JPS634317B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency induction heating coil wound around a joint of piping.

The patent No.
As shown in No. 957324, a residual stress improvement method using high-frequency induction heating coils has already been applied to straight pipe-straight pipe combinations.

FIG. 1 is a diagram showing the configuration of a high-frequency induction heating coil installed near the joint of a straight pipe-straight pipe combination. Pipes 1A and 1B of the same diameter are arranged coaxially and joined at a welding part 2. A high-frequency induction heating coil 3 is arranged around the welded portion 2 of the pipe 1 constituted by the pipes 1A and 1B, and is wound around the pipe 1. This high-frequency induction heating coil 3 is comprised of a conductive material comprising a strip-shaped copper plate 3A that comes into contact with the outer peripheral surface of the pipe 1, and a brazing material 3B attached to the strip-shaped copper plate 3A, as shown in the cross-sectional view of FIG. It consists of a rectangular hollow pipe 3C which is soldered together and has a wide width at the soldered part, and has terminals 4A and 4B.

The principle of the residual stress improvement method using high-frequency induction heating is to generate a temperature difference between the inner and outer surfaces of the pipe by heating the outer surface of the pipe and cooling the inner surface, and at the final point when the coil stops heating the outer surface, it is compressed into the inner surface of the pipe. This is a method of imparting a residual stress of
All of the areas to be improved are within the width of the coil, and from the point of view of sensitization, uniform heating of, for example, 550°C or less is required.

Cooling water is passed inside the rectangular hollow pipe 3C to prevent the coil from melting due to the heat generated by the coil itself due to high-frequency induced current and the radiant heat from the surface of the heated pipe that reaches up to 550°C. .

However, in this way, the rectangular hollow pipe 3C
There is no problem when the high-frequency induction heating coil 3, which mainly consists of It has been found that a drawback arises in the case of a pipe 1 having a nozzle 6 which is a branch pipe from 5. That is, a small-diameter nozzle 6 is welded to the main pipe 5 in a direction substantially perpendicular to the main pipe 5. As an example of arranging the high-frequency induction heating coil 3 over the welded part that is the boundary between the main pipe 5 and the nozzle stub 6, the nozzle stub 6 is wound and the winding reaches the outer peripheral surface of the main pipe 5 as it is. There are ways to maintain it.

In such a method, A- in FIG.
As is clear from FIGS. 5 to 7, which respectively show cross-sectional views along lines A, B-B, and C-C, in FIG. In contrast, in FIG. 7, there are parts that are almost horizontal. In FIG. 7, the wide portion of the rectangular hollow pipe 3C being in a horizontal state means that the wide portion coincides with the winding direction plane. For this reason, winding the rectangular hollow pipe 3C along one surface of the piping will generate a large stress in the rectangular hollow pipe 3C, and if this is done forcibly, cracks will occur in the rectangular hollow pipe 3C. There are many cases where the cooling water that is flowing in leaks out.

If such water leakage occurs, since the work place is inside the reactor containment vessel, the leaked water will contain radioactivity, which is extremely undesirable from the standpoint of radioactive contamination. This creates a risk of short circuit.

An object of the present invention is to avoid damaging the induction heating coil by winding it around the joint of piping without applying excessive bending stress to the high-frequency induction heating coil that covers the welded part where the nozzle stub is attached to the main pipe. The present invention provides a high frequency induction heating coil.

In order to achieve such an object, the present invention provides a high-frequency induction heating coil that is wound around the welded part of a pipe whose nozzle stub is welded to the main pipe.
This high-frequency induction heating coil is composed of a plate positioned on the piping surface and a circular hollow pipe fixed to the upper surface of the plate into which a cooling medium can flow.

The present invention will be explained in detail below using Examples.

FIG. 8 is a configuration diagram showing an embodiment of a high-frequency induction heating coil wound around a joint portion of piping according to the present invention. The same reference numerals as in FIG. 3 indicate the same materials. The high-frequency induction heating coil 7 is wound concentrically around the nozzle stub 6 with a gap G and extends as it is on the circumferential side of the main tube 5 near the nozzle stub 6.
As shown in detail in cross section in FIG. 9, a strip-shaped copper plate 7A that contacts the outer peripheral surfaces of the nozzle stub 6 and the main tube 5, a circular hollow pipe 7C soldered to the strip-shaped copper plate 7A with a brazing material 7B, and It is composed of 7D. Cooling water is flowing into the hollow pipes 7C and 7D.

The high frequency induction heating coil configured in this way is
Since it is made of a circular hollow pipe, the bending stress generated by it is constant no matter which direction you try to bend it in the direction perpendicular to its central axis.
Therefore, there is no possibility that a particularly concentrated stress will occur and damage the circular hollow pipe. Therefore, the cooling water flowing into the circular hollow pipe will not leak due to breakage, and accidents such as radioactive contamination and electrical short circuits will not occur.

In this embodiment, if there is another welded part near the main pipe 5 of the nozzle stub 6, the high-frequency induction heating coil 7 also covers the welded part and the welded part between the main pipe 5 and the nozzle stub 6. be able to place it.

FIG. 10 is a configuration diagram showing another embodiment of a high frequency induction heating coil wound around a joint of piping according to the present invention. In the same figure, the high-frequency induction heating coil 8 is wound concentrically around the main pipe 5, and especially at the attachment part of the nozzle stub 6, the nozzle stub 6 near the main pipe 5
It extends toward the nozzle 6 side along the side surface of the nozzle 6. The high-frequency induction heating coil 8 consists of a rectangular hollow pipe 8A at the part where the main tube 5 is wound, as shown in FIG. , consisting of a circular hollow pipe 8B. Cooling water flows into the rectangular hollow pipe and the circular hollow pipe.

In the high-frequency induction heating coil 8 configured in this way, the one wound at the attachment part of the nozzle stub 6 is twisted at approximately 90 degrees from the circumferential side of the nozzle stub 6 to the circumferential side of the main tube 5, but it is twisted in a circular hollow shape. Since it is composed of a pipe, the bending stress generated by bending in any direction perpendicular to its central axis is constant, and therefore, particularly concentrated stress occurs, causing a circular hollow pipe. There will be no chance of damaging it.

In each of the embodiments described above, two circular hollow pipes are arranged side by side on a strip-shaped copper plate, but it goes without saying that the number of pipes is not limited to two and may be one.

As is clear from the above description, according to the high frequency induction heating coil wound around the joint part of piping according to the present invention, the high frequency induction heating coil covering the welded part where the nozzle stub is attached to the main pipe has an unnecessary amount of heat. This can prevent damage to the induction heating coil without applying bending stress.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing an example of a conventional high-frequency induction heating coil wound around a joint of piping.
Fig. 2 is a diagram showing a cross section of a conventional high-frequency induction heating coil, Fig. 3 is an explanatory diagram showing a case where the high-frequency induction heating coil is wound around a main pipe with a nozzle attached, and Fig. 4 is a diagram showing a case where the high-frequency induction heating coil is wound around a main pipe to which a nozzle is attached. 5 to 7 are cross-sectional views taken along lines A-A, B-B, and C-C in FIG. 4, and FIGS. Figure 9 is an explanatory diagram showing the configuration of an embodiment of a high-frequency induction heating coil wound around a joint of piping in the present invention.
The figure shows a cross section of the high frequency induction heating coil wound around the joint of piping according to the present invention, and FIG. 10 shows another embodiment of the high frequency induction heating coil wound around the joint of piping according to the present invention. Configuration diagram shown, No. 11
12 and 12 are views showing cross sections of the high frequency induction heating coil shown in FIG. 10, respectively. 5... Main pipe, 6... Nozzle stand, 7... High frequency induction heating coil, 7A... Strip copper plate, 7B... Brazing metal,
7C, 7D...Circular hollow pipe.

Claims (1)

[Claims] 1. In a high-frequency induction heating coil that is wound around a welded part of a pipe whose nozzle stub is welded to the main pipe, this high-frequency induction heating coil is attached to a plate located on the piping surface and the upper surface of the plate. 1. A high-frequency induction heating coil wound around a joint of piping, characterized in that it is composed of a fixed circular hollow pipe into which a cooling medium can flow.