JPH0242907B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The object of the present invention is to protect the storage tank body by suppressing rusting and pitting of the bead and jig marks that occur during a water test of storage tanks.

As is well known, storage tanks are inspected before use by filling them with water at the time assembly work is completed to check for leakage of liquid from various parts of the weld line, the amount of foundation settlement, etc.
The law requires that the amount of deformation of storage tanks be investigated to ensure safety.

The number of days required for this water filling work depends on the size of the storage tank,
Although it varies depending on the water supply situation, it generally takes about one month for a storage tank with a capacity of tens of thousands of kiloliters. Furthermore, the period during which the inner surface of the storage tank is immersed in water may extend to about two months, including the period when the storage tank is left full of water and the period during which water is drained.

However, due to this long-term contact with the water, weld beads, jig marks, and markings on the inner surface of the side panels and top of the bottom panel of the storage tank were almost entirely covered, with a diameter of 1 mm and a depth of 1 mm. 0.5～
Pitting corrosion of about 1mm occurs. The degree of this corrosion is uniformly observed for all storage tanks, with little correlation to the type of water filled (industrial water, city water, seawater, etc.) or the length of the water filling period.

This pitting corrosion causes the release of iron components and colors the charging water a rust-red color, which requires physicochemical wastewater treatment before it can be discharged. An even more important problem is that if pitting corrosion occurs in areas that are particularly stressed, such as fillet welds or annular plates, it can grow into large defects over time.
This can lead to cracking and breakage of welded parts, which can lead to fatal accidents for storage tanks.

Furthermore, these pitting corrosion areas are detected as condensation defects during the Magna inspection of bead areas and jig marks performed after the water test, and it is difficult to distinguish them from serious defects such as cracks in actual welds, which can be fatal. There is a high possibility that defects will be overlooked, and some countermeasure is required.

Conventionally, corrosion prevention on the inside of the storage tank has been dealt with by painting with inorganic paints, resin paints, etc. that correspond to the properties of the storage tank liquid, or by lining with FRP, flake material, corrosion-resistant sheets, etc., which improves longevity and economy. Although there are some problems, some effects have been achieved.

However, since these anti-corrosion works interfere with water filling tests and various legal inspections, they are only installed after all inspections have been completed. As a result, temporary anti-corrosion measures when flooded with water have become an important issue.

In order to solve these problems, the following measures have been considered so far.

Countermeasures (1) Use steel materials coated with zinc or aluminum primer.

Countermeasure (2) Add an inorganic rust preventive agent (condensed phosphate) to the filling water.

Countermeasure (3) Install a galvanic anode (Mg or Zn alloy) inside the storage tank.

However, in either case, there are major problems in terms of water quality deterioration and economic efficiency. That is, countermeasure (1) can prevent rusting in the center of the plate material, but it cannot prevent pitting corrosion in the welded joint, which is the most important part, and has little effect on the high cost of raw steel materials. Furthermore, metal oxides contaminate the water, and some kind of treatment is required before it is discharged.

For countermeasure (2), although the unit price of the rust preventive agent is low, it is not effective unless a considerable amount (200mg/) is added in order to be effective, and the cost of the rust preventive agent is enormous when the storage tank capacity is tens of thousands of kiloliters. reach the amount. Furthermore, phosphorus, which is a component of this agent, is a substance that causes eutrophication of water bodies even when contained in extremely small amounts in wastewater, so when discharging water filled with water, it is necessary to install advanced wastewater treatment equipment. Is required.

Countermeasure (3) requires relatively low material costs, but requires a lot of spot welding to the inner surface of the storage tank for installation, and if you also include rework after draining the water, it will require a significant increase in man-hours. The present invention is an effective corrosion prevention method that solves these problems, and
This provides a construction tool that allows efficient corrosion protection construction.

The feature of this method is that it can be applied to parts of the inner surface of the storage tank that are particularly problematic in terms of strength, i.e. the joint between the annular plate and the side plate, and areas where pitting corrosion and rust are conventionally considered to be significant.
Before starting the water test, we affixed metal foil with a low potential potential formed into a strip to the beads and jig marks on the entire surface of the side and bottom plates from the bottom to the top of several steps, and then conducted the water test. There is a particular thing.

Moreover, in order to perform this application work efficiently, a construction tool is provided which is configured to continuously apply the anticorrosive tape rolled up into a roll to the area to be protected against corrosion.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the structure of an anticorrosive tape according to the method of the present invention and the state when it is applied.

1 is a steel material to be protected against corrosion, such as a side plate and a bottom plate of a steel plate storage tank. 2 is a joint between steel elements, that is, a weld line. During the tank water filling test period, welding lines 2 and jig marks may be damaged due to electrochemical and biochemical causes such as ventilation differential cell action due to differences in position inside the tank and oxygen concentration cell action due to biological activity. electrically activated,
Pitting corrosion is likely to occur.

In order to prevent this pitting corrosion, anti-corrosion tape as shown in 3 is pasted on the welded parts and jig marks prior to the start of water filling. The anti-corrosion tape 3 is made of a low-potential metal foil 4 formed into a thin band shape, and adhesive tapes 5 for adhering the material to the surface of the steel material 1 to be protected against corrosion are integrally attached to both edges of the material. . As the base potential metal foil 4, a metal that is electrically active (base potential) compared to the steel material 1 to be protected and has high ductility, such as a metal such as aluminum or magnesium, is used. This metal foil with a low potential serves as a sacrificial anode to prevent pitting corrosion. The adhesive tape 5 has an adhesive function of fixing the metal foil 4 to the surface of the steel material 1 to be protected against corrosion, and also allows water to freely circulate between the steel material 1 to be protected against corrosion and the metal foil 4 with a low potential in the pasted state. Like, porous (mesh type)
Manufactured from materials. The anti-corrosion tape applied in this way continues to be applied until the water test is completed.
After draining the water, peel it off and remove it.

The area to which the anti-corrosion tape was applied remains clean and free of corrosion even after the water test, and can be subjected to various tests such as the Vacuum test, Magna test, and Leak Color test without any problems.

According to this method, pitting corrosion that occurs during a water test can be completely prevented. In addition, compared to conventional methods that use chemicals, it is safe and easy to handle without staining the skin or clothes, and it has no effect on the water filling, so it has the advantage of being able to release the water filling without treatment. have

Figures 2 and 3 are conceptual diagrams of construction tools for pasting anti-corrosion tape according to the present invention.
The figure is a side view, and FIG. 3 is a plan view.

Reference numeral 11 denotes a roll holder, which has a function of holding a rolled anticorrosive tape 12 formed by rolling up a long anticorrosive tape 3 so that it can be easily expanded while rolling, and also has a mechanism that allows the roll to be replaced as appropriate. have. In addition, the roll holder 11
is provided with a work handle 13 for adjusting the construction course for applying the anticorrosive tape 3. A cap 14 made of rubber or resin may be attached to the grip portion of the work handle 13 to prevent slipping.

Reference numeral 15 denotes a pressure roller, which has the function of pressing the applied anticorrosion tape 3 so that it comes into sufficient contact with the surface of the steel material to be protected against corrosion. The pressure roller 15 is made of a flexible member such as rubber or sponge.

Its shape can be changed depending on the shape of the place where the anticorrosive tape is to be applied, so that it can be replaced as appropriate.

That is, when applying to flat parts such as the side plate parts and the bottom plate part, a cylindrical roller is used as shown in FIG. 4A. Further, as shown in FIG. 4B, a roller with a polygonal cross section is used for the fillet weld.

A cleaning brush 16 removes foreign matter adhering to the surface of the steel material to which the anticorrosive tape 3 is attached. The position of this brush can be adjusted up and down to follow changes in the roll diameter as the anti-corrosion tape is applied. Furthermore, if the brush tip is too light and the pressing pressure is insufficient, it is necessary to attach an appropriate weight.

If you use this construction tool, you can perform a series of tasks at the same time, such as cleaning the pasting area, pasting work, and pressing after pasting, by simply pressing downward along the weld line and making contact with the weld, reducing labor. This makes it possible to carry out efficient anti-corrosion construction.

As is clear from the above explanation, the pitting corrosion prevention method according to the present invention solves the shortcomings of conventional corrosion prevention methods, is extremely effective, and greatly contributes to improving the safety of storage tanks against corrosion. It also has the advantage of simplifying construction and reducing construction costs.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of an anticorrosive tape according to the method of the present invention and the state in which it is applied. Second
3 are conceptual diagrams of a construction tool for applying the anticorrosive tape according to the present invention, of which FIG. 2 is a side view and FIG. 3 is a plan view. FIG. 4 is a cross-sectional view of the crimping roller, Figure A is a cross-sectional view of the roller when working on a flat part, and Figure B is a cross-sectional view of the roller when working on a fillet weld. DESCRIPTION OF SYMBOLS 1... Steel material to be protected against corrosion, 2... Welding wire, 3... Anti-corrosion tape, 4... Low potential metal foil, 5... Adhesive tape, 11... Holder for roll, 12... Roll-shaped anti-corrosion tape, 13... ...Working handle, 14...
Cap, 15... crimping roller, 16... cleaning brush.

Claims (1)

[Scope of Claims] 1. An anticorrosion tape made of low-potential metal foil formed into a thin strip, which is used to adhere the material to the surface of steel materials to be protected against corrosion during a water test during assembly and construction of a steel plate storage tank. An adhesive tape having an adhesive tape having A method for preventing internal pitting corrosion in a water test of a steel plate storage tank, characterized in that a water test is performed after applying the adhesive to a jig mark. 2. A roll holder that holds a roll of anticorrosion tape, a work handle that adjusts the construction course for applying the anticorrosion tape, and a pressure roller that presses the applied anticorrosion tape onto the surface of the steel material to be protected from corrosion.
It consists of a cleaning brush that is located at the front of the roll holder and that removes foreign matter from the surface to which the anticorrosion tape is applied.The cleaning brush can move up and down to follow changes in the roll diameter as the anticorrosion tape is consumed. A construction tool for carrying out the method according to claim 1, which is adjustable and configured so that the pressing pressure of the tip of the brush can be adjusted.