KR100573688B1 - Anti-rust lining method by epoxy anti-corrosive coating liquid injection method inside the welded joint of steel pipe. - Google Patents

Abstract

The present invention is a method of rust-proof lining using a method of injecting the epoxy resin liquid into the uncoated portion of the weld joint portion inside the pipe after welding the inside and outside of the steel pipe when connecting the water coating coating steel pipe for pipes. More specifically, the plain pipe, bevel end, and bell end weld joints, which are generally used to connect water coated steel pipes, are used to connect the inner and outer parts of the steel pipes, and then to weld the steel pipes. To release lining of the unpainted part inside by injecting solvent-free epoxy paint solution, a release rubber plate ring (hereinafter referred to as rubber plate ring) which is not attached to epoxy resin is lined inside the pipe. It is a method of forming a perfect rustproof lining film by injecting and filling a solvent-free epoxy anti-corrosive paint into the space after making a welded partial steel pipe and a space by tightly fixing it.

Water coating coating steel pipe is about 6m in length, but the inside of the pipe where the pipe is welded and welded is dark and narrow like a cave, so the rust-proof coating work of the steel pipe welded joint is precisely done by the manual method of the contractor. It becomes an unsuitable environment and causes a disadvantage of shortening the life of the pipe due to the occurrence of corrosion inside the pipe after the passage of the pipe.

Therefore, the present invention is a method that can eliminate the defects caused by the manual work of the contractor and the defects caused by the working environment inside the pipe to completely remove the gap that can cause corrosion by injecting a solvent-free epoxy paint liquid in a liquid state. After sealing and peeling and separating the rubber plate ring after complete curing, it is possible to complete the method of welded steel pipe to maximize the life of the coated steel pipe for water.

Coated Steel Pipes for Water. Solvent free epoxy paint. Steel pipe welding joint. Antirust coating. Rubber plate ring. Tight band.

Description

Anti-rust lining method by epoxy anti-corrosive coating liquid injection method inside the welded joint of steel pipe. {An anticorrosion lining method for the inside of the welded pipe by injection of anticorrosion epoxy paint.}

Figure 1a is a cross-sectional view of the epoxy anti-corrosive coating method of the inner surface of the water coating coating steel pipe bell end weld joint

Figure 1b is a cross-sectional view of the inner surface of the anti-corrosion lining steel pipe bell end weld joint

Figure 2a is a cross-sectional view of the epoxy anticorrosive coating method of the inner surface of the water coating coating steel pipe bevel and plain end weld joint

Figure 3a is a close-up bend front view

Figure 3b is a detailed side and front view of the tight bend tightening bolt and nut structure

Figure 4 is a cross section of an epoxy anticorrosive paint injection and exhaust valve connection

<Description of Major Codes in Drawings>

1. Steel pipe 2. Steel pipe outer coathouse 3. Steel pipe inner coating

4. Weld bead 5. Close bend 6. Release rubber plate ring

7. Weld joint inner space 8. Injection valve 9. Exhaust valve and nibble

10. Antirust lining hardened coating film 11. Upper close bend 12. Lower close bend

13. Close tightening nut 14. Close tightening bolt 15. Upper close bend support plate

16. External nibble 17. Internal nibble 18. Inlet valve connection or exhaust nibble

19. Exhaust valve connection or injection nibble

The present invention is to be a welding joint method when connecting the water pipe coating water pipes, so that the welded parts should be rustproof after the internal and external welding of the steel pipe. When manufacturing coated water pipes for water supply (KSD3565-2002) are left unpainted in consideration of welding both ends of steel pipes, this part is rust-proofed at the site of burying pipes after welding. shall.

The welding joining method of steel pipe is mainly welded in three types, and there are a plain end method, a bevel end method, and a bell end method. The inner side of the uncoated portion of the welded joint of the waterworks coated steel pipe is deposited in water for a long time during water use, so if it is not thoroughly rusted, this part will corrode and the life of the coated steel pipe will be reduced very short, resulting in economic loss. In addition, the water supply coating steel pipe is mainly a large diameter pipe, which may cause a disaster due to the rupture of the pipe. The anti-corrosion painting work of the inner weld joint of the water coating coating steel pipe has a narrow inner space due to the connection of the steel pipe, and it becomes a very dark and long cave-like form. It is very difficult to get a perfect rustproof coating.

In the related art, when the welding is completed, the contractor manually paints the epoxy resin paste in a paste state with a spatula or a plastering knife, or the epoxy resin antirust paint with a brush or a roller. Due to such poor working environment, it is difficult to smooth the pretreatment of the surface to be coated, precise construction is impossible, it becomes very difficult to construct permanent rustproof coating due to uneven thickness of the coating or pinhole, etc. It takes about 1 ~ 2 days, so it is damaged before the coating is hardened due to the vibration of the steel pipe due to the laying of the steel pipe and the coming and going inside the pipeline of the worker. Corrosion of the joints shortens the life of the steel pipe and causes economic losses.

In order to completely rust-proof the inside of the special environment inside the welded joint pipe of the water coating coating steel pipe for water use, the present invention removes the welding slag and the welding sputter or the protruding part harmful to the coating after the welding of the steel pipe. After removing the coating film lost due to welding heat, the edge of the rustproof coating film on the inner surface of the straight pipe is roughened with sand paper. In this part, a ring 6 having the same inner diameter of a steel pipe made of a release rubber sheet is installed as shown in FIGS. 1A and 2A, and a close bend 5 is installed and fixed at both ends of the edge of the rubber sheet ring. Tighten the bolts of the tight bends tightly so that there are no gaps with the inner coating. The release rubber plate ring can be used by making a ring using Teflon resin coated on the surface of the rubber plate or urethane rubber or silicone rubber so that the epoxy resin liquid to be injected can be easily separated from the release rubber plate ring. It is also possible to apply a release agent to the ring and use it as a rubber plate ring (Fig. 3a). Thus, when the rubber plate ring is installed, a space 7 is formed between the inner surface of the steel pipe welded joint and the rubber plate ring, so that an epoxy resin antirust paint is injected into the space. It is a method to harden by making. In the configuration of the rubber plate ring, an injection valve 8 of an epoxy resin rust-preventive paint is provided at the bottom, and an exhaust valve 9 is provided at the top of the rubber plate ring. Solvent-free epoxy resin anti-corrosive paint is injected through the lower injection valve (5) with a mixed injection pump, and the epoxy resin liquid penetrates through all the gaps while exhausting the air in the inner space to the upper exhaust valve. Will be blocked.

The curing time of the solvent-free epoxy resin coating material used here is to peel off the rubber plate ring after curing to 1-2 hours. After hardening the coating film, it becomes a durable rustproof coating film 10 that is not affected by the environment inside the steel pipe, and is a method of maximizing the life of the coated steel pipe for water supply. There is a characteristic that can do perfect rust prevention work.

The present invention is to invent a method for maximizing the service life of the water supply coating steel pipes by welding the steel pipes in the buried piping construction of the water supply coating steel pipes and then completely rust preventive from the tap water passed through the steel pipes. .

Waterworks Dobokjang Steel Pipe (KSD3565-2002) is mainly a large diameter steel pipe and is a steel pipe with antirust coating on the inside and outside. In this steel pipe, when the water flows after the pipe, the internal coating is in the state of being deposited in the water for a long time.

When manufacturing coated steel pipe for water supply in the factory, it is unpainted to weld a certain length of both ends of the pipe. Antirust coating inside and outside the pipe is produced and shipped by controlling the thickness and performance of the coating film through prescribed inspection. . If the uncoated part due to welding is not constructed above the level of the rustproof coating inside the steel pipe after the buried steel pipe for water supply coating is buried, the service life of the pipe is shortened and a large economic loss occurs. When the steel pipe is welded and connected to the pipe, the inside of the pipe becomes a long cave and becomes narrow and dark, so that the rust-proof coating of the inner surface of the welded joint of the steel pipe becomes more difficult and the inspection of the coating film is not easy.

In order to solve this problem, the present invention provides a space between the welded portion and the rubber plate by installing a rubber plate ring (6) in the welded portion inside the pipeline and fixing the close bend (5) at both ends of the rubber plate ring. It is a method of injecting and hardening a solvent-free epoxy antirust coating having good fluidity, and peeling and separating the rubber plate ring 6 when the antirust coating is cured. After the coating film is cured, durability of the coating film is given, and the coating liquid penetrates to the minute portion of the weld joint site, thereby making it possible to make an antirust coating film 10 which does not cause any pinholes. It can be used for a long time without corrosion or rust.

The anti-rust lining method for preventing corrosion of uncoated welded joints on both inner surfaces of water coating coating steel pipes according to the present invention is left for 25 hours or more when a low hydrogen electrode is used to remove residual hydrogen in the fused metal. If ilmenite welding rods are used, they are left for 14 days or more, and the welding slags, sputters, and projections, which are harmful to the coating of the weld bead, which are harmful to the coating film, are removed by electric grinder, electric wire brush, etc. Remove the deteriorated parts of the lost rust preventive coating film and factory-painted primer, and completely remove oil, dust and other foreign substances attached to the steel surface using solvent, and at least 20 mm from the end edge of the painted part inside the steel pipe. Rub sandpaper, etc. to rough the surface of the existing coating film. To ensure proper mounting.

The rubber ring, such as the inner diameter of the steel pipe, can be covered to the steel pipe welded portion and the sandpaper processing portion of the inner surface of the steel pipe, spreading on the inner surface of the steel pipe, and a rubber band ring is installed on both ends of the rubber plate ring (6). In order to be in close contact with the coating film on the inner surface of the steel pipe, it is installed by tightening with a fastening bolt 14 so that the epoxy resin rust preventive coating liquid does not leak out, thereby creating an antirust coating liquid filling space 7 between the welded joint of the pipe and the rubber plate ring. The close contact bend is composed of an upper close bend 11 and a lower close bend 12 as shown in FIG. 3A, and are divided into two parts so as to facilitate transportation and assembly in the pipeline. ) Is welded. At both ends of the lower close bend, the close tightening nut 13 and the close tightening belt set are welded. Assembly of this close bend is installed in the shape as shown in Figure 3b by turning the tight tightening bolts 14 at both ends to widen the gap between the rubber plate ring (6) both sides close to the inner surface of the steel pipe.

The rubber ring installed in this way is provided with an injection valve (8) for injecting the anti-corrosive coating liquid at the bottom and an exhaust valve (9) for discharging the air inside. Solvent-free epoxy anticorrosive paint liquid is connected to the lower injection valve with a mixing injection pump and injected from the lower part into the space of the welded joint, and the air inside the space is discharged to the upper discharge valve, and the rust-preventive paint liquid penetrates into the minute gap. It fills up to the upper exhaust valve and paint is pushed out of the exhaust valve. In such a state, when the lower filling valve is closed and then the upper exhaust valve is also closed, the rust-preventive coating liquid is filled inside the weld joint to cure. When the filled epoxy rust preventive coating liquid is cured, the adhesive bend is dismantled, the exhaust valve fixing nib (17) installed on the upper part of the rubber plate ring is disassembled so that the rubber plate ring can be separated, and the rubber plate ring is separated from the cured coating film. The site is to create a lining coating film 10 in which the epoxy resin rust preventive paint is completely blocked in a set-in molding state so as to completely block the inner surface of the weld joint of the steel pipe from tap water when passing through the pipe.

The solvent-free fast-curing epoxy resin rust-preventive paint used as an example was used Hanseop Neo Coat SPW3565, the physical properties are shown in the following table.

Property Item result   State in container of paint  No mass and uniformity when mixed with main material and hardener   Mixed  Evenly mixed in the formulation   Gelation time (20 ℃, time)  10 minutes   Cure drying time (20 ℃, time)  2 hours   Bending test  No cracks and peeling.   Impact test (direct, indirect)  Direct impact, indirect impact, no peeling   Adhesion Test (25/25)  No peeling   Low temperature high temperature repeat test  No crack peeling   Moisture Resistance Test  No rust, swelling or peeling   Salt spray test (300 hours)  No rust, swelling or peeling Dissolution Test  Turbidity  0.5 degrees or less  Chromaticity  1 degree or less  Permanganate Calcium Consumption  1.2 mg / L  Residual Chlorine Loss  0.3 mg / L  flavor  clear  smell  clear  draft  Not detected  Phenols  Not detected  Epichlorohydrin  Not detected  Amines  Not detected  Toluidine isocyanate  Not detected

As described above, the anticorrosive lining of the water-proof coating steel pipe by the injection method of the solvent-free fast drying type epoxy resin rust-preventive coating is applied to the pipe inner surface welded joint, so that the dry coating film is uniform and the curing time is short, so the work efficiency is very high. Injecting solvent-free epoxy resin anti-corrosive paint with good fluidity completely blocks gaps that can cause corrosion. There was no defect that sparks occurred when it was tested with 1500V voltage with a pinhole flaw detector. In addition, since the rubber plate ring is separated after the coating film is completely cured, there is no defect that the coating film is damaged, which may occur in the uncured state of the coating film.

Claims (4)

Corrosion prevention by constructing a rubber plate ring 6 having a width that can be sufficiently covered inside the steel pipe coating film from the inner edge of the steel pipe welded to the water coating coating steel pipe and the end edge of the steel coating coating portion. An injection valve 8 for injecting paint liquid is placed at the lower part of the rubber plate ring, and an exhaust valve 9 is installed at the upper part of the rubber plate ring, and a close bend 5 is provided at both ends of the rubber plate ring. Tighten the tight fitting bolts (14) so that the steel pipe painted surface and the rubber plate ring are completely in contact with each other, so that a space (7) is formed between the welded joint of the steel pipe and the rubber plate ring, and the solvent-free epoxy rust-preventive coating liquid is injected into the rubber plate ring. It is connected to the inlet valve at the bottom to fill the welded joint of the steel pipe, and the air in the space 7 is discharged to the upper exhaust valve of the rubber ring to prevent the rust-proof epoxy paint solution. After filling until it is discharged to the air valve, the filling injection valve is closed, and then the upper exhaust valve is closed, and after hardening in the state where the rust-proof epoxy paint liquid is filled on the inner surface of the weld joint, the adhesive bend is dismantled, and the exhaust on the top of the rubber plate ring An anti-rust lining method by injecting epoxy anti-corrosive coating liquid in the inner surface of a welded joint pipe of a water coated coating steel pipe, which disassembles the valve, separates the rubber plate ring from the cured coating film, and forms a rust-proof lining film 10 on the inner surface of the welded steel pipe. The rubber plate ring (6) according to claim 1, wherein the rubber plate ring (6) uses a Teflon resin coated rubber plate or a rubber plate made of urethane rubber or silicone rubber that is not adhered to an epoxy anticorrosive paint, or a general vulcanized rubber plate coated with a release agent, such as an inner diameter. Anti-corrosion lining by injection of epoxy anti-corrosive coating liquid on the inner surface of the welded joint pipe of the water coating coating steel pipe, comprising a ring having a size, and having a hole formed to attach an exhaust valve to the upper portion of the rubber plate ring and an injection valve to the lower portion thereof. Method. The contact bend of claim 1, wherein the contact bends provided on both sides of the rubber plate ring are composed of an upper contact bend 11 and a lower contact bend 12, and contact ends of the upper contact bends support plates 15 are welded. At both ends of the lower tight bends, a set of tight tightening nuts 13 and a set of tight tightening bolts 14 are welded, and each end of the upper tight bend is tightly attached to both ends of the rubber plate ring by a tight tightening bolt. An anti-rust lining method by injecting epoxy anti-corrosive coating liquid into the inner surface of a welded joint pipe of a water coated coating steel pipe, wherein the support plate 15 is pushed up to bring the rubber plate ring 6 into close contact with the inner wall of the steel pipe. delete

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