JPH04294781A - Method for replacing bottom end plate of tank - Google Patents

Abstract

PURPOSE:To make shorter a construction period for the replacement work of a bottom end plate of a tank and ensure the safety of the work without damage to an existing foundation, thereby making welded connections after the replacement of the bottom end plate sound and strong. CONSTITUTION:A method for replacing a bottom end plate of tank includes the steps of: attaching jack-up jigs 2 to the lower part of a side plate of the tank to slightly lift a bottom end plate 5 to be replaced from a tank foundation (first step); removing welded section from a side plate 1 to separate a bottom end plate 4 adjacent to the plate 1 so that the plate 3 is carried out of the tank and a new bottom end plate 5 is welded to the plate 4 (second step); forming an opening 7 at the lower part of the side plate 1 to inspect the welded section 6 of the plate 5 and adjacent plate 4 (third step); setting the plate 1 on the plate 5 by means of the jigs 2 to close the opening 7 at the lower end of the side plate and weld the plate 1 to the plate 5 (fourth step).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of partially or entirely replacing a bottom end plate such as an annular plate of a tank with a new bottom end plate.

0002

[Prior Art] Bottom end plates such as annular plates located at the bottom of the side plates of oil tanks, etc., are susceptible to rainwater infiltration and are susceptible to corrosion due to heavy loads, so the thickness of the bottom end plates must be periodically adjusted. We inspected and replaced any severely corroded bottom end plates with new bottom end plates using jack-up or window-opening methods.

The conventional method for replacing the bottom end plate using the jack-up method is to install a jack base on the slope of the tank, attach a bracket to the lower part of the side plate, and push up the bottom end plate together with the jack installed on the jack base. The welded part between the bottom end plate and side plate that needs to be replaced is removed, the bottom end plate that needs to be replaced is separated from the adjacent bottom end plate, and the bottom end plate that needs to be replaced is carried out of the tank. Then, carry the new bottom end plate into the tank and weld it to the adjacent bottom end plate.
After completing the vacuum inspection and other inspections of the welded area, the side plate that had been jacked up was jacked down onto the bottom end plate, the side plate and the bottom end plate were welded, and then the welded area was The bottom end plate was replaced during the inspection procedure.

[0004] Furthermore, in the conventional method of replacing the bottom end plate using the window opening method, as disclosed in Japanese Patent Publication No. 2-49990, the side plate is removed at the position where the bottom end plate to be replaced is separated from the adjacent bottom end plate. Two openings are provided at the bottom, the bottom end plate to be replaced is separated from the adjacent bottom end plate through these openings, and the weld between the bottom end plate and the side plate is then removed from the bottom end plate to be replaced. As a result, the bottom end plate is removed by cutting it from the side plate and transporting it outside the tank, replacing it with a new bottom end plate, welding it to the adjacent bottom end plate, closing the opening in the side plate, and welding the side plate and bottom end plate. was being replaced.

[0005]

[Problems to be Solved by the Invention] In the conventional method of replacing the bottom end plate using the jack-up method, the side plate is placed at a height higher than that where a vacuum box can be inserted to vacuum inspect the welded part between the new bottom end plate and the adjacent bottom end plate. If the tank has to be jacked up, the tank may become unstable due to being supported high by the jack, or the length of the weld between the bottom end plate and side plate may be partially removed to remove the bottom end plate to be replaced. Even if it was a simple replacement, it would have been necessary to take a long time to restore it. In addition, in the conventional method of replacing the bottom end plate using the window opening method, the bottom end plate to be replaced has been pressed and intimately attached to the tank foundation for a long time, so the adjacent bottom end plate is cut off and the welded part with the side plate is removed. Even if the bottom end plate was removed, it was still difficult to pull out the bottom end plate to be replaced outside the tank and carry the new bottom end plate into the tank. In order to solve the above-mentioned drawbacks of the conventional construction method, this invention involves the work of jacking up the side plate to the extent that it lifts the bottom end plate to be replaced, pulling out the bottom end plate to be replaced, and carrying it out of the tank. An object of the present invention is to provide a method for replacing a bottom end plate of a tank, which facilitates the work of carrying a plate into a tank, and also allows safe and easy vacuum inspection of the welded part of a new bottom end plate and an adjacent bottom end plate. .

[0006]

[Means for solving the problem] When replacing the bottom end plate of a tank, first attach a jack-up jig to the bottom of the side plate and lift it off to the extent that the bottom end plate to be replaced is lifted, and then connect the bottom end plate and side plate to be replaced. The bottom end plate is cut away from the side plate by removing the welded portion. Next, the bottom end plate to be replaced and the adjacent bottom end plate are cut through the gap at the bottom of the side plate, the bottom end plate to be replaced is carried out to the outside of the tank, the new bottom end plate is carried inside the tank, and the adjacent bottom end plate is cut away. Weld to the end plate. Next, after inspecting the welded part between the new bottom end plate and the adjacent bottom end plate through an opening for inserting an inspection instrument cut out in the lower end of the side plate, the new bottom end plate is inspected using a jack-up jig. The bottom end plate of the tank is replaced by seating the side plate on top, closing the opening in the side plate, and welding the side plate and a new bottom end plate.

[0007]

[Operation] The height at which the bottom end plate to be replaced together with the side plate should be jacked up should be such that it can be easily jacked down in an emergency such as a storm, and it should be high enough to float above the tank foundation. The bottom end plate to be replaced is jacked up together with the side plate, lifted off the tank foundation to the extent that it floats, the welded part with the side plate is removed, and the bottom end plate is cut off from the side plate. At this time, the removal of welded parts is necessary for the bottom end plate to be replaced and both sides thereof, taking into account the work to carry out the bottom end plate to be replaced and the welding work of the new bottom end plate and the adjacent bottom end plate during restoration. Execute to the extent possible. Then, the bottom end plate to be replaced is separated from the adjacent bottom end plate, and the bottom end plate to be replaced is pulled out through the gap at the bottom of the side plate and carried out to the outside of the tank. The new bottom end plate will be carried into the tank by passing it between the tank foundation and the jacked up side plate.

The work of cutting off the bottom end plate to be replaced and the adjacent bottom end plate is done in such a way that the asphalt of the tank foundation, which is used as a rust preventive and solidifying agent, is not damaged by gas cutting flames or heat. Perform this with the bottom end plate separated from the tank foundation. The groove shaping work at the lower end of the side plate for welding the new bottom end plate and the lower end of the side plate is performed using the gap between the raised side plate and the new bottom end plate. To inspect the weld between the new bottom end plate and the adjacent bottom end plate, vacuum inspection or magnetic particle inspection is performed by inserting an inspection instrument through an opening cut out in the lower end of the side plate.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described with reference to the drawings. FIG. 1 is a perspective explanatory view showing an example of the method for replacing the bottom end plate of a tank according to the present invention, and FIG. 2 shows a state in which the side plate and the bottom end plate to be replaced are jacked up in the replacement method shown in FIG. FIG. 3 is a partial cross-sectional view illustrating a welding groove provided at the lower end of the side plate. First, a jack-up jig 2 is attached to the lower part of the side plate 1 outside the tank, sandwiching the position of the bottom end plate 3 to be replaced. The jack-up jig 2 includes a bracket 2a attached to the side plate 1, a jack base 2b provided on the slope of the tank foundation, and a jack base 2
b, and a jack 2c that is set on the bracket 2a to push up the bracket 2a.

When the jack 2c is pushed up, the bottom end plate 3 to be replaced, together with the side plate 1, leaves the tank foundation and floats up. The jack-up height at this time is such that the bottom end plate 3 to be replaced can be easily pulled out and carried out of the tank, the new bottom end plate 5 can be easily carried into the tank, and the welding groove at the lower end of the side plate 1 can be easily removed. The height of the part 9 is about 50 mm, which allows shaping work and quick jacking down in an emergency. The bottom end plate 3 to be replaced, which has been pressed against the side plate 1 for a long time and has been in close contact with the foundation, should be separated from the foundation by applying a light impact such as hammering, and the bottom end plate 3 to be replaced should be removed from the back side of the bottom end plate 3 to be replaced. After removing the asphalt mortar and the like on the foundation that makes it difficult to do so by light hammering, the bottom end plate 3 to be replaced is pulled out and carried out to the outside of the tank.

The welded portion 6 between the bottom end plate 3 to be replaced and the side plate 1 is removed by arc air gouging or grinding, and the bottom end plate 3 to be replaced and the adjacent bottom end plate 4 are separated by gas cutting or arc This is done by air gouging, and the bottom end plate 3 to be replaced is pulled out and carried out to the outside of the tank. This work of removing the welded parts and cutting out the parts is carried out while the bottom end plate 3 to be replaced is lifted off the foundation by jacking up, so that the flame and heat of the work will not damage the tank foundation made of asphalt mortar etc. . When removing the welded part between the bottom end plate 3 to be replaced and the side plate 1, take into account the work to carry out the bottom end plate 3 to be replaced and the welding work to the adjacent bottom end plate 4, etc. Remove welds to the required extent. The new bottom end plate 5 is carried into the tank through between the jacked up side plate 1 and the tank foundation, placed in the position where the bottom end plate 3 to be replaced was originally, and welded to the adjacent bottom end plate 4. Unify.

The lower end of the side plate 1, which is located above the weld between the new bottom end plate 5 and the adjacent bottom end plate 4, is half-sized enough to allow insertion of an inspection instrument 8 such as a vacuum box for vacuum inspection or a magnet for magnetic particle inspection. An opening 7 is formed by cutting out an arc. Using this opening 7, the welded portion between the new bottom end plate 5 and the adjacent bottom end plate 4 is inspected by vacuum inspection or magnetic particle inspection. If a defect is found in the welded part, repair and re-inspection are performed using this opening 7 again. Using the gap between the new bottom end plate 5 and the jacked up side plate 1,
A groove 9 to be welded is formed at the lower end of the side plate 1 by arc air gouging, gas cutting, grinding, etc. After lowering the jack and seating the grooved side plate 1 on the new bottom end plate 5 and closing the opening 7 at the lower end of the side plate 1, the side plate 1 and the new bottom end plate 5 are welded. After inspecting part 6, the bottom end plate replacement work is completed. By repeating this operation in sequence, the bottom end plate around the entire circumference of the tank can be replaced safely.

[0013]

Effects of the Invention: By jacking up the side plate and the bottom end plate to be replaced to such an extent that the bottom end plate to be replaced is lifted up, the bottom end plate to be replaced can be carried out of the tank through the gap at the bottom of the side plate. The work of carrying the bottom end plate into the tank is carried out extremely efficiently. Also,
The bottom end plate to be replaced is cut and welded parts are removed while the bottom end plate is slightly raised from the tank foundation, so the tank foundation is not damaged. By providing an opening large enough to insert an inspection tool into the lower end of the side plate located above the weld between the new bottom end plate and the adjacent bottom end plate, the bottom end plate can be safely removed without jacking up the side plate more than necessary. The end plate can be replaced, and the length of welded parts removed from the side plate and bottom end plate can be shortened compared to the conventional jack-up construction method. By using the space between the jacked-up side plate and the new bottom end plate, it is possible to form a welding groove between the side plate and the new bottom end plate at the lower end of the side plate or to shape the end, resulting in a good side plate. and a new bottom end plate weld is obtained.

In this way, by slightly jacking up and forming an opening at the lower end of the side plate, the construction period can be shortened without damaging the existing foundation, a strong and sound welded joint can be obtained, and the work can be carried out safely. The bottom end plate of the tank can be replaced.

[Brief explanation of drawings]

[Fig. 1] A perspective explanatory view showing a method for replacing the bottom end plate of a tank according to an embodiment of the present invention.

[Fig. 2] A cross-sectional explanatory diagram showing a state in which the side plate and the bottom end plate to be replaced are jacked up in the replacement method of Fig. 1.

[Fig. 3] Cross-sectional explanatory diagram showing the case where a welding groove is provided at the lower end of the side plate in the replacement method shown in Fig. 1.

[Explanation of symbols]

1 Side plate 2 Jack up jig 3 Bottom end plate to be replaced 4 Adjacent bottom end plate 5 New bottom end plate 6 Welded part of side plate and bottom end plate 7 Opening 8 Testing equipment 9 Welding groove at the bottom end of the side plate

Claims (1)

[Claims] The step of installing a jack-up jig at an appropriate position at the bottom of the tank side plate and lifting off the bottom end plate to be replaced to such an extent that it floats from the tank foundation together with the tank side plate, and the process of installing the bottom end plate to be replaced between the bottom end plate and the side plate. Remove the weld and cut it from the side plate, and then cut the adjacent bottom end plate through the gap at the bottom of the side plate and carry the bottom end plate to be replaced to the outside of the tank.
The process of replacing with a new bottom end plate and welding it to the adjacent bottom end plate,
The lower end of the side plate located at the welding part between the new bottom end plate and the adjacent bottom end plate is cut out to an extent that allows insertion of an inspection instrument, and an opening is formed to form an opening between the new bottom end plate and the adjacent bottom end plate. It consists of a process of inspecting the welded part, and a process of seating the side plate on the bottom end plate that has been inspected for the welded part using a jack-up jig, closing the opening of the side plate, and welding the side plate and the bottom end plate. How to replace the bottom end plate of a tank.