JP7588036B2 - How to remove residue from storage tanks - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies (1) Published on August 1, 2020 in "75th Annual Academic Conference of the Japan Society of Civil Engineers, 2020 National Convention, Abstracts of Lectures, page VI-1016, Japan Society of Civil Engineers" (2) Published on September 9, 2020 in "75th Annual Academic Conference of the Japan Society of Civil Engineers, 2020 National Convention, https://confit.atlas.jp/jsce2020"

The present invention relates to a method for removing residual material from a storage tank.

The following Patent Document 1 discloses a method for dismantling the side panels of a floating roof tank, which is characterized by pouring water into the tank and using the floating roof, which floats on the water surface, as a scaffold for the dismantling work.
The following Patent Document 2 discloses a spherical tank inspection method in which the tank body is filled with water and purged of residual gas, and then a floating scaffolding is installed above the water surface by expanding and contracting, and inspection work is performed on the tank body.
The following Patent Document 3 discloses a method for inspecting and maintaining the inside of a columnar tower vessel by injecting a fluid into the columnar tower vessel, assembling a raft-like work platform that has a shape corresponding to the cross section of the columnar tower vessel and floats on the fluid, and having an operator stand on this work platform.

Japanese Unexamined Patent Publication No. 62-78363 Japanese Patent Application Publication No. 62-283296 Japanese Patent Application Publication No. 9-217481

In the lower part of a storage tank or other vessel, there may be precipitated and solidified residues of heavy metals, organic solvents, pesticides, oil, harmful chemicals, high alkali, etc. In such cases, when dismantling or inspecting the tank, it is necessary to remove the residues present in the tank.
However, removing such remains by hand is inefficient, and depending on the type of remains, measures must be taken to prevent workers from coming into contact with the remains. In addition, since the storage tanks may be old, the removal work must be carried out carefully to prevent the tanks from collapsing and the remains inside from spilling out.
On the other hand, Patent Documents 1 to 3 make no mention of removing any residue from within the storage tank.
The present invention aims to solve the above-mentioned problems and to remove remaining material present at the bottom of a storage tank without using human power and while preventing the storage tank from collapsing.

In order to solve the above problems, the present invention provides a method for removing residual material in a storage tank, which removes residual material present in the lower part of the storage tank.
In this method for removing residual material from a tank, first, an upper structure installed on the top of the tank is removed by workers working from a floating scaffolding that is floating on the liquid surface above the residual material. Next, the strength characteristics of the residual material in the depth direction are determined by soil testing. Next, an excavation means suitable for the determined strength characteristics is selected. The residual material is then excavated and removed using the selected excavation means. The floating scaffolding is removed before the residual material is excavated.
In this invention, an excavation means suitable for the strength characteristics (hardness) of the remains is selected and used. This makes it possible to prevent the use of an excavation means with a digging force that is inappropriate for the strength characteristics of the remains, thereby preventing the tank from being subjected to excessive vibration or other loads. This makes it possible to prevent the tank from collapsing and the remains inside from spilling out. Furthermore, even if there is remains in the lower part of the tank, such as a substance such as a highly alkaline substance that has precipitated and solidified, the remains can be removed without direct human contact.
In this way, according to the present invention, residual material present in the lower part of the tank can be removed without using human force and while preventing the tank from collapsing.

In the method for removing residual material from within a storage tank, it is preferable that, before removing the residual material, the floating scaffolding is floated on the surface of the liquid above the residual material, and dismantling work for part of the storage tank is carried out on the floating scaffolding.
In this configuration, by using the floating scaffolding, the dismantling work of the tank can be carried out on the top of the tank. In addition, since the floating scaffolding can be lowered by lowering the liquid level, the dismantling work can be carried out sequentially from the top of the tank to the bottom. Moreover, by carrying out the dismantling work of the tank before removing the remaining objects, the tank becomes more stable when the work of removing the remaining objects begins because the top part has been removed and the center of gravity is lowered. This makes it possible to further prevent the tank from collapsing, and allows the dismantling work of the tank to be carried out efficiently.

In the method for removing remaining material from a tank, it is preferable that the floating scaffold is deformable so as to expand and contract on the liquid surface to match the internal shape of the tank.
In this configuration, even if the internal shape of the storage tank changes in the height direction, the floating scaffolding can be formed as close as possible to the wall surface of the storage tank, which makes it possible to more efficiently dismantle the storage tank.
In the method for removing remaining material from a storage tank, it is preferable that after the remaining material is removed, liquid is injected into the storage tank and the dismantling work is further carried out on the floating scaffold.
In this configuration, the floating scaffolding can be used to carry out the dismantling work as far down as possible into the tank. This allows the tank to be dismantled more efficiently. In addition, the tank becomes more stable because the remaining parts that have not yet been dismantled are reduced and the center of gravity is further lowered. Therefore, the remaining parts will not tip over even under loads such as lateral loads, and it becomes possible to dismantle the tank using heavy machinery, for example.
In the method for removing the remaining material in the tank, before removing the remaining material, dismantling work may be performed from the top of the tank to a predetermined height position above the remaining material. In this case, dismantling work is performed using heavy machinery or lifting and dismantling using a crane. By proceeding with the dismantling work of the tank before removing the remaining material in this way, the tank becomes more stable when the work of removing the remaining material begins because the top part has been removed and the center of gravity is lowered. Therefore, it is possible to further prevent the collapse of the tank without using a floating scaffold, and the dismantling work of the tank can be efficiently performed.

It is preferable that the excavation means includes a clamshell and a hammer grab, and the strength characteristics when the clamshell is selected are lower than the strength characteristics when the hammer grab is selected.
In this configuration, when the strength characteristics of the remains are not so high, clamshells are used, which are applicable to dredging and the like, and which require a relatively small vertical load on the remains, thus reliably preventing excessive load on the storage tank.
The soil test preferably includes at least one selected from a Swedish sounding test, an automatic ram sounding test, a portable cone penetration test, and a simplified dynamic cone penetration test.
In this configuration, by using soil tests to explore the properties of such ground, the strength characteristics of the remains in the depth direction can be easily and reliably grasped.

According to the present invention, it is possible to remove residual material present at the bottom of a storage tank without using human power and while preventing the tank from collapsing.

1 is a schematic side view showing an example of a storage tank to which a method for removing residual matter in a storage tank according to an embodiment of the present invention is applied. 1 is a flowchart showing the content of a method for removing residual matter in a storage tank according to an embodiment of the present invention. FIG. 11 is a schematic enlarged cross-sectional view for explaining how a floating scaffold is floated on the liquid surface. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 2 is a schematic enlarged side view showing a clamshell as an example of an excavation means. FIG. 2 is a schematic enlarged side view showing a hammer grab as an example of an excavation means. FIG. 13 is a schematic side view for explaining the manner in which remaining material is excavated and removed. 10 is a flowchart showing the content of a method for removing residual matter in a storage tank according to another embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings as appropriate. Note that in the drawings shown below, identical or similar components are given the same reference symbols, and duplicate descriptions will be omitted as appropriate. Also, for the convenience of explanation, the shapes and sizes of components may be represented diagrammatically by modifying, exaggerating, or omitting.

FIG. 1 is a schematic side view showing an example of a storage tank 100 to which a method for removing residual matter in a storage tank according to an embodiment of the present invention is applied.
As shown in FIG. 1, the storage tank 100 is, for example, a large cylindrical tank. The storage tank 100 includes a casing 10 that contains a liquid, a powder, a gas, or other stored material. The casing 10 includes a cylindrical portion 11 having a cylindrical shape, a cone portion 12 having an inverted cone shape provided on the lower side of the cylindrical portion 11, and an inner casing 13 disposed inside the upper portion of the cylindrical portion 11. The inner casing 13 has a bottomed cylindrical shape with an open upper end, and is supported by the cylindrical portion 11 via a hanging member 14. The casing 10 is installed on the ground 16 via a support structure 15 so that its central axis is aligned vertically. In addition, an upper structure 20 is installed on the upper portion of the casing 10 to provide a scaffold or support for various operations.

Residual material 30, which is precipitated and solidified substances such as heavy metals, organic solvents, pesticides, oils, harmful chemicals, and high alkali, is present in the lower part of the casing 10 of the storage tank 100. Therefore, when performing work such as dismantling and inspection of the storage tank 100, it is necessary to remove the residual material 30 present in the storage tank 100.
This embodiment provides a method for removing remnants 30 present in the lower part of a storage tank 100 when, for example, dismantling work is performed on the storage tank 100.

Next, a method for removing residual material from a tank according to an embodiment of the present invention will be described with reference to Figures 2 to 7. Figure 2 is a flow chart showing the content of the method for removing residual material from a tank according to an embodiment of the present invention. Figure 3 is a schematic enlarged cross-sectional view for explaining how a floating scaffold 40 is floated on the liquid surface. Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3.
As shown in Figures 3 and 4, first, the floating scaffolding 40 is floated (step S1 in Figure 2).
That is, the floating scaffold 40 is floated on the water surface (liquid surface) 50 of the water present above the remnants 30 (see FIG. 1). Specifically, a plurality of constituent members 41 of the floating scaffold 40 are brought to the water surface 50 and combined to float the floating scaffold 40 on the water surface 50. Here, water is poured into the casing 10 of the storage tank 100 as necessary. The constituent members 41 have, for example, a rectangular shape in a plan view, and every four constituent members 41 are connected by a pin (not shown) at their central position, which is their common contact point. The vertical position of the floating scaffold 40 is adjusted by changing the water level by pouring or draining water into or from the casing 10 of the storage tank 100.
Handrails 42 are provided around the entire outer and inner ends of the upper surface of the floating scaffolding 40. A walkway 21 is provided on the radially outer side of the upper part of the casing 10 to provide a passageway for workers, materials, tools, etc. Workers can move between the walkway 21 and the floating scaffolding 40 via a ladder 22.

Next, a part of the storage tank 100 is dismantled on the floating scaffolding 40 (step S2 in FIG. 2). Specifically, most of the upper structure 20 is cut, for example, by gas cutting, and moved by a lifting device such as a crane (not shown) and lowered onto the ground 16. The inner casing 13 is also cut, for example, by gas cutting, and moved by the lifting device and lowered onto the ground 16. Furthermore, if necessary, the upper part of the casing 10 is cut, for example, by gas cutting, and moved by the lifting device and lowered onto the ground 16.
Next, the floating scaffolding 40 is removed (step S3 in FIG. 2). Specifically, the floating scaffolding 40 is dismantled into a plurality of component members 41 and carried out from the water surface 50.

Next, the strength characteristics of the remnant 30 in the depth direction are grasped (step S4 in FIG. 2). Specifically, first, after the water in the storage tank 100 is drained, a scaffolding board (not shown) is installed, for example, suspended by a hanging wire. Next, using this scaffolding board, in this embodiment, a soil test, for example, a Swedish sounding test, is performed on the remnant 30. In this test, an iron rod with a drill-shaped part attached to the tip is vertically set on the ground, a weight is placed on the vertical iron rod, and the penetration amount against the load is measured to calculate the strength of the ground (hardness; converted N value). The Swedish sounding test has the advantage that the test equipment and test method are simple and can be easily performed. However, it is not limited to the Swedish sounding test, and for example, an automatic ram sounding test, a portable cone penetration test, a simplified dynamic cone penetration test, etc., or two or more of these may be performed.

Next, the excavation means 60 is selected (step S5 in FIG. 2). Fig. 5 is a schematic enlarged side view showing a clamshell 61 as an example of the excavation means 60. Fig. 6 is a schematic enlarged side view showing a hammer grab 62 as an example of the excavation means 60. That is, the excavation means 60 suitable for the strength characteristics in the depth direction of the remnant 30 identified by the soil test in step S4 is selected.
The excavation means 60 is, for example, a clamshell 61 (see FIG. 5) or a hammer grab 62 (see FIG. 6). The clamshell 61 is a bucket that grabs soil and sand by closing a suspended bucket from an open state. The hammer grab 62 is a grab that grabs soil and sand by driving it into the ground with a dropping force. The hammer grab 62 has a larger excavation force than the clamshell 61. On the other hand, the clamshell 61 has a larger excavation volume per excavation than the hammer grab 62. In this embodiment, the strength characteristics in the depth direction of the remnant 30 when the clamshell 61 is selected are set lower than the strength characteristics in the depth direction of the remnant 30 when the hammer grab 62 is selected.

Then, the remaining material 30 is excavated and removed by the selected excavation means 60 (step S6 in FIG. 2). FIG. 7 is a schematic side view for explaining the excavation and removal of the remaining material 30. Specifically, as shown in FIG. 7, the remaining material 30 present at the bottom of the casing 10 of the storage tank 100 is excavated and removed by the excavation means 60 supported by a wire 71 of a lifting device 70 such as a crane. Note that the remaining material 30 present in the cone section 12 may be removed by heavy machinery such as a long backhoe from the standpoint of workability.

After the remnants 30 are removed, the floating scaffolding 40 is floated again (step S7 in FIG. 2). Specifically, water is poured into the casing 10 of the storage tank 100, and the floating scaffolding 40 is set so as to float on the water surface 50 of the poured water in the same manner as in step S1.
Next, the dismantling work of the storage tank 100 is further carried out on the floating scaffolding 40 (step S8 in FIG. 2). Specifically, the remaining part of the storage tank 100 is cut off, for example, by gas cutting, and moved by a lifting device such as a crane (not shown) and lowered onto the ground 16.

As described above, the method for removing residual material from a tank according to this embodiment is a method for removing residual material 30 present in the lower part of the tank 100. In this method for removing residual material from a tank, first, a soil test is performed to determine the strength characteristics of the residual material 30 in the depth direction. Next, an excavation means 60 suitable for the determined strength characteristics is selected. Then, the selected excavation means 60 is used to excavate and remove the residual material 30.
In this embodiment, an excavation means 60 suitable for the strength characteristics (hardness) of the remnants 30 is selected and used. This makes it possible to prevent the use of an excavation means 60 with a large excavation force that is not commensurate with the strength characteristics of the remnants 30, thereby preventing excessive vibration or other loads from being applied to the storage tank 100. This makes it possible to prevent the storage tank 100 from collapsing and the remnants 30 inside from flowing out to the outside. Furthermore, even if remnants 30, such as highly alkaline substances, are present in the lower part of the storage tank 100 and have precipitated and solidified, the remnants 30 can be removed without direct human contact.
In this way, according to this embodiment, the remaining material 30 present at the bottom of the storage tank 100 can be removed without using human force and while preventing the storage tank 100 from collapsing.

In addition, in this embodiment, before removing the remnants 30, a floating scaffold 40 is floated on the water surface 50 of the water above the remnants 30, and a part of the storage tank 100 is dismantled on the floating scaffold 40. In this configuration, by using the floating scaffold 40, the dismantling work of the storage tank 100 can be performed on the upper part of the storage tank 100. In addition, since the floating scaffold 40 can be lowered by lowering the water level, the dismantling work can be carried out sequentially from the top to the bottom of the storage tank 100. Moreover, by proceeding with the dismantling work of the storage tank 100 before removing the remnants 30, the storage tank 100 becomes more stable at the start of the removal work of the remnants 30 because the upper part of the storage tank 100 has been removed and the center of gravity is lowered. Therefore, the collapse of the storage tank 100 can be further suppressed, and the dismantling work of the storage tank 100 can be carried out efficiently.

In addition, in this embodiment, the floating scaffolding 40 can be deformed to expand and contract on the water surface to match the internal shape of the storage tank 100. With this configuration, even if the internal shape of the storage tank 100 changes in the height direction, the floating scaffolding 40 can be formed as close as possible to the wall surface inside the storage tank 100. This makes it possible to more smoothly carry out the dismantling work of the storage tank 100.

In addition, in this embodiment, after the remaining material 30 is removed, water is injected into the storage tank 100, and further dismantling work is carried out on the floating scaffolding 40. In this configuration, the floating scaffolding 40 can be used to carry out dismantling work as far down as possible into the storage tank 100. This allows the dismantling work of the storage tank 100 to be carried out more efficiently. In addition, the storage tank 100 becomes more stable because the remaining parts that have not yet been dismantled are reduced and the center of gravity is further lowered. Therefore, the remaining parts will not tip over even under loads such as lateral loads, and it becomes possible to dismantle them using heavy machinery, for example.

In this embodiment, the excavation means 60 includes a clamshell 61 and a hammer grab 62. When the clamshell 61 is selected, the strength characteristics of the remnant 30 are lower than the strength characteristics of the remnant 30 when the hammer grab 62 is selected. In this configuration, when the strength characteristics of the remnant 30 are not so high, the clamshell 61, which is applied to dredging and the like and requires a relatively small vertical load on the remnant 30, is used. Therefore, it is possible to reliably prevent excessive load from being applied to the storage tank 100.
In this embodiment, the soil test includes at least one selected from a Swedish sounding test, an automatic ram sounding test, a portable cone penetration test, and a simplified dynamic cone penetration test. In this configuration, by using such a soil test for investigating the properties of the ground, the strength characteristics of the remnant 30 in the depth direction can be easily and reliably grasped.

Fig. 8 is a flow chart showing the contents of a method for removing residual matter in a storage tank according to another embodiment of the present invention. Below, differences from the embodiment shown in Figs. 1 to 7 will be mainly described, and explanations of commonalities will be omitted.
As shown in Fig. 8, in this embodiment, first, the strength characteristics of the remnant 30 in the depth direction are grasped (step S11 in Fig. 8). Specifically, a Swedish sounding test, which is one of the soil tests, is performed on the remnant 30 using, for example, a scaffolding board (not shown) suspended by a hoisting wire. Next, an excavation means 60 is selected (step S12 in Fig. 8). Steps S11 and S12 in Fig. 8 are similar to steps S4 and S5 in Fig. 2, so detailed explanations are omitted.
Next, the tank 100 is dismantled from the top to the height just before the remnants 30 (step S13 in FIG. 8). That is, dismantling work is performed from the top of the tank 100 to a predetermined height position above the remnants 30. In this case, heavy machinery dismantling or lifting and dismantling by a crane is performed. In this way, by proceeding with the dismantling work of the tank 100 before removing the remnants 30, the tank 100 becomes more stable at the start of the removal work of the remnants 30 because the top part of the tank 100 is removed and the center of gravity is lowered. Therefore, according to this embodiment, it is possible to further prevent the collapse of the tank 100 without using the floating scaffolding 40 (see FIG. 4), and to efficiently proceed with the dismantling work of the tank 100.
Next, the remaining objects 30 are excavated and removed by the excavation means 60 selected in step S12 (step S14 in FIG. 8). Step S14 in FIG. 8 is the same as step S6 in FIG. 2, so a detailed description will be omitted. Next, the remaining storage tank 100 is dismantled (step S15 in FIG. 8). Specifically, the remaining parts of the storage tank 100 are dismantled using heavy machinery or lifted and dismantled using a crane, for example.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit of the present invention.
For example, in the above embodiment, after the remaining objects 30 are removed in steps S7 and S8, water is poured into the storage tank 100 and further dismantling work is performed on the floating scaffolding 40, but these operations may be omitted. In this case, it is possible to perform the dismantling work directly using, for example, heavy machinery without performing steps S7 and S8.
Although the clamshell 61 and the hammer grab 62 are given as examples of the excavation means 60, the present invention is not limited thereto, and other excavation means may be used. For example, a dredger bucket may be used instead of the clamshell 61 to improve the excavation volume and excavation force.
The soil tests are not limited to Swedish sounding tests, automatic ram sounding tests, portable cone penetration tests, and simplified dynamic cone penetration tests, but other soil tests may be performed.
In the above embodiment, the constituent member 41 of the floating scaffolding 40 has a rectangular shape when viewed in a plan view, but this is not limited to this and may have other shapes, such as a hexagonal shape.
The present invention may be applied to a method for removing residual material 30 present at the bottom of a storage tank 100 when other work such as inspection is performed on the storage tank 100.

30 Remains 40 Floating scaffolding 50 Water surface (liquid surface)
60 Excavation means 61 Clamshell 62 Hammer grab 100 Storage tank

Claims (6)

A method for removing residual material present at the bottom of a storage tank, comprising the steps of:
The upper structure provided on the upper part of the storage tank is removed,
Grasping the strength characteristics of the remains in the depth direction through soil testing;
Selecting an excavation means suitable for the identified strength characteristics;
A method for removing residual material in a storage tank, comprising the steps of: excavating and removing the residual material using a selected excavation means,
The upper structure is removed by a worker working from a floating scaffolding that is floating on the liquid surface above the remaining objects,
A method for removing material remaining in a storage tank, comprising removing the floating scaffolding before excavating the material remaining . The method for removing material remaining in a tank as described in claim 1 , characterized in that the floating scaffolding is deformable so as to expand and contract on the liquid surface to match the internal shape of the tank. A method for removing residual material from a tank as described in claim 1 or claim 2 , characterized in that after the residual material is removed, liquid is injected into the tank and further dismantling work of part of the tank is carried out on the floating scaffolding. The method for removing residual material from a storage tank according to claim 1, characterized in that, before removing the residual material, dismantling work is carried out from the top of the storage tank to a predetermined height position above the residual material. A method for removing material remaining in a storage tank described in any one of claims 1 to 4, characterized in that the excavation means includes a clamshell and a hammer grab, and the strength characteristics when the clamshell is selected are lower than the strength characteristics when the hammer grab is selected. The method for removing residual material from a storage tank described in any one of claims 1 to 5 , characterized in that the soil test includes at least one selected from a Swedish sounding test, an automatic ram sounding test, a portable cone penetration test, and a simplified dynamic cone penetration test.

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