Method for checking earthquake resistance of heat storage tank

Abstract

To provide a method for confirming earthquake resistance of a heat storage tank capable of confirming that a sloshing absorbing mechanism properly acts and a function of a heat insulating lid can be held without leaking a heat medium being content water when an assumable earthquake occurs by using a constructed heat storage tank.SOLUTION: The method includes a step of determining a theoretical value of a natural period of the heat medium from a volume of the heat storage tank, a step of installing a pore water pressure gauge on an outer edge portion, a step of repeatedly loading and removing a weight on and from the heat insulation lid in a vertical direction at a period of the theoretical value of the natural period to generate sloshing in the heat medium, and a step of confirming whether the heat insulation lid and the sloshing absorbing mechanism are not damaged.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for verifying the earthquake resistance of a heat storage tank installed underground, and more particularly to a method for verifying the earthquake resistance of a heat storage tank provided with a sloshing absorbing mechanism in an insulating lid. [Background technology]

[0002] It has been known that when an earthquake causes vibrations in oil tanks installed in refineries or storage tanks installed in chemical plants, the liquid level stored in the tank shakes, causing fluctuations in the liquid level and causing the liquid to leak out of the tank, a phenomenon known as sloshing.

[0003] Various structures are known as countermeasures against such sloshing. For example, as described in Patent Document 1, there is a known sloshing absorption mechanism for a heat storage tank formed by excavating the ground so that a heat medium can be stored inside, which has a heat-resistant and water-shielding sheet that contacts the excavated part of the ground and an insulating lid that contacts the surface of the stored heat medium, and there is a predetermined clearance from the ground surface to the surface of the ground, and the outer edges of the heat-resistant and water-shielding sheet and the insulating lid have folded parts that are overlapped and joined along the clearance, and the folded part has a pressure vent that connects the inside and outside of the heat storage tank, and the pressure vent has a first pipe part extending from the folded part and a second pipe part formed by bending at approximately a right angle from the tip of the first pipe part.

[0004] In a heat storage tank equipped with a sloshing absorption mechanism as described in Patent Document 1, there is a predetermined clearance from the ground surface to the surface of the heat medium, and the heat-resistant water-shielding sheet and the insulating lid are joined by a folded portion that is folded along this clearance. Therefore, even if sloshing occurs and the stored heat medium sways, the clearance can prevent the heat medium from leaking outside the heat storage tank, and even if sloshing occurs that exceeds the clearance, the folded portion can be extended to absorb the swaying of the heat medium caused by sloshing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7365258 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although it can be proven in theory that the heat storage tank equipped with the sloshing absorption mechanism described in Patent Document 1 has the above-mentioned effects, there is a problem in that after actually constructing the heat storage tank, it is not possible to reproduce sloshing in the heat storage tank, as would occur if an earthquake actually occurred, to confirm that the insulating lid maintains the required function.

[0007] Therefore, the present invention has been made in consideration of the above problems, and aims to provide a method for confirming the earthquake resistance of a heat storage tank, which can be used to confirm that in the event of a conceivable earthquake, the sloshing absorption mechanism will function properly and the heat transfer medium (water content) will not leak, maintaining the function of the insulated lid. [Means for solving the problem]

[0008] The method for confirming the earthquake resistance of a heat storage tank according to the present invention is a method for confirming the earthquake resistance of a heat storage tank equipped with a sloshing absorption mechanism, which includes a heat storage tank excavated into the ground so that a heat medium can be stored therein, an insulated lid that contacts the surface of the stored heat medium, and a predetermined clearance from the ground surface to the surface of the ground, and the outer edges of the heat-resistant water-shielding sheet and the insulated lid have folded portions that are overlapping and joined along the clearance, and is characterized by comprising the steps of: determining the theoretical value of the natural period of the heat medium from the volume of the heat storage tank; installing a pore water pressure gauge on the outer edge; repeatedly loading and removing a weight in the vertical direction on the insulated lid at a period of the theoretical value of the natural period to cause sloshing in the heat medium, and repeatedly loading and removing the weight until the pore water pressure gauge reaches a predetermined water pressure; and checking for damage to the insulated lid and the sloshing absorption mechanism.

[0009] In addition, in the method for confirming the earthquake resistance of a heat storage tank according to the present invention, it is preferable that the specified water pressure is the water pressure at the outer edge measured by sloshing caused by seismic motion that has a probability of occurring at least once during the service life of the heat storage tank.

[0010] Furthermore, in the method for confirming the earthquake resistance of a heat storage tank according to the present invention, it is preferable that the specified water pressure is the water pressure at the outer edge measured by sloshing caused by the maximum earthquake motion that can be expected at the location where the heat storage tank is constructed.

[0011] In the method for checking the earthquake resistance of a heat storage tank according to the present invention, it is preferable that the weight is placed on and removed from a substantially central portion of the insulating lid.

[0012] Furthermore, the method for checking the earthquake resistance of a heat storage tank according to the present invention preferably includes a checking step of checking that the sloshing absorbing mechanism is not damaged before the step of repeatedly loading and removing the weight.

[0013] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions. [Effects of the Invention]

[0014] According to the method for confirming the earthquake resistance of a heat storage tank of the present invention, even if an earthquake does not actually occur, it is possible to use the constructed heat storage tank to confirm that in the event of a conceivable earthquake, the sloshing absorption mechanism will function properly and the heat transfer medium (water content) will not leak, maintaining the function of the insulated lid. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view of a heat storage tank for which a method for checking earthquake resistance of a heat storage tank according to an embodiment of the present invention is performed; [Figure 2] Enlarged view of part A in Figure 1. [Figure 3]A diagram showing the state in which the water level rises due to sloshing. [Figure 4] FIG. 2 is a flow diagram of a method for confirming the earthquake resistance of a heat storage tank according to the present embodiment. [Figure 5] 4A and 4B are diagrams for explaining a method of loading and removing a weight in the method for checking the earthquake resistance of a heat storage tank according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0017] FIG. 1 is a cross-sectional view of a heat storage tank for which the method for confirming the earthquake resistance of a heat storage tank according to this embodiment is performed, FIG. 2 is an enlarged view of part A in FIG. 1, FIG. 3 is a diagram showing a state in which the water level has risen due to sloshing, FIG. 4 is a flow diagram of the method for confirming the earthquake resistance of a heat storage tank according to this embodiment, and FIG. 5 is a diagram for explaining the method for loading and removing weights in the method for confirming the earthquake resistance of a heat storage tank according to this embodiment.

[0018] As shown in Fig. 1, the heat storage tank 1 according to this embodiment is a heat storage tank with a rectangular top surface and sides of approximately 90 m, and is provided with a heat plant (not shown) as a hot water production section that supplies hot water to the heat storage tank 1. This heat plant may have any configuration as long as it can produce hot water as a heat medium, but it is preferable to configure it as a solar heat plant using solar thermal panels, for example.

[0019] In the heat storage tank 1 according to this embodiment, hot water W serving as a heat medium is stored in the heat storage tank 1, and is supplied from a thermal plant (not shown) to a hot water supply and conveyance device 3 via a hot water supply and conveyance pipe 4. The hot water supply and conveyance device 3 is preferably held in place within the heat storage tank 1 by support piles 5.

[0020] The thermal storage tank 1 is preferably formed by excavating the ground G, and the side of the thermal storage tank 1 is formed on a plane approximately perpendicular to the ground surface GL by pouring the thermal storage tank wall 2 onto a foundation 6 made of replaced concrete or cobblestones having a predetermined thickness. The thermal storage tank wall 2 is disposed so that it protrudes from the ground surface GL with a clearance h between the top surface of the thermal storage tank wall 2 and the surface of the hot water W.

[0021] In addition, a heat-resistant, water-shielding sheet 11 is attached to and covers the heat storage tank wall 2 and bottom surface, which are the boundary surfaces between the heat storage tank 1 and the ground G, to prevent the intrusion of groundwater and heat exchange within the ground G. If the groundwater level is high and interferes with the heat storage of the hot water W stored in the heat storage tank 1, a water-shielding wall may be formed near the heat storage tank 1, and insulation may be achieved using groundwater pumping equipment such as a deep well.

[0022] The heat-resistant, water-shielding sheet 11 covering the heat storage tank wall 2 and bottom surface of the heat storage tank 1 is installed to insulate the hot water in the heat storage tank 1 and prevent the hot water from leaking into the ground G, and various materials such as polyethylene sheets can be used as long as they have insulating and water-proof properties.

[0023] The top surface of the heat storage tank 1 has an opening to the ground surface GL created by excavating the ground G, but this opening is closed by an insulating lid 20. Any material may be used for the insulating lid 20 as long as it can keep the hot water stored in the heat storage tank 1 warm, but for example, as shown in Fig. 2, an insulating sheet can be used in which an insulating material 21 made of polystyrene foam or the like is laminated with a skin 22 made of polyethylene or the like.

[0024] The heat storage tank 1 is provided with a sloshing absorption mechanism 30. When the water level in the heat storage tank 1 fluctuates due to an earthquake or the like, causing shaking, the sloshing absorption mechanism 30 absorbs the fluctuation of the water level and prevents the hot water in the heat storage tank 1 from leaking out of the heat storage tank 1.

[0025] Specifically, the surface of the hot water W stored in the heat storage tank 1 is stored with a freeboard h by the heat storage tank wall 2 that protrudes from the surface GL of the ground G. The freeboard h can be set as appropriate as long as it can absorb the swaying of the hot water W when the surface of the hot water W sways due to sloshing, but it is preferable to set it to about 1.5 m, for example. The height of the freeboard h can be calculated as appropriate from the history of the largest earthquake motions that have occurred in the past in the area where the heat storage tank 1 is constructed.

[0026] Additionally, the outer edge of the heat-resistant and water-shielding sheet 11 is formed with a heat-resistant and water-shielding sheet-side folded portion 32 that extends by the excess height h along the height direction of the heat storage tank wall 2, and the outer edge of the insulating lid 20 is formed with an insulating lid-side folded portion 31 that extends by the excess height h along the height direction of the heat storage tank wall 2. The heat-resistant and water-shielding sheet-side folded portion 32 and the insulating lid-side folded portion 31 overlap each other along the excess height h of the heat storage tank wall 2, and are joined together at the top surface of the heat storage tank wall 2 to form a sloshing absorption mechanism 30 with folded portions.

[0027] A pressure vent 40 is attached to the insulated lid-side folded portion 31 of the sloshing absorption mechanism 30, and allows communication between the inside and outside of the heat storage tank 1. The pressure vent 40 includes a tubular first pipe portion 41 extending from the insulated lid-side folded portion 31 and a second pipe portion 42 bent at a substantially right angle from the tip of the first pipe portion 41 and formed so as to face in the opposite direction to the sloshing absorption mechanism 30. A lid 43 serving as a release mechanism is fitted into and closed at the tip of the second pipe portion 42. The lid 43 is attached so as to easily come off when the pressure inside the heat storage tank 1 rises above a predetermined pressure. Alternatively, a one-way valve may be attached to the tip of the pressure vent 40 instead of fitting the lid 43.

[0028] It is preferable that the pressure vent 40 is formed in the sloshing absorption mechanism 30 near the joint between the insulated lid-side folded portion 31 and the heat-resistant water-shielding sheet-side folded portion 32. It is also preferable that a plurality of pressure vents 40 be formed along the outer edge of the insulated lid 20, preferably at intervals of 10 m, for example.

[0029] Furthermore, it is preferable that the tip of the second pipe section 42 of the pressure vent 40 be formed so as to face toward the center of the heat storage tank 1 when the insulated lid-side folded section 31 becomes horizontal due to a rise in the water level caused by sloshing, which will be described later. By arranging the tip direction in this way, the tip of the second pipe section 42 faces downward under normal circumstances, preventing the inclusion of foreign matter, and even if the water level rises due to sloshing and the lid body 43 comes off, the hot water W inside the heat storage tank 1 is discharged onto the insulated lid 20 of the heat storage tank 1, preventing damage to the neighborhood due to the hot water W leaking outside the heat storage tank 1.

[0030] As shown in Figure 3, when an earthquake or other event causes the surface of the hot water W in the heat storage tank 1 to sway and the level of the hot water W in the heat storage tank 1 to rise, the hot water W flows into the gap between the heat-insulating lid-side folded portion 31 and the heat-resistant water shield sheet-side folded portion 32 of the sloshing absorption mechanism 30, absorbing the sloshing by the freeboard h. At this time, because the heat-insulating lid-side folded portion 31 and the heat-resistant water shield sheet-side folded portion 32 are joined to each other, the hot water W is held within the heat-insulating lid 20, the heat-resistant water shield sheet 11, and the sloshing absorption mechanism 30, preventing it from leaking out of the heat storage tank 1.

[0031] Furthermore, when the hot water W sways violently, the water pressure on the pressure vent 40 increases, and the increase in water pressure causes the lid 43 to come off, causing the hot water W to be discharged from the pressure vent 40 to the outside of the heat storage tank 1. At this time, since the tip of the second pipe portion 42 is facing toward the center of the heat storage tank 1, the discharged hot water W is discharged onto the insulated lid 20.

[0032] Next, a method for confirming the earthquake resistance of a heat storage tank according to this embodiment will be described. The method for confirming the earthquake resistance of a heat storage tank according to this embodiment is preferably performed after the heat storage tank 1 is constructed and immediately before the demonstration facility is removed.

[0033] As shown in Figure 4, the method for confirming the earthquake resistance of a heat storage tank according to this embodiment includes the steps of: determining the theoretical value of the natural period of the hot water W, which is the heat medium, from the volume of the heat storage tank 1 (S101); calculating the water pressure when subjected to an expected earthquake motion from the calculated theoretical value of the natural period (S102); installing a pore water pressure gauge 60 on the outer edge of the heat storage tank wall 2 (S103); repeatedly loading and removing weights in the vertical direction on the insulated lid 20 at a period of the theoretical value of the natural period to cause sloshing in the hot water W, and repeatedly loading and removing the weights until the pore water pressure gauge 60 reaches a predetermined water pressure (S104); checking for damage to the insulated lid 20 and the sloshing absorption mechanism 30 (S105); and checking whether all levels have been checked (S106).

[0034] The step (S101) of determining the theoretical value of the natural period of the hot water W, which is the heat transfer medium, from the volume of the heat storage tank 1 can be performed by calculating the natural frequency f using the following formula (1) from the water depth H and width L of the heat storage tank 1, and then taking the reciprocal of the natural frequency f.

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[0035] In the step (S102) of calculating the water pressure when subjected to earthquake motion estimated from the calculated theoretical value of the natural period, it is preferable to calculate the water pressure by assuming earthquake motion at multiple levels. For example, Level 1 is set to a case where the thermal storage tank 1 is subjected to earthquake motion that has a probability of occurring once or twice during the service life of the thermal storage tank 1, assuming a history of past earthquakes in the area where the thermal storage tank 1 is constructed, and the water pressure generated near the sloshing absorption mechanism 30 corresponding to the sloshing height of the hot water W is calculated. Furthermore, Level 2 is set to a case where the thermal storage tank 1 is subjected to earthquake motion of the maximum strength that can be expected at that location from the present to the future.

[0036] In the step (S103) of installing the pore water pressure gauge 60 on the outer edge of the thermal storage tank wall 2, the pore water pressure gauge 60 is installed on the outer edge of the thermal storage tank wall 2 where the sloshing absorption mechanism 30 is disposed, as shown in Figure 5. Any of various conventionally known pore water pressure gauges can be used as the pore water pressure gauge 60, as long as it can measure changes in water pressure due to fluctuations in the liquid level of the hot water W. When installing the pore water pressure gauge 60, it is preferable to visually check for scratches or steam leaks in the insulating lid side folded portion 31 and the heat-resistant water-shielding sheet side folded portion 32, which are the insulating lid buffer areas of the sloshing absorption mechanism 30, or to check for the presence of bubbles by applying soapy water or the like.

[0037] In the step (S104) of repeatedly loading and removing weights in the vertical direction on the insulating lid 20 at a period of the theoretical value of the natural period to cause sloshing in the hot water W and repeatedly loading and removing the weights until the pore water pressure gauge 60 reaches a predetermined water pressure, first, it is confirmed whether the integrity of the insulating lid 20 or the sloshing absorption mechanism 30 is impaired by the vibration of the hot water surface caused by level 1 sloshing.

[0038] Specifically, as shown in Figure 5, a weight 50 of a predetermined weight, such as a ton pack, is placed near the center of the plane of the insulated lid 20, and the weight 50 is pressed against the surface of the insulated lid 20 to load it, and then the weight 50 is lifted and removed repeatedly. At this time, the loading and removal of the weight 50 is preferably performed using a crane or the like installed above the thermal storage tank 1, and the loading and removal of the weight 50 is performed by moving the weight 50 up and down at a period that is the theoretical value of the calculated natural period. The loading and removal of the weight 50 is repeated until the measurement value of the pore water pressure meter 60 corresponds to the sloshing height of a Level 1 earthquake motion.

[0039] In the step (S105) of checking for damage to the insulating lid 20 and the sloshing absorption mechanism 30, after the measurement value of the pore water pressure meter 60 reaches the sloshing of a Level 1 earthquake motion, loading and removal are terminated and it is checked for damage to the insulating lid 20 and the sloshing absorption mechanism 30. The check for damage can be performed by visual inspection or by checking for the presence of bubbles after applying soapy water.

[0040] In the step (S106) of checking whether all levels have been checked, it is checked whether checks have been completed at all assumed levels. Specifically, if Level 2 check has not been performed, the process returns to the step (S104) of repeatedly loading and removing weights in the vertical direction on the insulating lid 20 at a period equal to the theoretical value of the natural period to generate sloshing in the hot water W, and repeatedly loading and removing the weights until the pore water pressure gauge 60 reaches a predetermined water pressure. Then, the process goes to the step (S105) of checking whether the insulating lid 20 and the sloshing absorption mechanism 30 are not damaged by the vibration of the hot water surface caused by Level 2 sloshing.

[0041] Furthermore, if the checks at all levels have been completed, the method for checking the earthquake resistance of a heat storage tank according to this embodiment is completed.

[0042] In this way, according to the method for checking the earthquake resistance of a heat storage tank of this embodiment, sloshing is actually caused in the heat storage tank 1 to check for damage to the insulated lid 20 and the sloshing absorption mechanism 30, so it is possible to reproduce the sloshing that would occur if a specific earthquake actually occurred, and to check whether the insulated lid 20 and the sloshing absorption mechanism 30 can maintain the required functions and whether they can tolerate a certain degree of damage.

[0043] Furthermore, the method for verifying the earthquake resistance of a heat storage tank according to the present embodiment has been described above in terms of a case where the expected earthquake motion is divided into two levels and verified, but the expected earthquake motion is not limited to two levels, and the number of levels can be increased or decreased as necessary. Furthermore, the heat storage tank 1 has been described above in terms of a case where the heat storage tank wall 2 is formed substantially perpendicular to the ground surface GL, but the shape of the heat storage tank 1 is not limited to this, and for example, the heat storage tank wall 2 may be formed on a slope. It is clear from the claims that such modified or improved embodiments are also included within the technical scope of the present invention. [Explanation of symbols]

[0044] 1 heat storage tank, 2 heat storage tank wall, 3 hot water supply and conveyance device, 4 hot water supply and conveyance pipe, 5 support pile, 6 foundation, 11 heat-resistant and waterproof sheet, 20 insulation cover, 21 insulation material, 22 skin, 30 sloshing absorption mechanism, 31 folded part on insulation cover side, 32 folded part on heat-resistant and waterproof sheet side, 40 pressure relief, 41 first pipe section, 42 second pipe section, 43 cover body, 50 weight, 60 pore water pressure gauge, h freeboard, G ground surface, GL ground surface.

Claims

1. a heat storage tank formed by excavating the ground and capable of storing a heat medium therein; an insulating lid in contact with the surface of the stored heat medium; There is a predetermined clearance between the ground surface and the surface of the ground, A method for confirming the earthquake resistance of a heat storage tank equipped with a sloshing absorption mechanism for a heat storage tank, characterized in that outer edge portions of the heat-resistant and water-shielding sheet and the insulating lid have folded-back portions that are overlapped and joined along the freeboard, determining a theoretical value of the natural period of the heat medium from the volume of the heat storage tank; Installing a pore water pressure gauge on the outer edge; A step of repeatedly loading and removing a weight in the vertical direction on the insulating lid at a period of the theoretical value of the natural period to generate sloshing in the heat medium, and repeatedly loading and removing the weight until the pore water pressure gauge reaches a predetermined water pressure; A method for checking the earthquake resistance of a heat storage tank, comprising a step of checking whether the insulating lid and the sloshing absorbing mechanism are damaged.

2. The method for confirming the earthquake resistance of a heat storage tank according to claim 1, A method for confirming the earthquake resistance of a heat storage tank, characterized in that the specified water pressure is the water pressure at the outer edge measured by sloshing caused by seismic motion that has a probability of occurring at least once during the service life of the heat storage tank.

3. The method for confirming the earthquake resistance of a heat storage tank according to claim 1, A method for confirming the earthquake resistance of a heat storage tank, characterized in that the specified water pressure is the water pressure at the outer edge measured by sloshing caused by the maximum earthquake motion that can be expected at the location where the heat storage tank is constructed.

4. The method for confirming the earthquake resistance of a heat storage tank according to claim 1, A method for checking the earthquake resistance of a heat storage tank, characterized in that the weight is placed on and removed from approximately the center part of the insulating lid.

5. The method for confirming the earthquake resistance of a heat storage tank according to claim 1, A method for confirming the earthquake resistance of a heat storage tank, comprising a confirmation step of confirming that the sloshing absorbing mechanism is not damaged before the step of repeatedly loading and removing the weight.

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