JPS60222177A - Formation of inside surface coating for metallic pipe or the like - Google Patents

Abstract

PURPOSE:To form a coating layer having a uniform thickness by packing a granular resin into the space part facing the part to be coated of the inside surface of a pipe after or while removing the air from said space then welding the resin by heating. CONSTITUTION:The space part 16 facing the part 5 to be coated of the inside surface of the pipe 3 is formed of a core 11 and closing plate 12, 13 and the granular resin is packed into the space part 16. The granular resin in contact with the inside surface of the pipe is heated and welded by a heater 2 to form the coating layer. The granular resin is packed into the space part 16 through a passage 17, a powder supply and discharge hose 18, etc. after the air in said part 16 is removed or while removing said air through a suction port 19, a suction hose 20, etc. in this method. The generation of an air pocket in the part 16 is thus prevented, by which the uniform packing of the granular resin is made possible and the coating layer having a uniform thickness is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a resin coating layer on the entire or partial inner surface of metal pipes using powdered resin (hereinafter referred to as powder).

BACKGROUND ART Conventionally, metal pipes have been widely used, the inner surface of which is coated with an anticorrosive coating layer of bituminous paint or synthetic resin for the purpose of anticorrosion.

Among these, in metal tubes that are welded and joined on-site, the coating layer is thermally affected by welding heat, so an uncoated portion is provided in advance on the inner surface of the tube end. Therefore, after welding and joining at the site, it is necessary to form a coating layer on the uncoated portion of the inner surface of the joint. Further, during use of the metal tube, the coating layer may partially deteriorate or peel off, and it is necessary to form a coating layer on this portion for repair.

Conventionally, a method of applying a bitumen-based paint has been used to form a coating layer on a limited portion of the inner surface of the tube, but this method can be used in cases where the pre-formed coating layer is made of synthetic resin.

This results in the formation of a covering layer that is different from the existing covering layer.

The fusion was incomplete and the corrosion resistance of each coating layer was different, which caused problems in terms of anti-corrosion performance.

As a method to solve this problem, a method was developed in which a powder of the same material as the existing coating layer was heat-fused to the uncoated area to form a coating layer, and the method was patented 1N (Japanese Patent Laid-Open No. 56-11
No. 5668). The coating layer forming step according to the method disclosed in this patent application is performed by the following procedure.

The uncoated parts of the ill-welded joints are ground-treated by polishing, etc.

(2) Heat the part to be coated with a heating device from outside the tube.

(3) Inserting and setting the coating device into the pipe to form a space surrounding the part to be coated, and filling or scattering the powder into the space.

Note that the tube may be heated after it is filled with powder.

(4) After the powder filled or dispersed in the space comes into contact with the inner surface of the tube and an appropriate amount is heated and fused, the excess powder is collected with a collection hose.

(5) After taking the coating device out of the tube, it is reheated using a heating device to completely fuse.

(6) After complete fusion, let it cool or cool it with water from the outside. The coating layer forming process is thus completed.

Although this method is an excellent method in which a coating layer can be formed using powder of the same material at a welded joint or a portion where the coating layer is peeled off, it has been found that there are still some problems. That is, in the method disclosed in JP-A No. 56-115668, powder is introduced into the space formed by the inner surface of the tube and the coating device using a pressure feeding method, and then filled or dispersed. The upper part of the surface is only in momentary contact with the powder, resulting in a partially patchy coating, while the lower part is piled up with accumulated powder, resulting in a thicker coating layer.

It is difficult to form a coating layer with uniform thickness. In the filling method, while filling the powder into the space, an air vent with a filter is designed to release air from the opening, but only air escape is ensured, and air may accumulate in the upper part of the space. The remaining air may not be sufficiently filled with powder, and as a result, a complete coating layer cannot be expected to be formed on the inner surface of the tube facing this area, and it is difficult to form a coating layer with a uniform thickness. It was difficult.

Further, the following problem occurred when collecting excess powder after heat-sealing the powder. That is, after the powder is heated and fused to the desired thickness, the heating of the tube is stopped, and while the tube is allowed to cool naturally, the excess powder filled in the tube is suctioned by a suction blower and air is taken in from a nozzle leading to the outside of the device and stirred. However, when the powder is filled with pressure by pressure feeding, the agitating air that is taken in only by suction has a large flow resistance, making it impossible to easily collect the powder. Even though it takes time to collect the powder and the tube wall temperature gradually decreases during powder recovery, it still exceeds the melting temperature of the powder at the beginning, so even when the powder is recovered, the powder may be fused on a part of the inner surface of the tube. progresses, and the thickness of the coating layer becomes increasingly uneven. In addition, since the heated part during natural cooling has a soft coating layer that is above its softening point, there is a risk that the suction agitated air may create an impact on the surface, creating unevenness, or that the coating layer may be damaged due to accidents such as contact when taking out the device. There is.

The present invention advantageously solves the above-mentioned problems and provides an inner surface of metal tubing.
It is an object of the present invention to provide a method capable of forming a uniform coating layer using powdered resin.

In other words, the first invention of the present application is to fill the space facing the portion of the inner surface of the tube with powdered resin, and to heat-fuse the powdered resin that contacts the inner surface of the tube to the inner surface of the tube for coating. The method for forming the layer is characterized in that the space is filled with powdered resin after or while the air in the space is removed by suction, thereby preventing air pockets from forming in the space. This is a method for forming an inner surface coating of metal pipes, which enables uniform filling of powdered resin and forms a coating layer of uniform thickness. Here, a normal pressure feeding method may be used for transferring and filling the powdered resin, or a suction method using negative pressure within the space may be used for the acidic acid.

The invention in Box 2 of the present invention is in addition to the features of the first invention.

After heating and fusing a desired amount of granular resin to the inner surface of the metal tube, the metal tube is rapidly cooled to stop the formation of a coating layer in excess of the desired amount. Partially, it prevents the powdered resin from being heated and fused, and also prevents the formed coating layer from becoming uneven or damaged, making it possible to form a coating layer with a more uniform thickness. This is a method for forming an inner coating on metal pipes.

□The present invention will be described in more detail below with reference to embodiments shown in the drawings.

FIG. 1 shows an example of a coating device 1 and a heating device 2 used in carrying out the method of the present invention. 5 is shown set at a predetermined position for forming a coating layer. Note that the reference numeral 6 indicates a resin coating layer that is previously applied to the inner surface of the metal tube 3 at a factory.

The coating device l has a hollow cylindrical core 11. A blocking plate 12 is fixed to one end of the core 11 and a rectifying plate 1 is fixed to the other end of the core 11.
4, each occlusion plate 12 has a occlusion plate 13 fixed via
．． A hollow rubber seal ring 15 that can be inflated with compressed air is attached to the outer periphery of the ring 13. These closing plates 12, 13 and the core 11 form a powder filling space 16 surrounding the part of the inner surface of the tube to be coated. Note that the gap between the core 11 and the inner surface of the metal tube 3 is the space part 1.
In order to shorten the powder supply/filling time and the discharge/recovery time, it is preferable to minimize the volume of the container 6 so as to uniformly fill the powder. One of the closing plates 13 (the one on the right in the drawing) has a central tube section 13A and a conical section 13B following it, which conical section 13B has a conical section 13B connected to the end of the core 11 and communicating with the space section 16. shaped powder supply and discharge passage 1
form 7. A plurality of rectifying plates 14 are attached to the passage 17 in parallel in the axial direction. The conical passage 17 and the baffle plate 14 therein direct the powder from the tube part 13A to the space part 16.
It is suitable for uniformly supplying the powder to the tube portion 13A, and conversely for uniformly suctioning the powder from the space portion 6 into the tube portion 13A. The pipe portion 13A is connected to a powder tank 31 of a powder supply and recovery device 30 shown in FIG. 2 through a powder supply and discharge hose 18.

A suction port 19 with a filter is provided near the end of the core 11 on the opposite side from the passage 17, and the suction port 19 is connected to the suction side of a cube blower 32 shown in FIG. 2 via a suction hose 20. has been done. Although one suction port 19 is provided in the illustrated embodiment, the number is not limited to one, and a plurality of suction ports 19 may be provided in the circumferential direction. A large number of nozzles 21 are provided on the cylindrical surface of the core 11, and the tip of a compressed air introduction hose 23 connected to a compressor 33 in FIG. 2 is inserted into the core 11. The nozzle 21 blows out compressed air during powder recovery, stirs and rotates the powder in the space 16, and blows it in the direction of the passage 17, thereby speeding up the recovery of the powder. In addition, when collecting powder, the mixed fluid of powder and compressed air that is being stirred and rotated in the space 16 flows through the passage 1.
7, the water is rectified into an axial flow by the rectifying plate 14, so that it flows through the water supply and drainage basin 18 without any hindrance.

Transport wheels 24 and 25 are attached to both ends of the coating device 1, respectively, so that the coating device 1 can travel within the metal tube 3 to a predetermined position.

In FIG. 2, the powder supply and recovery device 30 is a powder tank 3 containing powder of the same material as the existing coating layer 6.
1. Turbo blower 32. It has a compressor holder 33, etc., and supplies the powder in the powder tank 31 to the space 16 using compressed air, and also collects the powder in the space 16 into the powder tank by the suction force of the turbo blower 32. It is something. Since these can be used as known ones, detailed explanation will be omitted.

Referring again to FIG. 1, the heating device M2 heats the portion of the metal tube on which the coating layer is to be formed to a temperature higher than the melting temperature of the powder, and in the illustrated embodiment, an induction heating coil is used. Note that devices other than induction heating, such as an electric heater or a gas burner, may be used.

Next, a method for forming a coating layer using the above apparatus will be explained.

ii + rst: 'As mentioned above, the coating device 1 is set at a predetermined position inside the metal tube 3, and the heating device 2 is attached to the outside of the coating layer forming section. Next, activate the heating device 2 to heat the inner surface of the tube.

The powder to be coated is heated to a temperature higher than its melting temperature, and then the powder is supplied to the space 16. In this case, the turbo blower 32 is operated to blow the air in the space 16 to the suction port 1.
9 and the suction hose 20, or while removing it by suction, the powder in the powder tank 31 is removed by the hose 18.
The space 16 is supplied and filled through the passage 17. The amount of air sucked by the turbo blower 32 is selected so that the inside of the pipe becomes negative pressure. In this way, the powder is uniformly and quickly filled in the space 16 without creating any air pockets. Note that when powder filling is performed while removing the air in the space 16 by suction, depending on the particle size and shape of the powder, it is not necessary to constantly perform the suction operation during the powder filling operation. It is sufficient to simply perform suction and create a negative pressure inside the tube for a period of time.

The powder filled in the space 16 is sequentially melted and fused to the inner surface of the tube starting from the powder that comes into contact with the inner surface of the tube, thereby forming a coating layer. Since the thickness of this coating layer increases over time.

After the time necessary to form a coating layer of desired thickness.

When the heating device 2 is energized to maintain the temperature, the operation of the heating device 2 is immediately stopped, and the heating temperature rising section is rapidly cooled from the outside surface of the tube by an appropriate cooling method 1, such as water cooling.

This ensures that the covering layer no longer grows and remains at the desired thickness. Note that the heating of the metal tube 3 is not limited to before filling with powder, but may be performed after filling.

Next, the suction force of the turbo blower 32 is applied to the powder tank 31 to bring the inside of the tank 31 into a negative pressure state.

Excess powder in the space 16 is sucked and collected into the tank 31 via the hose 18. At this time, by supplying compressed air from the compressor 33 into the core 11 and ejecting it from the numerous nozzles 21, the excess powder in the space 16 is agitated by this compressed air, and the air is supplied to the passage 17 and the hose 18. The powder is fed under the pressure of compressed air, and the powder is discharged and collected extremely quickly.

Note that although the air ejected from the nozzle 21 may impact the formed coating layer, since the coating layer has already been cooled to below its softening temperature, no unevenness will occur on the surface.

After the powder has been collected, the coating device 1 is taken out. Even in this case, the coating layer is not damaged by the coating device 1.

Thereafter, heating is performed again using the heating device 2 to a temperature higher than the melting temperature.

By forming a complete fused coating layer and finally cooling by cooling with air or water cooling from the outside, as shown in Figure 3,
A covering layer 26 of the same material is formed, partially overlapping the existing covering layer 6 and fixed to the integral G.

In the above example, after the required thickness of coating layer is formed using the filling powder, the coating layer forming part is immediately quenched from the outer surface of the tube and coating layer formation is stopped. Even if they are in contact, the coating layer does not grow, and even if the time difference between the start and end of the discharge and collection of excess powder becomes large, no difference in the thickness of the coating layer occurs. In this way, rapid cooling after forming the coating layer is extremely effective in forming a coating layer with a uniform thickness. However, depending on the powder used, or when it is not necessary to form a very uniform coating layer over the entire coating, rapid cooling from the outer surface of the tube may not be necessary and it may be sufficient to simply allow the powder to cool. For example, powders with a high melting point such as fluorocarbon resin require a large amount of heat when forming the molten coating layer, and the time it takes for the coating layer to grow is also long, so simply stopping the heating by the heating device 2 is sufficient. Subsequent growth of the coating layer does not occur much, and therefore, even if it takes time to discharge and collect the powder, the difference in film thickness does not become so large, and a coating layer with a relatively uniform thickness can be formed.

Next, FIG. 4 shows a modification of the coating apparatus 1 used to carry out the method of the present invention. In the coating device 1 shown in FIG.
The seal bearing 40 of one closing plate 12 and the other closing plate 1
A rotary core 43 is rotatably held by a sealed bearing 42 of a support 41 attached to a rotary core 43, and a motor 44 is used to rotationally drive the rotary core 43. In addition to the suction port 19 and the nozzle 21, a screw blade 45 is provided. Also.

The shaft end of the rotating core 43 is connected to the suction hose 20 through a suitable rotary joint. A compressed air introduction hose 23.46 is connected. The suction hose 20 is connected to the suction port 19 via a pipe inside the core, and acts to suck air from the space 16 when filling the space 16 with powder. The introduction hose 23 functions to supply compressed air into the one-rotation core 43 and blow it out from the nozzle 21 when collecting excess powder. The inlet hose 46 connects to the hollow rubber seal ring 1 via a pipe in the core and a suitable rotary joint (not shown).
5.

The coating device 1 shown in FIG. 4 having the above structure is also set in a tube in the same way as the one shown in FIG. . However, the two methods differ in terms of discharge and collection of excess powder. That is, in the coating device shown in FIG. 4, the core 43 is rotated nine times while sucking the powder from the right tube portion 13A, and most of the excess powder in the space 16 is transferred to the tube portion 13A side by the screw blade 45. send to.

At the same time, a small amount of powder remaining in the small gap between the tip of the screw blade and the surface of the coating layer, where the screw blade does not act, is sent to the pipe portion 13A side by air blown from the nozzle 21 and is discharged. Thus.

The device shown in Figure 4 can discharge excess powder in an extremely short time.

Collection can be carried out. This device is used as described above (because the surplus powder collection time is short, even if there is a slight time difference between the two discharges and collection, there will be no difference in the thickness of the coating layer formed), or when using powder that does not cause much difference in the thickness of the coating layer. If there is no problem, the quenching step after the fusion formation of the coating layer can be omitted, which is very suitable.

In all of the above embodiments, a powder feeding method is used to fill the space 16 with powder, but the powder feeding method is not limited to the pressure feeding method. Ah °ζ is also good. Also.

The apparatus shown in FIGS. 1 and 4 can be used not only to form a coating layer on the uncoated portion of the inner surface of an in-situ welded joint of an internally coated metal pipe, but also to repair a damaged portion of an existing coating layer.

Furthermore, the present invention is applicable not only to the case where the coating layer is formed only on a part of the inner surface of the tube as shown in the above embodiments, but also to the case where the coating layer is formed on the entire inner surface of the tube. FIG. 5 shows an example in which a coating layer is formed on the entire inner surface of the curved pipe 50. In the figure, first, a curved tube 50 is entirely heated in a furnace or the like, and then a powder supply tube 51 is connected to one end of the curved tube 50, and a suction tube 52 equipped with a filter 53 is connected to the other end. After the air inside the curved tube 50 is suctioned and removed by the suction tube 52, or while being suctioned and removed, powder is supplied from the supply tube 51 to fill the curved tube 50, and the powder in contact with the inner surface is heated and fused. After forming the coating layer of a desired thickness, the curved tube 50 is rapidly cooled, the coating layer formation is stopped, and the excess powder inside is discharged by an appropriate method. As described above, an extremely uniform resin coating layer can be formed on the entire inner surface of the three-bent tube 50. The curved tube 50 may be heated not only by a heating furnace but also by other means such as a burner or high-frequency induction heating. Alternatively, an appropriate core may be placed inside the curved tube 50 to fill the powder filling space. You can make it smaller. This method is not limited to forming a coating layer on a curved pipe of the shape shown, but can also be applied to straight pipes, flanges, and those having mechanical joints.

As explained above, according to the first invention of the present application, when the powder is force-fed and filled into the space surrounding the portion of the inner surface of the tube where the coating layer is to be formed, air is suctioned and removed from the space. Therefore, the air pocket that conventionally tends to exist on the filling upper side of the space is eliminated, and a coating layer of uniform thickness can be formed. Furthermore, according to the second invention of the present application, after a desired amount of powder is melted and fused to the inner surface of the tube.

Since this part is rapidly cooled to below the melting temperature of the powder, when collecting the excess powder, there is no possibility that the powder will be partially melted and fused to the previously formed coating layer of uniform thickness. Even if a compressed air jetting nozzle is used during discharge and collection, the jetted air does not cause unevenness in the coating layer, and a smooth coating layer with a more uniform thickness can be formed. As a result, not only can a uniform coating layer be formed on the entire inner surface of the tube, but also a coating layer of uniform thickness made of the same or similar material as the existing coating layer can be applied to a part of the inner surface of the cladding tube, including the uncoated parts and It can be formed completely integrated with the end of the existing coating layer, and a coating layer with excellent corrosion resistance and electrical insulation can be formed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a coating device and a heating device used in the method of the present invention, set in a predetermined position. FIG. 2 is a partially sectional side view showing the coating device of FIG. 1 and the powder supply and recovery device combined therewith. FIG. 3 is a sectional view showing a coating layer formed by the method of the present invention. FIG. 4 is a sectional view similar to FIG. 1, showing a coating device different from that in FIG. 1; FIG. 5 is a horizontal cross-sectional view showing the state in which a coating layer is formed on the entire inner surface of a curved pipe according to the method of the present invention. 1--Coating device 2-Heating device 3--Metal tube 4-Welded joint 5--Uncoated section 6-Existing coating layer 16-Space 18-Powder supply/discharge hose 19-Suction port 20-Suction hose 30 -Powder supply and recovery device 32-Turbo blower agent Patent attorney Kyo Matsu Sanga 1 figure, Fang 3 figure, Fang 4 figure

Claims (2)

[Claims] (1) In a method in which a space facing the portion of the inner surface of the tube that is to be coated is filled with granular resin, and the granular resin in contact with the inner surface of the tube is heated and fused to the inner surface of the tube to form a coating layer. . A method for forming an inner surface coating of metal pipes, characterized in that the space is filled with powdered resin after or while the air in the space is suctioned and removed. (2) In a method of filling the space facing the portion of the inner surface of the tube with granular resin and heating and fusing the granular resin that contacts the inner surface of the tube to the inner surface of the tube to form a coating layer. . After the air in the space is suctioned or removed, the space is filled with granular resin, and further. A method for forming an inner surface coating of metal tubes, which comprises heating and fusing a desired amount of granular resin ψ onto the inner surface of a metal tube, and then rapidly cooling the metal tube to stop forming a coating layer 9 in an amount greater than a desired amount.