JPS58121392A - Method of connecting long pipe having different quality of material - 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 The present invention relates to a method for preventing electrolytic corrosion that occurs at the joint when pipes made of different materials are joined, and in particular to a method for preventing electrolytic corrosion on the inner peripheral surface of the joint that connects both pipes. This invention relates to a method for preventing eclipse.

For example, when installing 4Ii/A heating equipment for LNG underground tanks in seaside areas, stainless steel pipes with corrosion-proofing treatment applied to the outer circumferential surface of the pipes in seawater are used, and in places buried in concrete, etc. For this purpose, a carbon steel pipe with Kvj corrosion treatment on the outer circumferential surface is used.

When connecting these pipes made of different materials, welding is used to ensure the reliability of the joints.

However, it is known that electrolytic corrosion (hereinafter referred to as electrolytic corrosion) occurs on the inner and outer circumferential surfaces of connecting portions of pipes made of different materials due to the so-called local battery action of the metal surfaces caused by metals made of different materials.

For this reason, conventionally both pipes have been connected using a corrosion-resistant method as shown in FIG.

In other words, when connecting pipe A and pipe B, which are made of different materials, the inner circumferential surface of the joint of both pipes is coated with a protective material (P) in advance, and both pipes are connected by λBf# connection2, and then both pipes are connected. The idea was to prevent electrolytic corrosion by applying similar anti-corrosion treatment to the outer peripheral surface of the steel.

However, the above conventional corrosion prevention methods have the following drawbacks.

<B> The anticorrosive material (P) that has been liquid-seed on the inner peripheral surfaces of both tubes is placed in the bath 1.
The corrosion prevention effect on the inner circumferential surface was lost due to burnout due to the high temperature at the time.
I can't expect much.

<Re> Therefore, even if the outer peripheral surface of the connection is possible, even if the inner peripheral correspondence prevention is incomplete, the distinctive life of the connection portion is the viper <ノ> -VM, and when the contact is completed, the connection part is completed. It is difficult to confirm whether the inner circumferential surface of the connector is completely coated with the corrosion-protective material, which reduces the reliability of preventing electrolytic corrosion at the connection part.

A method has also been developed in which the two pipes λB are connected by welding and then a corrosion-preventing material (P) is applied to the circumferential surface of the joint, but this method requires sophisticated coating technology and the pipes to be connected are small in diameter and long. In the case of pipes or curved pipes, it is practically impossible to apply the anti-corrosion material (P).

The present invention has been made to improve the shortcomings of the prior art as described above, and it is possible to simplify the construction of connecting both pipes, improve economic efficiency, and completely prevent electrolytic corrosion at the joint. Next, long pipe A and long pipe B (gl
An example of the third most advantageous method when connecting a wire (of a material different from that of A) will be described.

(1) Example 1 ■ Connection of a long pipe and a relay pipe In FIG. 1, the long pipe is a long steel pipe made of carbon steel, for example.

On the other hand, the relay pipe (1) is a short pipe with the same diameter as the pipe A and open at both ends, and is made of the same material as the long pipe B.

A connection port is open at one end of the long pipe A, and the connection port of the above-mentioned relay pipe (1) is butted against the connection port, and the joint circumference of both pipes is connected using a known # tangent line for metals of different materials. Connect the medium viscosity (1) from the long pipe A so that it does not easily come off by bathing the surfaces, ■ Formation of a corrosion-resistant coating (*: Figure 2) Relay with the long pipe A! After the connection of (1) has been completed, the inner circumferential surface of the joint between the two tubes (1) is treated with a known anti-corrosion treatment to form a complete anti-corrosion coating (2).

Corrosion-preventing treatment methods include coating with anti-corrosion materials such as tar epoxy, 2-in-1 boxy, and 2-in in polyethylene, or pasting fiberglass on the bottom.
The optimal corrosion-prevention treatment method is determined by considering the type or properties of the fluid that passes through the pipe, the design durability of the pipe, and the number of years it will last.

Since this corrosion-resistant treatment requires a relatively short connecting relay pipe (1), the process of forming the corrosion-resistant coating* (1) is easy, and the formation status of the corrosion-resistant coating (2) can be easily confirmed from the outside. can do.

■ Connection between relay pipe and long pipe Bo (Fig. 3) Corrosion-proofing treatment t- on the circumferential surface of the connecting part of long pipe A and relay pipe (1)
After the almsgiving, the end opening of the relay pipe (1) has a relay pipe (
One end opening of a long tube B made of the same material as 1), for example, stainless steel, is butted against each other, and both tubes (B) and (1) are connected by welding.

In order to prevent electrolytic corrosion at the joint of both pipes (B) (1), the welding rod used for connection should be made of the same metal as both pipes (B) (1).

Since no corrosion-proofing treatment is applied to the inside of the joint between the two pipes (1) and (B), there is no need to worry about the corrosion-resistant coating (2) being incinerated by the high heat during bath contact, as mentioned above. Able to do welding work.

<Example> Embodiment 2 This is a method in which the relay pipe (1) itself is formed of 21111 different metals.

Although the two types of gold are made of different materials, it does not mean that you can use any material; instead, you can use a short tube made of the same material as the long tube λ that is to be connected, and a short tube made of the same material as the k's. 1 by short tube
This is a method of forming four tubes inside the book.

■ Formation of the relay pipe (Fig. 5) The relay pipe (3) is a long pipe A and a short pipe (31) made of 181- material.
And, long 1i! It is composed of a short tube (32) made of the same material as the FB.

The short pipes (31) and (32) are hollow bones with both ends open, and the openings of the short pipes (31 and 32) are brought together and connected by bath welding using existing welding rods for metal glue made of different materials. .

■ Corrosion prevention treatment (Figure 5) Relay! After forming (3), the inner circumferential surface area of relay 1iF (3) is subjected to corrosion prevention treatment.

In other words, the inner circumferential surface is coated with anti-corrosion paint on both sides of the inner joint where both short pipes (31) and (32) connect.
! A corrosion-resistant coating (2) is formed using an existing corrosion-resistant method such as II coating or corrosion-resistant plating.

Further, if necessary, by sandblasting or shot blasting the inner circumferential surface before forming the corrosion-resistant coating (2), the corrosion-resistant coating (2) can be fixed more reliably.

Furthermore, as shown in FIG. 7, a corrosion-protective coating a!!(2) may be formed only on the joint and the inner periphery of one of the tubes.

■ Relay pipe and ¥! Connection of tA and H (Fig. 6) Next, connect the openings at both ends of the corrosion-resistant relay pipe (3) between long pipe A and long pipe B with pipes made of the same material. The opening of the short pipe (31) constituting the relay pipe (3) is butted to the opening of the long pipe A and connected using a welding rod made of the same material as the steel pipe (A) (31).

Similarly, the opening of the short tube (32) is butted against the opening of the long tube B, and both tubes (B) (32) are welded using a welding rod made of the same material.

Since the present invention is as described above, the following effects can be expected.

<A> In the joining of the present invention, long pipes made of different materials are not directly welded.

A relay pipe consisting of a short pipe of the same material as one long pipe is used, and this short pipe is welded to a long pipe or short pipe of a different material, and the inside of the part where the pipes of different materials meet is used. Corrosion-proofing treatment is applied, and then pipes of the same material are welded together.

In this way, the part to be heated last is the joining part of pipes made of the same material, and the part where pipes made of different materials are in contact, that is, the part that has been subjected to corrosion protection treatment, is not heated.

Therefore, unlike conventional methods, high heat during welding prevents corrosion! 1! There is no damage or loss of parts and the corrosion protection effect is complete.

<Mouth> In order to connect the relatively short relay pipe (2) to the joint of pipes made of different materials (blue A1 pipe B), the joint can be visually inspected to confirm the negative corrosion protection cap. Corrosion prevention treatment work can proceed.

〈〈〈〉〈〉It is economical because it is possible to use tubes made of different materials, such as stainless steel tubes and carbon steel tubes, depending on the need.

[Brief explanation of the drawing]

Figures 1 to 4: Explanatory diagrams of the connection method of the middle assembly shown in one embodiment of the present invention Figures 5 to 6: Connection methods of other embodiments (Explanatory diagrams Figure 7: Other implementations) Figure 8: Removal of relay pipe in example:
Illustration of an example of a conventional connection method 1.3: Relay pipe, 2: Corrosion-resistant coating Patent applicant: Taisei Corporation Patent attorney, Sakuo Yamaguchi

Claims (1)

[Claims] When connecting two long tubes made of different materials, a short tube made of the same material as one of the long tubes is used, and this short tube is first connected to a tube made of a different materialff! Corrosion prevention treatment 1 is applied to the inside of the part where pipes of different materials meet. A method for connecting long pipes made of different materials, characterized in that the short pipe is then welded to a long pipe made of the same material.