JPH09189395A - Corrosion-preventive covering method of buried pipe joint part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of capable of carrying out corrosion- preventive covering of a buried pipe joint part excellent in abrasion resistance without causing a burr even when a heat contraction tube is used by holding corrosion of the joint part by a simple covering means at a construction site. SOLUTION: A welded joint part 2 is formed as anticorrosive covered steel pipes 1a, 1b are welded. The corrosion resistivity covered steel pipes 1a, 1b are applied with anticorrosive coating 3a, 3b by polyethylene resin except for joint parts 2a, 2b on an outer periphery of a pipe body at a plant. 4 is a welded part. A heat contraction tube 5 covers the joint parts 2a, 2b and surfaces 3c, 3d of a pipe body corrosion resistivity covered end part, and it is applied with an epoxy resin covering 7 to cover the heat contraction tube 5 and a surface of a boundary part of the heat contraction tube 5 and a pipe body anticorrosive covering. Additionally, a smooth outer surface without a stepped part is made by injecting epoxy resin in a formwork and adhering the heat contraction tube on a steel surface and pipe body covered end part by pushing it on it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion coating method for a buried pipe joint.

[0002]

2. Description of the Related Art Generally, gas pipes, water pipes, electric power pipes, etc. are installed as buried pipes by underground burial work. In the above-mentioned plumbing work, a straight-line propulsion method of directly propelling a steel pipe into the soil without digging a trench and sequentially welding and embedding the steel pipes has been implemented.

Compared with the open-cutting method (a method of digging a groove in a site of a steel pipe to install a steel pipe and burying it by welding), the construction method as described above is resistant to the anticorrosion coating of the steel pipe due to the resistance of the earth and sand during propulsion. Wearability is required.

Therefore, a synthetic resin such as a resin such as polyethylene or polyurethane having excellent abrasion resistance is thickly coated in advance in a factory. If necessary, the surface of the synthetic resin coating is provided with a protective coating such as polymer cement.

However, at the construction site, there is no choice but to cover the welded joint portion, and a heat shrink tube is generally covered after welding.

FIG. 5 is a cross-sectional view of an anticorrosion coating of a heat-shrinkable tube of a buried pipe joint portion. The coated steel pipe 1a and the coated steel pipe 1b are welded at the construction site to form the welded joint portion 2.
The coated steel pipe 1a and the coated steel pipe 1b are obtained by applying anticorrosion coating 3a, 3b of resin such as polyethylene or polyurethane on the outer periphery of the pipe body in advance in the factory except for the joint portions 2a, 2b. 4 is a welded part.

After the joints 2a and 2b are welded, the welded joint 2 and the tubular body coating end are covered with a heat shrinkable tube 5. The heat-shrinkable tube 5 is made of a heat-shrinkable synthetic resin material such as crosslinked polyethylene that is heated and shrunk.

When the buried pipe having the heat-shrinkable tube coated on the welded joint 2 is propelled straight, the coating is rolled up from the paragraph 5a at the end of the heat-shrinkable tube, and this portion increases the resistance due to the propulsion and reaches the steel surface. May develop into defects.

When such a defect occurs, the defect can be found by an inspection after embedding, but it is very difficult to repair the defect. For this purpose, various countermeasures are being studied.

As an example of the above countermeasures, Japanese Patent Laid-Open No.
There is the following anticorrosion coating method for the anticorrosion coated steel pipe joint portion disclosed in Japanese Unexamined Patent Publication No. -87248 (Prior Art).

In this anticorrosion coating method, a heat shrinkable tube is coated on the outer circumference of a joint of a steel pipe having a polyolefin resin coated on the outer circumference of the tubular body as an anticorrosion coating, and the surface including the boundary portion between the anticorrosion coating and the heat shrinkable tube coating is adhered. After applying a primer with a paint, paint is applied, and before the paint is completely cured, F
It sprays a metal having a greater ionization tendency than that of e. As the primer, a urethane primer having adhesiveness with polyolefin resin is used. After the primer is applied, a paint such as urethane paint, acrylic urethane paint, acrylic paint, alkyd paint, acrylic emulsion paint, vinyl chloride paint, etc. is applied. , Zn and the like are sprayed smoothly.

[0012]

However, the above-mentioned prior art techniques have the following problems.

When the above-described corrosion protection is performed on the joint portion of the corrosion-resistant coated steel pipe at the construction site, it is necessary to consider timing for spraying a metal having a greater ionization tendency than Fe before the paint is completely hardened. The operation is complicated.

Further, in particular, in the anticorrosion coating method for the buried pipe joint portion by the straight-ahead propulsion method, generally, the pipe body anticorrosion coating is thickly coated, and similarly, the joint portion is also thickly coated.

However, in the above technique, it is essential to coat the surface including the boundary between the tube anticorrosive coating and the heat-shrinkable tube coating with an adhesive primer and then apply the paint. It takes time to paint the paint thickly with a brush, and it is difficult to uniformly coat the outer peripheral surface of the joint.

For this reason, the entire underground buried piping work is often delayed due to the anticorrosion coating of the joint portion.

The present invention is intended to solve the above-mentioned problems, and the corrosion resistance of the joint portion is maintained by a simple covering means at the construction site, and swelling occurs even if a heat shrinkable tube is used. It is an object of the present invention to provide a method capable of applying an anticorrosion coating to a buried pipe joint portion having excellent wear resistance.

[0018]

In order to achieve the above object, the present inventor believes that the heat shrinkable tube is rolled up to cause a defect due to the paragraph of the heat shrinkable tube. The present invention has been made by studying an epoxy resin having excellent adhesion performance with the steel surface of the welded joint portion.

According to a first aspect of the present invention, there is provided an anticorrosion coating method for a buried pipe joint portion when a steel pipe coated with a synthetic resin except for the joint portion is welded to the outer periphery of the pipe body in order to be buried. After welding, the joint and the end of the tubular body covering are covered with a heat-shrinkable tube, and the mold is attached so as to cover the surface of the heat-shrinkable tube and the boundary between the heat-shrinkable tube and the tubular body, A resinous substance containing an epoxy resin is injected into the heat-shrinkable tube and the surface of the boundary portion between the heat-shrinkable tube and the tubular body is coated with the resinous substance containing an epoxy resin. This is an anticorrosion coating method. The resinous substance containing the epoxy resin may be mixed with the main agent and the curing agent in advance before injection, or may be injected separately.

According to a second aspect of the invention, in the first aspect of the invention, the synthetic resin of the steel pipe coated with the synthetic resin is a polyolefin resin, and the joint portion and the tubular body coating end portion are coated with a heat shrinkable tube. After coating and curing chlorinated polyethylene or chlorinated polypropylene on the surface of the heat-shrinkable tube surface and the boundary portion of the tube covering with the heat-shrinkable tube, the heat-shrinkable tube and chlorinated polyethylene or chlorinated polypropylene coating part The surface is coated with a resinous substance containing an epoxy resin.

According to a third aspect of the present invention, in the first or second aspect of the invention, after coating with a resinous substance containing an epoxy resin, the coating portion is heated.

In the present invention, since the coating with the resinous substance containing the epoxy resin is performed by using the mold, the required coating thickness and the required surface shape can be easily obtained.

Further, the resinous material containing epoxy resin is coated so as to cover the surface of the boundary portion of the tubular body coating when the heat-shrinkable tube is built in the resinous material and the embedded steel pipe is propelled straight. This is to completely prevent curling.

Since the epoxy resin has a wide range of adhesion performance, it can be adhered to the steel surface of the welded joint portion, and when the surface layer of the tubular body coating is polyethylene or polypropylene, it can be adhered to polyethylene or polypropylene to improve the adhesion. The chlorinated polyethylene or chlorinated polypropylene having the adhesiveness of 1 is applied and cured to coat the coating film surface with an epoxy resin.

In the present invention, an epoxy resin coating having a required coating thickness and coating surface shape of the buried pipe joint portion can be applied.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an anticorrosion coating of a buried pipe joint portion according to the present invention. The same parts as those in FIG. 5 described above are denoted by the same reference numerals.

In FIG. 1, the anticorrosion coated steel pipe 1a and the anticorrosion coated steel pipe 1b are welded to each other to form a welded joint portion 2.
The anticorrosion-coated steel pipe 1a and the anticorrosion-coated steel pipe 1b are obtained by applying anticorrosion coating 3a, 3b of polyethylene resin having excellent impact resistance and abrasion resistance to the outer circumference of the pipe body in advance at the factory except for the joint portions 2a, 2b. 4 is a welded part.

The same applies to the case where an olefin resin such as polyethylene or polypropylene is applied as the tube anticorrosion coating and a protective coating such as polymer cement is applied to the surface thereof.

The heat-shrinkable tube 5 is connected to the joint portions 2a and 2b,
The surfaces 3c and 3d of the end portions of the tubular body anticorrosion coating are coated. The heat-shrinkable tube 5 is made of a heat-shrinkable synthetic resin material such as crosslinked polyethylene that is heated and shrunk.

Further, an epoxy resin coating 7 is applied so as to cover the surface of the heat-shrinkable tube 5 and the boundary portion between the heat-shrinkable tube 5 and the tubular body anticorrosive coating.

Here, it is necessary to apply the heat-shrinkable tube 5 so as to be built in the epoxy resin coating 7. This prevents curling of the heat-shrinkable tube 5.

The epoxy resin is not particularly limited, and includes bisphenol A type, halogenated bisphenol type, resorcin type, bisphenol F type, tetrahydroxyphenylethane type, novolac type, polyalcohol type, polyglycol type, glycerin triether type, An alicyclic epoxy resin is used.

A bisphenol A resin having excellent adhesiveness and easily industrially available is used.

Generally, in use, epoxy resins use amines, acid anhydrides, polyamide resins, etc. as curing agents.

Depending on the combination with the curing agent, various properties such as anticorrosion property as well as adhesive property are imparted.

Further, as a resinous substance containing an epoxy resin compounded with a thermoplastic resin such as polyamide, phenol resin or polyester, it is possible to utilize the advantages of the epoxy resin and the advantages of other resins in combination.

Next, the anticorrosion coating method of the present invention will be described with reference to FIG. In the factory, the steel pipes 1a and 1b are coated with polyethylene resin on the outer periphery of the pipe body except for the joint portions 2a and 2b.
3b is applied. As a coating method, an extrusion coating method using a die or the like is employed. Here, the end of the steel pipe is about 1
The pipe body is exposed by using about 00 mm as the joint portions 2a and 2b.

The anticorrosion coated steel pipes 1a and 1b are transported to the site where they are to be buried. At the construction site, welding of the joint portion is carried out in the starting shaft, with the anticorrosion coated steel pipes 1a, 1b as buried pipes. In this case, the heat-shrinkable tube 5 is one anticorrosion-coated steel pipe 1.
It is pierced by a and is brought close to the anticorrosion coating side so as not to be affected by welding.

After welding, the heat shrinkable tube 5 is attached to the joint portion 2a,
2b and the tubular body coated ends 3a, 3b are coated with a burner,
Heat shrink with a heater, etc. to bring them into close contact.

Next, the heat-shrinkable tube 5 and the mold 6 as shown in FIGS. 2 and 3 mounted so as to cover the surface of the boundary between the heat-shrinkable tube 5 and the tube covering portions 3a and 3b are used. Then, the liquid epoxy resin and the curing agent are mixed and poured into the mold 6 to form the epoxy resin coating 7.

FIG. 2 is a perspective view showing an embodiment of the mold used in the present invention, and FIG. 3 is a vertical section of FIG.

In FIGS. 2 and 3, the main body of the mold 6 is a vertically divided body 6a, 6b, and a flange 8 is used for assembly.
It is performed by fixing a and 8b with bolts or the like. The front and rear portions of the mold 6 are narrowed so that the epoxy resin coating 7 has a curved cross-sectional shape.

Here, diamine or triethylenediamine was dissolved using a mixed solvent of ketones, butanol, and an aromatic hydrocarbon solvent to prepare a curing agent, which was mixed with an epoxy resin as a main component to prepare a liquid material.

The mixed liquid is pressure-injected into the mold 6 through the injection port 9 provided in the upper divided body 6a, and the overflow from the discharge port 10 is caused to flow out so that the mold 6 is filled. To stop.

After a lapse of a predetermined time, the mold was removed, and an epoxy resin coating which was cured by drying at room temperature was applied to a predetermined portion.

In the above, the epoxy resin main agent and the curing agent may be separately poured into the mold. When a solid epoxy resin is used, it can be dissolved in a solvent and the same procedure as described above can be performed.

In the present invention, the drying time can be shortened by heating the epoxy resin coating with a heater or the like.

FIG. 4 is a diagram showing another embodiment of the present invention. Descriptions of parts common to FIG. 1 are omitted.

In FIG. 4, the heat-shrinkable tube 5 covers the joint portions 2a and 2b and the tubular body anticorrosion coating end portion. Coating films 11a, 11b, 1b made of chlorinated polyethylene or chlorinated polypropylene on the surface of the heat-shrinkable tube 5 and the surfaces of the tubular body coating portions 3a, 3b at the boundary with the heat-shrinkable tube 5.
1c is applied. Coating films 11a and 11b and coating film 1
The heat-shrinkable tube 5 which has been subjected to 1c is covered with an epoxy resin film 7.

Chlorinated polyethylene or chlorinated polypropylene is dissolved in a solvent and applied and cured by spraying or the like.

Chlorinated polyethylene or chlorinated polypropylene is obtained by chlorinating polyethylene or polypropylene and can be obtained from a rubber-like elastic body to a relatively hard polymer. Indirect adhesion between polyethylene or polypropylene and epoxy resin.

Liquid epoxy resin is mixed with a curing agent and poured into a mold to form an epoxy resin coating 7. After a lapse of a predetermined time, the mold is removed, and an epoxy resin coating cured by drying at room temperature is applied. It is possible to shorten the drying time by heating the epoxy resin coating with a heater or the like.

[0054]

Embodiments of the present invention will be described below.

At the factory, a 200 A steel pipe coated with polyethylene resin to an average thickness of 3 mm was welded and joined, and the joint portion and the end portion of the tube body were covered with a heat-shrinkable tube having an average thickness of 3 mm. A mold is attached to the surface including the boundary between the coating and the heat shrinkable tube coating and the polyethylene anticorrosion coating, and the epoxy resin is mixed in advance with the main agent and the curing material so that the outer surface is smooth and has an average thickness of 3 mm. It was injected and cured to obtain a test material 1.

At the factory, a 200 A steel pipe coated with polyethylene resin to an average thickness of 3 mm was welded and joined, and the joint portion and the end of the tube body were covered with a heat-shrinkable tube having an average thickness of 3 mm. A mold is attached to the surface including the boundary between the coating and the heat shrinkable tube coating and the polyethylene anticorrosion coating, and the epoxy resin is injected into the mold separately so that the epoxy resin has a smooth outer surface with an average thickness of 3 mm. ,
It was reaction-cured to obtain a test material 2.

At the factory, a 200 A steel pipe coated with polyethylene resin to an average thickness of 3 mm was welded and joined, and the joint portion and the end portion of the tube body were covered with a heat-shrinkable tube having an average thickness of 3 mm. A mold is attached to the surface including the boundary between the coating and the heat shrinkable tube coating and the polyethylene anticorrosion coating, and the epoxy resin is mixed in advance with the main agent and the curing material so that the outer surface is smooth and has an average thickness of 3 mm. After being injected, it was heated to 100 ° C. from the outside by a heater and cured to obtain a test material 3.

At the factory, a 200 A steel pipe coated with polyethylene resin to an average thickness of 3 mm was welded and joined, and the joint portion and the end of the pipe body were covered with a heat-shrinkable tube having an average thickness of 3 mm. Chlorinated polyethylene is applied to the surface of the product and the surface of the boundary between the heat-shrinkable tube and the polyethylene coating of the tube and cured to form a coating film. A mold is attached to the surface of the coating film, and the epoxy resin has an average thickness of 3 mm. A main material and a curing material were mixed in advance so that a smooth outer surface was obtained, and the mixture was poured into a mold and cured to obtain a test material 4.

In the factory, a 200 A steel pipe coated with polyethylene resin to an average thickness of 3 mm was welded and joined, and the joint portion and the end of the tube body were covered with a heat-shrinkable tube having an average thickness of 3 mm to form a heat-shrinkable tube. Chlorinated polypropylene is applied to the surface of the and the surface of the boundary between the heat-shrinkable tube and the polyethylene coating of the tubular body, the coating is applied after curing, a form is attached to the surface of the coating, and the epoxy resin has an average thickness of 3 mm.
Mix the base material and curing agent in advance to obtain a smooth outer surface, then inject it into the mold, and apply 100% heat from the outside with a heater.
The test material 5 was heated and cured at 0 ° C.

In the factory, a 200 A steel pipe coated with a polyethylene resin having an average thickness of 2 mm and further coated with a polypropylene resin having an average thickness of 2 mm was welded and joined.
The joint and the end of the tube covering are covered with a heat-shrinkable tube having an average thickness of 3 mm, and chlorinated polypropylene is applied to the surface of the heat-shrinkable tube and the surface of the boundary between the heat-shrinkable tube and the tube-shaped polypropylene coating. After curing and applying the coating film, attach the mold to the surface of the coating film, mix the main resin and the curing agent in advance so that the epoxy resin has a smooth outer surface with an average thickness of 4 mm, and inject it into the mold, A test material 6 was obtained by heating to 100 ° C. with a heater to cure it.

In the factory, a 200 A steel pipe coated with polyethylene resin having an average thickness of 3 mm was welded and joined,
This joint part and the end of the tube body are covered with a heat-shrinkable tube,
The test material of the comparative example was used.

Table 1 shows the test results of the test materials 1 to 6 according to the present invention and the comparative examples. As a test assuming direct propulsion, earth pressure of 1 kgf / c in soil mixed with sand and crushed stone
The test was conducted with 10 m propelled at m ² .

[0063]

[Table 1]

As is clear from Table 1, Examples 1, 2 and
In No. 4, there was no particular abnormality in that the coating surface of the buried pipe joint part was slightly scratched. In Examples 3, 5, and 6, there was almost no flaw on the surface of the buried pipe joint portion coating, which was good.

On the other hand, in the comparative example, there were several portions where the coating film was rolled up from the end of the heat shrinkable tube by about 5 cm.

Examples 1, 2 coated using a formwork,
The epoxy resin coatings 3, 4, 5 and 6 had smooth surfaces, and the workability was good.

The curing time of the epoxy resin of Examples 3, 5 and 6 in which the epoxy resin coating was heated was about 20 minutes, and the curing time could be shortened as compared with the curing time of about 4 hours without heating. .

The adhesive force between the epoxy resin of Examples 4, 5 and 6 coated with chlorinated polyethylene or polypropylene chloride and the polyethylene coating or polypropylene coating is 50 kgf / cm ² or more, which is higher than that of the polyolefin resin coating. , Got enough adhesion.

[0069]

As described above, in the present invention, the corrosion resistance of the joint portion is maintained by the simple coating means at the construction site,
Even if a heat-shrinkable tube is used, it is possible to apply an anticorrosion coating to the buried pipe joint portion that does not curl and has excellent wear resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view of an anticorrosion coating of a buried pipe joint portion according to the present invention.

FIG. 2 is a perspective view showing an embodiment of a mold used in the present invention.

FIG. 3 is a longitudinal sectional view of FIG. 2;

FIG. 4 is a cross-sectional view of an anti-corrosion coating of another buried pipe joint portion according to the present invention.

FIG. 5 is a cross-sectional view of a conventional buried pipe joint section in which a heat-shrinkable tube is used to prevent corrosion.

[Explanation of symbols]

 1a, 1b Anticorrosion coated steel pipe 2a, 2b Joint part 3a, 3b Anticorrosion coating 4 Welded part 5 Heat shrink tube 5a Paragraph part 6 Formwork 7 Epoxy resin coating 8a, 8b Flange 9 Injection port 10 Discharge port 11a, 11b Coating film

Claims (3)

[Claims] 1. A method of anticorrosion coating of a buried pipe joint portion, wherein a steel pipe coated with a synthetic resin excluding the joint portion is welded to the outer periphery of the pipe body in order to be buried, after the joint portion is welded, The joint portion and the end of the tubular body covering are covered with a heat-shrinkable tube, and the mold is attached so as to cover the surface of the heat-shrinkable tube and the boundary between the heat-shrinkable tube and the tubular body, and the mold contains an epoxy resin. A method for corrosion protection coating of a buried pipe joint portion, which comprises injecting a resinous substance and coating the surface of the heat-shrinkable tube and the boundary between the heat-shrinkable tube and the tubular body with a resinous substance containing an epoxy resin. 2. A synthetic resin for a steel pipe coated with a synthetic resin is a polyolefin resin, a joint portion and a tubular body coating end portion are coated with a heat shrinkable tube, and the surface of the heat shrinkable tube and the heat shrinkable tube are After coating chlorinated polyethylene or chlorinated polypropylene on the surface of the boundary part of the tube coating and curing, coat the surface of the heat-shrinkable tube and chlorinated polyethylene or chlorinated polypropylene coating part with a resinous substance containing epoxy resin. The method for corrosion protection coating of a buried pipe joint portion according to claim 1. 3. The method for corrosion protection coating of a buried pipe joint section according to claim 1 or 2, wherein the coating section is heated after coating with a resinous substance containing an epoxy resin.