JPH0318502Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a surface treatment device for a steel pipe whose outer surface is coated with powder epoxy resin.

Steel pipes coated with external powder epoxy have recently been used in pipelines such as gas pipes and oil pipes in place of polyethylene-coated steel pipes because of their wide operating temperature range.

Once pipelines are installed, they are used for several decades, so corrosion prevention is an important issue.
In addition to the above-mentioned outer surface coating, cathodic protection is usually used in combination.

However, when this cathodic protection is performed, if there is a pinhole or other penetrating damage in the outer coating, the steel surface of the penetrating damage becomes a cathode, and the adhering moisture is electrolyzed by the corrosion protection current, resulting in the generation of hydrogen and alkali. There is a drawback that so-called cathode peeling, in which the coating film peels off, occurs.

Powder expo resin-coated steel pipes have better cathodic peeling resistance than conventional asphalt- or coal tar-coated steel pipes, but they are still insufficient.In particular, cathodic peeling resistance increases as the environmental temperature rises, so Improving cathodic peeling resistance is an important issue for steel pipes coated with a wide range of powder epoxy resins.

The inventors of the present invention have carried out various experimental studies in order to solve these problems and have found that cathode peeling resistance can be significantly improved by applying chromate treatment as a pretreatment.

This invention relates to a surface treatment device that performs surface treatment in the production of steel pipes coated with powder epoxy resin on the outer surface.The invention relates to a surface treatment device that performs surface treatment in the production of steel pipes coated with powder epoxy resin on the outer surface. It is designed so that it can be applied to

Spraying is generally considered as a method for applying the treatment liquid, but spray painting is not preferred in terms of pollution prevention and operational safety when applying the chromate treatment liquid. Additionally, spray painting has the disadvantage that it is difficult to control the amount of treatment liquid applied. Therefore, the present inventors adopted a coating method using a roll coater, and developed a surface treatment method that preheats the steel pipe to a temperature in the range of 50 to 90℃ before that, and at the same time developed a surface treatment device for this purpose. It was developed.

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a front view, and FIG. 2 is a side sectional view. This apparatus is composed of a roll coater 1, a circulation tank 2, a filtering device 3, and a cooling device 4. The roll coater 1 is composed of a roll body 10 and a tray 11, and the roll body 10 is in contact with the steel pipe X from below. As shown in FIG. 3, the steel pipe X is supported by skie rolls 50 and rotates while moving in its axial direction. The roll main body 10 is arranged so that its axial direction substantially coincides with the axial direction of the steel pipe X, and rotates while contacting the steel pipe X. This roll body 10 has a bearing 1 mounted on a U-shaped support frame 12.
It is supported by 3. As shown in FIG. 2, the roll body 10 consists of a hollow roll shell 100 and an elastic body 101 attached to the outside thereof. The elastic body 101 is desirably a material with a hardness (Shore A) of about 40 or less and low absorbency, such as polyurethane. If a soft and highly absorbent sponge or the like is used, the processing liquid will tend to accumulate at the boundary of the contact area with the steel pipe X, causing the temperature of the processing liquid to rise.
Furthermore, it is unsuitable because the treatment liquid tends to contain iron powder attached to the surface of the steel pipe X. On the other hand, if the hardness is too high, it will not conform to the bead of the steel pipe X, which is inappropriate.

The tray 11 is fixed to the support frame 12, stores a chromate treatment liquid therein, and is adapted to immerse the lower part of the outer circumference of the roll body 10 in the treatment liquid. This tray 11 has a semi-cylindrical shape that follows the shape of a roll, and the bottom surface has a semicircular cross section, and is configured so that iron powder, iron rust, etc. coming out of the steel pipe X can easily accumulate on the bottom surface of the tray 11.

The support frame 12 is attached to a base 15 equipped with a cylinder 14, and is configured so that the roll body 10 and the receiving tray 11 can be raised and lowered by vertical movement of the cylinder 14, and can handle steel pipes of various pipe diameters. It's becoming like that.

Note that 16 is a cover.

A pipe 17 is provided at the bottom of the tray 11 and is connected to the circulation tank 2 via a filter device 3 . A cooling device 4 is installed around the circulation tank 2, and is configured to cool the processing liquid and maintain it at a constant temperature.

Another wiring 18 is provided at the upper part of the receiving tray 11 and connected to the circulation tank 2 via a pump 19, so that the processing liquid in the circulation tank 2 is supplied to the receiving tray 11 from the upper part.

FIG. 3 is a layout diagram of the above-mentioned surface treatment apparatus A in a production line for steel pipes coated with powder epoxy resin on the outer surface. As mentioned above, 50 is a ski roll, on which the steel pipe X rotates and advances in the direction of the arrow. Steel pipe X undergoes pre-treatment processes such as blasting,
The preheating device 5 heats it to a temperature in the range of 50 to 90°C. Here, the heating temperature was set in this range for steel pipe X.
This is because if the temperature is lower than 50°C, the drying rate of the treatment liquid is slow and thick coating cannot be achieved, resulting in insufficient adhesion. Moreover, if the temperature exceeds 90°C, the processing liquid becomes overheated, causing safety problems such as liquid scattering. The base treatment device A is arranged downstream of this preheating device 5,
Here, a chromate treatment liquid is applied to perform base treatment. Next, the steel pipe is heated to 230° C. in a pre-heating device 51, sprayed with powdered epoxy resin in an electrostatic coating device 52, and further heated to about 230° C. in a post-heating device 53 to form an epoxy resin film.
Thereafter, it is cooled in a cooling device 54 and subjected to normal post-processing such as inspection and tube end treatment to become a product.

In the structure of the surface treatment apparatus as described above, the roll main body 10 contacts the steel pipe X while rotating, and applies the chromate treatment liquid to the steel pipe X while receiving the supply from the receiving tray 11. Since the steel pipe X moves in the traveling direction at the same time as it rotates, iron powder and rust adhering to the steel pipe X are mixed into the processing liquid that is applied several times by the roll body 10. Due to its own weight, it accumulates on the bottom surface of the tray 11, which has a semicircular cross section, and is discharged from the pipe 17 together with the circulating processing liquid, and is passed through the filter device 3. The post-treatment liquid is in circulation tank 2.
can be stored in The temperature of the processing liquid increases as it comes into contact with the steel pipe X heated to 50 to 90°C, but while it is stored in the circulation tank 2, it is cooled by the cooling device 4.
Maintained at a predetermined temperature.

The processing liquid stored in the circulation tank 2 is again supplied to the receiving tray 11 from the piping 18 via the pump 19, and is subjected to application by the roll body 10.

As explained above, according to the base treatment apparatus of the present invention, since a roll coater is used, pollution and operational hazards can be eliminated, and the thickness of the base treatment film can be easily adjusted. Furthermore, since the temperature of the processing liquid is kept constant and iron powder etc. are removed, stable processing is possible.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the surface treatment apparatus according to the present invention, FIG. 2 is a side sectional view, and FIG. 3 is a layout diagram. 1...Roll coater, 2...Circulation tank, 3...
... filtration device, 4... cooling device, 5... preheating device, 10... roll body, 11... saucer, 12
... Support frame, 13 ... Bearing, 14 ... Cylinder,
15...base, 16...cover, 17 and 18...
Piping, 19...pump.

Claims (1)

[Scope of utility model registration request] A roll coater consisting of a roll body that contacts a steel pipe to apply a treatment liquid and a saucer that immerses the lower part of the outer periphery of the roll body in the treatment liquid; a circulation tank that discharges the treatment liquid from the lower part of the saucer and supplies it from the upper part; A steel pipe coated with powder epoxy resin on the outside, characterized in that it has a filtration device provided between the circulation tank and the receiving tray for passing through the processing liquid, and a cooling device provided in the circulation tank for cooling the processing liquid. Surface treatment equipment.