CN111810753A - Reinforced structure for built-in girth welds in metal bellows expansion joints - Google Patents

Abstract

The invention discloses a strengthening structure for a built-in circumferential weld of a metal corrugated pipe expansion joint, which comprises a connecting pipe, a corrugated pipe, a hoop and a circumferential weld. A section of circular straight pipe section is preset at each of the two axial ends of the corrugated pipe. The hoop is a section of thin-wall circular straight pipe, the hoop is sleeved with a straight pipe section preset by the matched corrugated pipe, and a port to be welded of the hoop is flush with an outward port of the straight pipe section preset by the matched corrugated pipe. The circumferential weld is positioned at the joint of the ferrule and the straight pipe section outer port of the corrugated pipe and the connecting pipe to form an angular connecting structure which takes the connecting pipe as a lining and is overlapped. The straight pipe section and the hoop of the corrugated pipe are directly sleeved on the connecting pipe, the formed butt joint is in a step shape, the butt joint structure is convenient for implementing angular welding, the fillet welding has better penetration than flat welding, and the formed circumferential weld joint has high connection strength.

Description

Reinforced structure for built-in girth welds in metal bellows expansion joints

technical field

The present invention relates to a welding structure of metal components, in particular, the present invention relates to a structure for built-in girth welds in metal bellows expansion joints, especially a reinforced structure for built-in girth welds in metal bellows expansion joints .

Background technique

During the operation of the industrial and civil heat pipe network, a certain amount of axial thrust and even a small amount of angular displacement will inevitably be generated due to changes in the temperature and pressure of the built-in medium. These objective axial thrusts and angular displacements are destructive to the erected thermal pipe network, so necessary technical measures must be taken during engineering design to minimize these destructiveness. The most commonly used technology in engineering is to add expansion joints at the relevant nodes of the thermal pipe network, and use the elastic deformation characteristics of the expansion joints to slow down or absorb the axial thrust and angular displacement. Most of the thermal pipe networks used in today's projects are equipped with metal bellows expansion joints. Such expansion joints have strong pressure bearing capacity, large axial elastic deformation, flexible compensation, safe and reliable, and relatively simple structure and low cost. The diameter of the industrial heat pipe network is usually large, so the diameter of the metal bellows configured is correspondingly large, usually hundreds of millimeters, and the wall thickness is relatively thin. In the project, on the basis of satisfying the pressure-bearing conditions, the wall thickness of the matching metal bellows is only a few millimeters, that is to say, the wall thickness only accounts for a few tenths of the diameter value. In addition to the thin wall, the structural features of the metal corrugated pipe are that there are straight pipes at both ends of the corrugated section in the axial direction. Since the wall thickness of the straight pipe of the metal bellows is quite different from the wall thickness of the matching nozzle, the welding of such unequal thickness girth welds is difficult to construct, requires high operating skills of the welders, and the molten pool is slightly biased during the welding process.

The straight pipe side of the metal bellows is easy to cause defects such as the thinnest straight pipe wall being welded through or collapsed. Although the expected quality of such welding defects can be achieved by repairing welding afterwards, the manufacturing man-hours are significantly increased, thereby increasing the manufacturing cost.

SUMMARY OF THE INVENTION

The invention mainly aims at the problem that the straight pipe sections at both ends of the metal corrugated pipe are easily welded through or collapsed during the welding process in the prior art, and proposes a strengthening structure for the built-in girth weld of the expansion joint of the metal corrugated pipe, and the structure is simple. , practical, on the basis of not reducing the elasticity of the metal bellows expansion joint, by adding ferrules on the straight pipe sections at both ends of the metal bellows, the formed laminated structure is convenient for corner welding. High seam connection strength.

The present invention achieves technical objectives through the following technical solutions.

Reinforced structure for built-in girth welds in metal bellows expansion joints, including nozzles, bellows, ferrules and girth welds. A circular straight pipe section is respectively preset at both ends of the bellows in the axial direction. The improvement lies in: the ferrule is a thin-walled circular straight pipe, its wall thickness is 1-5mm thicker than the wall thickness of the matching corrugated pipe, and the length is 1/4-1/2 shorter than the preset straight pipe section of the matching corrugated pipe. 2. The ferrule is fitted with the preset straight pipe section of the matching bellows, and the port to be welded of the ferrule is flush with the outward facing port of the preset straight pipe section of the matching bellows. The girth weld is formed at the junction of the outer port of the straight pipe section of the ferrule and the corrugated pipe and the connecting pipe to form an overlapping angular connection structure with the connecting pipe as a lining.

As a further improvement solution, the overhanging end of the nozzle is a circular tube of equal diameter, or a circular tube with a shoulder.

As a further improvement scheme, the material of the ferrule is the same as that of the matching corrugated pipe.

As a further improvement solution, the ferrule is a section of circular tube with a single-layer structure.

Compared with the prior art, the present invention has the following positive effects:

1. A ferrule is added at the straight pipe section of the corrugated pipe, which does not change the axial elastic deformation performance of the corrugated pipe, but also increases the structural strength. This kind of nesting structure is simple, easy to nest, and high production efficiency;

2. A ferrule is added at the straight pipe section of the corrugated pipe, which naturally forms a protective layer for the straight pipe section of the corrugated pipe, which directly increases the welding thickness of the girth weld, which is beneficial to improve the welding efficiency;

3. The straight pipe section and the ferrule of the corrugated pipe are directly sleeved on the nozzle, and the formed butt joint is stepped. This kind of butt joint structure is convenient for the implementation of corner welding, and the fillet welding has better penetration than flat welding. Angle girth weld joint strength is high.

Description of drawings

Figure 1 is a schematic structural diagram of the present invention.

FIG. 2 is an enlarged schematic view of the structure at FIG. 1A .

FIG. 3 is a schematic diagram of the simplified connection structure of FIG. 2 .

FIG. 4 is a schematic diagram of a further strengthened connection structure in FIG. 2 .

Detailed ways

The present invention will be further described below according to the accompanying drawings and in conjunction with the embodiments.

Figure 1 shows the strengthening structure for the built-in girth weld of the metal bellows expansion joint, which includes a nozzle 1, a bellows 2, a ferrule 3 and a girth weld 4. The bellows 2 is an elastic device of an expansion joint. In order to facilitate the axial connection, a circular straight pipe section 2.1 is preset at the axial ends of the bellows 2. The ferrule 3 is a reinforcing member in the structure, It is a thin-walled circular straight tube, and its wall thickness is determined according to the pressure bearing size of the matching expansion joint. Under normal working conditions, the thickness of the ferrule 3 is 1-5 mm thicker than the wall thickness of the matching corrugated pipe 2 to meet the safe use conditions. In order not to reduce the elastic deformation ability of the supporting corrugated pipe 2, the length of the ferrule 3 is limited. In the structure, the ferrule 3 is fitted with the straight pipe section 2.1 preset by the matching bellows 2 , and the port to be welded of the ferrule 3 is flush with the outward facing port of the straight pipe section 2.1 preset by the matching bellows 2 . The girth weld 4 is formed at the junction of the ferrule 3 and the outer port of the straight pipe section 2.1 of the corrugated pipe 2 and the nozzle 1 to form an overlapping angular connection structure with the nozzle 1 as a lining.

Example 1

Figure 2 shows a schematic diagram of the partial structure of the present invention, which is suitable for matching with medium pressure series expansion joints. The overhanging end of the connecting pipe 1 shown in the figure is a round pipe with a shoulder, and the matching corrugated pipe 2 is fitted with the overhanging end of the connecting pipe 1 by a preset straight pipe section 2.1. In order to further strengthen the welding quality of the straight pipe section 2.1 of the corrugated pipe 2 and the joint of the nozzle 1, a ferrule 3 is sleeved on the outer wall of the straight pipe section 2.1 of the corrugated pipe 2. Since the pressure bearing value of this embodiment belongs to the medium pressure range, the wall thickness of the ferrule 3 is appropriately increased, and the thickness of the adopted bellows is 3 mm thicker than the wall thickness of the matching corrugated pipe 2 . In order to improve the weldability and welding quality, the ferrule 3 is a single-layered circular pipe, and its length is 1/3 shorter than the straight pipe section 2.1 preset by the matching corrugated pipe 2 . On the other hand, it is made of the same material as the corrugated tube 2. In this embodiment, a 1Cr18Ni9Ti steel plate is used to roll and form. After the ferrule 3 is fitted in place, a butt joint with steps is formed, the annular butt joint is welded in an angle direction, and the formed girth welded seam 4 is an angle welding seam. Since the length of the additional ferrule 3 is shorter than the pre-set straight pipe section of the matching corrugated pipe 2, the axial elastic deformation performance of the corrugated pipe 2 is not changed in the structure, and the structural strength of the post-formed girth weld 4 can be increased. In addition, the newly added ferrule 3 naturally forms a protective layer for the straight pipe section 2.1 of the corrugated pipe 2, and the formed butt joint is stepped. This kind of butt joint structure facilitates the implementation of corner welding, and the fillet welding is more penetrating than flat welding. Good performance, the formation of the girth weld 4 has high connection strength, and it is beneficial to improve the welding efficiency.

Example 2

The structure shown in Figure 3 is the same as the main body of the structure shown in Figure 2, and only partial improvements have been made to the overhanging end of the connecting pipe 1. In this embodiment, the overhanging end of the connecting pipe 1 is a circular tube of equal diameter, and its function is the same as that of the first embodiment. same. This structure is simpler than the structure shown in Figure 2, and is especially suitable for low-pressure series expansion joints.

Example 3

The structure shown in FIG. 4 is the same as the main body of the structure shown in FIG. 2 , only the number and position of the matching ferrules 3 have been partially improved. In this embodiment, a sleeve is fitted on the inner and outer walls of the straight pipe section 2.1 preset in the corrugated pipe 2 respectively. Hoop 3. The structure and function of this double hoop 3 is the same as that of Embodiment 1, but the strength of the formed girth weld 4 is better than that of Embodiment 1, so this embodiment is especially suitable for high-pressure series expansion joints.

Claims (4)

1. A strengthening structure for a built-in circumferential weld of a metal corrugated pipe expansion joint comprises a connecting pipe (1), a corrugated pipe (2), a hoop (3) and a circumferential weld (4); a section of circular straight pipe section (2.1) is respectively preset at two axial ends of the corrugated pipe (2); the method is characterized in that: the hoop (3) is a section of thin-wall circular straight pipe, the wall thickness of the hoop is 1-5 mm thicker than that of the matched corrugated pipe (2), the length of the hoop is 1/4-1/2 shorter than that of a preset straight pipe section (2.1) of the matched corrugated pipe (2), the hoop (3) is sleeved with the preset straight pipe section (2.1) of the matched corrugated pipe (2), and a port to be welded of the hoop (3) is flush with an outward port of the preset straight pipe section (2.1) of the matched corrugated pipe (2); the circumferential weld (4) is formed at the joint of the ferrule (3) and the straight pipe section (2.1) outer port of the corrugated pipe (2) and the connecting pipe (1) to form an angular connecting structure which takes the connecting pipe (1) as a lining and is overlapped.

2. A strengthening structure for a metal bellows expansion joint built-in girth weld according to claim 1, wherein: the extending end of the connecting pipe (1) is a section of circular pipe with equal diameter or a circular pipe with a shoulder.

3. A strengthening structure for a metal bellows expansion joint built-in girth weld according to claim 1, wherein: the ferrule (3) is made of the same material as the matched corrugated pipe (2).

4. A strengthening structure for a metal bellows expansion joint built-in girth weld according to claim 1, wherein: the hoop (3) is a section of circular tube with a single-layer structure.

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