JPS6227869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an anti-corrosion layer using powdered resin on an in-situ joint or a limited inner surface of metal pipes.

Generally, an anti-corrosion coating layer is formed on the inner surface of the tube using bituminous paint or synthetic resin for the purpose of preventing corrosion.

However, in the case of metal pipes that are welded and installed at the piping site, if an anti-corrosion coating layer is provided over the entire length of the inner surface of the pipe at the factory,
Since the anti-corrosion coating layer on the tube end is affected by welding heat during welding and joining, when forming the anti-corrosion coating layer on the inner surface of the tube body in a factory, an uncoated portion (bare steel surface) is provided in advance on the inner surface of the tube end.

Previously, in the case of pipes with a bituminous inner corrosion protection layer, the unpainted areas were brushed or coated with a coating device using a material of the same quality as the anticorrosion material used in the factory. When the anti-corrosion material used is a synthetic resin, if a bituminous anti-corrosion material, which is different from this material, is applied to the unpainted area, the density and fusion of each anti-corrosion material will be incomplete, causing problems in terms of anti-corrosion performance. In addition, in order to take advantage of the features of the factory coating layer, flange joining is generally used instead of welding, but flange joining requires a considerably large joint diameter and requires packing and numerous bolts. This poses a problem in that the structure is complicated and the cost is high.

The object of the present invention is to provide a method for forming an anticorrosive layer on joints or limited inner surfaces of metal pipes, which can advantageously solve the above-mentioned problems.

Next, embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a filling method of a powder resin coating apparatus used in carrying out the present invention, and FIG. 2 shows an example of a dispersing method.

In the case of Figure 1, there is a hollow rubber seal ring 4 around the periphery.
A pair of circular obstructing plates 5, 5' are arranged at intervals slightly longer than the length of the metal tubing joint or the limited inner surface uncoated portion, and each circular obstructing plate 5,
5' is fixed to both ends of the center shaft 6 which is arranged concentrically with this, and one circular blocking plate 5 has a pressure feed port 11 for introducing powdered resin and excess powdered resin after heat fusion. A collection port 10 is installed to collect the
Furthermore, an air filter 22 for air removal and air nozzles 23, 23' for stirring during resin recovery are attached to the circular closing plate 5'. Note that an operating tube 7 for moving the device is fixed to the center of the coating device.

Further, the pressure feeding port 11 and the recovery port 10 are fixed to a support frame 9 having wheels 8 arranged at regular intervals in the circumferential direction and the longitudinal direction of the pipe.

Furthermore, a pressure feed hose 1 is provided at the powder resin pressure feed port 11.
3 is connected to the recovery port 10, and a recovery hose 12 is connected to the recovery port 10, and each is connected to a powder resin supply and recovery device 24 shown in FIG. 4 provided outside the tube.

In the case of Fig. 2, the air nozzles 23 and 23' in the case of Fig. 1 are omitted, and instead, a powder resin discharge port is provided on the circumferential surface of the shaft of the porous cylinder 6'. It has the same function as , and almost the same result can be obtained.

When applying this invention to form an anticorrosion layer on joints or limited inner surfaces of metal pipes, firstly, a metal pipe 15 such as a steel pipe is coated with a factory coating layer 14 on the inner surface of the portion excluding the inner surface of the tube end. After these are joined by welding 16 at a piping construction site, the uncoated inner surface 1 or a limited inner surface of the joint is subjected to surface treatment using a polishing device or the like.

The next step is common to both FIG. 1 and FIG.
A heating device 17 consisting of an electric heater or a gas burner is set, and the heating device 17 is used to heat the uncoated inner surface 1 to a temperature higher than the melting temperature of the resin to be coated at the joint or a limited inner surface (for example, 120° C. in the case of polyethylene). After heating, the powder resin coating device 2 or 3 is set so that a space for filling or dispersing is formed inside the uncoated inner surface 1 or the end of the factory coating layer 14, and then installed outside the pipe. The powder resin coating device 2 or 3 is passed from the powder resin supply and recovery device 24 through the pressure hose 13.
and the uncoated part, and the filled or scattered powdered resin is fused to the inner uncoated part 1 or both ends of the factory coating layer 14, and excess resin is removed as necessary. is collected by the collection device 24, the joint inner surface anti-corrosion layer 18 is formed, and then the coating device 2 or 3 is taken out of the tube.

In addition, after forming the inner surface anti-corrosion layer 18 at the bonded portion or a limited portion as shown in FIG. 3 in this manner, it may be reheated by the heating device 17 to further completely fuse.

Finally, by cooling by air or cooling with water from the outside, the factory coating layer 14 and the joint inner surface anticorrosion layer 18 are integrated, as shown in FIG. 3, and each layer 14,
It is possible to form a uniform synthetic resin anti-corrosion coating layer in which the ends of 18 are overlapped and fused to each other.

When carrying out this invention, as a heating device for heating the uncoated portion 1, an electric heater or a gas burner may be used in place of the induction heating device. May be heated.

Further, the timing of heating may be before or after filling the granular resin, or may be performed at the same time. Furthermore, humidity differences may be added partially.

Next, the type of resin constituting the joint inner surface anticorrosion layer 18 may be the same as that of the factory coating layer 14;
Or it may be something similar.

Example 1 using the filling method (Figure 1) A steel pipe whose inner surface is lined with polyethylene to a thickness of about 1 mm is welded, and a total of about 24 cm of uncoated space is placed in the longitudinal direction of the pipe, about 12 cm in front and back, centering on the weld line. The joint portion of an 8-inch steel pipe in section 1 was lined with powdered polyethylene.

(1) First, pre-treat the uncoated part and the coated end, place the coating device 2 with a length of about 50cm in the steel pipe with the weld line as the center line, and place the sealing tube 1.
The coating device 2 is inflated with atmospheric air and sealed while being fixed.

(2) Powder and granule are fed and filled into the coating device 2 by the powder and granule resin supply and recovery device 24 .

(3) Approximately 35cm around the welding line while applying pressure.
is heated from the outside of the pipe using an induction heating coil at approximately 250℃.

(4) Stop the pressure feeding 30 seconds after raising the temperature, switch to collecting the powdered resin, completely collect the unwelded resin, and take out the coating device 2.

(5) Using a 50cm induction heating coil, the welded area is again held at approximately 200℃ for 3 minutes to completely melt the powdered resin, and then cooled with water.

As a result of the above, a seamless coating with a thickness of approximately 1 mm was completed.

Example 2 using a filling method The specifications of the steel pipe used were the same as those in Example 1, so a description thereof will be omitted.

(1) Pre-treat the uncoated part and the coated end, and cut it to a length of approx.
A 50 cm coating device 2 is installed inside the steel pipe with the weld line as the center line, and about 35 cm of the central portion is heated to about 200° C. from the outside of the steel pipe by an induction heating coil.

(2) Polyethylene powder is fed and filled into the coating device 2 from the powder resin pumping tank 19 by the powder resin supply and recovery device 24, and held under pressure for about 1 minute.

(3) After that, the pressure feeding is stopped, the device is switched to collect the powdered resin, the excess powder that has not been welded is completely removed, and the coating device 2 is taken out.

(4) Furthermore, while moving the induction heating coil in the direction of the tube axis, the welded area is reheated to approximately 200°C, and after the resin is completely melted and fused, it is cooled with water.

As a result of the above, a seamless polyethylene coating with a thickness of approximately 1 mm was completed.

Example using the dispersion method (Figure 2) A 10-inch steel pipe with internal polyethylene lining was welded together, and the uncoated part 1 around the welded part, about 15 cm at each end of the pipe, about 30 cm in total, was lined by the following method. Summer.

(1) Pre-treat the uncoated part and the end of the coating (price coating), install the coating device 3 with a length of about 60 cm inside the pipe with the weld line as the center line, and apply the coating from the outside of the steel pipe with a burner. The center part is about 40cm
Heat to approximately 250℃.

(2) The powder resin supply and recovery device 24 spreads polyethylene powder almost uniformly over the entire circumference of the inner surface of the steel pipe from the spray holes of the coating device 3.

(3) After spraying for about 2 minutes, take out the coating device 3.

(4) Then, heat and maintain the welded part of the powdered resin from the outside of the steel pipe at about 200℃ again using a burner.
The powdered resin was completely melted and fused, and then cooled with water.

As a result of the above, a seamless coating with a thickness of approximately 1.2 mm was completed.

According to the present invention, before or after heating the uncoated portion 1 of the joint or limited inner surface of metal pipes, a powder resin coating device applies powder resin of the same or similar quality to the factory coating portion. 2 or 3, the uncoated part 1 is filled or sprayed and heat-fused, so it can be applied to straight pipe joints of metal pipes or the uncoated part 1 of limited inner surfaces in factories or on-site using extremely simple means. The anticorrosion layer 18 can be integrally formed, and the anticorrosion layer 18 can also be formed on curved pipe portions or irregularly shaped portions by making the central axis of the present coating device flexible.

In addition, since the ends of the inner surface anti-corrosion layer 18 can be overlapped and fused to the ends of the factory coating layer 14, these layers can be completely integrated to create a coating with excellent corrosion resistance and electrical insulation. Furthermore, the limited covering range of the metal tube is partitioned by a pair of circular closing plates 5, 5' having a seal ring 4, and the powdered resin is filled or dispersed. Since only a small amount is required, effects such as being economical can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional side view of the powder resin coating device used in the filling method of the present invention, and Fig. 2 shows the state in which an anticorrosive layer is formed on the inner surface of the joint of a metal pipe by the dispersion method of the present invention. Vertical side view of powder resin coating device,
FIG. 3 is a longitudinal side view showing a state in which the formation of an anti-corrosion layer has been completed on the inner surface of the joint of a metal pipe, and FIG. FIG. 2 is a longitudinal side view of the granular resin supply and recovery device. In the figure, 1 is an uncoated inner surface, 2 and 3 are powder resin coating devices, 4 is a rubber hollow seal ring, 5 and 5' are circular closing plates, 6 is a center shaft, 6' is a perforated tube, and 7 is a coating Operation tube for moving the device, 8 is a wheel,
9 is a support frame, 10 is a recovery port, 11 is a pressure feed port, 12 is a recovery hose, 13 is a pressure feed hose, 14
15 is a factory coating layer, 15 is a metal pipe, 16 is a welded joint of the metal pipe, 17 is a heating device, 18 is an anti-corrosion layer on the inner surface of the joint of the metal pipe, 19 is a granular resin pumping tank, 2
0 is a powder resin supply and recovery tank, 21 is a turbo blower, 22 is an air filter, 23 and 2
3' is an air nozzle for stirring the resin, and 25 is a compressor.

Claims (1)

[Claims] 1 Support frame 9 with wheels 8 for coating powdered resin on the inner surface of metal pipes or a limited uncoated area of metal pipes coated on the inner surface
A pair of circular closing plates 5, 5' having a central shaft 6 supported by a central shaft 6, and a seal ring 4 concentrically attached to both ends of the central shaft 6, and a pump for pumping powdered resin.
The pair of circular blocking plates 5, 5' in the coating device, which is equipped with collecting means, are arranged at an interval slightly longer than the length of the uncoated portion in a limited range inside the metal pipe, and then A heating device placed on the outside of the metal tube heats a limited range of uncoated portions of the metal pipes, and the coating device coats the central shaft 6 with powdered resin or powdered resin of the same or similar quality as the coated portion. A method for forming an inner surface anti-corrosion layer of metal pipes, characterized by supplying the powdered resin between the uncoated part and heating and fusing the powdered resin to the uncoated part in a limited range inside the metal pipe.