JPH0470345B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a material for forming a desired gap between the inner surface step of a socket joint and the end of a pipe in a pipe joint.

[Conventional technology and its problems]

Cracks may occur in the welds of pipe fittings in piping systems.

The mechanism of this crack occurrence is that, as shown in Fig. 4, when the inner step 1a of the socket joint 1, which has a large wall thickness, is welded with the end 2a of the pipe 2, which has a small wall thickness, and welds against each other, the pipe Socket joint 2 starts to expand first, and socket joint 1, which has a large heat capacity, expands later. As a result, the end 2a of the pipe 2 is blocked by the stepped portion 1a of the socket joint 1, and the force acts rearward, creating stress on the welded portion W, and it is thought that cracks occur.

Therefore, as a countermeasure for this, when connecting pipes in a piping system, as shown in FIG. Inner step part 1a
A gap s of 1.5 to 3 mm is provided between the socket joint 1 and the end 2a of the pipe 2, and then the socket joint 1 and the pipe 2 are welded.

However, in many joints, if the welding is done without the gap s provided, or if the gap s provided is small, the above-mentioned cracks will occur.

Based on the above circumstances, an assembly method is proposed in which the gap s is inevitably created by inserting the end 2a of the pipe 2 into the socket joint 1, abutting the end 2a of the pipe 2 against the stepped portion 1a, and welding. is required.

[Purpose of the invention]

The present invention aims to fulfill the above requirements.

[Means to achieve the purpose]

In order to achieve the above object, the present invention includes:
A gap-forming material is interposed between the inner step of the socket joint and the end of the pipe inserted into the socket joint, and the material is mixed with a water-soluble polymer, a water-soluble plasticizer, water, and a small amount of coloring agent if necessary. It was made by kneading with an antifoaming agent and drying the mixture.

Examples of the water-soluble polymer include nonionic cellulose derivatives, such as methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, and carboxymethylcellulose, or a mixture of two or more thereof.

Further, examples of the water-soluble plasticizer include glycerin, polyethylene glycol, propylene glycol, and the like.

[Effect]

In the present invention constructed as described above, the gap-forming material of the present invention is inserted into the inside of a socket joint, and the end of the pipe is abutted against the step on the inner surface of the socket joint through the gap-forming material. When both are welded and fixed, the gap-forming material becomes carbon monoxide, carbon dioxide, and water due to the heat during welding, and a gap corresponding to the thickness of the material is formed at the portion where the material is inserted.

Also, if the ring does not completely volatilize due to the heat during welding and some remains, the composition is water-soluble, so it will elute into the water flowing through the piping system, and the gap between the pipe fittings will be reduced. Formed reliably.

Therefore, if the thickness of the material is set to a gap greater than the difference in expansion length between the socket joint and the pipe, stress will not be generated in the joint weld and cracks will not occur.

〔Example〕

Next, examples of the present invention will be described.

Hydroxymethyl cellulose (Matsumoto Yushi Co., Ltd. trade name Marborose M-1500) and glycerin were mixed in a ratio of 1:1, a small amount of antifoaming agent and a water-soluble coloring agent were added, and water was gradually added to the mixture. The mixture was mixed and adjusted to about 100,000 CPS, poured onto a plate with edges that had a release property on the surface, and dried and solidified to form a plate. This plate was punched out as shown in Figure 2. A gap forming material 10 for a pipe joint of the present invention is formed. The thickness of this material 10 is the same as that of the socket joint 1.
and the expanded length of tube 2.

Gap forming material 10 for pipe joints prepared as above
is inserted into the inner surface stepped portion 1a of the socket joint 1, as shown in FIG. At this time, one side of the material 10 is slightly wetted and pressed against the stepped portion 1a to be adhesively fixed. Next, the end 2a of the pipe 2 to be connected is inserted into the socket joint 1, and the end 2a of the pipe 2 is butted against the inner surface stepped portion 1a of the socket joint 1 via the gap forming material 10, so that the socket joint 1 and the pipe 2 are connected. After temporary welding at several places around the pipe, welding W is performed on the entire surface to complete the pipe joining work.

Gap forming material 1 inserted during the above welding work
The temperature near 0 is about 900℃, and this heat makes the material 10
is volatilized as carbon monoxide, carbon dioxide, or water vapor, and a gap s is formed in the area.

If the gap forming material 10 is not completely volatilized by the heat during welding, since this mixture is water-soluble, it will be eluted into the water flowing through the piping system after the construction is completed.

In this way, the end 2a of the pipe 2 is attached to the socket joint 1.
When the end 2a of the pipe 2 is butted against the inner surface step 1a of the socket joint 1 via the gap forming material 10 and welded, a desired gap s corresponding to the thickness of the material 10 is formed, and the gap is I can never forget the formation of s. Therefore, there is no stress in the welded part, and a pipe joint of stable quality without cracking can be obtained.

Although this embodiment uses an L-shaped connection, it is not limited to this.

[Confirmation test]

Next, in order to confirm whether the gap forming material 10 is completely vaporized by the heat during welding, the material 10 is
When a test piece was taken and analyzed using a thermal balance, the results shown in Figure 3 were obtained. From this figure 450℃
It can be seen that most of the sample is vaporized.

Moreover, when material 10 was put into room temperature water of step 1 and stirring was continued, it completely dissolved and disappeared in about 3 hours.

From these results, it can be understood that the gap-forming material 10 completely disappears during welding or at the beginning of water flow, and the gap s is reliably formed.

〔effect〕

As explained above, by using the material for forming gaps in pipe fittings of the present invention, gaps are reliably formed in the pipe fittings, so that cracks do not occur in the welded parts of the pipe fittings and high-quality pipe fittings can be obtained. be able to.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of one embodiment of the material for forming a gap in a pipe fitting according to the present invention, inserted into a pipe fitting, Fig. 2 is a perspective view of the material, and Fig. 3 is a thermal analysis diagram of the material. ,
FIG. 4 is a sectional view of a conventional example, and FIG. 5 is a sectional view of a normal pipe joint. 10... Gap forming material, 2... Pipe, 1... Socket joint, 1a... Inner surface step, 2a... Pipe end,
W...Welding part.

Claims (1)

[Scope of Claims] 1. A material interposed in the pipe between the inner surface step of the pipe socket joint and the end inserted into the socket joint, which comprises a water-soluble polymer, a water-soluble plasticizer, water, and, if necessary, a small amount of a coloring agent. 1. A material for forming gaps in pipe joints, which is obtained by kneading the mixture with an antifoaming agent and drying the mixture. 2. The material for forming a gap in a pipe joint according to claim 1, wherein the water-soluble polymer is a nonionic cellulose derivative. 3. The pipe joint gap forming material according to claim 2, wherein the cellulose derivative is composed of one or a mixture of two or more of methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, and carboxymethylcellulose. 4. The material for forming a gap in a pipe joint according to any one of claims 1 to 3, wherein the water-soluble plasticizer is comprised of glycerin, polyethylene glycol, or propylene glycol.