JPH0561511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a flange structure that suppresses the occurrence of crevice corrosion in a flange fastening portion or the like in a corrosive environment.

[Background of the invention]

Conventionally, in flange structures used in seawater environments and environments that handle chlorine-containing aqueous solutions, there has been a lack of careful consideration in the shape of the flange fastening parts, especially the flange ends, which tends to cause crevice corrosion. There were flaws. Furthermore, the crevice corrosion inhibitor applied to prevent this crevice corrosion is washed away or consumed in a relatively short period of time, and a long-term corrosion prevention effect cannot be expected.

Therefore, regular and irregular inspections and maintenance must be performed, which has the drawback of lowering the operating efficiency of the equipment and increasing running costs.

[Purpose of the invention]

An object of the present invention is to provide a long-life flange structure that suppresses crevice corrosion that tends to occur in flange fastening parts for a long period of time.

[Summary of the invention]

In accordance with the above-mentioned purpose, the summary of the invention of this application is to solve the above-mentioned problems by making the gap width of the joint surface of the flow path side end between the flanges larger than the gap width of the joint surface other than this end, By applying a corrosion inhibitor to the joint surfaces other than the edges and connecting the flanges, the corrosion inhibitor is filled between the joint surfaces, and the edges have a clearance that is smaller than the critical gap for crevice corrosion in the forming material. By increasing the size and opening into the flow path, crevice corrosion is less likely to occur. By forming a recess on the end or joint surface, applying a crevice corrosion inhibitor, etc. to the recess along with the joint surface, and using an O-ring or ring-shaped anti-corrosion rubber, etc., the crevice corrosion inhibitor, etc. It is preferable to take technical measures to maintain the anticorrosion function by reducing the wear and tear of the metal.

[Embodiments of the invention]

Hereinafter, each embodiment of the present invention will be described based on the drawings. In addition, the same reference numerals are given to the same parts in the description.

The embodiment shown in FIG. 1 is a basic embodiment, and the gap between the end portion 3 of the flange 2 integrally formed with the pipe 1 is a set width d.

The pipe 1 and the flange are
It shall be made of SUS304 stainless steel.

In the above configuration, dimethylpolysiloxane
A crevice corrosion inhibitor 4 consisting of 13 wt% polystyrene polymer, 25 wt% polystyrene polymer, 2 wt% SiO ₂ powder with a predetermined particle size, and metal zinc powder with a predetermined particle size is applied to the entire joint surface 5,
The flanges 2, 2 are connected to each other by bolts and nuts (not shown). When the flanges 2 are fastened together, the distance between the main joint surfaces 5 must be smaller than the critical gap width.

Therefore, when the corrosive fluid flows inside the pipe, the fluid soaks into the joint surface 5 from the end 3 and tends to corrode the periphery of the joint surface 5 and even the inside thereof.

However, the gap width of the end portion 3 is larger than the critical gap width for the occurrence of crevice corrosion in the flange end forming material, that is, it is a size that makes it difficult for crevice corrosion to occur, and the joint surface 5 has no crevice corrosion. Inhibitor 4 is present, therefore,
Even if a corrosive fluid enters from the end portion 3, corrosion is prevented and the anti-corrosion function is fulfilled.

According to the experiment, the outer diameter of pipe 1 was 90 mm.
φ, inner diameter is 70mmφ, outer diameter of flange is 160mm
φ, the plate thickness is 20mm, and the gap width at end 3 is d=
0.2mm, and the crevice corrosion inhibitor 4 is applied to the joint surface 5.
It was applied to. Inside this pipe 1, 45℃NaCl3%
The solution was flowed at 80 atm and 72 mm/s for 4000 hours, and when the joint surface 5 was opened and observed, almost no corrosion damage was observed on the entire surface, and the applied crevice corrosion inhibitor remained. .

On the other hand, in an experimental example in which the gap width at the end portion 3 was not made larger than the above-mentioned limit gap width and no corrosion inhibitor was used, severe corrosion was observed at the end portion and the joint surface. In addition, in an experimental example in which crevice corrosion inhibitor 4 was applied but the gap width at end 3 was not made larger than the critical gap width, no significant corrosion damage was observed, but almost no crevice corrosion inhibitor remained. I hadn't done it.

The embodiment shown in FIG. 2 is an embodiment in which the shape of the end portion 3 is changed, and has substantially the same effect.

In the embodiment shown in FIG. 3, the gap width at the end portion 3 is made larger than the limit gap width (for example, d=0.2 mm),
In addition, a recess is provided on the circumference in a part of the joint surface 5, the crevice corrosion inhibitor 4 is applied and filled in the recess and the joint surface, and an O-ring 6 made of Viton is interposed in the recess. As a result of an experiment similar to that shown in FIG. 1, no corrosion damage was observed on the entire surface in this example. Furthermore, the remaining amount of crevice corrosion inhibitor 6 was as high as 85%.

The embodiment shown in FIG. 4 is an embodiment in which the shape of the recess is changed, and has substantially the same effect as the embodiment shown in FIG. 3.

The embodiment shown in FIG. 5 differs from the embodiment shown in FIG. 3 in that the length of the part where the gap width is d (for example, d = 0.2 mm) is increased, and the shape of the recess on the joint surface 5 is changed. According to experiments, substantially the same effect as the embodiment shown in FIG. 3 was obtained.

The embodiment shown in FIG. 6 is an embodiment in which the shape of the recess is changed, and has substantially the same effect as the embodiment shown in FIG. 5.

〔Effect of the invention〕

According to the present invention, the gap width at the flow path side end between the flanges is larger than the critical gap width for the occurrence of crevice corrosion, so crevice corrosion does not occur, and moreover, between the joint surfaces other than the ends, Since the corrosion inhibitor is present, the occurrence of crevice corrosion between these surfaces is sufficiently prevented. Furthermore, by using crevice corrosion prevention rubber, etc., the crevice corrosion inhibitor has a structure that prevents it from flowing or being consumed.
The occurrence of crevice corrosion in flanges can be suppressed for a long period of time, and significant effects can be expected in improving the reliability of equipment and structures, extending their lifespans, and reducing costs by using lower-grade materials.

[Brief explanation of the drawing]

The drawings are explanatory diagrams showing embodiments of the invention of this application. Fig. 1 is a sectional view of a basic embodiment, Fig. 2 is a sectional view of another embodiment, and Figs. FIGS. 5 and 6 are explanatory views of the example of the end portion and the joint surface. 1...Pipe, 2...Flanged joint, 3...End, 4...Crevice corrosion inhibitor, 5...Joint surface, 6
...O-ring or ring-shaped anti-corrosion rubber, 7...Bolt hole.

Claims (1)

[Claims] 1. The width of the gap between the joint surfaces at the end of the flow path between flanges is made larger than the width of the joint surface of the joint surfaces other than the end, and the flanges are bonded together by applying a corrosion inhibitor to the joint surfaces other than the end. By connecting, the corrosion inhibitor is filled between the joint surfaces, and the end portion is opened to the flow path with a width larger than a critical gap width for occurrence of crevice corrosion in the material to be formed. flange structure.