JPS6142808B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for testing for leaks in the outermost welds of a storage bottom plate with a fixed roof.

In recent years, various laws and regulations such as the Fire Service Act have been amended in the wake of accidents involving oil storage tanks, and there are calls for consideration of safety for residents in storage tank construction areas and prevention of environmental pollution (so-called pollution) of surrounding environments such as private houses and fishing grounds. be.

In view of these recent social environments, the present invention provides a more reliable method for inspecting leaks at the welded portion of the bottom plate of a storage tank in order to provide storage that is even safer than before. This particularly concerns inspection of the welds on the outermost periphery of the bottom plate, which are more dangerous in the event of a storage tank leakage accident.

Conventionally, most double-shell low-temperature storage tanks have a structure with a double cylindrical dome roof, and the space between the bottom plates of the inner tank and outer tank is designed to retain the cold heat of the low-temperature content liquid. It is filled with an insulating material, and the insulating material has various properties such as heat insulation, load resistance, and fire resistance. As shown in FIGS. 4a to 4c, the welded joints on the inner tank bottom plate of the storage tank are joined by overlap welding, butt welding with a backing plate, or butt welding without a backing plate.

The general method for assembling this inner tank bottom plate is
- As shown in Publication No. 150720, after the units forming the inner tank bottom plate are laid out and welded to each other on a stand assembled on the bottom cold insulation layer, inspections such as X-ray tests are conducted on the stand. ing. After the inspection is completed, the pedestal is removed, the inner tank bottom plate is suspended onto the bottom cold insulation layer, and finally the outer circumference of the inner tank bottom plate and the annular plate are welded.

In the inspection of the welded joint between the inner tank bottom plate and the annular plate, which is the final weld line of the bottom plate, since the welded joint is placed directly on the bottom insulation layer or ring-shaped block, the bottom surface of the welded joint is Because there is no space for installing wire film or transporting inspection materials, they are forced to use simple inspection methods such as vacuum testing or penetrant testing, which can be performed only from the top. It is something that Since all of these inspections were conducted from one side, there was a drawback that the inspection of the welds was not complete.

In view of the above-mentioned drawbacks, the present invention makes it possible to inspect the welded part from both sides, which means that it is possible to perform inspections on the welded part from both sides, such as X-ray transmission tests and ammonia leak tests, which were previously considered impossible. Our goal is to provide reliable and safe tanks.

Now, the embodiment will be described with reference to FIG. 1, in which a ring-shaped block 4 located at the bottom of the side plate 3 of a storage tank 2 having a fixed roof 1 is inspected by an inspection worker to inspect the final weld line 5 of the storage tank bottom plate. The ring-shaped block is shifted outward from the designed position (the position shown by the solid line in Figure 1) to the extent that it can be inspected, and an inspection work space is created between the shifted ring-shaped block and the inner ring-shaped block or the bottom insulation layer. After constructing the storage tank 2 and welding the final weld line 5 of the bottom plate (the position indicated by the dotted line in Figure 1) so as to form a After the inspection of the final weld line 5, which is to be tested, is completed, pressurized air is sent into the storage tank 2, and an upward force is applied to the side plate 3 by internal pressure, so that the side plate 3, roof 1, and bottom plate of the storage tank 2 are After raising the outer periphery a little (necessary amount), the ring-shaped block 4 is returned to the designed position, and the slightly raised outer peripheries of the side panels 3, roof 1, and bottom plate of the storage tank 2 are lowered to complete the construction. be.

The internal pressure required to float the outer edge of the bottom plate of storage tank 2 may be 0.1 Kg/cm ² or more, and when the outer edge of the bottom plate is slightly floated, the center of the bottom plate will be in contact with the bottom cold insulation layer. The entire storage tank 2 is supported in contact with the tank 2.

The above is a method common to both single and double storage tanks with fixed roofs, and this is the gist of the present application, but the embodiments of the present application will be explained in more detail based on FIGS. 2 and 3. I will explain. FIG. 2 shows the state before the final weld line is inspected, and FIG. 3 shows the state after the inspection is completed.

The perlite concrete block 10 to be laid under the annular plate 9 located at the bottom of the inner tank side plate 8 forming the inner tank 7 of the double-shell low temperature storage tank 6 is positioned from the designed position (the position of the block indicated by the broken line in Fig. 2). Shift it outward (to the position of the solid line block in Figure 2),
That is, the inner tank 7 is constructed by arranging the inner tank 7 so as to form an inspection space large enough to allow an inspection worker to inspect the final weld line 12 of the inner tank bottom plate 11.

After completing welding of the final weld line 12 of the inner tank bottom plate 11, inspection such as X-ray transmission test, and all welding related to the inner tank, as shown in FIG. Air is forced into the inner tank 7 and the internal pressure acts on the inner tank side plate 8 and the roof, causing the outer peripheral edge of the inner tank side plate 8 and the bottom plate 11 of the inner tank 7 to rise slightly (necessary amount) to form pearlite concrete. The block 10 is moved to the designed position and then lowered while exhausting the air in the inner tank 7 to complete the construction.

At this time, tie rods 14 are installed in the inner tank 7 and outer tank 15 to prevent overfloating, and a safety valve 16 for adjusting the pressure inside the storage tank is installed on the roof of the inner tank 7 to prevent overfloating or abnormalities. Inner tank 7 by pressurization
damage can be prevented.

In this application, since the inspection is performed as described above, by working on the final weld lines 5 and 12 from above and below, inspection can be performed with much higher reliability than in the past, and a tank with higher safety can be provided. Moreover, the construction method is simple and safe, as the construction method is simply sending in pressurized air.

As described above, the storage tank is constructed by shifting the ring-shaped block located at the bottom of the side plate of the storage tank with a fixed roof to the outside from the designed position, and after welding the final weld line of the bottom plate, the final welding line of the bottom plate is welded. After the inspection of the weld line is completed, pressurized air is sent into the storage tank to raise the outer peripheral edge of the tank bottom plate by the necessary amount, and then the ring-shaped block is returned to the designed position and the storage tank is lowered to complete the construction. Therefore, it is possible to inspect the final weld line from both the upper and lower sides, and in other words, it enables highly reliable inspections such as X-ray transmission tests and ammonia leak tests of the relevant parts, which is different from conventional methods. Eliminate the drawbacks of the inspection method,
This makes it possible to provide a storage tank with higher safety.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a single shell storage tank, Figures 2 and 3
The figure is a sectional view of the double shell storage tank, and FIG. 4 is a sectional view showing a method of welding the bottom plate.

Claims (1)

[Claims] 1. The ring-shaped block located at the bottom of the side plate of the storage tank with a fixed roof is shifted outward from the designed position in advance, the storage tank is constructed, the final weld line of the bottom plate is welded, and the inspection of the final weld line is completed. After that, pressurized air is sent into the storage to raise the outer periphery of the storage tank bottom plate by a required amount, and then the ring-shaped block is returned to the designed position and the outer periphery of the storage tank bottom plate is lowered to complete the construction. Leakage inspection method for welds on storage tank bottom plates.