JPH028584A - Pipe welded joint - Google Patents

Abstract

PURPOSE:To strengthen a welded pipe joint by applying weld around the circumferential part of a flange fitted to a pipe and jointing inner lining materials to each other with welding heat. CONSTITUTION:A joint ring 8 is set between flanges 11 and 21, and circumferential weld is applied to the external surfaces of the flanges 11 and 21. Lining materials 12 and 22 are softened and melted with welding heat, thereby being made monolithical with each other. According to the aforesaid construction, the lining materials 12 and 22 are integrated with each other and the bonding strength of pipes proper 1 and 2 is increased, thereby obtaining joint strength equivalent to the strength of the pipes proper 1 and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a welded pipe joint structure for internally lined pipes.

[Prior Art] Conventional pipe joint systems for internally lined pipes include the following.

(1) Threaded joint A threaded joint (socket, etc.) specifically designed for inner-lined pipes is used as a corrosion-resistant joint for inner and outer surfaces.

(2) The inner lining is applied to the flange joint sealing surface, and a gasket is inserted between the flange surfaces that are integrated with the pipe body and fastened with flange bolts.

(3) Welded joints If the joint strength is given priority over the corrosion resistance of the inner surface of the pipes at the joint, circumferential butt welding of the pipes is performed.

[Problems to be Solved by the Invention] When the conventional existing joints described above are used particularly for buried piping, etc., the following problems arise for each joint.

(1) In the case of threaded joints ■It is structurally impossible to make the joint strength higher than that of the main pipe ■Sealing performance is not reliable, and sealing performance tends to change over time due to external forces, etc.

(2) For flange joints ■It is difficult to make the joint strength higher than that of the main pipe.

■Sealing properties are not reliable, and sealing properties tend to change over time due to deterioration of the sealing material or external forces.

(3) In the case of welded joints (butt welding of main pipes) - The lining material on the inner surface of the pipe burns out due to welding heat, and if left as is, it is impossible to protect the inner surface of the pipe at the joint, causing red water in water pipes.

■It is necessary to repair the inner lining of the joint after welding.

■After welding, burnt material from the lining material accumulates inside the pipe.

An object of the present invention is to provide a welded pipe joint that solves the problems associated with the conventional welded pipe joint structure described above.

[Means to solve the problem] The pipe welding joint according to the present invention is constructed as follows.

(1) Butt weld the main pipe and the flange, which has a groove for on-site welding on the outer periphery.

(2) Perform integrated inner lining treatment on the inner surface of the main pipe and the flange surface.

(3) Set the coupling ring between the flange surfaces and temporarily attach the flange.

(4) Weld both flanges.

(5) The flange inner lining material is softened by welding heat.
Melt and integrate.

(6) Shape with mastic.

(7) Cover the joint with shrink tube.

In the pipe welded joint having the above configuration, it is preferable that (1) to (2) are configured at the factory and (3) to (7) are configured at the site.

The pipe welding joint according to the present invention performs circumferential welding on the outer periphery of a flange attached to the pipe during on-site welding of internally lined pipes, and uses the welding heat generated at that time to weld the internal lining material on the flange surface. This pipe welding joint is characterized by softening and melting the pipes and joining them by welding shrinkage, thereby integrating the inner lining of the joint.

[Function] The pipe welded joint of the present invention has a joint strength greater than that of the main pipe by butt welding at the outer circumference of the flange attached to the pipe,
The welding heat softens and melts the inner lining material on the flange surface, and the inner lining material of the joint is joined by welding shrinkage, thereby forming a corrosion-resistant layer on the inner surface of the joint.

Next, examples of the method of the present invention will be described.

[Example] FIG. 1 is an explanatory diagram of a directly buried type insulating joint which is an embodiment of the present invention, and FIG. 2 is an enlarged explanatory diagram of the main part of FIG. 1.

In both figures, (1) and (2) are the pipe bodies to be joined, (1
1) and (21) are the flanges of the tube bodies (1) and (2), (
12) and (22) are linings. (3) is the first welded portion, and (4) is the second welded portion. The first welding part (3) joins the pipe bodies (1), (2) and the flanges (11), (21), and the second welding part (4) joins the pipe bodies (1) and (2).
join. (5) is mastic and (6) is a shrink tube. (7) is the groove for the second weld, (8)
is a ring for a joint.

An example of the construction of the pipe welded joint of the present invention having the above-mentioned configuration can be roughly divided into the following two steps.

(Factory process) A flange (11) and (
21) to form the tube bodies (1) and (2).

The connection between the flange (11) or (21) and each main pipe is as follows:
This is achieved by welding the first weld (3). In this case, the outer circumferences of the flanges (11) and (21) are provided with opposing inclined surfaces for forming the groove (7) of the second welded portion (4). In addition, the flanges (11), (21) have grooves for butt welding (13), ( 23
), and the main pipe side is joined to the flanges (11) and (21) by butt welding.

Next, the inner surfaces of the tube bodies (1) and (2) are subjected to an integral lining treatment with a uniform layer thickness. Lining (12), (
As the material 22), for example, tetrafluoroethylene resin having high corrosion resistance is used.

The inner linings (12') and (22) are similar to the existing flanged inner lined straight pipes, and are attached to the pipe body (1).
The sides of (2) and (2) are integrated, and the outer corners have a large curvature to alleviate the stress concentration of the axial load.

(On-site process) In on-site construction, a coupling ring (8) as shown in the figure is first set between flanges (11) and (21).

This joint ring (8) is intended to prevent the inner lining material from being burnt out due to spatter and arcs associated with welding, and is used as necessary.

This joint ring (8) has a lining (12) and (2)
The width is slightly thinner than the layer thickness in 2).

Then, an adhesive (of epoxy type), for example, is applied to the opposing side surfaces of the flanges (11) and (21), and the coupling ring (8) is adhered thereto. When the coupling ring (8) is glued, the pipe bodies (1) and (2) and the second welded part (
After centering the groove (7) for 4), the tube bodies (1) and (2) are temporarily attached by welding.

Next, the second welded part (4) of flanges (11) and (21)
Then, they are joined by circumferential butt welding using the groove (7).

The welding of the second welding part is so-called main welding. In this main welding, the first layer is welded using a special welding rod for Uranami to prepare the inner bead shape. Welding conditions for each bus should be selected in consideration of the pipe diameter, pipe thickness, size and shape of the flange, and material and thickness of the lining material, so that a sufficient lining joint can be obtained through good heat supply and heat conduction.

The welding heat of the second welding part (4) causes the flange (11) to
and (21), and the linings (12) and (22), which had been separate and merely touched each other, soften and melt and become integrated. The state at this time is shown in the enlarged view of FIG.

As shown in the figure, the lining material is once melted by the high temperature welding heat, and then the component molecules are recombined and integrated. This phenomenon of integration of the lining material occurs not only in the part near the second welded part (4) but also in the pipe body (1) and (2) of the pipe body (1) and linings (12) and (22). The degree of cohesion is also strengthened.

Subsequently, tests and inspections are performed to confirm the welding condition of the welded portion after welding. X-ray inspection of welds,
Non-destructive tests such as ultrasonic waves and penetration tests will be conducted on all or a sample of items as necessary. If no abnormality is found in the test results, then as a pretreatment for corrosion prevention work on the outer periphery near the joint, use mastic (for example, a two-component reactive epoxy resin-based high-viscosity filler) to clean the corners and edges at obtuse angles. It is molded and finished.

Then, the heat-shrinkable tube that has been attached in advance is heated to form a corrosion-resistant layer on the outer surface of the joint.

After these processes are completed, the pipe body (
1) and (2) will be joined and buried underground.

[Effects of the Invention] According to the pipe welded joint of the present invention, the following effects can be obtained.

(1) Strength of joints between main pipes etc. can be obtained.

(2) An integral inner lining layer containing the joint is formed.

(3) No sealing material (gasket) is required for the joint.

(4) There is no change in joint sealability over time.

(5) Red water does not occur.

(6) Burnt objects and welding slag caused by welding work do not enter the pipes.

(7) There is no need to repair the inner lining after welding.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a directly buried type insulating joint which is an embodiment of the present invention, and FIG. 2 is an enlarged explanatory diagram of the main part of FIG. 1. In the figure, (1) and (2) are the tube body, (3) is the first welded part, (4) is the second welded part, (5) is the mastic, and (6) is the first welded part.
) are shrink tubes, (7), (13) and (23)
(11) and (21) are flanges, (12) and (
22) is the lining. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] In on-site welding of internally lined pipes, circumferential welding is performed on the outer periphery of the flange attached to the pipe, and the welding heat generated during this process is used to soften and melt the internal lining material on the flange surface, causing welding shrinkage. A pipe welding joint characterized in that the inner lining of the joint part is integrated with the inner lining of the joint part.