JPS63140198A - Inner-surface corrosion protective method of weld joint section - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for preventing corrosion of the inner surface of a welded joint, which performs anticorrosion treatment on the inner surface of the welded joint when on-site welding pipes whose inner surfaces are coated with anticorrosive coating. .

[Prior art] Normally, when butt welding an internally anti-corrosion coated pipe on-site,
Since anticorrosion coating has a negative effect on welding, the inner surface coating near the joint is removed before welding, and after welding is complete, the surface from which the coating was removed is repainted for anticorrosion treatment.

Conventionally, methods for preventing internal corrosion of welded joints in the field have been divided into two methods, depending on the size of the pipe and other factors: a hand-sealing method and a machine-coating method. In other words, the Tekin method involves a worker entering the pipe after welding is complete and applying anti-corrosion paint to the surface from which the paint has been removed, and is used for painting the inside surfaces of large-diameter pipes, while the mechanical coating method involves inserting a coating machine into the pipe. The anti-corrosion paint f is applied to the surface from which the paint has been removed, and is used for painting the inner surfaces of small diameter pipes.

[Problem that the invention attempts to solve] However, in the manual mb method for large diameter pipes.

It is difficult to work in the narrow pipe because the worker is forced to take an awkward working posture, and the pipe is filled with vapor caused by the volatilization of the solvent, creating a poor working environment. Furthermore, it is not possible to obtain a uniform film thickness as with spray coating. If condensation occurs on the inner surface of the tube, the paint cannot be applied to the painted surface because it does not blend well with the painted surface. - In the mechanical coating method for small diameter pipes, the coating machine cannot pass through the curved parts of the pipes, so it can only be applied to straight pipes! Due to limited JJ, it is not possible to paint joints of pipe bodies with bends.

Further, during painting, other work such as connecting other joints has an adverse effect on the operation of the coating machine, so other work is interrupted. Therefore, with the nine mechanical coating methods, the overall work efficiency of the construction work is low.

Furthermore, since paint adheres to the main body of the paint sprayer after painting is completed, there is a problem in that maintenance and inspection of the paint sprayer, such as removing the adhered paint, requires a great deal of effort.

This invention has been made in view of the above circumstances, and in anti-corrosion treatment of the inner surface of the welded joint of a pipe, it eliminates the need for workers to cheat on money regardless of the shape of the pipe, and it also eliminates the need for painting. A welded joint that can form a uniform thickness of anti-corrosion M on the surface from which the paint has been removed without using a machine, can also provide anti-corrosion treatment to curved parts of the pipe, and is not affected by condensation inside the pipe. The purpose of this invention is to provide a method for preventing corrosion of circular surfaces.

[Rounding Means to Solve the Problems] The method for preventing corrosion of the inner surface of a welded joint according to the present invention involves rolling a cylindrical thermally deformable member made of a material that becomes deformable when heated to a cylindrical welded joint. An expansion bag that is placed inside and expands when fluid is supplied is placed inside the thermally deformable member, and an adhesive that melts when heat is applied is placed on the outer surface of the thermally deformable member to deform the thermally deformable member by heating. At the same time, the adhesive is melted in a heating bath, an expansion bag is expanded, and the thermally deformable member is brought into close contact with the inner surface of the weld joint by the expansion bag.

[Function] In the method for preventing corrosion of the inner surface of a welded joint according to the present invention,
A cylindrical heat-deformable member that becomes deformable when heat is applied is placed inside the welded joint, and an adhesive that melts when heat is applied is provided on the outer surface of the heat-deformable member. Further, an expansion bag is arranged inside the thermally deformable member, and the thermally deformable member is heated and a fluid is supplied to the inside of the expansion bag.

Then, the heated thermally deformable member becomes deformable, the expansion bag expands and expands from the inside of the thermally deformable member, and the outer surface of the thermally deformable member is pressed against the inner surface of the weld joint. Therefore, the molten adhesive adheres to the inner surface of the welded joint, and the thermally deformable member comes into close contact with the welded joint.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing welding in which the method for preventing internal corrosion of a welded joint according to the first embodiment of the present invention is used;
Figures (&) to (d) are cross-sectional views of the pipe for explaining the construction steps in Figure 1, and Figure 3 is a partial cross-sectional view of the heater. As shown in Fig. 2(a), steel pipes 10 of the same diameter
and steel pipes 11 are arranged approximately horizontally with their axes aligned. The inner surfaces of the steel pipes 10.11 are anti-corrosion coated. The steel tube 10.11 has ends cut at substantially right angles to the axial direction, each end having a bevel surface 12.1 inclined outwardly in the axial direction.
13 is formed. Then, a pair of groove surfaces 12°1
3 face each other with a predetermined interval (root gap),
The welding groove is bent such that a welding groove is formed between the groove surfaces 12,13. The inner surface coating near this groove has been removed. An annular thermally deformable member 18 is inserted into the tube, and the thermally deformable member 18 is arranged inside the tube (on the back side) of the welding groove via the heat insulating material 16. That is, the heat insulating material 16 is attached to the outer surface of the thermally deformable member 18, and the outer surface of the heat insulating material 16 and the inner surface of the pipe near the groove are in close contact. For this reason,
The root gap is closed from the inside of the tube by a heat insulating material 16. When the thermally deformable member 18 is heated to a temperature range of 120° C. to 150° C. for about 10 minutes, the thermally deformable member 18 has a diameter of about 150° C. to 2° C.
It is made of a material that has 00% thermal expansion, such as polyethylene, vinyl chloride resin, or vulcanized rubber. A true melt type adhesive (not shown) which has the property of melting when heated to the above-mentioned temperature is applied to the outer surface of the thermally deformable member 18.

- The airbag 20 is inserted into the tube from the side of the tube 11 and placed inside the thermally deformable member 18. The airbag 20 is a flexible cylindrical bag, and a heat insulating material 22 is wound around the outer periphery of the airbag 20. Further, a heater 24 is wound around the outer periphery of the heat insulating material 22, and the outer surface of the heater 24 and the inner surface of the thermally deformable member 18 face each other. As shown in FIG. 3, the heater 24 is in the form of a sheet, and a resistance heating wire 27 is embedded in 25 circles of rubber. rubber
251'i: For example, the airbag 20 is connected to the hose 2.
6 to an air supply source 32.

The hose 26 is provided with a pressure gauge 28 and a pressure regulating valve 30, so that the air pressure supplied into the air bag 20 from the air supply source 32 can be adjusted. On the other hand, heater 2
4 is connected to a power source 36 via a cable 34. The power source 36 is capable of current control, and is adapted to adjust the heating temperature of the heater 24 by controlling the current supplied to the heater 24.

Next, the construction procedure of the first embodiment is shown in Figure 2 (&
) to (d). Bevel surfaces 12 and 13
After removing the inner surface coating in the vicinity of each, the grooves of the steel pipes 10 and 11, which are disposed substantially horizontally, are aligned. At this time, the heat deformable member 1 has a heat insulating material 16 attached in advance to the center of the length of the outer surface.
st- Insert only half the length into one steel pipe 10, move the other steel pipe 11 horizontally from the direction in which the heat deformable member 18 is disposed, and insert the remaining half length of the heat deformable member 18 into the other steel pipe 10. While inserting into the steel pipe 11, the grooves of the steel pipes 1θ and 11 are aligned. When the other steel pipe 11 is short.

After aligning the grooves of the steel pipes 10 and 11, the heat deformable member 18 is attached to the steel pipe 1.
Next, a small amount of air is sealed in the air pack 20 to inflate the air pack 20 into a substantially cylindrical shape, and a heat insulating material 22 is placed around the outer periphery of the air pack 20. and wrap the heater 24 around it. This airbag 20
Insert into the steel pipe from the 1st side. At this time, hose 2
6 or the feeding length of the cable 34 while detecting the insertion position of the air pack 20.
Place it inside 8. Eventually, when welding starts, welding heat is conducted to the back side of the groove, but since the heat insulating material 16 insulates the welding groove and the thermally deformable member 18, the thermally deformable member 18 does not deform. I won't wake you up. As shown in FIG. 2(b), when the welding is completed and the welded joint 14 is formed, the pressure regulating valve 32 adjusts the pressure t-p+ and the air supply source 3
6 supplies compressed air into the airbag 20. As a result, the airbag 20 expands and the outer surface of the heater 24 comes into close contact with the inner surface of the thermally deformable member 180. Next, the heater 24 is energized to heat the thermally deformable member 18 to a temperature range of 120 to 150°C. Then, as shown in FIG. 2 (Q), the thermally deformable member J8 undergoes fin-stretching deformation and is pressed against the heated surface (paint-removed surface), causing the thermally-deformable member 18 to come into close contact with the entire area of the paint-removed surface. do. The heating time by the heater 24 at this time is, for example, about 10 minutes. Eventually, when the heater 24 stops running for 1 t, the internal pressure of the air pack 20 is reduced to the pressure before welding starts, and the diameter of the air bag 20 is changed to that shown in FIG.
Return to the state shown in &). Then, the hose 26 and cable 34' are pulled, and the air pack 20 is carried out.

FIG. 4 is a sectional view showing the inside of the pipe after construction when the air pack 20t is not used. When the thermally deformable member 18 is heated without using the air pack 20.

The upper part of the thermally deformable member 18 is buckled and the sag is 9, and the thermally deformable member 18 extends over the entire area of the removed surface of the steel pipe 10.11.
is no longer in close contact. On the other hand, in the first embodiment, as shown in FIG. 2(d), even after the air pack 20 is removed, the thermally deformable member 18 is firmly attached to the entire area of the painted surface of the steel pipe 10.11. Can be placed in close contact.

FIG. 5 is a sectional view showing the inside of a welded pipe in which the method for preventing corrosion of the inner surface of a welded joint according to the second embodiment of the present invention is used. Descriptions of parts common to the first embodiment will be omitted. In this second example.

After welding is completed, the heat deformable member 18t- is removed together with the air pack 20.
Insert into the tube. That is, a sheet-shaped heater 24 is wrapped around the outer periphery of the air pack 20 that has been expanded to a predetermined diameter via a heat insulating material 22, and a thermally deformable member 18 is placed around the outer periphery of the heater 24.
Install. In this way, air pack 20. The heater 24 and the thermally deformable member xgt are assembled together in advance, and are inserted into the pipe so that the paint-removed surface on the back side of the weld joint portion 14 faces the thermally deformable member 18. Then, the internal pressure of the air pack 20 is increased to a predetermined pressure, the air pack 20 is expanded, and the air pack 20 is brought into close contact with the surface of the thermally deformable member 18t from which the paint is to be removed. After a while, the heater 24 is energized and the heat deformable member 18 is moved to the heater 2.
◎This heats the heat deformable member 18 to a predetermined temperature in Step 4.
is adhered to the surface from which the paint was removed. Eventually, the power supply to the heater 24 is stopped, the internal pressure of the air pack 20 is reduced to the pressure before heating starts, and the diameter of the air pack 20 is returned to its original size.
The air pack 20 is carried out of the tube.

In the second embodiment, the thermally deformable member 18 and the steel pipe 1
Since there is no heat insulating material between the steel pipe 10.11 and the steel pipe 10.11, the heat deformable member 18 can be directly bonded to the entire area of the painted surface of the steel pipe 10.11, and the heat deformable member 18 can be bonded more firmly. I can do it.

FIG. 6 is a schematic diagram showing a welded pipe in which the best inner corrosion prevention method for bath welded joints according to the third embodiment of the present invention is used.

Descriptions of parts common to the first and second embodiments will be omitted. This third embodiment locates the steel pipe 10.1
The heater 40 is connected to a power source 44 that can control current via a cable 42, and the heat deformable member 18 inside the pipe is heated by the heater 40 from the outside of the steel pipe 10.11. .

In the thirteenth embodiment, since the air pack 20 and the heater 40 are arranged separately, the air pack 20 is lightweight and can be easily inserted into the air pack 20t-pipe. Furthermore, since the air pack 20 and the heater 40 are separated from each other, the influence of heat on the air pack 20 can be further reduced. Furthermore, since the heater 40 is placed outside the tube, heaters of various sizes can be freely selected.

FIG. 7 is a sectional view showing welding Wt in which the method for preventing corrosion of the inner surface of a welded joint according to the fourth embodiment of the present invention is used. Explanation of parts common to the first to third embodiments will be omitted. In this fourth embodiment, the main body of the air pack 50 is made of heat-resistant and flexible rubber 25 such as silicone rubber, and a resistance heating wire 27 is embedded in this rubber 25. 5θ itself is a heater. The hose 52 is connected to an air supply source (not shown), and the cable 54 is connected to a power source (not shown). According to such an air pack 50, the air pack 50 itself operates a heater. Since the air pack 50 also has the same function as the air pack 50, the air pack 50 can be easily handled and can be constructed with even simpler work.

[Effects of the Invention] According to the present invention, since the thermally deformable member is pressed against the inner surface of the welded joint by W tensioning, thermal deformation and manual work by one worker are not required, so that the workpiece to be welded is Regardless of the shape, a safe and sanitary working environment can be ensured. Moreover, since the painting work using a paint machine is not necessary, it becomes possible to perform anti-corrosion treatment on the inner surface of the curved portion of the cylindrical body, and the maintenance and inspection work of the paint machine becomes unnecessary. Further, by using a thermally deformable member having a uniform thickness, a more uniform anti-corrosion coating layer can be formed. Furthermore, even if anti-corrosion work is being carried out, welding work on other joints can be carried out in parallel without interruption. Therefore, the work efficiency of the entire construction work is improved, so that construction costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the inside of a round pipe in which the method for preventing corrosion on the inner surface of a welded joint according to the first embodiment of the present invention is used, and FIG.
, ) to ( are cross-sectional views of the pipe for explaining the construction procedure of the first embodiment, FIG. 3 is a partial cross-sectional view of the heater, and FIG. 4 is a partial cross-sectional view of the heater.
The figure is a cross-sectional view showing the inside of the pipe after construction when no expansion bag is used, FIG. 5 is a cross-sectional view showing the inside of the pipe of the second embodiment, and FIG. 6 is a cross-sectional view showing the inside of the pipe of the third embodiment. The schematic diagram and FIG. 7 are cross-sectional views showing the inside of the tube of the fourth embodiment. 10.11... Steel pipe, 14... Welded joint part, 16°22 River insulation material, 18... Heat deformable member, 20.50...
・amp (air pack), x4, 4o...heater. Client agent Patent attorney Takehiko Suzue1)
, Ω0
°0Figure 4 7L'! 1 Written amendment, ρ2.h.28th, Commissioner of the Patent Office, Black 1) Mr. Akihiro 1. Indication of the case Japanese Patent Application No. 61-288126 2. Name of the invention Method for preventing internal corrosion of welded joints 3. Make amendments. Patent applicant (412) Nippon Kokan Co., Ltd. 4, agent UBE Building 7, 3-7-2 Kasumigaseki, Chiyoda-ku, Tokyo,
Contents of the amendment (1) In the specification, on page 7, line 11, "approximately 150 to 20096J" is replaced with "approximately 1.2 to 2.0 times".
Correct. (2) In the specification, on page 10, line 43, “Pressure regulating valve 3
2" should be corrected to "Pressure regulating valve 30J. (3) In the specification, on page 10, line 4, "Air supply source 36
” should be corrected to “air supply source 32.”

Claims (6)

[Claims] (1) A cylindrical thermally deformable member made of a material that becomes deformable when heated is placed inside a cylindrical welded joint, and an expansion bag that expands when fluid is supplied is placed inside the thermally deformable member. An adhesive that melts when heated is disposed on the outer surface of the thermally deformable member, and the thermally deformable member is heated and deformed, the adhesive is heated and melted, and an expansion bag is expanded. A method for preventing corrosion on the inner surface of a welded joint, characterized by bringing the material into close contact with the inner surface of the welded joint. (2) The method for preventing internal corrosion of a welded joint according to claim 1, wherein the expansion bag is made of silicone rubber or fluororubber reinforced with glass fibers. (3) The welded joint according to claim 1 or 2, wherein the expansion bag is connected to a pressure regulating valve, and the internal pressure thereof is regulated by the pressure regulating valve. Internal corrosion protection method. (4) Any one of claims 1 to 3, characterized in that a resistance heating element is installed inside the expansion bag, and the resistance heating element is energized to generate heat to heat the thermally deformable member. A method for preventing internal corrosion of welded joints as described in . (5) A patent claim characterized in that a resistance heating element attached to a sheet-like silicone rubber substrate or a fluorine rubber substrate is wound around an expansion bag, and the resistance heating element is energized to generate heat to heat a thermally deformable member. A method for preventing internal corrosion of a welded joint according to any one of items 1 to 3. (6) Any one of claims 1 to 3, characterized in that a resistance heating element is disposed on the outer surface of the weld joint, and the resistance heating element is energized to generate heat to heat the thermally deformable member. The method for preventing corrosion on the inner surface of a welded joint according to item 1.