30 Outer tank 62 Side cold insulation layer (cold insulation layer)
50 Liquid barrier 100 Low temperature liquid storage tank L Liquefied natural gas (low temperature liquid)

Claims (8)

A cold insulation layer is arranged between the inner tank in which the low temperature liquid of 0 ° C. or lower is stored and the outer tank covering the outside thereof, and the outer surface of the outer tank is covered with a concrete liquid barrier. The inner surface of the outer tank is coated with a side cooling heat resistance relaxing layer having a heat insulating layer containing a hard urethane foam as the cold insulating layer in order to suppress leakage of the low temperature liquid and alleviate the cold shock. It ’s a liquid storage tank,
In the side cooling resistance relaxation layer, a fixed layer made of hard urethane foam is applied to the inner surface of the heat insulating layer.
A low-temperature liquid storage tank in which at least a part of a reinforcing sheet having a mesh structure arranged on the surface of the heat insulating layer is contained in the fixed layer. A plurality of temporary fasteners for holding the reinforcing sheet in a shape matching the undulations of the inner surface of the heat insulating layer are provided.
The low-temperature liquid storage tank according to claim 1, wherein the temporary fixing tool is arranged in an undulating recess of the heat insulating layer. The low-temperature liquid storage tank according to claim 2, wherein the temporary fixing tool is made of resin. The low-temperature liquid storage tank according to any one of claims 1 to 3, wherein the inner surface of the heat insulating layer and the fixed layer are chemically and / or physically linked to each other by being in direct contact with each other. .. The low-temperature liquid storage tank according to any one of claims 1 to 4, wherein the fixed layer has a thickness of 5 to 30 mm. The low-temperature liquid storage tank according to any one of claims 1 to 5, wherein the reinforcing sheet has a mesh size of 1.5 to 4 mm. A cold insulation layer is arranged between the inner tank in which the low temperature liquid of 0 ° C. or lower is stored and the outer tank covering the outside thereof, and the outer surface of the outer tank is covered with a concrete liquid barrier. The inner surface of the outer tank of the low-temperature liquid storage tank is coated with a side cooling heat resistance relaxation layer having a heat-shielding layer containing a hard urethane foam as the cold insulation layer in order to suppress leakage of the low-temperature liquid and alleviate the cold impact. It is a construction method to be done
The first step of applying a urethane foam raw material to the inner surface of the outer tank and foaming and curing it to form a heat insulating layer.
A second step of stacking a reinforcing sheet having a mesh structure on the inner surface of the heat insulating layer and temporarily fixing the reinforcing sheet with a plurality of temporary fixing tools.
From the inside of the reinforcing sheet, a urethane foam raw material same as or different from the heat insulating layer is applied and foam-cured to form a fixed layer containing at least a part of the reinforcing sheet.
A method for constructing a side cooling resistance relaxing layer that coats the inner side surface of the outer tank with the side cooling heat resistance relaxing layer including the heat insulating layer, the reinforcing sheet, and the fixed layer. A method for manufacturing a low-temperature liquid storage tank, which manufactures a low-temperature liquid storage tank by using the method for constructing a side cooling heat resistance relaxation layer according to claim 7.

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