JPH06281057A - Pipe circumferential joint welding method and pipe fit-up device - Google Patents

Abstract

PURPOSE:To provide a method for efficiently and high-quality performing the circumferential joint welding of pipes and to provide a pipe fit-up device to be used in order to carry out the method. CONSTITUTION:A pipe fit-up device 10 is formed by pressing shoes 12 and pressing shoe retreating mechanisms 16 for advancing and pressing the pressing shoes 12 toward an inner wall surface 14 of a pipe 14, and retreating the pressing shoes 12 from the inner wall surface 14. High frequency induction coils 24 as a heat generating body are embedded in the pressing shoes 12 along the outer surface of the pressing shoes 12. When the pressing shoe 12 is brought in contact with the inner wall surface of a pipe 14 whose inside diamter is smaller, the high frequency induction coils heat the pipe wall, expand it, and extend the circumferential length of the pipe, that is, the inside diameter, so as to comforme it to the inside diameter of a large pipe. Moreover, the pressing shoes press the inner wall surface of the pipe so as to correct the sectional shape of the pipe into prefect roundness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding peripheral joints of pipes, and more particularly to aligning the ends of one pipe with the ends of the other pipe with a predetermined gap. Or in a circumferential joint welding method for pipes in which both pipes are completely butted together and the joints are welded to join the pipes in the longitudinal direction, the difference in inner diameter and circularity between the ends of both pipes can be efficiently achieved. The present invention relates to a method of performing high-quality circumferential joint welding of pipes by keeping the value within a predetermined value, and also to a pipe fit-up device used for performing the method.

[0002]

2. Description of the Related Art In recent years, in the case of performing circumferential joint welding by abutting both ends of a pipe, a pipe for laying a large-diameter long-distance pipe by continuously joining pipes with a large diameter continuously in the longitudinal direction. When performing pipe joint welding in construction, etc., automatic arc welding is often used using an automatic welding device. In this case, the quality of welding depends on the degree of fit-up at both ends of the pipes to be joined. Here, the fit-up of the pipe means that the relative dimensional relationship between both ends of the pipes to be joined is within an allowable value, including the groove formed by processing the ends of the pipes. An important item among the items of the fit-up work is to keep the circularity and the inner diameter difference of the pipe within a predetermined value. However, in the manufacture of pipes, certain manufacturing tolerances are recognized regarding roundness and inner diameter, so when the pipes to be joined are abutted, the circularity at the ends of both pipes and the mutual difference in inner diameter are Usually, it is not within the specified value. If the roundness and inner diameter difference are not within the predetermined value, it is difficult to perform good peripheral joint welding, the quality of the welded weld is poor, or there is a defect in the welded joint. Welding and reworking are often necessary.

When the welder performs the peripheral joint welding of the pipe by manual welding, the welder can perform the welding work while appropriately adjusting it in accordance with the actual relative dimensional relationship of the ends. When automatic welding is performed by the apparatus, since the welding is uniformly performed based on the set operating conditions of the automatic welding apparatus, pipe fit-up is more important than in the case of manual welding.

[0004] Conventionally, in the welding of pipe-to-pipe peripheral joint welding, in particular, to the peripheral joint welding of a pipe having a large diameter, the pipe shape is mechanically changed in order to keep the circularity and the inner diameter difference of the pipe within predetermined values. Often, a straightening jig, or mechanical tube fit-up device, was used. FIG. 5 (a) is a front view of an example of a conventional mechanical pipe fit-up device seen from the end of the pipe, and FIG. 5 (b) is a side view of the pipe fit-up device shown in FIG. 5 (a). And each is shown in the state of being mounted in the tube.

The pipe fit-up device shown in FIG. 5 advances and contacts the pressing shoe 12 and the pressing shoe 12 toward the inner wall surfaces of the tubes 14 and 15, and further presses the inner wall surface and from the inner wall surface. Push back and forth mechanism 1 for retracting
6 and 6. In this example, the eight pressing shoes 12 form four pairs of pressing shoes that press the inner wall surfaces of the pipes in the opposite directions toward the outside in the radial direction to expand the pipes. The pressing shoe 12 of the tube 1
A surface that matches the inner wall surfaces of the pipes 4 and 15 is provided on the side facing the inner wall surfaces of the pipes 14 and 15. The pressing shoe advancing / retreating mechanism 16 includes a hydraulic cylinder 18 provided in each of the pressing shoes 12, and a supporting member for fixing the hydraulic cylinder 18, for example, a cylindrical supporting member 20. The pressing shoe 12 is attached to the tip of a shaft 22 that freely expands and contracts by a hydraulic cylinder 18.

In order to fit the pipe, the hydraulic cylinder 18 is driven to extend the shaft 22, and the pair of pressing shoes 12 are radially outwardly separated so that the inner wall surface of the pipe 14 is separated from each other. Press. The shapes of the tubes 14 and 15 are mechanically corrected by expanding the tubes 14 and 15 by the pressing of the pressing shoe 12, and the circularity and the inner diameter difference of the ends of the tubes 14 and 15 are kept within a predetermined value.

[0007]

However, by using the above-described pipe fit-up device, the large diameter pipe is deformed only by a mechanical external force, and the joint end size of the pipe is adjusted to a predetermined roundness and inner diameter difference. It was extremely difficult and required a lot of time and manpower, so that the work efficiency of the plumbing work was very poor. Another method for keeping the circularity and the inner diameter difference of the pipe within a predetermined value is to tighten the pipe manufacturing tolerance at the time of manufacturing the pipe. However, this method naturally increases the manufacturing cost of the tube. Also, at the groove processing stage when manufacturing the pipe,
Although it is possible to adopt a method of machining the inner surface of the pipe so that there is no difference in inner diameter, it is necessary to increase the wall thickness of the pipe to secure the pipe wall part to be machined. Production costs are high.

In view of the above situation, an object of the present invention is to provide a method for efficiently performing high-quality pipe-to-pipe peripheral joint welding, and further a pipe fit-up device used for carrying out the method. Is to provide.

[0009]

In order to achieve the above object, a method of welding a pipe circumferential joint according to the present invention is to butt one end of one pipe and the other end of the other pipe, In a method of welding a pipe circumferential joint by welding both pipes in a longitudinal direction, at least one pair of pressing shoes adapted to press inner wall surfaces of the pipe ends in directions opposite to each other outward in the radial direction. Is placed on the inner wall surface of the pipe end, and the pipe end with the smaller inner diameter is heated by the heating element attached to the inner or outer circumference of the pipe end, and the inner peripheral length is expanded by thermal expansion. To match the inner circumference of the larger end of the pipe, and then press the inner walls of the pipe in the opposite directions toward the outside in the radial direction with a pressing shoe to correct the cross-sectional shape into a perfect circle. Keep the roundness of the pipe end and the mutual difference in inner diameter within a specified value, and in this state, pipe circumference connection It is characterized in that to perform the welding.

Further, the pipe fit-up device according to the present invention for carrying out the above-mentioned method of the present invention comprises at least one pair of pressing shoes for pressing the inner wall surface of the pipe in mutually opposite directions radially outward. A push-shut advancing / retracting mechanism for advancing and contacting the push-shut toward the inner wall surface of the pipe, further pushing the inner wall surface, and retracting the push-shut from the inner wall surface, and a heating element mounted on the inner or outer circumference of the pipe. It is characterized by having.

In the present invention, the abutting of the pipe ends means that the ends of the pipes to be joined are aligned as shown in FIG. 2 (a) so that the groove has a predetermined gap. As shown in FIG. 2 (b), it is a concept including both of perfect butting so that the groove does not have a gap. A hydraulic cylinder, a pneumatic cylinder, or an electric motor, for example, is used as a drive source of the push-shut advancing / retreating mechanism of the pipe fit-up device according to the present invention. A high-frequency induction coil or the like is used as the heating element, and it is wound around the outer circumference or the inner circumference of the tube end. The heating temperature is such that the pipe with the smaller inner diameter is heated to that temperature and thermally expanded, and the inner peripheral length of the pipe is approximately equal to the inner peripheral length of the pipe with the larger inner diameter. It depends on the material of the tube and the tolerance at the time of manufacturing the tube, but in the case of stainless steel tube, for example, about 120 ° C to about 200 °
Temperatures in the range C are sufficient.

The pipe fit-up device of the preferred embodiment of the present invention is characterized in that the heating element is embedded in the pressing shoe. This simplifies the configuration and facilitates mounting of the heating element.

[0013]

The operation of the present invention will be described by taking as an example the welding process of a stainless steel pipe having an inner diameter of 900 mm, a manufacturing tolerance of ± 3 mm in perimeter, and a diameter of ± 1 mm. If one side is 1 mm smaller and the other is 1 mm larger than the 900 mm diameter, a maximum discrepancy of 2 mm will occur. If this difference is to be adjusted by thermal expansion, 2/900 = αT = 16 × 10 ⁻⁶ × T, where α is the thermal expansion coefficient of stainless steel, which is 16 × 10.
^-6 / ° C. Therefore, T = 2 / (900 × 16 × 10 ⁻⁶ ) = 139 °
C Theoretically, it is possible to adjust the inner diameter difference of a 2 mm stainless steel tube by heating the tube and raising the temperature of the tube wall by 139 ° C. for thermal expansion.

When the present invention is applied to this embodiment, a band of a heating element, for example, a high frequency induction coil is wound around the outer circumference or the inner circumference of a tube having a smaller inner diameter, and a pressing shoe is brought into contact with the inner wall surfaces of both tubes. . Next, the inner wall length of the tube with the larger inner diameter is increased by heating the inner wall of the tube with the smaller inner diameter with the heating element so that the temperature difference between the wall with the larger inner diameter and the diameter of the larger inner diameter is about 139 ° C. To match. Next, while maintaining the temperature, the inner wall surfaces of both ends of the tube are pressed by the pressing shoe to correct the shape of the tube so as to have a desired roundness. Subsequently, welding is performed while maintaining this state. By heating and raising the temperature to a relatively low temperature by the heating element and thermally expanding the pipe to the required inner peripheral length, it is possible to easily keep the difference in inner diameter within the predetermined value, and the inner wall surface of the pipe with the pressing shoe. By pressing, the cross-sectional shape can be easily corrected to a perfect circle. Further, the tube flattened by its own weight can be mechanically and easily corrected into a perfect circle by the pressing shoe.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail based on embodiments with reference to the accompanying drawings. FIG. 1 (a) is a front view showing the configuration of an embodiment of the pipe fit-up device according to the present invention, and FIG. 1 (b) is a side view of the pipe fit-up device shown in FIG. 1 (a). It is shown mounted inside the pipe. Of the parts shown in FIG. 1, the same parts as those shown in FIG. 5 are designated by the same reference numerals. A main pipe fit-up device (hereinafter, simply referred to as a device for simplicity) 10 is a device for correcting a shape of a pipe wall of a pipe to be joined into a desired shape and maintaining the shape during welding.

The device 10 comprises a pressing shoe 12 and a pressing shoe advance / retreat mechanism 16 for advancing and pressing the pressing shoe 12 toward the inner wall surfaces of the pipes 14 and 15 or for retracting the pressing shoe 12 from the inner wall surfaces. ing. Here, it is assumed that the inner diameter of the pipe 14 is smaller than that of the pipe 15. For example, in the case of a stainless steel pipe having an inner diameter of 900 mm, the device 10 is provided with eight pressing shoes 12 uniformly arranged along the inner circumference of the pipe 14, and two pressing shoes 12 are paired with each other. It is located at the opposite position in the radial direction.
The length (L) of one pressing shoe is slightly shorter than 1/16 of the inner peripheral length of the pipe 14 as shown in FIG. 1 (a), and the width (W) is shown in FIG. 1 (b). As shown, the width is such that it can contact both ends of the tubes 14 and 15 to be joined. The surfaces of the pipes 14 and 15 that come into contact with the inner wall surfaces have contours that substantially match the inner wall surfaces of the pipes 14 and 15.

Two rows of high-frequency induction coils 24 (shown as shadowed portions in FIG. 1) as heating elements are embedded in the pressing shoe 12 along the outer surface of the pressing shoe 12.
The high frequency induction coil 24 connects the pressing shoe 12 to the tubes 14, 1
The tubes 14 and 15 can be heated when brought into contact with the inner wall surface of the tube 5. A power supply cable (not shown) extending along the shaft 22 is connected to the induction coil 24 of the pressing shoe 12, and electric power is supplied from an external power supply.

The pressing shoe advancing / retreating mechanism 16 includes a pressing shoe 1
2 is provided for advancing and pressing the inner wall surfaces of the pipes 14 and 15 and for retracting the inner wall surfaces. The pressing shoe advancing / retreating mechanism 16 is provided on each of the shaft 22 and the shaft 22 that extends radially from the center toward the pressing shoes 12 of each pair, and extends the shaft 22 radially outward or radially inward. Hydraulic cylinder 1 to contract
8 and. The hydraulic cylinders 18 are mounted radially around a cylindrical support member 20 provided in the center of the device 10. Instead of the hydraulic cylinder 18,
It is also possible to use pneumatic cylinders or electric motors. When the hydraulic cylinder 20 is operated so that the shaft 22 extends by the configuration of the pressing shoe advancing / retreating mechanism 16 described above, the pressing shoe 12 presses the inner wall surface of the pipe 14 so that the shaft 22 contracts.
Is operated, the pressing shoe 12 retracts from the inner wall surfaces of the tubes 14 and 15.

Next, the application of the method of the present invention using the apparatus 10 will be described with reference to FIG. In addition, in FIG.
4, the pipe 15 is a stainless steel pipe, the inner diameter of the pipe 14 is about 900 mm, which is slightly smaller than the inner diameter of the pipe 15, the inner diameter difference between the pipes 14 and 15 is larger than a predetermined value, and the pipes 14, 1
It is assumed that the roundness of 5 is not within the predetermined value. First, FIG.
As shown in (a), the ends of one pipe and the ends of the other pipe are aligned while maintaining a predetermined gap d. Unlike FIG. 2 (a), as shown in FIG. 2 (b), the peripheral joint welding of the pipe of the present invention is also performed when the pipe ends are aligned so that the groove is completely in contact. Methods and tube fit-up devices can be applied. Next, as shown in FIG. 1, the pipe fit-up device 10 is installed at the joint portion of the pipes 14 and 15 to be joined. Next, the push-shut advancing / retreating mechanism 16 is operated to extend the shaft 22, and the four pairs of push-shu 12 are brought into contact with the inner wall surface of the end portion of the tube 14.

With the pressing shoe 12 in contact with the inner wall surface, the induction coil 24 is energized to generate heat to generate about 150 to 2
The tube wall at the end of the tube 14 is heated to a temperature in the range of 00 ° C. to thermally expand the tube 14 so that the inner diameter difference from the tube 15 falls within a predetermined value. Next, while maintaining this temperature, the pressing shoe 12 further presses the inner wall surface of the end portion,
The shape of the tube 14 is corrected so as to obtain a predetermined roundness. Next, when the pressing shoe 12 comes into contact with the inner wall surface of the pipe 15, the shaft 22 is further extended by the hydraulic cylinder 18 so that the pressing shoe 12 presses the inner wall surface of the pipe 15 to obtain a predetermined roundness. Then, the end shape of the tube 15 is corrected.
When pressing, the pressure of each pair of pressing shoes 12 or the length of the extended length of the shaft 22 is adjusted by the operation of the hydraulic cylinder 18 in accordance with the cross-sectional shape of the tubes 14 and 15. By the above operation, the pipe 14 and the pipe 15
The roundness and the difference in inner diameter between and fall within the predetermined values. In this state, the pipe 14 and the pipe 15 are welded according to the conventional method.

Alternatively, as shown in FIG. 3, the two pipe fit-up devices 10 according to the present invention can be mounted independently on the ends of the pipes 14 and 15, respectively. In this case, the pipe fit-up device 10 installed in the pipe 14 and the pipe fit-up device 10 installed in the pipe 15 are separately operated according to the above-mentioned procedure, and the circularity and the inner diameter difference between the pipe 14 and the pipe 15 are adjusted. It is kept within a predetermined value and then welded.

As another embodiment, the high frequency induction coil 24
It can be separated from the pressing shoe 12. Figure 4
FIG. 4 is a schematic cross-sectional view in which a high frequency induction coil 24 is arranged on the outer circumference.

[0023]

The pipe fit-up device according to the present invention is
Since the smaller inner diameter of the pipe ends to be joined is heated and thermally expanded, the difference in inner diameter, that is, the difference in inner peripheral length is eliminated.
Very easy to operate. Also, since the tube end is pressed by the pressing shoe while maintaining the tube end at high temperature,
Without requiring large mechanical external force as in the past,
The cross-sectional shape of the pipe end can be easily corrected to a perfect circle. Even if the shape is flat due to its own weight, it can be easily corrected to a perfect circle by using the pipe fit-up device according to the present invention. In the welding according to the method of the present invention, a pipe fit-up device is used to eliminate the difference in inner diameter by heating, and while maintaining a high temperature, the pipe cross-sectional shape is corrected to a perfect circle by a pressing shoe. Work efficiency and accuracy are greatly improved. The method of the present invention has a predetermined roundness,
Since the butt joint welding of pipes is performed while maintaining the inner diameter difference, good welding quality can be obtained,
Redo is greatly reduced.

[Brief description of drawings]

FIG. 1 (a) is a front view showing the configuration of an embodiment of a pipe fit-up device according to the present invention, and FIG. 1 (b) is FIG.
It is a side view of the pipe fit-up device shown in (a).

FIG. 2 (a) is a diagram showing alignment when there is a gap d, and FIG. 2 (b) is a diagram showing alignment when there is no gap.

FIG. 3 is a side view showing a case where two pipe fit-up devices according to the present invention are independently attached to both ends of a pipe to be joined.

FIG. 4 is a cross-sectional view showing a state where a heating element is attached to the outer circumference of a pipe.

5 (a) is a front view showing the configuration of a conventional pipe fit-up device, and FIG. 5 (b) is a side view of the pipe fit-up device shown in FIG. 5 (a).

[Explanation of symbols]

 10 Pipe fit-up device according to the present invention 12 Pressing shoes 14, 15 Joining pipe 16 Pressing shoe advancing / retreating mechanism 18 Hydraulic cylinder 20 Supporting member 22 Shaft 24 Heating element

Claims (3)

[Claims] 1. A circumferential joint welding method for pipes, wherein one pipe end and the other pipe end are butted and the butted parts are welded to join both pipes in a longitudinal direction. At least one pair of pressing shoes adapted to press the inner wall surface of the pipe end portion in opposite directions toward each other are arranged on the inner wall surface of the pipe end portion, and further mounted on the inner circumference or outer circumference of the pipe end portion. The inner diameter of the pipe end with the smaller inner diameter is heated by the generated heating element and thermally expanded to match the inner peripheral length of the pipe end with the larger inner diameter. The inner wall surfaces of the pipes are pressed in opposite directions toward each other to correct the cross-sectional shape into a perfect circle, and the roundness of both ends of the pipe and the difference in inner diameter are kept within a specified value. A pipe circumferential joint welding method, characterized in that the pipe circumferential joint welding is performed. 2. A pair of pressing shoes that press the inner wall surface of the pipe in opposite directions to each other in a radially outward direction, and advance and contact the pressing shoe toward the inner wall surface of the pipe.
A pipe fit-up device further comprising a push-shue advancing / retreating mechanism for pushing the inner wall surface and retracting the push-shut from the inner wall surface, and a heating element mounted on the inner circumference or the outer circumference of the pipe. 3. The pipe fit-up device according to claim 2, wherein the heating element is embedded in the pressing shoe.