JP5158643B2 - Thermal insulation structure of anchor part of above-ground cryogenic tank - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat retaining structure for an anchor portion of a ground type low temperature tank, and relates to a heat retaining structure for an anchor portion intended to prevent a temperature decrease of bottom slab concrete when a tank storing cryogenic liquid such as an LNG tank leaks .

  In a ground-type low temperature tank that stores extremely low temperature liquefied gas (content liquid) such as liquefied natural gas (hereinafter referred to as LNG), a double shell type low temperature conventionally composed of an inner tank and an outer tank is used. Tanks have been commonly used. However, in recent years, PC-structured LNG tanks are becoming mainstream, where an outer tank and a breakwater made of prestressed concrete (hereinafter referred to as “PC”) are integrated, and the liquid leakage of the liquid should be minimized.

  In this type of PC structure LNG tank, the peripheral wall that becomes the breakwater consists of a PC structure in which PC steel wires are wired over almost the entire height at predetermined intervals in the height direction, and a basic circular version Since the flat area is large, it is designed with a PC reinforced concrete structure or the like in which a PC steel wire is wired only on the outer peripheral edge and prestressed.

  In addition, as a structure that blocks the internal cold and keeps warm, non-structural materials with high thermal insulation properties such as cellular concrete, foam glass, pearlite concrete, etc. are used between the inner tub and the outer tub. Over the entire surface of the bottom slab, heater tubes are embedded in a predetermined circumferential shape or a plane spiral shape, and measures are taken to prevent the low temperature brittle strength of the reinforcing bars in the bottom slab concrete.

  FIG. 7 is a cross-sectional view showing a schematic configuration of the internal structure of a conventional underground LNG tank. FIG. 8 is a plan sectional view showing an example of the piping of the heater pipe, taken along section line VIII-VIII in FIG. In FIG. 7, illustration of the cold insulating material filled between the inner tank and the peripheral wall is omitted. As shown in FIG. 7, the inner tub 51 generally made of stainless steel or the like is provided with an anchor structure 50 as a tensile resistance material on the outer peripheral edge of the lower end in order to prevent floating during an earthquake or the like. As the anchor structure 50, an anchor strap made of a stainless steel rod having a shape disclosed in Patent Documents 1 and 2 is attached to the outer peripheral surface of the inner tank. In the bottom concrete 55, the anchor strap and the anchor structure 50 are located in the inner tank so as to be positioned between the pipes of the heater pipes 60 piped in multiple circumferential shapes as shown in the plan sectional view of FIG. (It is not shown in figure) It arrange | positions at predetermined intervals along the outer peripheral surface.

As for a general manner of attaching the anchor strap to the inner tank, Patent Documents 1 and 2 disclose configurations in which the anchor strap is viewed from the side. The lower end fixing portion of the anchor 12 disclosed in Patent Document 1 is housed and fixed in an anchor box 16 formed in a part of bottom slab concrete. The bottom of the anchor strap 30 disclosed in Patent Document 2 is welded to the secondary barrier 8 at a position of a fixing member 33 made of a shape steel welded to the lower surface of the secondary barrier 8.
JP 2003-240196 A JP 2003-247699 A

By the way, when cryogenic LNG (internal liquid) leaks from the inner tank, the cold region expands to the concrete around the anchor box due to heat conduction through the anchor box provided in the bottom slab concrete. A heater tube is also arranged around the anchor box in order to suppress a temperature drop due to the expansion of the cold region. FIG.
(1) Positional relationship between the anchor box 51 formed on the bottom slab concrete 55 and the heater pipe 60 piped on the bottom slab concrete 55
(2) When the brine of a predetermined temperature is circulated in the heater pipe 60 and the bottom slab concrete 55 that is affected by the cold heat during operation is maintained at an appropriate temperature (hereinafter simply referred to as “insulation of the bottom slab concrete”). It is the model top view which showed the behavior of the bottom slab concrete 55 around the anchor box 51 which arises. As shown in FIG. 9, the heater pipe 60 is usually piped at a depth similar to the installation level of the anchor box 51 formed in the bottom slab concrete 55 as shown in FIG. A brine set to a degree is circulated. At this time, if there is a place where liquid leakage or the like has occurred, the cryogenic liquid flows into the anchor box 51 from the cold storage tank (not shown) of the bottom plate, and a cryogenic cooling part is formed in the anchor box 51. Is done. In this state, heat expansion deformation due to a temperature difference between the concrete temperature around the pipe and the cryogenic concrete around the anchor box 51 due to heat radiation from the heater pipe 60 that is piped in the vicinity of the anchor box as a hot part. Furthermore, a temperature difference also occurs between the concrete at the intermediate position between the anchor boxes 51 and 51 and the concrete around the pipe, and a tensile force corresponding to each temperature difference is generated. In the range exceeding the tensile strength of concrete, there is a risk of temperature cracking. For the sake of explanation, FIG. 9 illustrates the position and size of a crack that may occur.

  The present invention has been made to solve such problems, and it is possible to effectively prevent the temperature of the anchor portion of the above-mentioned cryogenic tank that effectively prevents the occurrence of temperature cracks in the concrete around the anchor box of the cryogenic tank. The purpose is to provide a structure.

In order to achieve the above-mentioned object, the present invention is constructed integrally with an inner tub in which a cryogenic liquid is stored and supported on a bottom slab concrete via a heat retaining member, and on the outer periphery of the bottom slab concrete. An anchor portion for fixing and supporting a lower end of an anchor strap disposed on an outer peripheral surface of the inner tank, the bottom plate being provided along the outer periphery of the inner tank. An anchor portion of a ground-type cryogenic tank that is disposed on concrete and that retains the heat by blocking diffusion of cold heat transmitted from the liquid through the anchor portion by a first heater pipe piped in the bottom slab concrete. a thermal insulation structure, in addition to the first heater tube, and the second heater tube piping in the bottom plate concrete below the anchor portion bottom, yet a third said heater tube of the first heater tube first Intermediate position in the height direction of the heater tube, characterized in that the pipe so as to surround the anchor portion.

  It is preferable that the second heater pipe is piped so as to pass through the bottom slab concrete located inside the outer contour line of the anchor portion.

  At this time, the third heater pipe is a continuous pipe line meandering so that the pipes piped on the inner and outer peripheral sides of the anchor part are switched between adjacent anchor parts, Alternatively, it is composed of a pipe provided in a circumferential shape on the inner peripheral side and the outer peripheral side of the anchor part, and a connecting pipe communicating these inner peripheral side and outer peripheral side pipes between the adjacent anchor parts. It is preferable to use a conduit.

  As described above, according to the present invention, the heater pipe effective for keeping the concrete warm by shutting off the cold and securing the thermal region is provided around the anchor portion formed in the bottom slab concrete of the low temperature tank. As a result, it is possible to effectively prevent occurrence of temperature cracks in the bottom slab concrete.

  Embodiments of the best mode for carrying out the heat retaining structure of the anchor portion of the above-mentioned ground type cryogenic tank according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a partially enlarged view showing a joint portion between a bottom plate and a side wall (PC breakwater) of a ground type LNG tank made of prestressed concrete as an example of a conventional ground type low temperature tank 10 shown in FIG. It is. In the bottom slab concrete 30 shown in the figure, anchor boxes 51 and heater pipes 35 and 36 piped around the concrete are shown. The inner tank 11 of this embodiment is manufactured by processing 9% nickel steel and has sufficient toughness and strength that does not cause brittle fracture even at extremely low temperatures. A PC breakwater 12 that also serves as an outer tub is constructed outside the inner tub 11. The PC breakwater 12 is used for minimizing damage when a trouble occurs in the inner tank 11 and a cryogenic liquid as a content liquid leaks outside the inner tank 11, and as an external structure of the tank body. Has been built. As its structural form, PC tendons 14 are wired at predetermined intervals in the vertical direction and the circumferential direction, and a predetermined tension (pre-stress) is introduced to each PC tendon to improve the concrete tensile strength. For simplification of the drawing, FIG. 1 shows only the cross section of the circumferential PC tendon 14 disposed on the outer periphery of the wall of the breakwater and the bottom slab concrete. A heat insulating material layer 13 is provided on the inner surface side of the inner tub 11 and the PC liquid breakwater 12 so as to prevent an abrupt temperature drop of the concrete due to liquid leakage from the inner tub 11. As the heat insulating material layer 13, a thermal resistance relaxation material made of polyurethane foam (hereinafter abbreviated as PUF) or the like is used. Further, a cold insulating material layer (not shown in FIG. 1) formed of a pearlite concrete block or the like is formed between the side surface of the inner tank 11 and the inner surface of the PC liquid-proof tank 12.

  In addition to the heat retaining function, the bottom of the inner tank 11 is responsible for the weight of the inner tank 11 and the weight of LNG (liquid), and therefore, a material / structure with sufficient bearing performance is required. Therefore, the inner tub 11 is supported on the bottom slab concrete 30 with a material 15 that serves both as heat retention and support, such as cellular concrete, foam glass, and pearlite concrete. The bottom slab concrete 30 is made of reinforced concrete, and is supported by a support pile (not shown) disposed on the lower surface to support the entire low temperature tank 10.

  As shown in FIG. 8, a heater tube 35 having a circumferential shape is buried in the bottom slab concrete 30 almost horizontally at a predetermined depth over the entire surface. As for the system of the heater pipe 35, only one system for sending back is shown in FIG. 8, but the extension of each heater pipe 35 can be shortened to reduce the pipe resistance by piping a plurality of systems. Has also been done.

  Here, the structure of the anchor structure will be briefly described with reference to FIG. LNG, which is a liquid, is a cryogenic liquid having a liquid temperature of −162 ° C., and the temperature of the inner tank 11 differs greatly between when LNG (liquid) is stored and when it is empty. Therefore, large thermal expansion and thermal contraction occur in the entire inner tub 11 installed on the bottom plate according to the storage condition. Generally, the bottom surface of the inner tub 11 is not fixed in order to prevent the thermal stress caused by these from being generated in the inner tub 11. However, it is necessary to prevent the inner tank 11 from sliding and falling during an earthquake. Therefore, the anchor structure 50 of the inner tub 11 is employed that prevents thermal deformation in the radial direction and the height direction of the inner tub 11 due to thermal expansion and contraction and prevents the inner tub 11 from sliding and falling due to an earthquake. Yes.

  The anchor structure 50 shown in FIG. 1 has an anchor strap 40 in which an upper end 40 a is fixed to the outer surface of the inner tank 11 and a lower end 40 b is fixed to the bottom slab concrete 30, and the lower end of the anchor strap 40 is attached to the bottom slab concrete 30. It consists of a cylindrical anchor box 51 to be fixed. A portion of the anchor strap 40 located in the anchor box 51 is covered with glass wool 41, and the lower end 40b is held in the anchor box 51 so as to protrude from the lower surface of the anchor box 51.

  Hereinafter, a fixing structure of the anchor strap 40 in the anchor box 51 will be described. The portion embedded in the bottom slab concrete of the anchor box 51 is made of a steel cylindrical sleeve. Further, a molded PUF 43 having a layer thickness of about 50 mm is accommodated at the bottom of the anchor box 51, and the anchor strap lower end 40b protruding from the lower surface of the box is fixed. A plug-like molded PUF 45 is fitted into the upper end portion 42, and the space in the anchor box is in a state where glass wool 41 covering the anchor strap 40 is filled and solidified with the foamed PUF 44.

[Heater tube layout]
In the present invention, a carbon steel pipe for pressure piping (JIS G 3454) is used as the heater pipe 35. The heater pipe 35 is bent at a predetermined radius so that the entire surface of the bottom plate can be piped in a circular shape, and is piped in a flat shape as shown in FIG. Yes. The pipe is fixed on a steel pipe mount (not shown) assembled on the bottom slab, and finally buried in the concrete placed on-site, thereby forming a predetermined piping system in the bottom slab concrete 30. In addition, when piping the heater pipe 35 on the pipe mount, a synthetic rubber such as chloroprene rubber is coated around the heater pipe 35 placed and fixed on the steel pipe mount, and heat conduction to the mount by metal touch. To prevent this.

  In the present invention, as shown in FIGS. 1 and 2, in addition to the heater tube 35 for heat insulation of the conventional bottom slab concrete 30 as a heater tube for heat insulation of the anchor portion, the cross section shown in FIG. The two rows of heater tubes 36, 36 shown below pass by a distance L from the bottom surface of all the circumferentially arranged anchor boxes 51, and in addition to the action of the heater tube 35, the bottom of the bottom slab concrete 30 It is piped so as to ensure a predetermined thermal area on the side. At this time, in order to reliably block the cold heat transmitted from the anchor box 51, it is preferable to pipe the pipe at a position passing through the inside of the outline of the anchor box 51 as shown in FIG. Thereby, it is possible to prevent the freezing range from reaching the lower ground by securing a hot region below the bottom of the anchor box 51 and reducing the cold.

  The arrangement position of the heater tube 3 at this time will be described with reference to FIGS. When the temperature distribution of the cold region below the anchor box 51 is taken into consideration, the heater tube 36 is positioned at a lower distance from the anchor box 51 ((if the anchor strap 40 protrudes from the anchor box 51 and is fixedly held, the lower end of the anchor strap 3), L is preferably about (L <2φ) in relation to the diameter φ of the anchor box 51, as shown in Fig. 3A. If the heater pipe 36 is piped within the range up to crossing the outer contour of the anchor box 51, the effect of keeping the anchor box 51 warm from below can be expected (see FIG. 3B). Depending on the size of the pipe and the set temperature of the brine, it is possible to secure a sufficient insulation range of the concrete around the pipe. The number of heater pipes 36 to be piped downward may be one (see Fig. 3C), and Fig. 3D shows the relationship between the anchor box 51 and the heater pipe 36 shown in Fig. 3A. Fig. 3 is a plan view schematically showing a planar positional relationship, and the heater pipe 36 is preferably arranged in a range shown in Fig. 3 (a) to Fig. 3 (b) in plan view. The temperature of the brine to be circulated in the pipe 36 is assumed to be about 10 to 40 ° C. Further, when trouble such as liquid leakage occurs, the brine is circulated to provide a relatively high temperature region, and from the anchor box 51 side. It is preferable to prevent rapid expansion of the cold region.

  FIG. 2B shows an embodiment showing an example in which a heater pipe 37 for securing a thermal region is provided around the side portion of the anchor box 51. As shown in the figure, the heights of the conventional heater pipe 35 (hereinafter referred to as the upper heater pipe 35) and the heater pipe 36 (hereinafter referred to as the lower heater pipe 36) below the anchor box 51 described above. Middle heater tubes 37 are piped on both the inner and outer sides of the anchor box 51 at an intermediate height in the direction. As shown in FIG. 2B, the middle heater pipe 37 is piped away from the side surface of the cylindrical anchor box 51 by about a distance H (H <2φ). That is, in order to secure this distance H, the middle heater tube 37 of the present embodiment is bent with a predetermined curvature in accordance with the pitch of the adjacent anchor boxes 51 as shown in FIGS. The distance H between the anchor boxes 51 can be almost secured. In the piping shown in FIG. 4A, two anchor pipes are connected so that a pipe located on the inner side and a pipe located on the outer side are switched between adjacent anchor boxes 51. The pipes are bent so as to meander between the pipes, and are piped so as to surround the periphery of the adjacent anchor box 51 as a set of two pipes. As described above, since the thermal region is secured between the adjacent anchor boxes 51, it contributes extremely effectively to the temperature cracks that may occur between the anchor boxes 51 as shown in FIG. FIG. 4A shows an example of piping in which piping is bent so that the S-shape is continuous and meandering into a continuous shape, and each anchor box 51 is positioned at the center of the arc. By changing the pipe height to about the pipe diameter and surrounding the anchor boxes 51 in alternate directions, the heater pipes are positioned at substantially equal distances from each anchor box 51 as shown in the figure. It becomes the same as that 37 was piped. FIG. 4B shows a modification in which the pipes are bent so that the periphery of each anchor box 51 is piped in consideration of simplification of pipe bending. Although the same temperature control can be performed by this pipe shape, it is necessary to consider that the resistance of the brine flowing through the pipe increases. In each of FIGS. 4A and 4B, the lower heater pipe 36 piped below the anchor box 51 is indicated by a virtual line. As shown in the figure, the thermal region can be reliably secured by the heat retaining action of the lower heater tube 36 and the above-described middle heater tube 37 around the anchor box 51.

  Each drawing in FIG. 5 is a schematic plan view showing another example of piping that secures a thermal region around the anchor box 51 by piping the middle heater tube 37 in the same manner as shown in FIG. FIG. 5A shows a piping example in which main pipes 37A are provided on both the inside and outside of the anchor box 51, and a communication pipe 37B is connected between the inside and outside main pipes 37A. In FIG. 5A, the communication pipe 37B has the same diameter as the main pipe 37A, is piped at an intermediate position between the adjacent anchor boxes 51, and is joined to the main pipe 37A bent to a predetermined loose curvature in a T shape. ing. The communication pipe 37 </ b> C shown in FIG. 5 (b) is a pipe having a small diameter arranged in the vicinity of each anchor box 51. As described above, the communication pipe 37 </ b> C using the small-diameter pipe is effective when the distance between the adjacent anchor boxes 51 is large, can secure a thermal region around the anchor box 51, and is an intermediate position between the anchor boxes 51. It is possible to effectively prevent temperature cracks in the case.

  FIG. 6 shows an embodiment in which the anchor box 51 has a double structure and a heat insulating material layer 46 is formed in a cylindrical space between the inner and outer cylinders. In this embodiment, the cylindrical heat insulating material layer 46 is intended to make it difficult for cold heat in the anchor box 51 to be transmitted to the outside. At this time, a heat insulating material such as glass wool (not shown) may be coated around the anchor strap 40, or the foamed PUF may be solidly filled in the space 45 in which the anchor strap 40 is inserted. Since the filling material of the heat insulating material layer 46 is filled in the manufacturing process of the box, a high-magnification foamed resin such as foamed polyurethane, foamed polystyrene, vinyl chloride resin, or polyethylene can be appropriately adopted as the material.

The partial sectional view of the tank bottom which showed one example of the heat retention structure of the anchor part of the above-mentioned ground type low-temperature tank of the present invention. The expanded sectional view which paid its attention to the example of arrangement | positioning of the heat retention structure (heater pipe | tube) of the anchor part in FIG. The schematic cross section explaining the example of arrangement in the heater pipe shown in FIG. The schematic top view which showed the piping example of the middle stage heater pipe. The schematic top view which showed the other piping example of the middle stage heater pipe. The schematic cross section which showed the structural example of the heat insulating material layer in an anchor box. The general | schematic whole sectional view which showed the conventional ground-type cryogenic tank including the inner tank anchor structure. FIG. 8 is a schematic plan cross-sectional view showing an example of the heater tube piping and an example of the anchor box arrangement at section line VIII-VIII in FIG. 7. Explanatory drawing which showed typically the example of the temperature crack which may generate | occur | produce in the concrete around an anchor box.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Low temperature tank 11 Inner tank 12 PC breakwater 30 Bottom slab concrete 35, 36, 37 Heater pipe 40 Anchor strap 50 Anchor structure 51 Anchor box

Claims (4)

An inner tank in which a cryogenic liquid is stored and supported on the bottom slab concrete via a heat retaining member, and a liquid-proof liquid that is constructed integrally on the outer periphery of the bottom slab concrete and prevents external leakage of the liquid from the inner tank An anchor portion provided with a bank and fixing and supporting a lower end of an anchor strap disposed on an outer peripheral surface of the inner tub is disposed on the bottom slab concrete along an outer periphery of the inner tub, and the anchor portion from the liquid The heat retaining structure of the anchor portion of the ground-type low-temperature tank that keeps the heat from being transmitted through the first heater pipe piped in the bottom slab concrete,
In addition to the first heater pipe, a second heater pipe is piped into the bottom slab concrete below the bottom of the anchor portion, and a third heater pipe is connected between the first heater pipe and the second heater pipe. A heat insulation structure for an anchor portion of a ground-type cryogenic tank , wherein piping is provided so as to surround the anchor portion at an intermediate position in a height direction .   2. The heat retaining structure for an anchor portion of a ground-type cryogenic tank according to claim 1, wherein the second heater pipe is piped so as to pass through the bottom slab concrete located inside the outer contour of the anchor portion. The third heater tube and the inner periphery side and the pipe that is plumbed to the outer peripheral side of the anchor portion, meanders as out between adjacent anchor portions are interchanged is conduit successive claim 1 The heat insulation structure of the anchor part of the above-mentioned ground type cryogenic tank described in 1. The third heater pipe includes a pipe provided in a circumferential shape on the inner peripheral side and the outer peripheral side of the anchor part, and pipes on the inner peripheral side and the outer peripheral side between the adjacent anchor parts. The heat insulation structure for an anchor portion of a ground-type cryogenic tank according to claim 1 , wherein the heat insulation structure is a conduit composed of a connecting pipe that communicates.

Images