JPH09159096A - Anticorrosion method for anticorrosion coated pipe joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an air layer form being in a pipe end coating part by heat contraction material in the case of coating a welded part and its periphery by the heat contraction material, after an anticorrosion coated layer of the end part of the anticorrosion coated pipe is removed and butt welded. SOLUTION: A heat contraction tube 1 is so disposed as to coat the outer circumferential part of a welded part and an adjoining part of the welded part of an anticorrosion coated steel pipe, and a vacuum holder 15, which is composed of a plurality of arc chamber pieces mutually connected by hinge into a chain state, is so disposed as to cover a part where the heat contraction tube 1 is disposed. A clearance between the welded part and the adjoining part of the welded part coated by the vacuum holder 15 and the heat contraction tube 1 is held vacuum by the vacuum holder 15 and in this state, the heat contraction tube 1 is contracted by heat so that the welded part and the adjoining part of the welded part are anticorrosively coated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion method for a joint portion of an anticorrosion coated steel pipe used for pipelines for transportation of city gas, tap water, oil, steam for district heating, etc.

[0002]

2. Description of the Related Art Steel pipes are generally used as pipelines for transporting city gas, tap water, oil, steam and the like. Steel pipes are easily corroded in the presence of water and oxygen.
Therefore, it is common practice to coat the surface of the steel pipe with asphalt, coal tar enamel, polyethylene (PE), epoxy, urethane or the like to form an anticorrosion coating layer. Since such an anticorrosive coating layer is formed in a factory, it is also called a factory coating layer.

When the pipe ends of the anticorrosion coated steel pipe having the anticorrosion coating layer formed on the surface thereof are butt welded to each other to perform the piping work, there is a problem that the anticorrosion coating layer is deteriorated by the heat generated during welding.

Therefore, in order to prevent the deterioration of the anticorrosion coating layer, conventionally, the anticorrosion coating layer in the vicinity of the pipe end of the anticorrosion coated steel pipe is removed in advance, and the pipe ends are welded to each other and connected at the pipe construction site. The outer periphery of the welded portion and the outer portion of the portion where the anticorrosion coating layer is adjacent to the welded portion and the portion where the anticorrosion coating layer is present are coated with a heat-shrinkable tube for anticorrosion and a heat-shrinkable sheet for anticorrosion, and then heated with propane gas or the like. The heat-shrinkable tube or sheet is used to cover the pipe end portion with anticorrosion.

According to such an anticorrosion coating method at a piping construction site, the anticorrosion coating steel pipe is protected from corrosion factors such as water and air by sufficiently wrapping the anticorrosion coating layer and the heat shrinkable material. Since it can prevent corrosion, it is excellent in anticorrosion performance and has many practical examples.

[0006]

However, the above-mentioned anticorrosion coating method has the following problems. That is, the flat portion of both ends of the anticorrosion-coated steel pipe that requires anticorrosion, that is, the surface of the anticorrosion coating layer and the surface of the steel pipe from which the anticorrosion coating layer has been removed, the welded portion's built-up portion, and the anticorrosion coating layer. The surface of the steel pipe and the surface of the stepped portion of the anticorrosion coating layer, etc., caused by the removal of are not necessarily smooth and have unevenness.

As a result, when the heat-shrinkable tube for anticorrosion is heat-shrinked, an air layer may remain in the build-up portion or stepped portion of the welded connection. Further, even in the flat portion of the steel pipe surface or the anticorrosion coating layer, inclusion of air voids is unavoidable during heat shrinkage. Although the amount of such residual air is not an amount that poses a practical problem, many are concerned with the progress of corrosion due to the residual air and the safety of the mechanical strength of the residual air part due to impact, etc. Is worried about.

Various methods have been conventionally used to eliminate air remaining in the anticorrosion coating portion of the heat-shrinkable material described above. For example, the stepped portion is pre-filled with a sealing material containing butyl rubber as a main component. Alternatively, a method of applying a hot-melting material containing asphalt, butyl rubber or the like as a main component to a flat portion such as the surface of the steel pipe or the anticorrosion coating layer in advance is used.

However, such a method cannot completely prevent the air voids from remaining. In addition, in the latter method, the hot-melt material needs to be melt-painted at the piping construction site, which causes problems such as generated gas and safety of handling high-temperature fluid.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a method of anticorrosion coating of a joint portion of an anticorrosion coated steel pipe in which an air layer does not remain in the portion of anticorrosion coating made of a heat shrinkable material. is there.

[0011]

Means for Solving the Problems The present inventors have solved the above-mentioned problems by removing the anticorrosion coating layer in the vicinity of the end portion of the anticorrosion coated steel pipe in advance and exposing the steel pipe surface to each other. After butt-welding was performed by in-situ welding, when the joint portion was anticorrosion-coated with a heat-shrinkable material, earnest research was conducted on means for preventing an air layer from remaining in the anticorrosion-coated portion with the heat-shrinkable material.

As a result, if the heat-shrinkable material is heat-shrinked in a vacuum, an air layer does not remain in the anticorrosion coating portion, and in particular, the heat-shrinkable tube is heat-shrinked and the heat-shrinkable tube is made into a steel tube by an adhesive. It was found that when the surface of the welded portion of the joint and the surface of the adjacent portion thereof were brought into close contact with each other, air remained almost completely.

The present invention has been made on the basis of the above-mentioned findings, and when butt-welding the ends of the anticorrosion coated steel pipe having the anticorrosion coating layer formed on the outer surface thereof, the welded portion of the anticorrosion coated steel pipe is A heat-shrinkable tube is disposed so as to cover the outer periphery and the outer periphery of the anticorrosion coating layer-removed portion adjacent to the welded portion and the anticorrosion coating layer-existing portion, and the welded portion and the heat-shrinkable tube are disposed. A vacuum holding device including a plurality of arc-shaped chamber pieces hinged to each other in a chain shape is arranged so as to cover the outer periphery of the welding part adjacent portion, and the welding is covered by the vacuum holding device. The gap between the portion and the portion adjacent to the welded portion and the heat shrink tube is held in a vacuum,
Thus, the heat-shrinkable tube is heat-shrinked in a state of being held in a vacuum, and the heat-shrinkable tube covers the welded part and the part adjacent to the welded part with anticorrosion.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-shrinkable tube used in the present invention may be any heat-shrinkable tube, and a heat-shrinkable plastic tube is particularly preferable. As a plastic material,
Fluorine resins such as polyethylene, modified polyethylene, polyvinyl chloride, polypropylene, ethylene-vinyl acetate copolymer, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer are used.

The heat-shrinkable tube is formed into a tube shape from the beginning, is formed into a tube shape by stitching and joining the ends of the band-shaped body, or is provided at the end of the band-shaped body. What is made into a tube shape by a chuck is used.

By forming an adhesive layer on the inner peripheral surface of such a heat-shrinkable tube, almost no air remains in the welded part and the part adjacent to the welded part, and the heat-shrinkable tube is adhered to both parts. Then, there is an advantage that the coating can be easily formed.

The adhesive layer may be formed simultaneously with the molding of the heat-shrinkable tube, or may be formed by a method of applying an adhesive to the inner peripheral surface of the heat-shrinkable tube after molding. As the adhesive, a pressure sensitive adhesive, a hot melt adhesive, a thermosetting adhesive, a mastic type adhesive, or the like is used.

By disposing an electric heater inside or outside the heat-shrinkable tube, the heat-shrinkable tube can easily generate heat. The electric heater is not limited to a linear heater such as a copper wire, but a layered body in which a heating wire such as a copper wire is embedded may be used. That is, when arranging the electric heater inside the heat-shrinkable tube, a heat wire such as a copper wire is built in the heat-shrinkable tube, and when the electric heater is arranged around the outer periphery of the heat-shrinkable tube. Is a layered body in which a heat wire such as a copper wire is embedded outside the heat shrinkable tube.

When the heat wire is arranged inside the heat-shrinkable tube, the heat-shrinkable tube is bent and arranged so as to meander along its circumference in order to follow the heat shrinkage of the heat-shrinkable tube. It is preferable to install it. When the electrically conductive heater is disposed on the outer peripheral portion of the heat shrinkable tube, the electrically conductive heater may or may not follow the heat shrinkage of the heat shrinkable tube. The constituent material of the layered body in which the above-mentioned heating wire is embedded is not particularly limited, and plastic, rubber or the like is used.

As a device for heating and shrinking the heat-shrinkable tube, a heating device such as an electric heater manufactured separately from the heat-shrinkable tube may be arranged near the heat-shrinkable tube, or as described above. As described above, the electric heater may be built in the heat shrink tube. In this case, the heat-shrinkable tube becomes an internal heat-generating type, the number of parts is reduced and the work is reduced compared to the case where a heating device separate from the heat-shrinkable tube is used.

The vacuum holding device for covering the outer periphery of the welded portion in which the heat-shrinkable tube is disposed, the portion for removing the anticorrosion coating layer adjacent to the welded portion, and the portion for the anticorrosion coating layer existing are a plurality of hinge-joined chains. It consists of an arc-shaped chamber piece. Therefore, by suspending and setting this from the above-ground portion, it can be easily attached to the joint portion of the anticorrosion coated steel pipe laid in a narrow place such as in a dug.

The material of the vacuum holding device is not particularly limited, but steel is preferable when strength is required, and lightness is required for transportation and setting. , Aluminum, FRP and the like are preferable, and aluminum is preferable in the dugout and the cave.

Next, the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing an example of a heat-shrinkable tube used in the present invention, and FIG. 2 is a partial sectional view thereof. As shown in FIGS. 1 and 2, the heat-shrinkable tube 1
Is a heat-shrinkable outer layer 2 made of polyethylene or the like, a copper wire 3 embedded in the outer layer 2, an inner layer 4 made of an adhesive layer provided on the inner peripheral surface of the outer layer 2, and an inner layer 4.
The separator 5 is detachably temporarily attached to the inner peripheral surface of the separator. Reference numeral 6 is a lead wire, and 7 is a connection terminal.

FIG. 3 is a partial sectional view showing another example of the heat shrinkable tube used in the present invention, and FIG. 4 is a partially cutaway perspective view thereof. In this example, as shown in FIGS. 3 and 4, the heat-shrinkable tube 1 includes a heat-shrinkable tube body 9 and a plastic film provided on the outer peripheral surface of the heat-shrinkable tube body 9 and which is not fused at the heat-shrinkable temperature. Of the release agent layer 10, the heat generating layer 11 provided on the outer peripheral portion of the release agent layer 10, the adhesive layer 13 provided on the inner peripheral surface of the heat shrinkable tube body 9, and the adhesive layer 13 The separator 8 is detachably temporarily attached to the peripheral surface. In the heating layer 11, a heating wire 12 made of, for example, a copper wire is arranged in a meandering shape along the circumferential direction.

In the present invention, the heat-shrinkable tube 1 having the structure shown in FIGS. 1 and 2 or the heat-shrinkable tube 1 having the structure shown in FIGS. 3 and 4 is connected to the welded portion of the steel pipe joint. Arranged on the outer periphery and on the outer periphery of the adjacent portion where the surface of the steel pipe is exposed after the anticorrosion coating is removed, and further, a vacuum holding device 15 for holding the gap between the both portions and the heat shrinkable tube 1 in vacuum is arranged. To do.

FIG. 5 is a schematic front view showing an example of the vacuum holding device. As shown in FIG.
It is formed into a cylindrical shape by arcuate chamber pieces 15a, 15b, 15c, 15d, 15e which are divided and are connected to each other by a hinge 14 in a chain shape.

Arc-shaped chamber pieces 15a to 15 divided into five parts
Among e, the first chamber piece 15a to the fourth chamber piece 15
A guide roller 16 is provided in each of d, a fixing member 17 is provided in the fifth chamber piece 15e, and a wire 19 whose one end is fixed to the winding drum 18 is used for the first to fourth chamber pieces 15a to 15a. It is wound around each guide roller 16 of 15d,
And, the other end is the fixture 1 of the fifth chamber piece 15e
7 is fixed.

As shown in the partially enlarged front view of FIG.
Air cylinders 19a, 19b are attached to the tip of chamber piece 15a.
Is provided, and a hook 20 is attached to the tip of the rod of the air cylinder 19b. On the other hand, at the rear end of the fifth chamber piece 15e, an engagement piece 22 with a compression spring 21 is attached, with which the hook 20 of the air cylinder 19b is engaged.

FIG. 7 is an explanatory view showing the order of attaching the vacuum holding device 15 to the steel pipe joint portion. As shown in FIG. 7 (a), a vacuum holding device 15 consisting of arcuate chamber pieces 15a, 15b, 15c, 15d, 15e hinged to each other in a chain shape was laid in a digger by a crane or the like. It is hung on the joint of the anticorrosion coated steel pipe A to be welded. Next, as shown in FIG. 7 (b), a power terminal is attached to the heat-shrinkable tube side, and then arcuate chamber pieces 15a to 15e are hooked around the joint portion of the steel pipe A as shown in FIG. 7 (c). Fifth
The chamber piece 15e is lifted upward by a wire rope, and as shown in FIG. 7 (d), the hook 20 at the tip of the first chamber piece 15a is engaged with the engaging piece 22 at the rear end of the fifth chamber piece 15e. Tighten the joint of the steel pipe A, then
The exhaust hose 27 and the power terminal 28 are attached as shown in FIG.

Arc-shaped chamber pieces 15a to 15 divided into five parts
The means for attaching the vacuum holding device 15 consisting of e to the steel pipe joint is not limited to the above, but as shown in the schematic front view of FIG. 8 and the schematic side view of FIG. May be used.

That is, as shown in FIGS. 8 and 9, arcuate guide rollers 23a, 23b which are divided into two and which have wheels 24 made of urethane, for example, at regular intervals are arranged so as to surround the outer circumference of the steel pipe joint portion. Then, they are connected to each other to form an annular shape, and the rear end of the fifth chamber piece 15e of the arcuate chamber pieces 15a to 15e divided into five is attached to a predetermined portion of such an annular guide roller 23. Next, the vacuum holding device 15 is attached to the steel pipe joint portion by rotating the annular guide roller 23 along the outer circumference of the steel pipe joint portion.

The vacuum holding device 15 is attached as shown in FIG.
As shown in 0, one end of the rope 25 is connected to the fifth chamber piece.
Alternatively, the vacuum holding device 15 including the first to fifth chamber pieces 15a to 15e may be wound around the steel pipe joint portion after the rope 25 is attached to the rear end portion of 15e.

The number of chamber pieces constituting the vacuum holding device 15 is not limited to 5, but may be any number of 3 or more. FIG. 11 is an explanatory diagram showing an example in the case of three divisions. In this example, the vacuum holding device 15 has three arc-shaped chamber pieces that are hinged to each other.
15a, 15b, 15c. The second arc chamber piece 15b in the middle part is hung by the wire rope 25 on the steel pipe joint, and the second arc chamber piece 15a and the third arc chamber piece 15c are connected. By doing so, it can be attached to the steel pipe joint portion.

The anticorrosion coating of the pipe end joints of the anticorrosion coated steel pipes A and B by the heat shrinkable tube 1 and the vacuum holding device 15 described above is performed as follows. As shown in FIG. 12, the heat of separating the separator 5 so as to cover the butt-welded portion C of the anticorrosion-coated steel pipes A and B from which the anticorrosion coating layer at the end to be butt-welded has been removed in advance, and the adjacent portion D thereof. Set shrink tube 1 and heat shrink tube 1
The lead wire 6 attached to the connection terminal 7 is connected to the output terminal 26 of the power supply controller (not shown).

Next, an arc-shaped chamber piece divided into five
A vacuum holding device 15 consisting of 15a to 15e is set so as to cover the butt welded portion C of the anticorrosion coated steel pipes A and B and its adjacent portion D and the heat shrink tube 1, and a vacuum pump (not shown) is operated to hold the vacuum. The inside of the apparatus 15 is kept in a vacuum state until the heat shrink of the heat shrink tube 1 is completed. In this state, the copper wire 3 of the heat-shrinkable tube 1 is energized to generate heat, whereby the outer layer 2 of the heat-shrinkable tube 1 is heat-shrinked, and the butt welded portion C and its adjacent portion D are anticorrosion coated by the heat-shrinkable tube 1. It

When using the heat-shrinkable tube 1 shown in FIGS. 3 and 4 in which the heat-generating layer 11 is provided on the outer peripheral surface of the heat-shrinkable tube body 9 via the release agent layer 10, the heat-shrinkable tube body is used. After heat-shrinking 9, the heat-generating layer 11 is removed.

In order to improve the driving rate during heating, a reflection plate is attached to the inner surface of the vacuum holding device 15 to reuse radiative diffusion heat, or a heat insulating material is attached to the inner or outer surface of the vacuum holding device 15. Alternatively, in order to shrink the heat-shrinkable tube 1 from the central portion thereof, a reflecting plate may be provided only on the inner surface of the vacuum holding device, and a heat insulating material may be provided only on the inner surface of the central portion or the outer surface of the central portion of the vacuum holding device.

In order to control the degree of vacuum, a recorder or a computer may be used for monitoring, or an alarm device may be provided. Further, two vacuum pumps may be provided, and one of them may cause trouble and It may be used as a backup in case of a drop. The sealing material for holding the vacuum is not particularly limited, but it is preferable to provide a material that can be compressed to 0.75 times or less on the contact surface of the vacuum holding device in order to follow the variation in the shape of the contact surface. .

[0039]

【Example】

[Embodiment 1] Next, the present invention will be described with reference to embodiments.
As the anticorrosion coated steel pipe, a city gas pipe having a diameter of 750 mm and having a polyethylene anticorrosion coating layer formed on the outer peripheral surface was butt welded. The anticorrosion coating layer on the end of the pipe to be welded was previously removed by 150 mm in the longitudinal direction. At the welded portion of such a city gas pipe, a heat-shrinkable outer layer 2 made of polyethylene having a thickness of 1.5 mm and a heat shrinkage ratio of 50%, as shown in FIGS. 1 and 2, and an inner peripheral surface of the outer layer. A heat-shrinkable tube 1 having an inner diameter of 850 mm and a length of 600 mm, which is composed of an inner layer 4 made of a pressure-sensitive adhesive layer having a thickness of 1.5 mm and a separator 5 temporarily attached to the inner layer 4, was attached. A copper wire 3 was embedded in the outer layer 2 in a meandering shape, and a lead wire having a connection terminal was connected to the copper wire 3.

A vacuum holding device 15 formed in a cylindrical shape by five arcuate chamber pieces 15a to 15e hinged in a chain shape as shown in FIGS. 1 was attached so as to cover 1 and the inside of the vacuum holding device 15 was maintained at a vacuum degree of about 200 Torr or less.

With such a vacuum holding device 15, the gap between the butt-welded portion of the pipe and the portion adjacent to the welded portion and the heat-shrinkable tube 1 is kept in a vacuum,
The heat-shrinkable tube 1 was heat-shrinked, and the heat-shrinkable tube 1 covered the welded portion and the portion adjacent to the welded portion with anticorrosion.

After the welded portion and the portion adjacent to the welded portion are anticorrosion-coated as described above, the outer layer 2 of the heat-shrinkable tube 1 is removed to check whether there is residual air in the welded portion, the surface of the steel pipe, the stepped portion, or the like. did. As a result, there was no residual air at the welded portion of the joint, the surface of the steel pipe, the stepped portion, and the like.

Example 2 The same city gas pipe as in Example 1 was butt welded. At the weld of the pipe,
And the inner diameter of 850 mm and the length of 600 mm shown in FIG.
A heat-shrinkable tube 1 made of "Neo Heat Cover 1150E" manufactured by Nitto Denko Corporation was attached. The heat-shrinkable tube 1 has a thickness of 1.5 mm, a heat-shrinkage rate of 50%, and a heat-shrinkable temperature of 130 ° C. The heat-shrinkable tube body 9 made of polyethylene is wrapped with polypropylene once to form a release agent layer 10. A heat generating layer 11 made of polyethylene in which a copper wire 3 having a diameter of 0.7 mm is arranged on the outer periphery of the release agent layer 10 and has no heat shrinkability
(Thickness 1 mm) is provided, and the separator 8 is temporarily attached to the adhesive layer 13 on the inner peripheral surface of the tube. The copper wire 3 was arranged in the heating layer 11 in a meandering shape.

The vacuum holding device 15 shown in FIGS. 5 and 6 formed in a cylindrical shape by the five arcuate chamber pieces 15a to 15e, which are hinged in a chain shape, is provided with a heat-shrinkable tube in the steel pipe joint portion. 1 was attached so as to cover 1 and the inside of the vacuum holding device 15 was maintained at a vacuum degree of about 200 Torr or less.

With such a vacuum holding device 15, the gap between the butt-welded portion of the pipe and the portion adjacent to the welded portion and the heat-shrinkable tube 1 is kept in vacuum,
The heat-shrinkable tube 1 was heat-shrinked, and the heat-shrinkable tube 1 covered the welded portion and the portion adjacent to the welded portion with anticorrosion.

After the welded portion and the portion adjacent to the welded portion were coated with anticorrosion as described above, the heat-shrinkable tube body 9 was removed in order to check the welded portion, the surface of the steel pipe, the stepped portion, and the like for residual air. As a result, there was no residual air at the welded portion of the joint, the surface of the steel pipe, the stepped portion, and the like.

[0047]

As described above, according to the present invention,
In order to butt-weld the pipe ends of the anticorrosion-coated steel pipe with the anticorrosion coating layer formed on the surface, the corrosion-prevention coating layer near the pipe ends is previously removed and the steel pipe surface is exposed, and then the joint is heated. When the anticorrosion coating is performed with the shrinkable material, an air layer does not remain in the anticorrosion coated portion with the heat shrinkable material.
Therefore, corrosion does not occur due to the residual air layer, and there is no problem in terms of strength against mechanical load such as impact,
Moreover, many industrially useful effects are brought about, such as easy construction even in a narrow place such as in a main digging.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a heat-shrinkable tube used in the present invention.

FIG. 2 is a partial sectional view of FIG.

FIG. 3 is a partial cross-sectional view showing another example of the heat-shrinkable tube used in the present invention.

FIG. 4 is a partially cutaway perspective view of another example of the heat-shrinkable tube used in the present invention.

FIG. 5 is a schematic front view showing an example of a vacuum holding device.

6 is a partially enlarged front view of FIG.

FIG. 7 is an explanatory view showing the order of attaching the vacuum holding device to the steel pipe joint.

FIG. 8 is a schematic front view showing another example of attachment means of the vacuum holding device.

FIG. 9 is a schematic side view of FIG.

FIG. 10 is a schematic front view showing still another example of attachment means of the vacuum holding device.

FIG. 11 is an explanatory diagram showing another example of the vacuum holding device.

FIG. 12 is an explanatory view showing an anticorrosion coating of a pipe end joint portion according to the method of the present invention.

[Explanation of symbols]

 1 Heat-shrinkable tube 2 Outer layer 3 Copper wire 4 Inner layer 5 Separator 6 Lead wire 7 Connection terminal 8 Separator 9 Heat-shrinkable tube body 10 Release layer 11 Heat-generating layer 12 Heat-generating line 13 Adhesive layer 14 Hinge 15 Vacuum holding device 15a to 15e Arc-shaped Chamber piece 16 Guide roller 17 Fixing bracket 18 Winding cylinder 19 Air cylinder 20 Hook 21 Compression spring 22 Engagement piece 23 Guide roller 24 Wheel 25 Wire rope 26 Output terminal 27 Exhaust hose 28 Power terminal A Corrosion-resistant steel pipe B B Corrosion-resistant steel pipe C Projection Mating welding part D Adjacent part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Shoji 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Toshiyuki Namioka 3-11, Namiki, Kanazawa-ku, Yokohama, Kanagawa −301 (72) Minor Omura Minoru 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Ryoichi Ikeda 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (3)

[Claims] 1. When butt-welding the ends of an anticorrosion coated steel pipe having an anticorrosion coating layer formed on its outer surface, the outer periphery of the welded portion of the anticorrosion coated steel pipe and the anticorrosion coating layer removed portion adjacent to the welded portion, and A heat-shrinkable tube is disposed so as to cover the outer periphery of the anticorrosion coating layer-existing portion, and a chain is formed so as to cover the outer periphery of the welded portion and the weld-adjacent portion where the heat-shrinkable tube is disposed. A vacuum holding device consisting of a plurality of arcuate chamber pieces hinged in a circular shape is provided, and the welding part and the welding part adjoining part covered with the vacuum holding device and the heat shrink tube are provided. The gap between them is held in vacuum, and the heat-shrinkable tube is heat-shrinked in a state of being held in such a vacuum, and the heat-shrinkable tube causes the welded portion and the welded portion. The contact portion, characterized in that anti-corrosion coating, corrosion method anticorrosive coated steel pipe joints. 2. The heat-shrinkable tube is formed with an outer layer having a copper wire for heating embedded on the outer peripheral surface thereof, and
The method according to claim 1, wherein an adhesive layer is formed on the inner peripheral surface thereof. 3. The heat-shrinkable tube has a heat-generating layer formed on the outer peripheral surface of the heat-shrinkable tube via a release agent layer, and an adhesive layer formed on the inner peripheral surface of the heat-shrinkable tube. The method according to claim 1, wherein the heating layer is removed after the heating.