JPH0811206B2 - Tubular anticorrosion spray coating method - 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 thermal spray coating method and apparatus for a pipe such as a steel pipe, in which an inner surface or an outer surface of a tubular body is provided with a plastic anticorrosion coating by thermal spraying. Steel pipes coated with polyethylene or other plastic on the inside are used for water and sewage pipes, seawater intake and drainage pipes for nuclear power plants, oil gas transport pipes, etc. to prevent corrosion of the inner surface of the pipe by fluid. . Further, in a pipeline buried in the soil or laid in the sea, a steel pipe having an outer surface coated with the same coating as the inner surface is used in order to prevent corrosion of the outer surface of the pipe body.

[0002]

2. Description of the Related Art Conventionally, the following methods have been known as a method for applying an anticorrosive coating of plastic on the inner and outer surfaces of a tubular body. First, there is a method in which the tubular body is heated in advance and the melted plastic such as polyethylene is extrusion-coated on the outer surface of the tubular body. Next, a method in which the tubular body is preheated and the heated tubular body is immersed in a tank in which plastic powder such as polyethylene is flown to fuse the plastic to the outer surface of the tubular body is disclosed in Japanese Examined Patent Publication No. 43-12666. It is disclosed in the official gazette. Further, there is a method in which the tubular body is preheated, and a plastic powder such as polyethylene is sprayed, filled or sprayed on the inner surface of the tubular body so as to be fused to the inner surface of the tubular body.
It is disclosed in Japanese Patent Publication No. 080, Japanese Patent Publication No. 40-15977, Japanese Patent Publication No. 40-15978, and Japanese Patent Publication No. 2-2624.

[0003]

In any of the above-mentioned conventional methods for applying the anticorrosive coating of plastic to the inner and outer surfaces of the tubular body, the method is to heat the tubular body to a temperature above the melting point of the plastic and fuse it. A heating device such as induction heating for heating the tube is essential. Therefore, since it is necessary to install a heating device, the outer diameter and length of the pipe that can be covered are limited, and it is difficult to apply it to a large-diameter pipe. There was a problem that it was difficult to do. Further, there is a problem that heating time is required for heating the tubular body, the time required for the anticorrosion coating is long, and the cost of the anticorrosion coating is increased due to the necessity of the heating device. Furthermore, if the tube body is not heated uniformly, the quality of the anticorrosion coating tends to deteriorate, so that the heating device costs higher because the tube body is heated uniformly, and the inner and outer surfaces of the tube are different. In the case of applying the anticorrosion coating, there is a problem that the process and materials are restricted so that the coating film previously coated is not deteriorated by heating the tube.

The present invention has been made in order to solve the above-mentioned problems, does not require preheating of the tubular body, can perform anticorrosion coating even on a large-diameter tubular body, and can be installed on site or after installation,
It is an object of the present invention to provide a tubular body anticorrosion spray coating method capable of improving the quality of the anticorrosion coating and reducing the cost.

[0005]

SUMMARY OF THE INVENTION A method for corrosion protection spray coating of a tubular body according to the present invention is a modified polyamidoamine cure which has adhesiveness to both the tubular body and the thermoplastic resin powder to be sprayed and does not deteriorate by heat during thermal spraying. Type epoxy resin or polychloroprene phenolic resin synthetic resin primer is applied to the inner or outer surface of the tube to form a primer layer, and the tube coated with the synthetic resin primer is kept at room temperature for at least 30%.
Minutes, at most 120 hours, to naturally dry to cure the primer layer, and after the drying time has elapsed, the primer film is formed on the tubular body until the primer film is completely cured after surface drying. Without preheating the tube on the primer layer, heat and melt the thermoplastic resin powder of polyethylene, polypropylene or ethylene vinyl acetate copolymer also discharged from the spray gun by the combustion flame of the mixed gas discharged from the spray gun, The thermoplastic resin powder in the form of liquid droplets is sprayed onto the inner surface or the outer surface of the pipe to spray the thermoplastic resin powder, and the spray gun is rotated with respect to the pipe, or the spray gun is used. By rotating the pipe in the state of being close to the pipe and moving the thermal spray gun in the axial direction of the pipe at the same time, a plastic anticorrosion coating of the desired thickness is formed on the inner or outer surface of the pipe. It is made of a step for forming.

[0006]

In the present invention, a modified polyamidoamine-curable epoxy resin or a synthetic resin of polychloroprene phenol resin which has adhesiveness to both the tubular body and the thermoplastic resin powder to be sprayed and does not deteriorate by heat during spraying. A step of applying a primer to the inner surface or the outer surface of the tubular body to form a primer layer; and allowing the tubular body coated with the synthetic resin primer to naturally dry at room temperature for at least 30 minutes and at most 120 hours. The step of curing the primer layer and the thermal spray gun without preheating the tube on the primer layer formed on the tube after the drying time elapses and after the primer coating is completely dried on the surface The thermoplastic resin powder of polyethylene, polypropylene or ethylene vinyl acetate copolymer, which was also discharged from the spray gun by the combustion flame of the mixed gas discharged from Thermally melting, spraying a droplet-shaped thermoplastic resin powder onto the inner surface or outer surface of the pipe body, spraying the thermoplastic resin powder adhered, and rotating the spray gun with respect to the pipe body, Alternatively, by rotating the pipe in a state where the spray gun is close to the pipe and moving the spray gun in the axial direction of the pipe at the same time, an anticorrosive coating of a desired thickness of plastic is formed on the inner surface or the outer surface of the pipe. By the process of forming, the anticorrosive coating of plastic is formed on the inner surface or outer surface of the tubular body, so heating of the tubular body by a heating device is not required as in the conventional case, and even for large-diameter tubular bodies. Can perform anticorrosion coating. Also, before applying the anticorrosion coating of the thermoplastic resin by thermal spraying, the synthetic resin primer having adhesiveness to both the tubular body and the thermoplastic resin powder is applied to the inner surface or the outer surface of the tubular body. The molten coating of the molten thermoplastic resin powder is easily and firmly adhered to the tube body, and when the molten coating is cooled and solidified, defects such as peeling and cracking are prevented.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the outline of an apparatus for carrying out the method of the present invention, and FIG. 2 is a sectional view showing the outline of the apparatus.
In the figure, 1 is a tubular body such as a steel pipe, 2 is a primer layer of a synthetic resin primer applied to the inner surface of the tubular body 3, 3 is a plastic anticorrosive coating applied on the primer layer 2, and 4 is each of the tubular body 1. A tubular body support base having four rollers 4a for rotationally supporting the ends, 5 is a motor for rotationally driving one roller 4a of the tubular body support base 4, 6 is a tubular body rotation device, and two tubular body support bases 4 are provided.
And one motor 5. Reference numeral 7 is a spray gun for spraying thermoplastic resin powder, 8 is a gun horizontal support arm having the spray gun 7 at its tip, 9 is a spray gun driving device for supporting the gun horizontal support arm 8 and moving it horizontally. Is a spray material supplying device for supplying the thermoplastic resin powder and a mixed gas of oxygen and fuel to the spray gun 7 through a pipe 11, 12 is a compressor for sending oxygen to the spray material supplying device 10, and 13 is a spray material supplying device 10 It is a fuel gas cylinder for feeding a fuel gas such as propane gas into.

Next, the case where the method of the present invention is carried out by using the apparatus shown in FIG. 1 will be described. First, a modified polyamidoamine-curable epoxy resin-based synthetic resin primer is applied to the inner surface of the tube body 1 which is a steel tube having a diameter of 2 m rotatably supported by the tube body rotation device 6. This synthetic resin primer is required to have good adhesiveness to both the tubular body 1 and the anticorrosion coating resin and not be thermally deteriorated due to a temperature rise during thermal spraying. The application of such synthetic resin primer is carried out by using a coating tool such as a spray, a brush or a roller, and the application conditions are for the purpose of optimizing the adhesion with the plastic spray coating and the quality of the spray coating. 100 to 30
The range is 0 g / m ² and the dry film thickness is 50 to 150 μm.
The interval between the application of the synthetic resin primer and the subsequent plastic spraying is preferably in the range from the time until the synthetic resin primer dries to the time when the adhesion between the primer and the sprayed coating is optimized. For example, when the environmental temperature is about 20 ° C., the range is from 30 minutes to 48 hours. When a synthetic resin primer of polychloroprene phenol resin type is used, it takes 30 minutes to 12 minutes.
A range of 0 hours is desirable.

Next, a thermoplastic resin powder is sprayed on the inner surface of the tube body 1 to form a plastic anticorrosion coating on the inner surface of the tube body 1, and the tube body rotating device 6 is driven to fix the tube body 1 thereon. While rotating, the gun horizontal support arm 8 is horizontally driven by the spray gun driving device 9 to move the spray gun 7 arranged on the inner surface side of the tube body 1 in the tube axial direction in parallel with the inner surface of the tube body 1. Move to. Then, during such movement, polyethylene powder, which is a thermoplastic resin supplied from the thermal spray material supply device 10 from the thermal spray gun 7, is melted and sprayed by a flame of a mixed gas of oxygen and propane gas, and a polyethylene anticorrosive coating is formed on the tubular body. It is formed continuously on the inner surface of 1. At this time, although not shown, two spray guns 7 are provided on the gun horizontal support arm 8, and the polyethylene powder, which is a thermoplastic resin powder, has a particle size of 250 μm or less. The rotational speed of the tube body 1 is 2 rpm, and the spray gun 7
At a moving speed of 60 mm / min, a discharge rate of powder from the spray gun 7 of 200 g / min (per spray gun), and a film thickness of 1
A polyethylene anticorrosion coating of mm was obtained with an efficiency of 18 m ² per hour.

In the above embodiment, after the synthetic resin primer is applied to the inner surface of the tubular body 1, the thermal spray gun 7 disposed on the inner surface side of the tubular body 1 is sprayed while the tubular body 1 is rotated by the tubular body rotating device 6. Since the gun driving device 9 moves the inner surface of the tube 1 in the tube axial direction to spray the polyethylene powder from the spray gun 7, the polyethylene anticorrosion coating is continuously formed on the inner surface of the tube 1. Since the tube 1 is not heated by a heating device as in the conventional case, a plastic anticorrosion coating can be applied to a large-diameter tube, the length of the tube 1 is not restricted, and the cost of anticorrosion coating can be reduced. Can be reduced and the quality can be improved. Further, by not heating the tubular body 1 in advance, there is no restriction on the anticorrosion construction process and the material that prevent the coating of the outer surface of the tubular body 1 from being deteriorated. Although polyethylene powder is used as the material for the anticorrosion coating of plastic in this embodiment, it is needless to say that it may be thermoplastic resin powder such as polypropylene, nylon, ethylene-vinyl acetate copolymer and the like.

Further, in the above embodiment, the spray gun 7 is connected to the tube body 1.
The inner surface of the tube body 1 is coated with a plastic anticorrosion coating, but the thermal spray gun 7 is arranged on the outer surface side of the tube body to apply a plastic anticorrosion coating to the outer surface of the tube body 1. It goes without saying that you can do it. Further, in order to continuously form the plastic anticorrosive film on the inner surface of the pipe body 1, while rotating the pipe body 1 by the pipe body rotating device 6,
Although the thermal spray gun 7 is moved in the axial direction with the inner surface of the tubular body 1 by the thermal spray gun drive device 9, the thermal spray gun 7 is fixed and the tubular body 1 is rotated and the tubular body is moved in the axial direction. The plastic anticorrosion coating can be continuously formed on the inner surface of the tubular body 1 by using the apparatus.

FIG. 3 is a block diagram showing the outline of another apparatus for carrying out the method of the present invention. In the figure, the same configurations as those of the embodiment shown in FIG. Reference numeral 14 is a spray gun rotating device for rotating the spray gun 7 in the pipe circumferential direction in a state of being brought close to the inner surface of the pipe body 1,
It has a built-in drive source and rotation mechanism. Reference numeral 15 denotes a thermal spray gun traveling device which mounts the thermal spray gun rotating device 14 and travels on the inner surface of the tubular body 1 in the axial direction of the tubular body. Reference numeral 15a is a traveling wheel of the spray gun traveling device 15.

Next, the case where the method of the present invention is carried out using the apparatus shown in FIG. 3 will be described. First, a modified polyamidoamine-curable epoxy resin-based synthetic resin primer is applied to the inner surface of the tubular body 1 which is a steel pipe having a diameter of 2 m. The conditions for applying the synthetic resin primer are the same as in the case of carrying out the present invention using the apparatus of the embodiment shown in FIG. Next, a thermoplastic resin powder is sprayed on the inner surface of the tube body 1 to form a plastic anticorrosion coating on the inner surface of the tube body 1. The spray gun 7 is formed on the inner surface of the tube body 1 by the spray gun rotating device 14. The pipes are moved close to each other in the pipe circumferential direction, and are moved in the pipe axial direction in parallel with the inner surface of the pipe body 1 by the spray gun traveling device 15. Then, during such movement, the polyethylene powder supplied from the thermal spray material supply device 10 from the thermal spray gun 7 is melted and sprayed by the flame of a mixed gas of oxygen and propane gas, and the polyethylene protective coating is continuously applied to the inner surface of the tubular body 1. Form.

At this time, the polyethylene powder which is the thermoplastic resin powder has a particle size of 250 μm or less. The rotation speed of the spray gun 7 was 2 rpm, the moving speed of the spray gun 7 was 30 mm / min, the amount of powder discharged from the spray gun 7 was 200 g / min, and the polyethylene anticorrosion coating with a thickness of 1 mm was 9 m ² per hour. It was obtained with the efficiency of. In this embodiment, after applying a synthetic resin primer to the inner surface of the tubular body 1,
While rotating the spray gun rotating device 14 in the circumferential direction of the pipe, the spray gun traveling device 15 moves the pipe parallel to the inner surface of the pipe 1 to spray polyethylene powder from the spray gun 7.
Since the polyethylene anticorrosion coating is formed continuously on the inner surface of the pipe body 1, there are no restrictions on the dimensions of the pipe body 1, the cost of the anticorrosion coating can be reduced, and the quality can be improved. Not only is the restriction of no.
Since the spray gun 7 moves inside the tube body 1 while rotating, it can be installed locally or after installation. In this embodiment, polyethylene powder is used as the material for the plastic anticorrosion coating, but any thermoplastic resin powder may be used as in the above embodiment, and the synthetic resin primer is also a modified polyamidoamine-curable epoxy resin type. Needless to say, a polychloroprene phenolic resin-based material may be used instead of the above-mentioned materials.

[0015]

According to the present invention, a modified polyamidoamine-curable epoxy resin or polychloroprene phenolic resin which has adhesiveness to both the tubular body and the thermoplastic resin powder to be sprayed and does not deteriorate by heat during spraying. A step of applying a synthetic resin primer to the inner surface or the outer surface of the tube to form a primer layer, and allowing the tube coated with the synthetic resin primer to stand at room temperature for at least 30 minutes and at most 120 hours to naturally dry. , A step of curing the primer layer, and after the drying time has elapsed and the primer film is surface dried,
Until the tube completely cures, the tube is not preheated on the primer layer formed on the tube, and the polyethylene, polypropylene or ethylene vinyl acetate mixture discharged from the spray gun is also discharged by the combustion flame of the mixed gas discharged from the spray gun. The thermoplastic resin powder of the polymer is heated and melted, and the droplet-shaped thermoplastic resin powder is sprayed onto the inner surface or the outer surface of the pipe body to spray the thermoplastic resin powder, and the spray gun is used. By rotating the tube with respect to the tube or by rotating the tube with the spray gun in the vicinity of the tube and moving the spray gun in the axial direction of the tube, the inner surface or the outer surface of the tube is changed. Since the plastic anticorrosive coating is formed on the inner surface or the outer surface of the pipe by the step of forming the plastic anticorrosive coating of the desired film thickness, it is possible to heat the pipe by a heating device as in the conventional case. Needed next, there is no restriction of the outer diameter and the length of the tube to perform plastic anticorrosive coating, improved quality can be reduced the cost of anticorrosion coating, there is an effect that restriction of corrosion construction processes and materials is eliminated. Also,
Before the anti-corrosion coating of the thermoplastic resin by thermal spraying, the synthetic resin primer, which has adhesiveness to both the tubular body and the thermoplastic resin powder, is applied to the inner or outer surface of the tubular body, so that it is melted by the flame due to thermal spraying. In addition, the molten coating of the thermoplastic resin powder can be easily and firmly adhered to it, and defects such as peeling and cracking can be prevented when the molten coating is cooled and solidified.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of an apparatus in which a method of the present invention is implemented.

FIG. 2 is a cross-sectional view showing an outline of the same device.

FIG. 3 is a schematic diagram showing another apparatus in which the method of the present invention is carried out.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipe 2 Primer layer 3 Plastic anticorrosion coating 6 Pipe rotating device 7 Thermal spray gun 9 Thermal spray gun drive 10 Thermal spray material supply device

Claims (1)

[Claims] 1. A method for applying an anticorrosive coating of plastic to the inner surface or outer surface of a tubular body, which comprises a modified polyamidoamine cure which has adhesiveness to both the tubular body and the thermoplastic resin powder to be sprayed and does not deteriorate by heat during thermal spraying. Type
Epoxy resin or polychloroprene phenolic resin
The step of applying the synthetic resin primer of 1. to the inner surface or the outer surface of the tubular body to form the primer layer, and the tubular body coated with the synthetic resin primer is allowed to stand at room temperature for at least 30 minutes and at most 120 hours, and then naturally dried. Then, the step of curing the primer layer, and after the drying time has elapsed, after the surface of the primer film is dry, until the tube is completely cured, do not preheat the tube on the primer layer formed on the tube. , Po was also discharged from the spray gun by the combustion flame of the gas mixture discharged from the spray gun
Polyethylene, polypropylene or ethylene vinyl acetate
The thermoplastic resin powder of the polymer is heated and melted, and the droplet-shaped thermoplastic resin powder is sprayed onto the inner surface or the outer surface of the pipe body to spray the thermoplastic resin powder, and the spray gun is used. By rotating the tube with respect to the tube or by rotating the tube with the spray gun in the vicinity of the tube and moving the spray gun in the axial direction of the tube, the inner surface or the outer surface of the tube is changed. And a step of forming a plastic anticorrosion coating having a desired film thickness.