JPS6010571B2 - Leakage inspection method for bottom plate of cylindrical storage tank - Google Patents

Description

[Detailed Description of the Invention] Conventionally, the bottom plate of a low-temperature storage tank was constructed by welding a rectangular steel plate onto a basic cold insulation material, but a foaming test called a vacuum box test was developed to inspect this welded part. There is.

However, it is known that ammonia gas is more effective in detecting leaks, but ammonia gas has a strong pungent odor and is toxic, making it difficult to handle, and it is corrosive, so it cannot be used with the bottom plate. When ammonia gas is sealed between the basic insulation materials, the ammonia gas is adsorbed by the cold insulation material.
Touching the bottom plate over a long period of time will cause corrosion of the bottom plate. In addition, in the past, we were looking for a method of lifting the bottom plate and having people go underneath it, attaching a circular tube cut in half to the bottom of the weld line, and filling it with ammonia gas. This involves dangerous conditions for humans to work on it. In this application, by installing an airtight sheet of steel plate, aluminum plate, synthetic resin, etc. between the bottom plate and the basic cold insulation material, ammonia gas is sealed in the space surrounded by this sheet and the garden slope. If there is a leak hole in the welded part of the bottom plate, this ammonia gas passes through the hole and reacts with the reactant applied to the top surface of the bottom plate, thereby detecting the leak point.

In other words, this sheet prevents ammonia gas from coming into direct contact with the basic cold insulation, and since the ammonia gas is sealed between the bottom plate and the sheet and is confined only to this space, the amount of ammonia is small and does not come into contact with the human body. In addition, it is possible to avoid the dangerous situation of lifting the bottom plate and having people work underneath it, and furthermore, it is possible to immediately dismount the bottom plate and pump air into the space surrounded by the sheet to avoid other problems. This invention is characterized in that by discharging the ammonia gas in this space from the outlet, the ammonia gas can be completely removed, so that the sheet can be left as it is laid.

To explain one embodiment to achieve the above object, when constructing a single storage tank or a double storage tank with inside and outside, a bottom concrete ring 1 is laid on the foundation or the bottom plate of the outer tank, and a concrete ring 1 is placed on the top of the bottom concrete ring 1. An annular plate 2 formed into a ring shape by welding is laid on top of which an airtight and strong sheet 6 made of steel plate, aluminum plate, or synthetic resin is laid.

The sheet 6 is sized to sufficiently protrude into and out of the annular plate 2. After that, the inner tank side plate 3 is erected and fixed on the annulus plate 2, and a frame of an appropriate height, for example, 1.8 cm, is assembled inside the inner tank side plate 3, and the inner tank bottom plate 4 is arranged on the frame. After completing the welding (including double-sided welding) inspection of the back side, we used the inner tank side plates 3 and the existing roof plate 8 to place the finished inner tank bottom plate 4 on a stand using a wire. lift.

After that, while removing the frame, a bottom insulation layer is constructed on the foundation or on the slope of the bottom of the outer tank, and after the bottom cold insulation work is completed, a sheet 6 is laid on top of the bottom cold insulation layer 5, and the outer peripheral sheet 6 and the sheet 6 are After airtightly connecting the inner tank bottom plate 4 while loosening the suspended wires, fixing it on the bottom cold insulation layer 5, welding and fixing the inner tank bottom plate turtle and the annular plate 2, and fixing the inner tank bottom plate 2. The sheet 6 protruding to the outside of the tank is folded upward and attached airtight to the outside of the inner tank side plate 3, and an ammonia gas filling port 7 is provided in the bag-shaped portion 6a of the sheet 6 located outside the inner tank side plate 3. ~ After applying the reactive substance to the welded part of the inner tank bottom plate 4, raise the entire tank with the jack 9 or
Gas filling port 7 for ammonia gas without jacking up
Closer examination is conducted to check for gas leakage from the leakage part of the welded part by checking for changes in reactants.

After the inspection is completed, air is sent through the gas filling port 7 and ammonia gas is discharged from an appropriately provided discharge port in addition to the gas filling port 7 of the bag-like portion 6a of the sheet 6 to completely remove the ammonia gas. The sheets 6, 6' are to be left as they are.

In addition to laying the sheets 6 and 6' using the method described above, the entire completed tank is jacked up and floated, and the annular plate 2, inner tank bottom plate 4, and bottom concrete ring 1 are installed.
Also, a single sheet may be laid between the bottom cold insulation layer 5. Furthermore, after laying the bottom concrete ring 1 and laying the bottom cold insulation layer 5 inside the bottom concrete ring 1, a sheet 6 capable of covering the whole is laid on the top, and then an annular plate 2 is placed on top of the sheet 6. It is also possible to adopt a construction method in which the side plate 3 is fixed upright and the inner tank bottom plate 4 is fixed.In other words, by constructing the tank on the upper part of the seat 6, the later jack-up seats 6, 6 can be installed.
′ can be saved. That is, in the present application, a sheet sufficiently larger than the bottom plate is laid between the bottom plate of the tank and the foundation or a bottom cold insulation layer provided on the foundation, the end of the sheet is airtightly attached to the side plate of the tank, and ammonia gas is sealed between the sheet and the bottom slope. The construction process up to that point was based on the design and construction based on the size of the tank, etc., and the purpose of the application could not be achieved no matter what method was adopted during the construction process. However, any method of laying the sheet under the L bottom plate does not depart from the gist of the present application.

In this application, as described above, an airtight sheet is laid between the bottom plate and the basic cold insulation material, the end is folded upward and sealed airtightly to the side plate, and then ammonia gas is sealed between the bottom plate and the sheet. It reacts with the reactive substance applied to the top surface to detect leakage points, and after the inspection is completed, air is pumped in to exhaust ammonia gas, which has the following effects: .

a) The sheet prevents ammonia gas from coming into direct contact with the bottom cold insulating layer. Since ammonia gas does not come into contact with the bottom plate for a long period of time, corrosion of the bottom plate can be prevented.

b Ammonia gas is sealed between the bottom plate and the seat~
Since it is limited only to this space, the amount of ammonia gas is small and the bottom plate can be inspected for leakage without coming into contact with the human body.

c It is possible to avoid the dangerous situation of lifting the bottom plate and having workers work underneath it.

d Immediately after the inspection is completed, the ammonia gas can be completely removed by pumping air into the space surrounded by the bottom plate and sheet and discharging the ammonia gas in this space from another outlet, so this sheet can be left in place. You can leave it there.

e By laying the sheet as is as described in the previous section, even if the liquid in the tank should leak, it will be avoided that it will accumulate on the sheet and immediately seep into the cold insulation layer.

[Brief explanation of the drawing]

Figure 1 is an overall sectional view, and Figure 2 is a partially enlarged sectional view. Figure 1 Figure 2

Claims (1)

[Claims] 1 An airtight sheet is laid between the bottom plate and the basic cold insulation material, the end is folded upward, and the sheet is airtightly placed on the side plate. Ammonia gas is sealed between the bottom plate and the sheet, and a reaction mixture is applied to the top surface of the bottom plate. A leak testing method for the bottom plate of a cylindrical storage tank, characterized by reacting with a substance to detect a leak location, and after the test is completed, air is pumped in to discharge ammonia gas.