JPH0996378A - Site work execution method of coating steel pipe joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a site work execution method of coating steel pipe joint which can prevent a defect such as a coating burr and a crack in a simple process, and can reduce the work execution time. SOLUTION: In a work execution method of having steel pipes coated to their outer peripheries except the joint in the factory and of welding and burying them in order at the site, differences in level 5a and 5b of the step form are formed beforehand, at the ends of the shop coating parts 2a and 2b of the main pipe, and after the welding work at the site, the parts of the coating parts are superposed on the differences in level, not to project the height of the main pipe joint coating parts, that is, the adhesive type thermal contraction tubes 4a and 4b, higher than the height A of the surface of the shop coating parts 2a and 2b, and the joint is coated and buried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-site construction method for coating and coating a steel pipe joint portion in a construction method in which steel pipes coated on the outer periphery of a pipe except for a joint portion are sequentially welded and buried in the field.

[0002]

2. Description of the Related Art In recent years, in the underground burial construction work, a direct propulsion method has been implemented in which a steel pipe is directly propelled into the soil without digging a trench and the steel pipes are sequentially welded and buried.

Since the direct propulsion method is a method of directly propelling the steel pipe into the soil, the anticorrosion coating of the steel pipe is required to have impact resistance and abrasion resistance because it receives the resistance of the earth and sand during propulsion.

Therefore, at the factory, a resin such as polyethylene or polyurethane having excellent performance is thickly coated in advance.

However, the joint portion welded and joined at the construction site has to be coated locally, and a heat-shrinkable tube is covered or a polyurethane coating is applied after welding.

[0006] In the construction site, when the heat-shrinkable tube is coated on the welded joint on-site, the heat-shrinkable tube coating on site is steel surface as compared with the coating pre-coated at the factory due to the limitation of on-site coating. Is inferior in adhesion.

The impact resistance is also inferior to that of the coating previously coated in the factory.

As a typical example of the above measures, Japanese Patent Laid-Open No. 63-251692 (Prior Document 1) discloses a propulsion method using a coated steel pipe for direct propulsion.

Here, the outer surface of the anticorrosion coating layer made of polyethylene or urethane resin is protected by a layer of glass fiber or metal fiber-containing polyester, or glass fiber or metal fiber-containing acrylate.

Further, Japanese Unexamined Patent Publication No. 3-87248 (Prior Document 2) discloses a method of anticorrosion coating of an anticorrosion coated steel pipe joint.

Here, in a construction method of sequentially welding and embedding a steel pipe coated on the outer periphery of the pipe except the joint portion, heat is applied to the outer periphery of the joint portion of the steel pipe whose outer periphery is coated with a polyolefin resin or polyurethane resin as the anticorrosion coating. After coating the shrinkable tube, and then applying a primer having an adhesive property on the surface including the boundary portion between the anticorrosion coating and the heat shrinkable tube, a paint is applied, and the F coating is applied before the paint is completely cured.
It sprays a metal having a greater ionization tendency than that of e.

By this, the metal having the anticorrosion property is smoothly sprayed, and the resin layer coated for the purpose of anticorrosion is protected,
Even in the direct propulsion method for burial work, it is said that a durable coating can be formed without causing defects such as coating blistering.

[0013]

As described above, since the direct propulsion method is a method of directly propelling the steel pipe into the soil, the anticorrosion coated steel pipe joint part receives the resistance of earth and sand at the time of propulsion so that impact, abrasion, etc. It tends to occur, and defects such as coating blisters and cracks are likely to occur.

On the other hand, since the coating of the anticorrosion coated steel pipe joint portion is carried out on-site, it is required that it can be completed in a short time with simple construction.

However, the technique according to the above-mentioned prior art document 1 has the following problems. Here, a protective coating layer such as glass fiber or metal fiber-containing polyester is provided on the anticorrosion coating layer made of polyethylene or urethane resin, but metal fiber-containing polyester or the like requires time for curing during construction. Also, be careful in transportation and handling.

In particular, when the coating of the on-site joint portion is applied, the hardening time of the protective layer becomes a bottleneck, hindering the improvement of the propulsion work efficiency of the steel pipe.

Further, the technique according to the prior art document 2 has the following problems. "Step of coating a heat-shrinkable tube on the outer periphery of the joint part", "step of applying an adhesive primer to the surface including the boundary portion between the anticorrosive coating and the heat-shrinkable tube", "step of applying paint", It requires a minimum of four steps, "a step of spraying a metal having a higher ionization tendency than Fe before the paint is completely cured".

For this reason, at least four steps for coating different types of coatings are required, a large number of equipments for construction are required, the handling thereof tends to be complicated, and the construction time is long.

Further, the thickness of the joint coating portion is thicker than that of the pipe coating portion. Therefore, the joint portion coating portion projects from the surface of the pipe coating portion.

Even if a metal layer having a higher ionization tendency than Fe is sprayed on the surface layer of the coating portion of the joint portion, the raised portion is subjected to the resistance of the earth and sand due to the force in the propulsion direction at the time of propulsion to cause impact and wear. And the like, and defects such as coating blisters and cracks are likely to occur.

When the above-described coating blisters, cracks, etc. occur, the coating blisters, cracks, etc. rapidly progress from that location as a starting point, and the function of the joint portion coating and covering portion such as anticorrosion deteriorates.

The present invention is intended to solve the above-mentioned problems, and it is possible to prevent defects such as coating blisters and cracks with a simple construction and to shorten the construction time. The purpose is to provide the on-site construction method of.

[0023]

According to a first aspect of the present invention, there is provided a method of constructing a steel pipe, which is covered with a factory except for a joint portion on the outer circumference of the pipe, by sequentially welding and burying the steel pipe in the field. A step-like step is formed in advance on the end part, and after welding on site, the height of the main pipe joint coating does not protrude beyond the factory coating surface, so that the step coating This is an on-site construction method for coating and coating a steel pipe joint, which is characterized in that a part of the joint is coated and covered and buried.

Since the joint coating by the propelling direction does not protrude from the surface height of the factory coating, the coated steel pipe with the joint coating is used as a steel pipe for propulsion in the soil. Even if it is propelled, it does not receive an external force in the soil depending on the direction of propulsion, and it does not cause defects such as coating blisters and cracks.

According to a second aspect of the invention, in the above invention,
A protective coating is applied to the coated surface of the main pipe joint portion so that the height of the protective coating does not protrude beyond the factory coated surface.

In this case as well, since the height of the protective coating does not protrude from the surface height of the factory coating, the same function and effect as the invention according to claim 1 can be obtained.

In the invention according to claim 3, the above-mentioned protective coating is a coating by plastic spraying. Since the surface formed by the plastic spraying is slippery, the resistance when propelled in the soil can be further reduced.

In the invention according to claim 4, the protective film is a film formed by coating a urethane resin or epoxy resin type quick-curing resin. These are excellent in abrasion resistance, can be installed in a short time, and require almost no curing and curing time after installation, and are therefore excellent in on-site installation.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The steel pipe used for the construction of the present invention is coated in advance in a factory except for the heat-affected zone of the on-site joint at the pipe end. If the local joint coating is applied to the factory coating of the end, steps are provided in steps so that it will be flat.

By superimposing the heat-shrinkable tube of the local joint coating on the thin film portion of the step, the end of the local joint coating does not protrude from the factory coating, and the coating is flat.

Polyethylene, which is excellent in mechanical strength and chemical stability, and is excellent in coating workability by extrusion coating, is used for factory coating.

There are two types of polyethylene coating covering, one is an adhesive type using an epoxy resin and a polyolefin resin as an adhesive between polyethylene and a steel pipe, and the other is an adhesive type using a rubber-based material. The adhesive type is mainly used because resistance to external propulsion force (friction force, etc.) is required.

For coating the field joint, a heat-shrinkable tube made of cross-linked polyethylene of the same system as the main factory coating is used. Similar to main factory coating, heat-shrinkable tubes are available in adhesive type (hot-melt type) that uses polyolefin-based or polyamide-based materials as adhesives and adhesive type that uses rubber-based materials. Uses an adhesive type because it requires adhesive strength as in the main pipe.

A combination of an adhesive-type main factory coating and an adhesive-type heat-shrinkable tube field joint coating,
Durability for propulsion construction can be obtained by preventing the projecting end of the coating coating end that causes damage to the local joint coating coating by the above step structure of the factory coating coating end and making it flat coating coating. To be

Since the adhesive type heat-shrinkable tube is coated on the main factory coating end portion by partially overlapping it, the adhesiveness is good, and the adhesive heat-shrinkable tube is the main factory coating case. It can exert the same adhesive function as.

If desired, this adhesive heat-shrinkable tube may have a two-layer or three-layer structure within a range in which the joint coating covering portion does not protrude from the surface height of the main pipe coating covering portion.

In the present invention, since the number of kinds of materials for coating and covering may be about one or two, the number of steps for coating and covering is small and the handling thereof is easy.

In addition, in particular, as a field joint coating covering having durability for long-distance or propulsion construction in gravel soil, the adhesive type heat-shrink tube described above is used for coating and wear resistance. Apply a protective film that excels in

As the protective coating, a thermal spray coating of an olefin material such as polyethylene or polypropylene, or a rapid curing type coating of polyurethane or epoxy can be used.

These are excellent in wear resistance, can be applied in a short time, and require almost no curing and curing time after application, and are therefore excellent in on-site application.

[0041]

【Example】

(Embodiment 1) FIG. 1 is an explanatory view of a method of on-site construction for coating and coating a steel pipe joint portion according to an embodiment of the present invention. Here, a propulsion simulation test was conducted in a soil tank that replaces the soil in the field. As the steel pipe, a 300A steel pipe was used as a test body. The coating of the steel pipe in the factory was an adhesive polyethylene coating (thickness of 3 mm), and the main factory coating coating part having a step portion at the end was formed.

In FIG. 1, a joint portion 3a of a steel pipe 1a having a main factory coating coating portion 2a and a joint portion 3b of a steel pipe 1b having a main factory coating coating portion 2b are welded. 8 is a welded part. The adhesive heat-shrinkable tubes 4a and 4b are coated and formed so as to form a two-layer structure.

Here, the adhesive heat-shrinkable tubes 4a and 4b are used.
For this, a cross-linked polyethylene having a thickness of 1.5 mm and a hot melt adhesive having a thickness of 1 mm is used. The ends of the adhesive heat-shrinkable tubes 4a, 4b are superposed on the step portions 5a, 5b of the main factory coating coating portions 2a, 2b. The adhesive heat-shrinkable tubes 4a and 4b are heat-shrinked by heat treatment, and the joint portion 3
It is in close contact with a and 3b and the stepped portions 5a and 5b. The joint coating covering portion 7 formed by the adhesive heat shrinkable tubes 4a, 4b is formed so as not to protrude from the surface height A of the main factory coating covering portions 2a, 2b.

As a result of the test, it was confirmed in the propulsion test in soil containing no lexy material that even if propelled for 500 m, only slight scratches were produced on the coated surface, and the durability was sufficient. Further, the coating of the joint portion was completed in about 30 minutes, and it was confirmed that the workability at the site was also good.

(Embodiment 2) FIG. 2 is an explanatory view of a method for on-site construction of a steel pipe joint coating of another embodiment of the present invention. Here, a propulsion simulation test in a soil tank instead of on-site soil is carried out. I went there. As the steel pipe, a 300A steel pipe was used as a test body. FIG.
In the same manner as in (1), the coating of the steel pipe in the factory was an adhesive polyethylene coating (thickness of 3 mm), and the main factory coating coating part having a step portion at the end was formed.

In FIG. 2, the joint portion 3a of the steel pipe 1a having the main factory coating coating portion 2a and the joint portion 3b of the steel pipe 1b having the main factory coating coating portion 2b are welded. 8 is a welded part. The adhesive heat-shrinkable tubes 4a and 4b are coated and formed so as to form a two-layer structure. Here, the adhesive type heat-shrinkable tubes 4a and 4b are made of crosslinked polyethylene having a thickness of 1.5 mm and a hot melt adhesive having a thickness of 1 mm. Here, further, a polyethylene powder irradiation having a thickness of about 1 mm was performed on the adhesive heat-shrinkable tubes 4a and 4b to form a protective coating portion 6 by the polyethylene powder irradiation.

The ends of the adhesive-type heat-shrinkable tubes 4a, 4b are laid on the step portions 5a, 5b of the main factory coating coating portions 2a, 2b. The adhesive heat-shrinkable tubes 4a, 4b are heat-shrinked by heat treatment, and the joint portions 3a, 3b and the step portion 5a are
It is closely attached to 5b. Adhesive heat shrink tube 4a,
The joint coating portion 7 and the protective coating portion 6 formed by 4b are the main factory coating portion 2a. It is formed so as not to protrude from the surface height A of 2b. Here, the surfaces of the main factory paint coating portions 2a and 2b and the surface of the protective coating portion 6 form a smooth surface.

As a result of the test, in the test in soil containing 20 to 50% of the rake, even when propelled for 250 m, only slight scratches (about 0.2 mm depth) were produced on the protective coating,
It was confirmed to have sufficient corrosion resistance.

As shown in the above-mentioned embodiment, it is carried out on site so that the height of the joint coating or the height of the protective coating on its surface does not protrude from the main factory coating coating surface. Since it is a simple method, construction time can be significantly shortened.

[0050]

As described above, according to the present invention, the adhesion of the coating and covering can be maintained, defects such as coating blisters and cracks can be prevented by a simple on-site construction, and the construction time can be shortened.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method of on-site construction for coating and coating a steel pipe joint portion according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a method for on-site construction of a steel pipe joint part coating covering according to another embodiment of the present invention.

[Explanation of symbols]

 1a1b Steel pipe main pipe 2a, 2b Main pipe factory coating portion 3a, 3b Joint portion 4a, 4b Adhesive heat shrink tube 5a, 5b Step 6 Protective coating portion 7 Joint coating portion 8 Welding portion

Claims (4)

[Claims] 1. A construction method in which steel pipes, which are covered with a factory except for a joint portion, are welded to the outer periphery of the pipe and sequentially buried at the site,
In order to prevent the height of the main pipe joint coating from protruding from the factory coating surface after forming a step-like step on the factory coating end of the main pipe in advance, after welding on site. A field construction method for coating and coating a steel pipe joint portion, characterized in that a part of the coating material is overlapped on the step portion and the joint portion is coated and buried. 2. The steel pipe joint portion according to claim 1, wherein the coated surface of the main pipe joint portion is provided with a protective coating so that the height of the protective coating does not protrude beyond the factory coated surface. On-site construction method of paint coating. 3. The method for on-site construction of a steel pipe joint coating according to claim 2, wherein the protective coating is a plastic spray coating. 4. The method for on-site application of coating coating for a steel pipe joint portion according to claim 2, wherein the protective coating is a coating made of urethane resin or an epoxy resin based quick-curing resin coating.