JP3976308B2 - Method of electrostatic coating of steel tower - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of coating a metal tower such as a transmission line tower, a radio tower, a sign tower, and a notice tower by electrostatic coating.
[0002]
[Prior art and its problems]
Transmission line towers and the like that are exposed to the outdoors for a long period of time are usually coated with a paint in order to extend the life and impart aesthetics. Conventionally, these steel towers have been painted by using a scaffolding log or the like to form a frame around the steel tower and then attaching a paint splash prevention net to cover the steel tower. It was done.
However, since the conventional coating method is painting using a brush or a roller, the efficiency is not sufficient, and it takes a long time to paint, and it is difficult to paint the narrow part and the back part. Have. Holding hands with paint tools such as brushes and paint cans can be dangerous when working at heights because both hands are blocked. Furthermore, many years of experience are required to paint a coated surface with a uniform film thickness and an excellent finished appearance, and the finish varies depending on the skill of the operator.
[0003]
[Means for Solving the Problems]
The object of the present invention is to eliminate the above-mentioned various defects in the painting of steel towers such as power transmission line towers, and as a result of extensive research, a part or all of the vicinity of the steel towers is formed with a conductive mesh net. It was found that the object can be achieved by coating a steel tower by an electrostatic coating method in an interior covered with a jig and surrounded by a net, and the present invention has been completed.
That is, the present invention is characterized in that a part or all of the vicinity of the steel tower is covered with a conductive mesh net through a jig, and the steel tower is painted by an electrostatic coating method inside the net surrounded by the jig. The present invention relates to a method for electrostatic coating of steel towers.
[0004]
The steel tower electrostatic coating method (hereinafter referred to as “the present method”) according to the present invention will be specifically described below.
The steel tower in this method is a structure assembled into a truss structure using conductive metals such as angle steel, H-shape steel, I-shape steel and steel pipe material (hollow pipe), for example, for sending electric power Examples include radio towers for receiving and transmitting radio waves from power transmission towers, Tokyo tower, etc., notice towers such as Osaka Tsutenkaku, sign towers and monuments installed at airfields, etc. The height of these steel towers is not particularly limited, and 2 m or more, preferably in the range of 3 to 200 m is suitable.
The mesh net used in this method prevents the paint fine particles sprayed from the electrostatic coating machine from being applied to the object to be coated (the surface of the steel tower) and scattered to the outside. It is effective to improve the coating environment inside the net by adsorbing it to the net. This net is a sheet of synthetic resin fibers knitted in a mesh shape. Examples of the material of the synthetic resin include known ones such as polyethylene, nylon, Teflon (registered trademark of DuPont), polyester, and acrylic resin. The mesh size of the net is usually in the range of 30 to 100 mesh.
[0005]
Further, these mesh nets are required to have conductivity, and the degree thereof is suitably in the range of 0.5 to 1.0 MΩ / 500 V based on the insulation resistance value. As a method for imparting conductivity to the net, for example, a conductive material (for example, carbon, graphite, etc.) is mixed in the synthetic resin fiber constituting the net, or a conductive paint is applied to the net. Among these, it is more preferable to apply a conductive paint because the strength of the net itself is not lowered.
As the conductive paint to be applied to the net, known organic solvent-based or water-based paints containing a conductive substance (for example, carbon, graphite, etc.) in a base resin such as polyester resin, alkyd resin, and epoxy resin. can give. It is preferable to apply the conductive coating to the net so that the net of the net is not blocked by spray coating, dip coating, or the like.
[0006]
In order to cover part or all of the vicinity of the steel tower, there may be a single conductive mesh net, but it is possible to use multiple layers to prevent scattering of uncoated paint particles to the outside and uncoated paint particles. Is preferable in terms of efficient adsorption, and double or triple is particularly suitable.
The size and shape of the mesh net are not particularly limited. For example, it is a square having a width of 1.8 m and a length of 5 m to 10 m. Based on this, the size, shape, height, etc. of the steel tower are used. They can be used together as appropriate. Examples of the net joining method include a hook type, a string type, a magic tape (registered trademark of Kuraray Co., Ltd.) type, an insulation lock type, and an interlock type. Among these, the interlock type that connects the end portions of the nets in an overlapping manner can be connected without gaps, and therefore it is more preferable because it can efficiently prevent the uncoated paint particles from being scattered outside.
[0007]
If the conductive net comes into contact with the steel tower due to wind pressure, etc., the coating operation will be hindered, and if the wet paint film is touched, the paint film may adhere to the net and reduce the finished appearance. It is preferable to cover so that the sex net does not contact the steel tower due to wind pressure or the like.
It is desirable to use a jig to cover the conductive mesh net so that it does not contact the steel tower. The structure of the jig is mainly composed of a fixing portion that is fixed to a truss structure portion such as a tower column and a ground wire portion, and an armrest portion that extends from the fixing portion. The fixing portion preferably has a structure that can be easily attached to and detached from the steel tower. As a method of fixing to the steel tower, bolt fastening or a clamp type (such as a catch clamp) is suitable. The length of the armrest is preferably such that the distance between the steel tower and the conductive net is about 50 cm to 1 m. The arm metal part itself is preferably a mechanism that can be expanded, contracted, moved, or folded so that it can be adapted to the scale, form, etc. of the steel tower. In addition, it is suitable to provide an attachment member for facilitating attachment of the mesh net at the end of the arm metal part. The material of the jig is preferably made of FRP or reinforced plastic from the viewpoint of strength, but even if it is made of metal, it can be used as long as it is provided with an insulating coating for preventing electric shock. Furthermore, it is effective for the surface of the jig to be insulative to prevent electric shock during painting. Furthermore, it is suitable that the jig is lightweight in order to efficiently perform operations such as attachment to a steel tower and transportation.
[0008]
A known electrostatic coating machine for coating a steel tower with paint can be used. Specifically, an electrostatic air spray system, an electrostatic airless spray system, an electrostatic airless spray system, etc. are suitable, and these coating machines include an electrostatic coating gun, an air compressor, a plunger pump for controlling paint pressure, and a control. It is composed of units. It is suitable that the DC applied voltage during electrostatic coating is -30 to -80 KV, the paint pressure is 2 to 8 MPa, and the assist air pressure is 0.2 to 0.8 MPa. As for the specifications of the plunger pump for paint pressure feeding, the suction method is preferably a direct suction method, a maximum pressure of 12 MPa, and a maximum discharge amount of 6 liters / minute.
[0009]
The distance from the tip of the spray gun to the surface to be coated (steel tower) is preferably 20 to 40 cm, and the coating film thickness is preferably 20 to 100 μm as a dry coating film. The air compressor for paint and air pumping and the electrostatic coating machine are connected by an air pumping pipe, and the distance is usually 5 to 30 m. Therefore, if the height of the steel tower exceeds this level, painting becomes difficult. In addition, it is necessary to suspend equipment such as a paint tank and a plunger pump for paint feeding on the upper part of the tower with a storage box.
A known paint can be used as a paint to be applied to the steel tower. Specific examples include organic solvent-type or water-based paints such as chlorinated rubber, epoxy resin, polyurethane resin, alkyd resin, polyester resin, acrylic resin, acrylic silicon, and fluororesin. The solid content of these paints during electrostatic coating is preferably 30 to 70% by weight, and the electrical resistance value of the paint during coating is preferably 0.3 to 1.0 MΩ. These can be used as undercoating paints, intermediate coatings and top coatings, and according to the purpose of the tower, they are appropriately selected from these to form a single-layer coating film or two or more multilayer coating films Is also possible.
[0010]
In this method, in which part or all of the steel tower is covered with a conductive mesh net and the paint is electrostatically applied to the steel tower inside the tower, of the fine paint particles sprayed from the coating machine, it has not been applied to the steel tower. Most of the coated fine particles are electrically attracted to the conductive net, but there are also those that float further and eventually fall to the ground surface. Therefore, it is preferable to attach a suction device for sucking the air inside the steel tower surrounded by the conductive net. Specifically, a dust collector with a duct fitted with a filter or the like is installed on the ground, and one opening of this duct reaches the inside of the steel tower surrounded by a conductive net. When activated, the air in the vicinity of the opening is sucked, purified by the dust collector, and released to the outside. In other words, by installing the device, unpainted paint particles floating in the air inside the tower surrounded by the conductive net are sucked and captured by the dust collector, and only clean air is external Therefore, the recovery rate of uncoated paint fine particles is further improved. By installing this apparatus, an air flow is generated inside the steel tower surrounded by the conductive net, and the suction rate of uncoated paint fine particles is improved.
[0011]
This method is preferably performed in the order of the following steps, but is not limited to this step alone.
Process 1: The jig | tool for attaching a conductive mesh net | network to the appropriate part of a steel tower is mounted | worn. The lower part can cover the entire surface at the same time, but the upper part depends on the stopping condition of the transmission line, and is mounted at a position where a safe separation can be maintained from the live line part.
Step 2: A conductive net is attached to the tip of the arm part of the jig to cover part or all of the steel tower. The covering portion can be arbitrarily selected according to the type, shape, and scale of the steel tower. For example, in the power transmission tower, it is preferable to cover a part where power transmission is partially stopped, for example, the upper one side, the entire upper part, or the entire tower (non-live line part). It is preferable to coat the radio tower, advertising tower, sign tower, monument and the like other than the power transmission tower after covering the entire surface.
Process 3: The base of the steel tower is adjusted as follows. Specifically, (1) the second type keren is processed by an electric tool such as a desk sander or grinder, and (2) the third and fourth type kelen is processed by a sandpaper, a wire brush or the like. (3) It should be noted that rust, old paint film, dust, etc. are captured on the net and do not scatter outside the tower.
[0012]
Process 4: Painting by electrostatic painting. It is preferable that a painting worker on the tower wears a Class A safety belt for painting work, and uses a high throw (3 m) for painting work and a moving rope (3 to 5 m) with a lip for elevating and painting the steel tower. One vertical guide rope should be placed on each leg for 154KV or less, and one rope going through the tower is preferred. For 275KV or more, one vertical guide rope for each leg and one for the center of each surface. It is preferable to do.
In principle, it is necessary to use a framework that can be removed and attached to the frame material to maintain the distance between the steel tower and the conductive mesh net, and that can accommodate the scale of the steel tower and different structures. It is preferable not to use and to attach an elastic pipe between the columns of the steel tower as necessary. Since this pipe is shorter than the scaffold log when in use, it is convenient to handle and can be shrunk when stored, so it does not require a large area and is preferable.
[0013]
Using a grounded object (steel tower) as an anode and an electrostatic coating machine as a cathode, when a high DC voltage is applied between them, an electric field is formed between the two electrodes and atomized from the atomizer at the tip of the electrostatic coating machine. The fine paint particles are negatively charged and sucked by the positive object to be coated to form a coating film on the surface of the steel tower. Since the coating film is also formed on the back side of the iron part of the truss structure, the workability is improved. The fine paint particles that have not been applied to the object are scattered as they are, reach the conductive net, and can be sucked and collected there. If the net is non-conductive, the fine particles of paint are difficult to be sucked in and float in the space surrounded by the net for a long time, which is unfavorable for workers in terms of safety and hygiene. .
Step 5: After the coating is completed and the coating film is dry-cured, the method is completed by removing the conductive mesh net, the jig, the stretch scaffold, and the like.
[0014]
【Example】
Examples relating to the present invention will be described.
Example 1
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
A 66KV ground wire single-strand tower with a height of 30m was painted by electrostatic coating method assuming a one-line stop. First, the fixing portions of the net mounting jigs 2a to 2l were attached to appropriate locations such as the ground wire portion, the end of the armature portion, and the steel tower support of the steel tower 1. The length of the brace part of the jigs 2a to 2l is 50 cm to 1 m. Next, a conductive mesh net having a size of 1.8 m × 5 m was attached to the tip of the arm part of each of the jigs 2a to 2l attached while being connected by an interlock type so as not to cause a gap between the nets. The net used is a raschel knitted polyethylene fiber (mesh size is about 50 mesh), and is given conductivity by applying a conductive carbon coating (insulation resistance is 0.7 MΩ / 500V), used in duplicate. All of the tower 1 was covered with this conductive net (3a and 3b).
[0015]
Inside the hood covered with the conductive nets 3a and 3b, rust on the surface of the steel tower, blisters, cracks, dirt, etc. on the old paint film were removed using a desk sander, wire brush, spatula or the like. Rust, coating film pieces, etc. scattered by this work fell to the lower part and were collected, and were hardly scattered outside the net.
The electrostatic coating apparatus includes an electrostatic coating gun, an electric plunger pump 4 and a control unit 5. The specifications of the electrostatic coating gun are as follows: the voltage is DC-60K volts, the paint pressure is 5-6 MPa, the assist air pressure is 0.2-0.4 MPa, and the cable length is 30 m. The electric plunger pump 4 is a direct suction type and has a maximum pressure of 12 MPa and a weight of 50 kg. The control unit 5 has an applied voltage of DC-60 KV, an output adjustment of a switching type, a cutoff current range of 30 to 150 μA, an input voltage of AC 100 V ± 10%, and a weight of 5 kg.
[0016]
Epoxy resin paint “Epomarine GX” (trade name, undercoat paint manufactured by Kansai Paint Co., Ltd.) and urethane paint “Letane 6000” (trade name, top coat paint manufactured by Kansai Paint Co., Ltd.) were used as the paint. These electric resistance values are 0.3 to 1.0 MΩ.
The electric plunger pump 4 and the control unit 5 are installed, the painter raises the step bolt with an electrostatic paint gun, and the diagonal material during the painting work of the steel tower covered with the conductive nets 3a and 3b. The iron tower 1 was electrostatically coated so that the distance from the tip of the gun to the surface to be coated was about 25 cm, using a horizontal material or the like as a scaffold. Even without the experience of the operator, it was possible to easily paint tower cross-fired intersections, armature tips, bolt concentrating points, etc., where painting was difficult. The coating thickness is about 40 μm for each of the undercoat and the topcoat. The film thickness of the coated film was almost uniform with no variation and good smoothness.
The attachment and detachment of the jigs 2a to 2l to the steel tower 1 is simpler than the conventional scaffold log and can be performed in a short time. Electrostatic coating has shortened the work time by about one-third compared to conventional brush coating. Since the supply of paint decreases when the tower height exceeds 30 m, it is preferable to move the coating machine to the upper part.
Most of the paint particles sprayed by electrostatic coating and not applied to the steel tower 1 are applied to the conductive nets 3a and 3b. Therefore, the inside surrounded by the nets 3a and 3b has good visibility, and the painting workability is improved. Will not be reduced.
[0017]
【The invention's effect】
1. Since electrostatic coating is performed while covered with a conductive net, the scattered uncoated paint particles do not stay in the air for a long time and are immediately applied to the object and attracted to the net. In addition, it hardly scatters to the outside, and the painting work can be performed smoothly and is excellent in safety.
2. Because it is an electrostatic coating method, it does not require skill as compared with brush coating or roller coating, can reduce the coating time, and can easily paint narrow spaces. Furthermore, since it was possible to paint a thick film with a single coating, it was possible to reduce the number of coating steps, and the coating film had a uniform film thickness and an excellent finished appearance.
3. The jig for attaching the conductive mesh net is easy to attach and detach, can be used repeatedly, can easily cope with steel towers of different scales and shapes, and compared to conventional scaffold logs Because of its small size, the painter's movement in the tower was smooth and the paint workability was improved.
4). Since electrostatic coating is performed inside the conductive net, most of the scattered uncoated paint particles are collected, rarely leaking outside the tower, and almost free to float inside the tower. I can't.
In FIG. 1, an air compressor 6 and a generator 7 are also components of the electrostatic coating device, and an intake duct 8 and a dust suction device 9 are configured of a dust collecting device that sucks and purifies floating uncoated paint particles in the net. Is an element.
[Brief description of the drawings]
FIG. 1 is a schematic view for explaining an electrostatic coating method for an upper part of a steel tower according to the method of the present invention.
FIG. 2 is a schematic view for explaining an electrostatic coating method for a lower part of a steel tower according to the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel tower 2a-2l Net installation jigs 3a and 3b Conductive mesh net 4 Electric plunger pump 5 Control unit 6 Air compressor 7 Generator 8 Intake duct 9 Dust collector

Claims (2)

An electrostatic painting method for a steel tower in which a steel tower is painted by an electrostatic painting method inside an encircled conductive net, and at least a part of the steel tower or at least a part to be painted is Conduction of a jig composed of a fixed part detachably fixed to the truss structure part and a brace part extending from the fixed part to a certain length and provided with a conductive mesh net attachment member at the end part The DC applied voltage is −30 to −80 KV inside a conductive composite mesh net that is formed by connecting a plurality of rectangular conductive mesh net units through a conductive mesh net mounting member and is spaced apart from each other. Electrostatic coating was performed under the conditions of a paint pumping pressure of 2 to 8 MPa and an assist air pressure of 0.2 to 0.8 MPa, and the conductive composite mesh net that was not sucked and captured by the conductive composite mesh net Apply paint fine particles Electrostatic coating method tower, characterized by completely captured by the mouth opening is ducted dust collector to reach the tower interior surrounded by conductive composite reticulated net. The electrostatic coating method according to claim 1, wherein the steel tower is a power transmission line steel tower .

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