METHOD OF DISMANTLING CYLINDRICAL STORAGE TANK

Abstract: According to the present invention, when a side wall of a cylindrical storage tank is cut away from a bottom plate and the sidewall is cut in spirally from the bottom end toward the top end to remove the cut-away pieces, temporary supporting for gradually lowering the bottom ends of the sidewall at a cut-in portion in accordance with the progress of the work of removal is successively transferred with the progress of the work of removal. According to the present invention, the work can be performed safely, the cost is low, the work can be performed when there is other structure therearound, and moreover, the work can be performed easily without providing a rotatable support member and rotating the top side of the storage tank.

Description: This invention relates to a method for knocking down a circular tank, particularly to a method for knocking down a deteriorated circular tank for storing oil, gas, water, etc. Conventionally, to knock down a circular tank, one must construct a false work surrounding the tank, and using the false work, start to disjoin pieces in the upper part of the structure of the tank. However, the method that starts from the step of disjoining pieces in the upper part of the structure inevitably includes works at an elevated spot, and thus involve a great risk. The method also needs an additional step of constructing a false work surrounding the tank, which makes the knocking down process expensive. Further, when there are other constructions around the tank, a false work is difficult to be constructed. Thus, several methods for knocking down a circular tank that starts from a step of disjoining pieces in the lower part of the tank are proposed. For example, the Japanese TOKKYO-KOKAI-KOHO (18-month Publication of Unexamined Patent Application) SHOWA 62(1987)-185965 (hereinafter referred to as TOKKAISHO 62-185965) discloses a knocking down method comprising, steps for cutting the circular tank along a spiral line provided on the periphery of the side wall in the lower part of the circular tank and a cutting line connecting the starting and ending points of the spiral line, in order to divide the tank into upper and lower pieces; providing in the cutting portion along the spiral line means for rotatably supporting the upper piece of the tank; and for step-by-step removing the portions of the side wall of the upper tank piece including the step portion of the cutting line in the form to extend the spiral line while rotating the upper piece of the tank so that the step portion of the cutting line moves toward the step portion of the cutting line. The above method includes only works done at a spot near the ground and thus is safe. Since it does not need to construct a false work, and thus is inexpensive. Further, this knocking down method is available even if some structures exist in the periphery of the tank. However, the method disclosed in the Japanese TOKKAISHO 62-185965 needs an additional step for providing in the spiral cutting portion along the spiral line means for rotatably supporting the upper piece of the tank. This step is not easy to implement, and great efforts are required to provide such means in the cutting portion, because rotating the upper piece of the tank is not easy. Accordingly, the object of this invention is to provide a knocking down method for a circular tank, which method includes only safe work steps; which method is inexpensive; which method is available even if a construction exist in the peripheral of the tank; and which method is easy to implement. Means for solving the object of this invention will be described below. First, this invention provides a method for knocking down a circular tank, comprising steps of separating the side wall of the tank from its bottom plate, cutting the side wall into portions along a spiral line provided on the periphery of the tank in the direction from the lower end to the upper end, and removing the portions until the whole side wall is removed. Second, this invention provides a method for knocking down a circular tank, comprising steps of separating the side wall of the tank from its bottom plate, cutting the side wall into portions along a spiral line provided on the periphery of the tank in the direction from the lower end to the upper end, and removing the portions while temporarily supporting the side wall. In said step for temporarily supporting the side wall, any means can be used for temporarily supporting the side wall. Such temporarily supporting means include not only jacks or the likes but also means including support means as well as transfer means, for example, trucks having roller conveyers each comprising roller conveyers as supporting means and a truck as transfer means. A forklift or the likes may be used. Further, the supporting means does not need an additional supporting member because it is structured to mainly support the tank at the lower end of the side wall. However, the supporting means can be so structured to support the side wall via supporting members provided on the side wall. Third, this invention provides a method for knocking down a circular tank, comprising steps of separating the side wall of the tank from its bottom plate, cutting the side wall into portions along a spiral line provided on the periphery of the tank in the direction from the lower end to the upper end, and removing the portions while temporarily supporting the side wall, said temporarily supporting step being conducted so that the lower end of the removed portion is gradually lowered and the location to support the side wall shifts as the removing step proceeds. After the side wall of the tank is separated from the bottom plate, the side wall is cut into portions along a spiral line provided on the periphery of the tank in the direction from the lower end to the upper end, and these portions are removed. When part that has been cut into portions and removed is small, the lower end of the portion that remained of the side wall supports the whole body of the tank. When part that has been cut into portions and removed becomes big, the balance of the whole body of the tank makes the tank be inclined so that a spot of the removed portion contacts with the bottom plate. The lower end of the side wall also supports the whole body of the circular tank. As the removing step proceeds, the balance of the whole body of the tank changes the location of the lower end of the removed portion of the side wall that supports the whole body of the tank, in other words, the location where the removed portion of the side wall and the bottom plate contact. Therefore, as the removal step proceeds, the whole body. of the tank other than the bottom plate is inclined a little at the same location while the location where the removed portion of the side wall and the bottom plate shifts along the peripheral of the bottom plate. In short, the tank indicates a movement of braying in a mortar (so-called "misosuri" movement). Since the method for knocking down a circular tank of this invention includes only steps conducted at a spot near the ground, one can safely operate these steps. Since the method of this invention does not need to structure a false frame, its operation cost is inexpensive. The method of this invention can be used even if some structures exist in the peripheral area of the circular tank. Further, the balance of the whole body of the tank can be so controlled that the lower end of the removed portion of the side wall support the whole body. Thus, this method does not need a step for providing rotatably movable means nor step for rotating the upper part of the tank, resulting in a simple method that is easy to implement. Fig. 1 to Fig. 3 are schematically views of a circular tank which is knocked down according to the steps of the method of this invention. Fig. 1 shows the tank after the first portion is removed from the side wall. Fig. 2 shows the tank in a tilted position. Fig. 3 shows the tank having a cutting line extends one whole peripheral of the side wall along which portions have been cut and removed from the side wall. Fig. 4 shows a jack for temporarily supporting the side wall. Fig. 5 shows the side view of a truck having roller conveyers for temporarily supporting the side wall. Fig. 6 shows the front view of a truck having roller conveyers for temporarily supporting the side wall In these drawings, 1 indicates a circular tank; 2 and 2a indicate the side wall of the circular tank; 3 indicates the bottom plate; 4 indicates a cutting starting point; 5 indicates a line for cutting into the side wall; 6 indicates a parallel joint; 7 indicates a jack; 8 and 8a indicate removed portions; 9 indicates a side wall receiving piece; 10 indicates a truck having roller conveyers; 11 indicates roller conveyers; 12 indicates a truck; and 13 indicates a rail. By making reference to drawings, preferred embodiments of this invention will be described below. First, as shown in Fig. 1, the side wall 2 of a circular tank 1 is separated from the bottom plate 3. A lower part of the side wall 2 is then cut into portions along a spiral line provided on the periphery of the tank 1 as shown by the cutting line 5 starting from the cutting starting point 4 at the lower end of the side wall 2 to the upper end. When the side wall 2 is cut a little, it is further cut to go through to the lower end of the side wall 2 to remove a portion. The lower part of the side wall 2 is again cut into along the spiral line, and another portion is removed by cutting through to the lower end of the side wall 2. If the removed portion is small, the whole body of the circular tank 1 is supported at the lower end of the portion of the side wall 2 that is not removed. In Fig. 1, 6 indicates a parallel joint on the side wall 2 of the circular tank 1. In this way, portions are repeatedly removed from the lower part of the side wall 2, as shown in Fig. 1, jacks 7 are placed to temporarily support the lower end of the side wall 2 to facilitate a further step of cutting and removing portions, and to keep the balance of the whole body of the tank 1. In turn, the jacks 7 placed beneath the portions that are removed at the beginning are jacked down until they are removed to lower the lower end of the side wall 2 from which side wall portions are removed. As shown in Fig. 2, the balance of the whole body of the tank 1 results the tank 1 to be inclined to contact part of the removed portion of the side wall 2 with the bottom plate 3. As a result, the tank 1 is also supported at the lower end of the removed portion of the side wall 2. As the removal step proceeds and jacks 7 are moved, the balance of the whole body of the tank 1 changes the location of the lower end of the removed portion supporting the whole body of the tank 1, in other words, the location where the removed portion of the side wall 2 and the bottom plate 3 contact. Therefore, as the removal step proceeds, the whole body of the tank 1 other than the bottom plate 3 is inclined a little at the same location while the location where the removed portion of the side wall 2 and the bottom plate 3 contact shifts along the periphery of the bottom plate 3. In short, the tank 1 indicates a movement of braying in a mortar (so-called " misosuri " mouvement). Fig. 3 indicates the tank 1 from which another portion 8 is removed after portions have been removed along the spiral cutting line 5 into the side wall 2 extending over the whole periphery of the tank 1 to return to the starting point 4. In Fig. 3, dotted line 8a indicates the removed portion that will be removed in the next step. By repeating the above steps, the side wall 2 of the tank 1 is gradually removed by cutting into portions along a spiral line and removing them from its lower part and then from the upper part until the whole tank 1 is completely divided into pieces. By making reference to Fig. 4, the status of jacks 7 temporarily supporting the side wall 2 will be explained below. Jacks 7 are placed on the periphery end of the bottom plate 3 to support the side wall 2 via side wall receiving pieces 9. In Fig. 4, 2a indicates the tilted side wall. Further, Fig. 5 and Fig. 6 indicate a truck having roller conveyers 10 supporting the side wall 2. The truck having roller conveyers 10 comprises a truck 12 provided with roller conveyers 11 which engages with the rail 13 to support the side wall 2.

Claims: A method for knocking down a circular tank, comprising steps of separating the side wall of the tank from its bottom plate, cutting the side wall into portions along a spiral line provided on the periphery of the tank in the direction from the lower end to the upper end, and removing the portions until the whole side wall is removed. A method for knocking down a circular tank, comprising steps of separating the side wall of the tank from its bottom plate, cutting the side wall into portions along a spiral line provided on the periphery of the tank in the direction from the lower end to the upper end, and removing the portions while temporarily supporting the side wall. A method according to claim 2, characterized by said temporarily supporting step being conducted so that the lower end of the removed portion is gradually lowered and the location to support the side wall shifts as the removing step proceeds.

Inventors: KATO HIDEO, KATO, HIDEO
Applicants: KYUSEKI KOGYO CO LTD, KYUSEKI KOGYO CO., LTD.
Application year: 1992
Main classification: E04G23
IPC codes: B65D88, E04H7, E04G23