CN101932866A - Loose flange type flared tube joint and method of joining steel tubes using the same - Google Patents

Abstract

The loose flange type horn pipe joint comprises: the steel pipe comprises a flared part and loose flanges, wherein the flared part is formed at the end parts of the two steel pipes respectively, the loose flanges are abutted to the flared part respectively, and the angle theta DEG of the end surface of the flared part relative to the central axis of the steel pipe is 87-89 deg. The method for joining steel pipes includes: forming a flare at an end of the steel pipe so that the angle θ [ ° ] is 87 ° to 89 °; a step of butt-jointing the flared parts formed at the ends of the two steel pipes; and a step of mechanically connecting the butted horn-shaped parts by clamping the horn-shaped parts with two loose flanges.

Description

Loose-fit flange-type trumpet pipe joint and method for joining steel pipes using the same

technical field

The present invention relates to a pipe joint for joining pipes by bolting flanges together, and more specifically, to a mechanical joint having a flared portion provided at the end of a steel pipe and a loose flange abutting on the flared portion .

This application claims priority from Japanese Patent Application No. 2008-075953 filed on March 24, 2008, the contents of which are incorporated herein by reference.

Background technique

For the connection of indoor piping that conveys fluids such as water, air, and steam, mechanical joints that connect flanges with bolts can be used. The flange of this type of mechanical joint is installed at the end of the steel pipe by welding the end of the steel pipe or making a flared portion provided at the end of the steel pipe abut the loose flange.

In recent years, there has been an increasing demand for loose-fit flange-type flared fittings that do not require welding, can be easily flared at the construction site, and can shorten construction time. Also, for indoor piping, steel pipes are usually designed so that no axial force and no bending occur, and the pipes are joined by loose-fit flange joints (for example, Patent Documents 1 and 2).

However, there is a need to cope with alignment, etc. during construction on site, and bending stress and tensile stress may act on steel pipes and joints. In addition, when a high-temperature fluid such as steam passes through the piping, axial stress and bending stress due to thermal expansion and contraction may act on the steel pipe and the joint. In addition, it is also necessary to consider the case where an excessive axial force or bending load acts on the steel pipe and the joint, for example, there may be a case where sufficient vibration resistance is required.

In addition, when an excessive load acts on the piping, the load is particularly concentrated on the joints joining the steel pipes. However, a joint capable of maintaining the airtightness of the conveyed fluid under the action of such excessive external force has not been developed so far. Furthermore, a loose-fit flange-type pipe joint in which the higher the internal pressure is, the greater the sealing force has been proposed (for example, Patent Document 3). However, in this technique, the sealing performance cannot be ensured even when an axial force and a bending load act.

In addition, methods of improving the strength and fatigue properties of the flared portion have also been proposed (for example, Patent Documents 4 and 5). However, this is only an invention to improve the characteristics of the processed flared portion, and does not take into account the leak-tightness of the loose flange type flared pipe joint.

On the other hand, as a pipe joint aimed at improving the fracture resistance when stress is applied to the flange portion, a loose-fit flange-type flare pipe in which the contact surface with the flange of the flare portion is processed into a tapered shape has been proposed. linker (for example, Patent Document 6). However, in order to form the flared portion having such a tapered shape, it is necessary to replace the tool during processing, and the process of flaring the flared portion becomes complicated.

Patent Document 1: Japanese Patent Laid-Open No. 2007-211811

Patent Document 2: Japanese Patent Laid-Open No. 2000-55239

Patent Document 3: Japanese Utility Model Registration No. 3136954

Patent Document 4: Japanese Unexamined Patent Publication No. 2005-351383

Patent Document 5: Japanese Patent Application Laid-Open No. 5-329557

Patent Document 6: Japanese Utility Model Publication No. 7-22193

Contents of the invention

The problem to be solved by the present invention is: in the loose-fitting flange-type trumpet pipe joint that is provided with a trumpet-shaped part at the end of the steel pipe, connects the end faces of the trumpet-shaped part at the joint part of the steel pipe and is clamped by a loose-fitting flange, improve Tightness when a particularly large external force is applied.

The present invention relates to a loose-fit flange-type flared pipe joint that controls the angle of the end face of the flared portion and improves the sealability when particularly large tensile, bending, and other stresses act. The gist of the invention is as follows.

The loose flange flared pipe joint of the present invention has flared portions formed at the ends of two steel pipes, and loose flanges respectively abutting against the flared portions. The end faces of the flared portions are opposite to the The angle θ[°] of the central axis of the steel pipe is 87° to 89°.

In the loose-fit flange-type flared pipe joint of the present invention, there may be a gasket inserted between the above-mentioned flared portions. The trumpet-shaped part is butted by inserting the gasket, and the trumpet-shaped part can also be clamped by the loose flange.

The method of joining steel pipes using the loose-fit flange-type flared pipe joint of the present invention includes a step of forming a flared portion by flaring the ends of the steel pipes, the end surface of the flared portion being opposite to the center of the steel pipe The angle θ[°] of the axis is 87°～89°; the process of butting the above-mentioned trumpet-shaped parts formed at the ends of the two above-mentioned steel pipes; clamping the above-mentioned butt-joined trumpet-shaped parts with two loose flanges Hold, and the process of mechanical connection.

In the method of joining steel pipes using a loose flange type flared pipe joint according to the present invention, the flared portions may be butted together by inserting a gasket.

According to the present invention, even when excessive tensile loads, bending loads, etc. act on the loose-fit flange-type flared pipe joints at the joints of the pipes, it is possible to seal the conveyed fluid in the pipes, making an extremely industrial contribution significantly.

Description of drawings

FIG. 1 is a schematic diagram of an example of a loose-fit flange-type trumpet pipe joint according to an embodiment of the present invention.

Fig. 2 is a diagram showing the angle θ of the end surface of the flared portion.

Fig. 3 is a graph showing the influence of the angle θ of the end surface of the flared portion on the contact surface pressure of the mating portion.

Fig. 4 is a graph showing the influence of the angle θ of the end face of the flared portion on the sealing performance.

Fig. 5 is a schematic diagram of trumpet processing.

Instructions for marks in the figure:

1, 1a, 1b: steel pipe

2, 2a, 2b: Flared part

3: Gasket

4a, 4b: Loose flange

5: Bolt

6: Nut

7: Cone

8: The central axis of the steel pipe

9: End face of flared part

Detailed ways

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In addition, in this specification and drawings, the same code|symbol is attached|subjected to the component which has substantially the same function structure, and repeated description is abbreviate|omitted.

In FIG. 1 , a part of a loose-fit flange-type trumpet pipe joint according to one embodiment of the present invention is schematically shown as an example. The loose-fit flange-type flared pipe joint of this embodiment has: flange-shaped flared portions 2a, 2b formed by expanding the ends (joint portions) of two steel pipes 1a, 1b; and flared portions 2a, 2b. Abutting loose flanges 4a, 4b. The structure of the loose sleeve flange type horn pipe joint is as follows: at the junction of two steel pipes 1a, 1b, the horn-shaped parts 2a, 2b are butted through the gasket 3, and the two horn-shaped parts 2a, 2b that have been butted are separated from their Both sides are clamped by loose flanges 4a, 4b, and mechanically connected by bolts 5 and nuts 6.

In addition, in the drawings of this application, the sizes of bolts 5 and nuts 6 and the thicknesses of loose flanges 4a, 4b are drawn larger than actual steel pipes 1a, 1b to clarify their positional relationship. Therefore, the dimensional ratios of the components in the drawings and the relative positions of the central axes 8 of the steel pipes 1a, 1b do not necessarily agree with the actual trumpet pipe joints.

Described in more detail, the steel pipes 1a, 1b have flared portions 2a, 2b formed by flaring at respective ends. The flared portions 2a, 2b are portions that have been formed (that is, flared) by extending the ends of the steel pipes 1a, 1b so as to be bent outward in order to join the two steel pipes 1a, 1b to each other. .

Loose flanges 4a, 4b abut against the flared portions 2a, 2b, respectively. The loose flanges 4a, 4b (hereinafter referred to as flanges 4a, 4b) are annular flanges having through holes having an inner diameter larger than the outer diameter of the steel pipes 1a, 1b. The steel pipes 1a, 1b are passed through the through holes of the flanges 4a, 4b. When not connected, the inner peripheral surfaces of the flanges 4a, 4b can slide along the outer peripheral surfaces of the steel pipes 1a, 1b. Furthermore, the flanges 4a, 4b abut against the flared portions 2a, 2b and cannot be removed from the ends of the steel pipes 1a, 1b.

Between the end faces 9 (see FIG. 2 ) of the flared portions 2 a and 2 b of the steel pipes 1 a and 1 b , gaskets 3 are inserted and butted as necessary. The gasket 3 is, for example, an annular sealing member having the same outer diameter as that of the flared portions 2a, 2b, and has a function of sealing between the end surfaces 9 of the two butted flared portions 2a, 2b. The abutting portions of the flared portions 2a, 2b are sandwiched by the above-mentioned flanges 4a, 4b from both sides (surfaces on the outer peripheral surface side of the steel pipes 1a, 1b as the outer surfaces opposite to the abutting surfaces), and the flanges 4a, 4b Connect with bolt 5 and nut 6.

The procedure for joining the steel pipes 1a and 1b using this loose-fit flange-type flared pipe joint will be described.

First, the washer 3 is inserted between the flared portion 2a of the steel pipe 1a and the flared portion 2b of the steel pipe 1b which are arranged oppositely, and the end surface 9 of the flared portion 2a and the end surface 9 of the flared portion 2b are butted in this state. Next, the butted flared portions 2a, 2b are sandwiched by flanges 4a, 4b from the outside. Then, the flanges 4a, 4b are mechanically connected and fixed by the bolts 5 and nuts 6 passing through the flanges 4a, 4b. In this way, the flared portions 2a, 2b are pressed from both sides. Through the above operations, the two steel pipes 1a, 1b can be properly joined using this joint. The members for fixing the flanges 4a and 4b are not limited to the bolts 5 and nuts 6 described above, and any fixing member can be used as long as they can mechanically connect and fix the flanges 4a and 4b. In addition, although only one bolt 5 and one nut 6 are shown in FIG. 1 , a plurality of two or more bolts 5 and nuts 6 may be used.

In addition, piping materials such as STPG (JIS G 3454) and SGP (JIS G 3452) are used for piping that transports water, air, and steam. The outer diameter is 50A to 350A, and steel pipes of about 100A are the mainstream. Therefore, the inventors of the present invention analyzed the design elements that affect the leak-tightness of the loose-fit flange-type flared pipe joint by finite element analysis (FEA) assuming 100A of SGP piping.

As a result, the inventors noticed the angle θ[°] of the end surface 9 of the flared portion 2 with respect to the central axis 8 of the steel pipe 1 shown in FIG. FIG. 3 shows the relationship between the angle θ of the end surface of the flared portion and the distribution of surface pressure generated at the butt joint of the loose-fit flange type flared pipe joint. Fig. 3 shows the contact on the washer 3 of the mating part when a loose-fit flange-type flared pipe joint with various flared end face angles θ is connected with a bolt 5 and a nut 6 and a bending load equivalent to 80 MPa acts. The relationship between the surface pressure and the position where the contact surface pressure occurs (position (mm) from the inner diameter of the gasket).

From the analysis results by FEA shown in FIG. 3 , it can be seen that as the angle θ of the end surface of the flared portion becomes smaller, the surface pressure generated on the gasket 3 when a bending load acts increases. Therefore, it is considered that the smaller the angle θ of the end surface of the flared portion is, the higher the sealing performance of the joint is when a bending load and a tensile load act.

Therefore, flared steel pipes 1 in which the angle ?

First, two SGP steel pipes 1a and 1b of 100A (114.3 mm in outer diameter and 4.5 mm in thickness) are flared to form flared portions 2a and 2b. Make the flanges 4a, 4b contact the horn-shaped parts 2a, 2b, insert the gasket 3 to connect the two horn-shaped parts 2a, 2b, and connect the flanges 4a, 4b with bolts 5 and nuts 6, so as to make a loose flange trumpet pipe connector.

Next, 1 MPa of air was filled into the loose flange flared joint, and a tensile axial force was applied, and at the same time, the load (leakage load) at which a sharp drop in air pressure was observed was obtained. The leakage load was divided by the body yield strength of the steel pipe to calculate the airtightness index α [%]. It should be noted that the body yield strength of the steel pipe was measured by collecting test pieces from steel pipes of the same batch as the steel pipe 1 on which the flared portion 2 was formed, and performing a tensile test.

FIG. 4 shows the relationship between the airtightness index α obtained by the above evaluation test and the angle θ of the end face of the flared portion. It can be seen that as the angle θ of the end face of the flared portion decreases, the index of sealing performance α increases, and the sealing performance improves. In particular, it has been proved in practice that when the angle θ of the end surface of the flared portion is less than 89°, the sealability index α is 80% or more, and the load resistance characteristic of the sealability is improved. However, when the end face angle θ of the flared portion is less than 87°, the gasket 3 is damaged when the joint is connected or when an axial force acts. This can be presumed to be that the contact surface pressure is locally excessive, exceeding the load resistance of the washer 3 .

It has been confirmed through the actual pipe test above that in order to maintain airtightness and not damage the gasket 3 until an axial force of 80% or more relative to the yield load of the pipe body acts, the angle θ of the end surface of the flared portion is controlled to be 87° or more , Values below 89° are important. Furthermore, according to the result of Fig. 4, if the angle θ of the end surface of the flared portion is 88° or less, the sealing index α is 90% or more, so by making the angle θ of the end surface of the flared portion 87° to 88°, the airtightness index α can be further improved. Sealing performance.

Furthermore, the processing method for forming the flared portion 2 at the end of the steel pipe 1 of this embodiment is not limited, but, for example, as shown in FIG. Rotation, and a method of making contact by repeating rotation and revolution relative to each other is ideal. By this method, if the angle formed by the axis of the cone 7 and the axis of the steel pipe 1 is gradually increased, the angle θ of the end surface of the flared portion can be gradually increased, and the angle θ of the end surface of the flared portion can be controlled with high precision.

Example

Next, as an example of the present invention, a test for evaluating the sealability index α when the angle θ of the end surface of the flared portion is changed in various steel pipes 1 will be described.

In this test, first, the ends of various SGP steel pipes 1 were flared by the method shown in FIG. 5 to form the flared portion 2 . Then, the angle θ of the end face of the flared portion was measured ( FIG. 2 ). Two steel pipes 1a, 1b having the same flared portion end face angle θ are used as a set, and loose flanges 4a, 4b are brought into contact with the flared portions 2a, 2b. Then, the gasket 3 is inserted to butt the end faces 9, 9 of the flared parts 2a, 2b, and the bolts 5 and nuts 6 are used to connect them, thereby manufacturing a loose-fit flange-type flared pipe joint. As shown in Table 1, the SGP steel pipes used in the test are forged steel pipes and electric seam steel pipes of sizes 65A to 200A. In addition, tensile test pieces were collected separately from these steel pipes, and yield strength was measured.

In addition, in this test, as the gasket 3, "Universal NA connection packing TOMBO No. 1995" manufactured by Nichias Co., Ltd. was used. The gasket 3 is a non-asbestos joint sealing ring composed of inorganic fibers, aramid fibers, inorganic fillers and adhesives in combination with oil-resistant synthetic rubber. The dimensions of this gasket 3 are as follows. In addition, its specifications are JIS F06 02HJ, ASTM104F712100-B5E12M5. In addition, this gasket 3 is an example used in this experiment, and the gasket 3 of this invention is not limited to this example.

(i) Steel pipe of size 65A: the outer diameter of the gasket 3 is 124mm, the inner diameter is 77mm, and the thickness is 3mm

(ii) Steel pipe of size 100A: the outer diameter of the gasket 3 is 159mm, the inner diameter is 115mm, and the thickness is 3mm

(iii) A steel pipe of size 200A: the outer diameter of the gasket 3 is 270mm, the inner diameter is 218mm, and the thickness is 3mm

A tensile axial force is applied to the loose-fit flange-type flared pipe joint with air of 1 MPa, and at the same time, the load (leakage load) when the pressure drops suddenly is obtained. The leakage load was divided by the yield load of the pipe body to calculate the leaktightness index α [%]. The test results are shown in Table 1 below.

Table 1

In Examples 1 to 12, θ was within the range of the present invention (87° to 89°), and α was 80% or more. In contrast, in Comparative Examples 1 to 4, 6 to 10, and 13 to 16, θ was too large, so α was less than 80%. In addition, in Comparative Examples 5, 11, 12, and 17 in which the angle θ of the end surface of the flared portion was too small, the gasket 3 was damaged during joint connection or when a tensile load was applied.

Therefore, according to the test results, when the angle ? On the other hand, when θ is less than 87°, the gasket 3 is damaged. Therefore, it is not suitable for all occasions. On the other hand, it has been verified that if the angle θ of the end face of the flared portion is 87° or more and 89° or less, the sealing index α is 80% or more, and good sealing can be achieved even when excessive external force acts on the joint. performance, and gasket 3 is not damaged.

As mentioned above, the loose-fit flange type horn pipe joint of this embodiment was demonstrated in detail. According to this embodiment, by adjusting the angle θ of the end surface of the flared portion of the steel pipe 1 to an appropriate angle (87° to 89°), the contact surface of the gasket 3 inserted between the butted flared portions 2 can be appropriately increased. pressure. Therefore, even when an excessive tensile load, bending load, etc. act on the joint during an earthquake or the like, the sealing performance of the joint can be ensured, and leakage of the conveyed fluid in the piping can be prevented.

In addition, in the loose flange type flared pipe joint of this embodiment, in order to improve the sealing performance of the joint portion of the steel pipe 1, only the angle θ of the end surface of the flared portion may be adjusted when the flared portion 2 is flared. Therefore, it is not necessary to change the tool in the middle of the forming process in order to form the flared portion having a tapered shape as in the above-mentioned Patent Document 6. Therefore, the process of flaring the flared portion 2 can be simplified.

Although the preferred embodiment of the present invention has been described in detail above with reference to the accompanying drawings, the present invention is not limited to this example. Obviously, if a person has common knowledge in the technical field to which the present invention pertains, various modifications and amendments can be obtained within the scope of the technical ideas described in the scope of the patent claims. For this, it can be understood that they also belong to the The technical scope of the present invention.

Industrial Applicability

The loose-fit flange-type flared pipe joint of the present invention can seal the conveyed fluid in the piping without leakage even when excessive tensile loads, bending loads, etc. act. Therefore, it can be applied to sites requiring sufficient shock resistance. In addition, even when axial stress and bending stress caused by thermal expansion and contraction act on the joint, as in the case of high-temperature fluid such as steam passing through the pipe, the conveyed fluid in the pipe can be sealed without leakage. , so it can be used as a joint for piping for high-temperature fluid circulation.

Claims (2)

1. loose flange-type flared pipe joint is characterized in that:

Have: the tubaeform portion that forms respectively in the end of two steel pipes and respectively with the lap joint flange of above-mentioned tubaeform butt,

The end face of above-mentioned tubaeform portion with respect to the angle θ of the central shaft of above-mentioned steel pipe (°) be 87 °～89 °.

2. a joint method that has used the steel pipe of loose flange-type flared pipe joint is characterized in that, comprising:

Form the operation of tubaeform portion by the end of steel pipe being carried out enlarging processing, the end face of above-mentioned tubaeform portion with respect to the angle θ of the central shaft of above-mentioned steel pipe (°) be 87 °～89 °;

The operation of above-mentioned tubaeform the butt joint that will form respectively in the end of two above-mentioned steel pipes; And

With above-mentioned tubaeform of having docked with two lap joint flange clampings, and the operation that mechanicalness links.

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