JP3151138B2 - Corrosion protection method for anti-corrosion coated steel pipe joints - Google Patents

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 of an anticorrosion coated steel pipe used for a pipeline for transporting city gas, tap water, petroleum, steam for district heating, and the like.

[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 susceptible to corrosion 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 or polyethylene (PE), epoxy, urethane or the like to form an anticorrosion coating layer. Such an anticorrosion coating layer is formed as a coating in a factory, and is therefore also called a factory coating layer.

[0003] When the pipe ends are butt-welded to each other with pipe ends of the anticorrosion-coated steel pipe having the anticorrosion-coated layer formed on the surface, there is a problem that the heat generated during welding deteriorates the anticorrosion-coated layer.

Therefore, in order to prevent the deterioration of the anticorrosion coating layer, conventionally, the anticorrosion coating layer near the pipe end of the anticorrosion coated steel pipe was previously removed, and the pipe ends were welded and connected to each other at a piping work site. The outer periphery of the welded portion and the outer periphery of the portion where the anticorrosion coating layer is removed and the outer periphery of the portion where the anticorrosion coating layer is present adjacent to the welded portion are covered with an anticorrosion heat-shrinkable tube or an anticorrosion heat-shrinkable sheet and heated with propane gas or the like. In this case, the heat-shrinkable tube or sheet is used to perform anticorrosion coating on the tube end.

[0005] According to such an anticorrosion coating method at a pipe construction site, by sufficiently wrapping the anticorrosion coating layer and the heat-shrinkable material, the anticorrosion coated steel pipe is protected from corrosive factors such as water and air. Since it can prevent corrosion, it has excellent anticorrosion performance and has many practical examples.

[0006]

However, the above-mentioned anticorrosion coating method has the following problems. That is, the flat portions at both ends of the anticorrosion-coated steel pipe, ie, 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 connection portion, and the welded portion, which require anticorrosion, and the anticorrosion coating layer The surface of the steel pipe surface and the surface of the stepped portion between the anticorrosion coating layer and the like, which are caused by the removal of, are not necessarily smooth but have unevenness.

As a result, when the anti-corrosion heat-shrinkable tube is thermally shrunk, an air layer may remain in the welded portion at the built-up portion or the step portion. In addition, even in a flat portion such as a steel pipe surface or an anticorrosion coating layer, it is unavoidable that air voids are generated at the time of heat shrinkage. Although the amount of such residual air is not an amount that is practically problematic, the progress of corrosion caused by residual air and the safety of the mechanical strength of the residual air due to impact and the like in terms of strength and safety are often large. Anxiety has arisen.

Various methods have hitherto been used to eliminate the residual air and the like in the anticorrosion coating portion of the above-mentioned heat-shrinkable material. For example, a step portion is preliminarily filled with a sealing material containing butyl rubber as a main component. For example, a method of previously applying a hot-melt material mainly containing asphalt, butyl rubber, or the like to a flat portion such as a steel pipe surface or an anticorrosion coating layer is used.

However, such a method cannot completely prevent air voids from remaining. In addition, in the case of the latter method, it is necessary to melt-coat the hot-melt material at a pipe construction site, and thus there are also problems such as generated gas and safety in handling high-temperature fluid.

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

[0011]

Means for Solving the Problems The present inventors have solved the above-mentioned problems, and have previously removed the anticorrosion coating layer near the end of the anticorrosion coated steel pipe, and then connected the pipe ends with the steel pipe surface exposed. After butt-welding of the joints by in-situ welding, when the joint portion was coated with a heat-shrinkable material for corrosion protection, intensive research was conducted on means for preventing an air layer from remaining in the portion of the heat-shrinkable material.

As a result, if the heat shrinkage of the heat shrinkable material is performed under vacuum, no air layer remains in the anticorrosion coating portion. In particular, the heat shrinkable tube is heat shrunk, and the heat shrinkable tube is formed by the adhesive. It was found that when the joint was brought into close contact with the surface of the welded portion and the surface of the adjacent portion, the air remained almost completely eliminated.

According to the first aspect of the present invention, when the end portions of the anticorrosion coated steel pipe having the anticorrosion coating layer formed on the outer surface are butt-welded, the outer periphery of the welded portion of the anticorrosion coated steel pipe and the portion adjacent to the welded portion are welded. so as to cover the outer periphery of the anti-corrosion coating removal portion and anticorrosive coating layer occupied part, the outer periphery
An outer layer in which a copper wire for heating is embedded is formed on the surface,
Then, a heat-shrinkable tube having an adhesive layer formed on its inner peripheral surface is provided , and the heat-shrinkable tube is provided so as to cover the outer periphery of the welded portion and the welded portion adjacent portion where the heat-shrinkable tube is provided. A vacuum holding device comprising a plurality of arc-shaped chamber pieces hinged to each other in a chain shape, and the welding portion and the welding portion adjacent portion covered with the vacuum holding device are covered by the vacuum holding device. The gap between the heat-shrinkable tube and the shrinkable tube is held in a vacuum, and the heat-shrinkable tube is heat-shrinked in the state where the vacuum is held as described above. In particular, it has features. According to a second aspect of the present invention, when the end portions of the anticorrosion coated steel pipe having the anticorrosion coating layer formed on the outer surface are butt-welded to each other, the outer periphery of the welded portion of the anticorrosion coated steel pipe and the anticorrosion coating layer adjacent to the welded portion are provided. In order to cover the outer periphery of the removed part and the part where the anticorrosion coating layer exists, it is applied via a release agent layer on the outer peripheral surface.
A thermal layer is formed, and an adhesive layer is formed on the inner peripheral surface
A plurality of heat-shrinkable tubes are arranged, and a plurality of hinge-joined chains are formed so as to cover the outer periphery of the welded portion where the heat-shrinkable tube is provided and the outer periphery of the welded portion adjacent portion. A vacuum holding device composed of an arc-shaped chamber piece is provided, and the gap between the welded portion and the welded portion adjacent portion and the heat-shrinkable tube covered with the vacuum holding device is held by a vacuum, The heat-shrinkable tube is heat-shrinked while being held in a vacuum as described above, and the heat-generating layer is formed after the heat-shrinkable tube is heat-shrinked.
, And the heat-shrinkable tube covers the welded portion and the portion adjacent to the welded portion with anticorrosion coating.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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,
Fluororesins such as polyethylene, modified polyethylene, polyvinyl chloride, polypropylene, ethylene-vinyl acetate copolymer, polytetrafluoroethylene, and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer are used.

Further, the heat-shrinkable tube is formed into a tube shape from the beginning, formed into a tube shape by sewing and joining the ends of the band-shaped body, or provided at the end of the band-shaped body. A tube or the like that is formed into a tube shape at the time of construction by a chuck is used.

If an adhesive layer is formed on the inner peripheral surface of the heat-shrinkable tube, almost no air remains in the welded portion and the portion adjacent to the welded portion, and the heat-shrinkable tube is bonded to the two portions. This makes it easy to form a coating.

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

If a current-carrying heater is provided inside or on the outer periphery of 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 may be a layered body in which a heat wire such as a copper wire is embedded. That is, when an energized heater is disposed inside the heat-shrinkable tube, a heat wire such as a copper wire is built in the heat-shrinkable tube, and when an energized heater is disposed on the outer peripheral portion of the heat-shrinkable tube. Laminates a layered body in which a heat wire such as a copper wire is embedded outside a heat-shrinkable tube.

When a heat ray is provided inside the heat-shrinkable tube, the heat-shrinkable tube is bent in a meandering state along its circumference in order to follow the heat shrinkage of the heat-shrinkable tube. It is preferable to provide them. When the energized heater is provided on the outer peripheral portion of the heat-shrinkable tube, the energized heater may or may not follow the heat shrinkage of the heat-shrinkable tube. The constituent material of the layered body in which the heat rays are 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 provided in the vicinity of the heat-shrinkable tube. As described above, the energized heater may be incorporated in the heat-shrinkable tube. In this case, the heat-shrinkable tube is of an internal heat generation type, and the number of parts is reduced as compared with the case where a heating device separate from the heat-shrinkable tube is used, thereby reducing the work.

The vacuum holding device for covering the outer periphery of the welded portion where the heat-shrinkable tube is disposed, the portion where the anticorrosion coating layer is removed adjacent to the welded portion, and the portion where the anticorrosion coating layer exists is a plurality of pieces that are hinged to each other in a chain shape. Of arc-shaped chamber pieces. Therefore, by suspending and setting this from the 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 digging cloth.

The material of the vacuum holding device is not particularly limited, but steel is preferred when strength is required, and when lightness is required for transportation and setting, , Aluminum, FRP and the like are preferable, and aluminum is preferable in a cloth excavation and a 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 FIG. 1 and FIG.
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
And a separator 5 temporarily attached releasably to the inner peripheral surface. 6 is a lead wire, 7 is a connection terminal.

FIG. 3 is a partial cross-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 is composed of a heat-shrinkable tube main body 9 and a plastic film that is provided on the outer peripheral surface of the heat-shrinkable tube main body 9 and does not fuse at the heat shrinkage temperature. A heat-generating layer 11 provided on the outer peripheral portion of the release agent layer 10, an adhesive layer 13 provided on the inner peripheral surface of the heat-shrinkable tube main body 9, and an inner layer of the adhesive layer 13. And a separator 8 temporarily detachably attached to the peripheral surface. On the heat generating layer 11, heat generating wires 12 made of, for example, copper wires are 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. A vacuum holding device 15 for holding the outer periphery and the outer periphery of the adjacent portion where the anticorrosion coating is removed and exposing the surface of the steel pipe, and further maintaining a vacuum between the above-mentioned portions and the heat-shrinkable tube 1 is provided. I do.

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

The arc-shaped chamber pieces 15a to 15 divided into five parts
e, the first chamber piece 15a to the fourth chamber piece 15a
Each of d is provided with a guide roller 16, a fifth chamber piece 15e is provided with a fixing bracket 17, and a wire 19 having one end fixed to a winding drum 18 is provided with a first to fourth chamber pieces 15a to 15a. 15d around each guide roller 16,
And the other end is the fixture 1 of the fifth chamber piece 15e.
7 is fixed.

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

FIG. 7 is an explanatory diagram showing the order of mounting the vacuum holding device 15 to the steel pipe joint. As shown in FIG. 7 (a), a vacuum holding device 15 consisting of arc-shaped chamber pieces 15a, 15b, 15c, 15d, 15e hinged to each other in a chain shape was laid in a cloth digger by a crane or the like. It is hung at the joint of the anticorrosion coated steel pipe A to be welded. Next, as shown in FIG. 7 (b), a power terminal was attached to the heat-shrinkable tube side, and as shown in FIG. 7 (c), the arc-shaped chamber pieces 15a to 15e were wrapped around the joint portion of the steel pipe A. 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 engagement piece 22 at the rear end of the fifth chamber piece 15e. And tighten it to the joint of steel pipe A.
As shown in FIG. 7 (e), the exhaust hose 27 and the power terminal 28 are attached to complete the setting.

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

That is, as shown in FIGS. 8 and 9, two divided arcuate guide rollers 23a and 23b having, for example, urethane wheels 24 at regular intervals are arranged so as to surround the outer periphery of the steel pipe joint. Then, the rear end portion of the fifth chamber piece 15e of the five arc-shaped chamber pieces 15a to 15e is attached to a predetermined position of such an annular guide roller 23. Next, by rotating the annular guide roller 23 along the outer periphery of the steel pipe joint, the vacuum holding device 15 is attached to the steel pipe joint.

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

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

The anti-corrosion coating of the pipe end joints of the anti-corrosion coated steel pipes A and B by the above-mentioned heat-shrinkable tube 1 and the vacuum holding device 15 is performed as follows. As shown in FIG. 12, the separator 5 is peeled off 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 and the adjacent portion D thereof. Set the shrink tube 1 and heat shrink tube 1
Is connected to the output terminal 26 of a power controller (not shown).

Next, the arc-shaped chamber piece divided into five parts
The 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 the adjacent portion D and the heat-shrinkable tube 1, and operates a vacuum pump (not shown) to hold the vacuum. The inside of the device 15 is kept in a vacuum state until the heat shrinkage of the heat shrinkable tube 1 is completed. In this state, when the copper wire 3 of the heat-shrinkable tube 1 is energized to generate heat, 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 coated with the anti-corrosion by the heat-shrinkable tube 1. You.

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

In order to improve the driving rate at the time of heating, a reflection plate is attached to the inner surface of the vacuum holding device 15 to reuse radiant 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 cause the heat-shrinkable tube 1 to shrink from the center, a reflector 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 or the outer surface of the center 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. Two vacuum pumps may be installed, and one of them may cause a trouble and reduce the degree of vacuum. It may be used for backup in case of a fall. Further, the sealing material for maintaining 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 an embodiment.
As the anticorrosion coated steel pipe, a 750 mm diameter city gas pipe having a polyethylene anticorrosion coating layer formed on the outer peripheral surface was butt-welded. The anticorrosion coating layer at the end of the pipe to be welded was previously removed by 150 mm in the longitudinal direction. 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 are provided on the welded portion of such a city gas pipe. A heat-shrinkable tube 1 having an inner diameter of 850 mm and a length of 600 mm comprising 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 meandering shape in the outer layer 2, and a lead wire having a connection terminal was connected to the copper wire 3.

The vacuum holding device 15 shown in FIGS. 5 and 6, which is formed into a cylindrical shape by five arc-shaped chamber pieces 15a to 15e hinged in a chain, is connected to a steel pipe joint by a heat-shrinkable tube. 1, and the inside of the vacuum holding device 15 was maintained at a degree of vacuum 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 held in a vacuum state.
The heat-shrinkable tube 1 was heat-shrinked, and the welded portion and the portion adjacent to the welded portion were subjected to anticorrosion coating by the heat-shrinkable tube 1.

As described above, after the welded portion and the portion adjacent to the welded portion are subjected to anticorrosion coating, the outer layer 2 of the heat-shrinkable tube 1 is removed in order to check whether there is residual air in the welded portion, the surface of the steel pipe, and the stepped portion. did. As a result, no residual air was present 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. Fig. 3
And an inner diameter of 850 mm and a 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-shrinkage temperature of 130 ° C. A polypropylene is wound once around an outer peripheral surface of a heat-shrinkable tube main body 9 to form a release agent layer 10. A heat-shrinkable polyethylene heat-generating layer 11 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
(1 mm thick), and a separator 8 was temporarily attached to the adhesive layer 13 on the inner peripheral surface of the tube. The copper wires 3 were arranged in a meandering manner in the heat generating layer 11.

The vacuum holding device 15 shown in FIGS. 5 and 6, which is formed into a cylindrical shape by five arc-shaped chamber pieces 15a to 15e hinged in a chain, is connected to a steel pipe joint by a heat-shrinkable tube. 1, and the inside of the vacuum holding device 15 was maintained at a degree of vacuum 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 held 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.

As described above, after the welded portion and the portion adjacent to the welded portion were subjected to anticorrosion coating, the heat-shrinkable tube main body 9 was removed in order to examine whether there was any residual air in the welded portion, the surface of the steel pipe, the stepped portion, and the like. As a result, no residual air was present 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 having the anticorrosion coating layer formed on the surface, the anticorrosion coating layer near the pipe end is removed in advance and welding is performed with the steel pipe surface exposed, and then the joint is heated. When the anticorrosion coating is performed with the shrinkable material, no air layer remains in the anticorrosion coated portion formed of 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 loads such as impacts.
In addition, many industrially useful effects are provided, such as easy construction in a narrow place such as inside a main excavation.

[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 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.

FIG. 6 is a partially enlarged front view of FIG. 5;

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 the mounting 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 the mounting means of the vacuum holding device.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat shrink tube 2 Outer layer 3 Copper wire 4 Inner layer 5 Separator 6 Lead wire 7 Connection terminal 8 Separator 9 Heat shrink tube main body 10 Release layer 11 Heat generation layer 12 Heat generation wire 13 Adhesive layer 14 Hinge 15 Vacuum holding device 15a to 15e Arc shape 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-proof coated steel pipe B Corrosion-resistant coated steel pipe C Joint welding part D Adjacent part

──────────────────────────────────────────────────続 き Continuing on the front page (72) Norio Shoji, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Toshiyuki Namioka 3--11, Namiki, Kanazawa-ku, Yokohama, Kanagawa 2- 301 (72) Inventor Minoru Komura 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nippon Denko Corporation (72) Inventor Ryoichi Ikeda 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (56) References JP-A-8-132449 (JP, A) JP-A-6-182287 (JP, A) JP-A-4-90783 (JP, U) JP-B-47-31198 (JP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) F16L 58/00-58/18 F16L 11/12

Claims (2)

(57) [Claims] 1. An anticorrosion-coated steel pipe having an anticorrosion-coated layer formed on an outer surface thereof, when butt-welding the ends of the anticorrosion-coated steel pipe to an outer periphery of a welded portion of the anticorrosion-coated steel pipe and a part where the anticorrosion-coated layer is removed adjacent to the welded part; A copper wire for heating is buried on the outer peripheral surface so as to cover the outer periphery of the portion where the anticorrosion coating layer exists
Outer layer is formed, and adhered to its inner peripheral surface
A heat-shrinkable tube provided with an agent layer is provided , and the heat-shrinkable tube is hinged to each other in a chain shape so as to cover the outer periphery of the welded portion and the welded portion adjacent portion where the heat-shrinkable tube is provided. A vacuum holding device comprising a plurality of arc-shaped chamber pieces is provided, and the gap between the heat-shrinkable tube and the welded portion covered with the vacuum-holding device and the heat-shrinkable tube is covered by the vacuum holding device. Wherein the heat-shrinkable tube is heat-shrinked while being held in such a vacuum, and the welded portion and the portion adjacent to the welded portion are subjected to anticorrosion coating by the heat-shrinkable tube. Corrosion prevention method for joints. 2. The method according to claim 1, wherein when the end portions of the anticorrosion coated steel pipe having the anticorrosion coating layer formed on the outer surface thereof are butt-welded to each other, an outer periphery of a welding portion of the anticorrosion coating steel tube and a portion where the anticorrosion coating layer is removed adjacent to the welding portion; In order to cover the outer periphery of the portion where the anti-corrosion coating layer exists, the outer peripheral surface is exposed via a release agent layer
A thermal layer is formed, and an adhesive layer is formed on the inner peripheral surface
A plurality of heat-shrinkable tubes are arranged, and a plurality of hinge-joined chains are formed so as to cover the outer periphery of the welded portion where the heat-shrinkable tube is provided and the outer periphery of the welded portion adjacent portion. A vacuum holding device comprising an arc-shaped chamber piece is provided, and the gap between the heat-shrinkable tube and the welded portion and the welded portion adjacent portion covered by the vacuum-holding device is held by the vacuum holding device, The heat-shrinkable tube is heat-shrinked while being held in a vacuum, and the heat-shrinkage is performed.
A method of preventing corrosion of a corrosion-resistant coated steel pipe joint , wherein the heat- generating layer is removed after heat-shrinking the tube, and the welded portion and the portion adjacent to the welded portion are subjected to corrosion protection by the heat-shrinkable tube.