JPS62209293A - Expansion joint for piping - 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] [Object of the Invention] (Industrial Field of Application) The present invention relates to a piping expansion joint installed, for example, in the primary piping of a fast breeder reactor, and in particular to a piping expansion joint using metal bellows. Regarding.

(Prior Art) For example, in a fast breeder reactor, high-temperature liquid metal or the like flows through piping connecting equipment, especially secondary piping, so that the amount of thermal expansion becomes extremely large. Therefore, in order to absorb thermal expansion, such piping is generally routed around more often. However, such piping takes up a large amount of space in the reactor building, and is one of the factors that unnecessarily increases the size of the building.

In addition, since such piping is subject to severe seismic resistance conditions, a high-strength piping support device is required, and as the length of piping increases, the number of piping support devices required increases. It has become.

From this point of view, when it comes to reducing the installation cost of conventional loop-type fast breeder reactors, it is difficult to route the pipes.

In recent years, as a countermeasure to this problem, studies have been conducted to install expansion joints for piping using bellows-shaped metal bellows, thereby reducing the amount of piping that needs to be routed and suspended. FIG. 5 shows an example of the configuration of such a piping expansion joint. A pair of piping ia, l
Annular brackets 2a and 2b are attached to the connection portion b. A cylindrical guide 3 is attached to each bracket 2a, 21).
cylindrical guides 3a and 3b are provided in a protruding manner, respectively.
An outer bellows 4a and an inner bellows 4b are arranged in layers inside the bellows b. Note that the outer bellows 4a and the inner bellows 4b are each doubled in the axial direction, and an outer sleeve 5a and an inner sleeve 5b are provided in the middle part of each.
are connected to form a double ring.

Displacement of the connecting portion due to thermal expansion of each piping 1a, lb is absorbed by expansion and contraction of each bellows 4a, 4b. The bellows 4a, 4b, the brackets 2a, 2b, and the sleeves 5a, 5b are in close contact with each other, and a leak detection device (not shown) is installed in the gap between the bellows 4a, 4b. Being hit.

By the way, metal bellows made of stainless steel or the like are used for the outer bellows 4a and the inner bellows 4b in consideration of heat resistance. The metal bellows is, for example, a bellows (hereinafter referred to as a molded bellows) 6 formed by integral molding as shown in FIG. A bellows (hereinafter referred to as a welded bead) 9 that is joined by a welded bead is considered.

(Problems to be Solved by the Invention) In the case of the molded bellows 6 shown in FIG. 6, the bidge p cannot be made very large due to molding considerations. That is, in the conventional molded bellows 6, the ratio of the height h of the pleats to the pitch p is about 1:1. Therefore, in order to obtain sufficient elasticity, it is necessary to shorten the length, and it is also necessary to avoid running a lot of piping. Furthermore, if the length of the bellows is made small, the elasticity becomes insufficient or a large number of joints are required, making it difficult to necessarily obtain the desired effect.

On the other hand, in the welded bellows 9 shown in FIG. 7, the inner and outer peripheral edges of a metal element 447 are welded. That is, seal welding is mainly performed. However, in the welded bellows 9, since the maximum bending stress when the bellows expands and contracts acts on the welded portion 8, the reliability of the welded portion 8 is likely to be impaired. Also,
Since the welded portion 8 is located at the inner and outer peripheral edges, non-destructive inspection of the welded portion 8 is difficult, and quality control regarding the welded portion 8 cannot necessarily be performed sufficiently.

In addition, the molded bellows 6 shown in Figure 6 is attached to the primary piping of the fast breeder reactor.
When we examined the possibility of installing expansion joints for piping in series, we found that the stress generated in the molded bellows 6 would become too high when absorbing the axial displacement of the piping. For this reason, we also considered a method of using the pipes, which are arranged with their axes offset from each other, by providing a routing section in the direction perpendicular to the axis and attaching an expansion joint to that section.

However, even in this case, a problem arose in that a considerable length of piping was still required, and the number of joints to be installed was increased.

The present invention was made in view of the above circumstances, and by reducing the ratio of the bidge to the height of the folds of the bellows, it is possible to sufficiently absorb piping displacement with a small joint length, and to reduce the amount of piping during expansion and contraction. Reliability against stress is sufficiently high, and non-destructive testing is also easy.
Plumbing requirements that can be fully planned! The purpose is to provide an I-joint.

[Structure of the invention]

(Means for Solving the Problem) The expansion joint for piping according to the present invention has a welded bead in which a dish-shaped metal material is butt-V-welded at the inner and outer peripheral portions, and has a welded portion and a non-welded portion. By making the wall thickness different from that of the welded part, the shape is set such that the bending stress is maximum at parts other than the welded part.

(Function) By using a welded bellows as the bellows, it becomes possible to reduce the ratio of the pitch to the height of the folds. That is, the axial length of the bellows is short and the joint has sufficient expansion and contraction. Therefore, by butt-welding the metal material to the welded part, for example, when performing non-destructive testing (RT) using radiation, the radiation li5
! By arranging the source and the detector in opposition to each other in the direction of transmission through the peripheral wall of the bellows, it is possible to easily and reliably carry out the inspection in (a).
2 Ru. Therefore, the reliability of the welded portion can be improved. In addition, by setting the shape so that the bending stress is maximum at the part 11 other than the welded part, it is possible to avoid applying large bending stress to the welded part, thereby preventing the occurrence of cracks in the welded part. This makes it possible to prevent this, and ensures sufficient reliability under various usage conditions.

Therefore, a large axial displacement and high reliability are ensured as a straight pipe type expansion joint, making it suitable for use in situations where piping is to be straightened and shortened. Furthermore, since the bellows has a small pitch, the risk of vibration damage due to earthquakes, etc. is also prevented.
The earthquake-resistant structure will also be strengthened.

(Example) An example of the present invention will be explained below with reference to Figs. It is something.

FIG. 1 shows the overall structure of the joint. Annular brackets 1 to 12a and 12b are respectively attached to the connecting portions of a pair of pipes 11a and 11b connected with a predetermined gap. Each bracket 12a.

Cylindrical outer piping 13a, 131) is provided on the outer circumference of 12b.
It is installed protrudingly with a predetermined gap. This outer guide 1
A cylindrical space is formed by the inner guides 14a and 14b consisting of the abutting U portions of the pipes 11a and llb and the outer bellows 15a and the inner bellows 15 are arranged in layers in this space. are doing. Each bellows 15a,
Reference numeral 15b is attached closely to the brackets 12a and 12b.

An outer sleeve 16a and an inner sleeve 16b are closely connected to each bellows 15a, 15t) at an axially intermediate portion of each bellows 15a, 15t). Each of these sleeves 16a, 16t) is arranged? f
It is arranged in a double ring shape to cover the joining gap between f11a and f11b. In the initial stage of installation, a bellows protection rod 17 is attached to the outer peripheral end N- of the brackets 12a and 12b.
A plurality of are arranged in the circumferential direction, and the bellows protection rod 17 protects the brackets 12a and 12b! ! This prevents the bellows from moving in the 1fJ direction and prevents the bellows from being damaged due to overstretching. After installing the joint, remove the bellows protection rod 17 from the brackets 12a, 12b, and
2b is welded and fixed to the pipes 11a and 11b.

Note that the outer bellows 15a has a function as a backup when the inner bellows 15b leaks. Furthermore, gas pressure can be applied between the sleeves 16a and 16b, so that the sealing function of the bellows can be checked.

In addition, the outer guides 13a, 13b and the inner guide 14a,
14b means that each bellows 15 may come into contact with each other during excessive internal pressure due to an accident or excessive load due to an earthquake.
The function to prevent the occurrence of buckling deformation of a + I J b is provided.

Furthermore, the outer sleeve i 5 Fl and the inner sleeve 16
The sleeves 16a and 11b are designed to prevent the bellows from being deformed at the connection between the pipes 11a and 11b if the pipes 11a and 11b are shifted from each other during an earthquake, etc.
16b makes it easy to absorb the displacement of the young T in the lateral direction.

FIG. 2 shows an enlarged cross-sectional shape of each bellows 15a, 15b.

Each of the bellows 15a, 15b is a metal bellows, and is a welded bellows protection rod made by butt-welding a dish-shaped metal material 18 at its inner and outer peripheral portions. Each metal material 18 has a large wall thickness at its inner and outer circumferential portions, and the welded end surfaces 18 at the inner and outer circumferential portions are thicker.
a is a plane along the direction perpendicular to the axis. Welding #i and 1
The width S of the metal moon 8a is set to be larger than the thickness t of the middle portion of the metal moon 18. In addition, each metal material 18 is made by cutting stainless steel, and the welding end surface 18 a
They are each welded together using electron beam welding.

In the case of a welded bellows structure having such a wide welded portion 19, the ratio of the pitch p to the height h of the pleats to η゛ is a small value ( 1/3).

In addition, since the structure is joined by a welded part 19 with a wide welded end surface 18a bsr, even though the welded part 19 is located at the inner and outer circumferential edges where the expansion and contraction load is large, the stress generated in that part is small. can be sufficiently reduced by 1" compared to other parts. Therefore, as shown in Figure 7, it has much greater strength than conventional welded beads, and has high reliability with respect to elastic strength. It will be 1tfI.

Furthermore, since the bellows 158.15t) has a butt welded structure, when non-destructive testing (RT) is performed on the welded portion 19 using radiation, for example, the peak (upper part in Figure 2) will be detected above it. The test can be carried out by installing a small film and guiding the radiation source toward the inner diameter side (lower side in Figure 2). In other words, a non-destructive test can be performed by irradiating the welded portion 19 with radiation after it has healed in the welding direction. For the welded part 19 in the valley (lower part in Figure 2), place the film on the inside of the bellows in the opposite way to the above and release it from the outside. Non-destructive testing can be carried out by irradiating with a single source. Therefore, since the welded portion is made into a butt shape, the volume inspection of the welded portion 19 becomes possible. Regarding the surface inspection performed by applying a test liquid to the welded part, as shown in Figure 7, unlike conventional welded bellows, the test liquid does not easily flow down, so surface inspection can also be carried out effectively. . Therefore, for the welded bellows structure, which was conventionally only possible through visual inspection, non-destructive inspection other than visual inspection can be easily and reliably performed, and quality control can be adequately controlled. Being hit.

According to the above-mentioned embodiment, although it is an expansion joint for piping that uses metal bellows, it is able to absorb a large change in ridges, and also satisfies the necessary quality control requirements, making it suitable for fast breeder reactors. The primary joint t3 can be effectively used as a joint for absorbing thermal displacement. That is,
When compared with conventional molded roses, the stress in the case of the above-mentioned example was too large or the overall length of the bell was too long to be used as a straight pipe expansion joint, making it less practical. According to the expansion joint for piping having a bellows structure, it can be used as a compact and highly practical expansion joint. In particular, when used as the primary piping of a fast breeder reactor, by arranging the equipment nozzles for connecting the piping in a straight line, it becomes possible to connect the equipment in a straight line, and the piping length increases. This makes it possible to minimize the length of time. This allows the piping space to be reduced and contributes to downsizing of the single-storey structure.

In addition, by adopting a highly elastic bellows structure,
It is possible to deal with not only axial displacement but also complex displacement that includes radial displacement, and it has great advantages on piping stage S1, such as expanding the range of choices for compact piping design. Become.

In the above-mentioned embodiment, as shown in FIG.
As shown in the figure, the outer part of the pleats can also have a structure in which the thickness changes. If this configuration is adopted, the axial width S of the welded portion 19. This makes it possible to make ordinary welding such as arc welding and 'I' IG welding larger.Also, by making the inner surface of the pleats straight, the inner gap in the radial direction of the welding part 19 can be made larger. the second
Since it can be made larger than the one shown in the figure, it is easier to carry out volumetric inspections such as radiographic inspections as described above. Therefore, according to the embodiment shown in FIG. 3, in addition to the effects obtained in the embodiment described above, the range of selection of welding methods can be broadly expanded, and volume inspection etc. can be easily performed. 1. °1 It is something that can be done.

Furthermore, in each of the embodiments described above, the welded portions 19 are set at the inner and outer peripheral portions of the bellows, but as shown in FIG. 4, the welded portions 19 may be butt-welded at the side wall portions near the inner and outer peripheral portions. According to the embodiment shown in FIG. 4, the welded portion 1
9 is placed differently from the position of the bellows where the maximum stress is applied, it is possible to avoid applying the maximum stress to the welded portion 19. Therefore, reliability in terms of strength can be greatly improved. In the case of the embodiment shown in Fig. 4, each time each metal material is welded, a non-destructive inspection is performed by arranging the radiation detector and the detector in a direction parallel to the axial direction. be.

In the above embodiments, the present invention was applied to the primary piping of a fast breeder reactor, but it goes without saying that the present invention can be applied to piping that undergoes large thermal expansion due to the flow of high-temperature fluid, as well as various other types of piping. be.

〔Effect of the invention〕

As described above, according to the piping expansion joint according to the present invention,
By using a welded bellows made by butt-welding a dish-shaped metal material at or near the inner and outer peripheries, and by adjusting the wall thickness of the welded and non-welded parts, bending stress is reduced in areas other than the welded parts. Because the shape is set to the maximum angle, it has high elasticity characteristics similar to conventional welded bellows, and it also improves the reliability of the welded part structure1, and allows for easy non-destructive testing such as radiographic testing. This has the excellent effect of ensuring reliable and sufficient quality control.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view of a joint rest showing one embodiment of the present invention, Fig. 2 is an enlarged sectional view of the bellows portion shown in Fig. 1, and Fig. 3 shows another embodiment of the invention. FIG. 4 is an enlarged sectional view showing another embodiment, FIG. 5 is a partial sectional view of a joint rest showing a conventional example, and FIG. 6 is an enlarged sectional view of a bellows in a conventional joint. , and FIG. 7 is an enlarged cross-sectional view showing the structure of a different bellows of a conventional joint. 11a, 11b...Piping, 15a, i5b...B1
Cause, 19...Welding section. Representative Patent Attorney Yudo Ken Chika, IJII
Hiroshi Mimata Buncha 2 figure $3 In 4th eye 5th wiro 6 figure σ Fig. 7

Claims (1)

[Claims] In a piping expansion joint that has a bellows-shaped metal bellows and connects piping on the same axis, the metal bellows is a welded bellows in which a dish-shaped metal material is butt-welded at or near the inner and outer peripheral portions, and the welded portion 1. An expansion joint for piping characterized by having a shape in which the bending stress is maximized at a portion other than the welded portion by having different wall thicknesses between the welded portion and the non-welded portion.