WO2009119410A1

WO2009119410A1 - Loose flange-type flared pipe joint and steel pipe joining method using the same

Info

Publication number: WO2009119410A1
Application number: PCT/JP2009/055300
Authority: WO
Inventors: 英司津留; 哲己近藤; 哲佐藤; 宏長谷川
Original assignee: 新日本製鐵株式会社
Priority date: 2008-03-24
Filing date: 2009-03-18
Publication date: 2009-10-01
Also published as: CN101932866B; KR20100092986A; CN101932866A; JP4551462B2; JP2009228825A; KR101146829B1

Abstract

A loose flange-type flared pipe joint has flared sections respectively formed at ends of two steel pipes, and also has loose flanges respectively in contact with the flared sections. The angle θ (˚) of an end surface of each flared section relative to the center axis of the steel pipes is in the range from 87˚ to 89˚. A steel pipe joining method includes a step of forming the flared sections at the ends of the two steel pipes so that the angle θ is in the range from 87˚ to 89˚, a step of butting against each other the flared sections formed at the ends of the two steel pipes, and a step of mechanically fastening the two pipes together with the butted flared sections clamped by the two loose flanges.

Description

Loose flange type flare pipe joint and method of joining steel pipes using the same

The present invention relates to a pipe joint that joins pipes by fastening a flange with a bolt, and more specifically, a mechanical joint having a flare provided at an end of a steel pipe and a loose flange abutted on the flare. About.
This application claims priority to Japanese Patent Application No. 2008-075953 filed on Mar. 24, 2008, the contents of which are incorporated herein by reference.

機械 Mechanical joints with flanges fastened with bolts are used to join indoor pipes that transfer fluids such as water, air, and steam. The flange of such a mechanical joint is provided at the end of the steel pipe by a method such as welding to the end of the steel pipe or bringing a flare provided at the end of the steel pipe into contact with the loose flange. .

In recent years, there has been an increasing demand for loose flange flare fittings that do not require welding, can be easily flared at the construction site, and can shorten the construction time. Moreover, in indoor piping, piping design which does not involve axial force and a bending is normally performed to a steel pipe, and piping is joined by a loose flange type pipe joint (for example, patent documents 1 and 2).

However, it is necessary to deal with alignment during construction on site, and bending stress and tensile stress may be applied to steel pipes and joints. In addition, when a high-temperature fluid such as steam is passed through the piping, the steel pipe and the joint may be subjected to axial stress and bending stress due to thermal expansion and contraction. Furthermore, it is necessary to consider a case in which an excessive axial force or bending load is applied to the steel pipe and the joint. For example, sufficient earthquake resistance may be required.

Also, when an excessive load is applied to the piping, the load is concentrated especially on the joint that joins the steel pipes. However, a joint that can maintain the sealing performance of the transfer fluid when such an excessive external force is applied has not been developed so far. In addition, the loose flange type pipe joint which increases a sealing force, so that internal pressure becomes high is proposed (for example, patent document 3). However, even with this technique, sealing performance cannot be ensured when an axial force or bending load is applied.

Also, methods for improving the strength and fatigue characteristics of the flared portion have been proposed (for example, Patent Documents 4 and 5). However, these improve the characteristics of the molded flare part, and the sealing performance of the loose flange type flare fitting is not considered.

On the other hand, a loose flange flare pipe joint has been proposed in which the contact surface with the flange of the flare part is processed into a tapered shape as a pipe joint for the purpose of improving fracture resistance when stress is applied to the flange part ( For example, Patent Document 6). However, in order to form a flare portion having such a tapered shape, it is necessary to change the tool during the processing, and the flare processing process of the flare portion becomes complicated.
JP 2007-211811 A JP 2000-55239 A Registered Utility Model No. 3136954 JP 2005-351383 A JP-A-5-329557 Japanese Utility Model Publication No. 7-22193

The present invention is a loose flange type flare pipe joint in which a flare is provided at the end of a steel pipe, the end face of the flare is abutted at the joint of the steel pipe, and is sandwiched by a loose flange. The problem is to improve the sealing performance.

The present invention relates to a loose-flange type flare pipe joint that controls the angle of the end face of the flare part and improves the sealing performance when stress such as excessive tension or bending is applied, and the gist thereof is as follows. .

The loose flange type flare pipe joint of the present invention has a flare part formed at each end of two steel pipes, and a loose flange that abuts the flare part, respectively, and the flare part with respect to the central axis of the steel pipe The angle θ [°] of the end face is 87 ° to 89 °.
The loose flange type flare pipe joint of the present invention may further include a gasket interposed between the flare portions. The flare part may be abutted through the gasket, and the flare part may be sandwiched between the loose flanges.

In the method of joining steel pipes using the loose flange type flare pipe joint of the present invention, the angle θ [°] of the end face of the flare part with respect to the central axis of the steel pipe is 87 ° to A step of forming the flare portion of 89 °, a step of abutting the flare portions respectively formed at the ends of the two steel pipes, and holding the abutted flare portions by two loose flanges And a mechanical fastening process.
In the steel pipe joining method using the loose flange type flare pipe joint of the present invention, the flare portion may abut with a gasket interposed.

According to the present invention, even when an excessive tensile load, bending load, or the like is applied to the loose flange type flare pipe joint at the joint portion of the pipe, it becomes possible to seal the transferred fluid in the pipe. The contribution of is very remarkable.

Drawing 1 is a mimetic diagram of an example of a loose flange type flare fitting concerning one embodiment of the present invention. FIG. 2 is a diagram showing the flare end face angle θ. FIG. 3 is a diagram showing the influence of the flare end face angle θ on the contact surface pressure of the abutting portion. FIG. 4 is a diagram showing the influence of the flare end face angle θ on the sealing performance. FIG. 5 is a schematic diagram of flare processing.

Explanation of symbols

1, 1a, 1b: Steel pipe, 2, 2a, 2b: Flare part, 3: Gasket, 4a, 4b: Loose flange, 5: Bolt, 6: Nut, 7: Cone, 8: Central axis of steel pipe, 9: Flare End face of the part.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

FIG. 1 schematically illustrates a part of a loose flange type flare pipe joint according to an embodiment of the present invention. The loose-flange type flare pipe joint according to the present embodiment includes flange-

shaped flare portions

2a and 2b formed by expanding ends (joint portions) of two

steel pipes

1a and 1b, and flare

portions

2a and 2b. Loose

flanges

4a and 4b are in contact. In this loose flange type flare pipe joint, at the joint part of two

steel pipes

1a and 1b, the

flare parts

2a and 2b are abutted via the gasket 3, and the

abutted flare parts

2a and 2b are arranged on both sides thereof. It is sandwiched by

loose flanges

4a and 4b and mechanically fastened by bolts 5 and nuts 6.
In the drawings of the present application, the sizes of the bolts 5 and nuts 6 and the thicknesses of the

loose flanges

4a and 4b are described to be larger than actual with respect to the

steel pipes

1a and 1b so that the positional relationship between them is clear. ing. For this reason, the dimensional ratio of each member in the drawing and the relative position of the central axis 8 of the

steel pipes

1a and 1b do not necessarily coincide with the actual flare pipe joint.

More specifically, the

steel pipes

1a and 1b have flared

portions

2a and 2b formed at the respective end portions by a ribbing process. The

flare portions

2a and 2b are formed (ie, flared) portions that are expanded so as to bend the end portions of the

steel pipes

1a and 1b to bond the two

steel pipes

1a and 1b to each other. It is.

Loose flanges

4a and 4b are in contact with the

flare portions

2a and 2b, respectively. The

loose flanges

4a and 4b (hereinafter referred to as “

flanges

4a and 4b”) are annular flanges having through holes having an inner diameter larger than the outer diameter of the

steel pipes

1a and 1b. The

steel pipes

1a and 1b are inserted into the through holes of the

flanges

4a and 4b. When not fastened, the inner peripheral surfaces of the

flanges

4a and 4b can slide along the outer peripheral surfaces of the

steel pipes

1a and 1b. The

flanges

4a and 4b are in contact with the

flare portions

2a and 2b so as not to be detached from the ends of the

steel pipes

1a and 1b.

The end faces 9 (see FIG. 2) of the

flare portions

2a and 2b of the

steel pipes

1a and 1b are abutted with each other with a gasket 3 interposed therebetween as necessary. The gasket 3 is, for example, an annular sealing member having an outer diameter approximately equal to the outer diameter of the

flare portions

2a and 2b, and seals between the end faces 9 of the two

flare portions

2a and 2b that are abutted. It has a function. The abutting portions of the

flare portions

2a and 2b are sandwiched by the

flanges

4a and 4b from both sides thereof (surfaces on the outer peripheral surface side of the

steel pipes

1a and 1b, which are outer surfaces facing the abutting surfaces). Are fastened by bolts 5 and nuts 6.

A procedure for joining the

steel pipes

1a and 1b using the loose flange type flare pipe joint will be described.
First, the gasket 3 is interposed between the flare portion 2a of the steel pipe 1a and the flare portion 2b of the steel pipe 1b, which are opposed to each other, and the end surface 9 of the flare portion 2a and the end surface 9 of the flare portion 2b are abutted in this state. Let Next, the abutted

flare portions

2a and 2b are sandwiched by the

flanges

4a and 4b from the outside. Thereafter, the

flanges

4a and 4b are mechanically fastened and fixed by the bolts 5 and nuts 6 inserted into the

flanges

4a and 4b. Thereby, the

flare parts

2a and 2b are pressed from both sides. By the above, the two

steel pipes

1a and 1b can be suitably joined using this joint. The means for fixing the

flanges

4a and 4b is not limited to the example of the bolt 5 and the nut 6, and any fixing member can be used as long as the

flanges

4a and 4b are mechanically fastened and fixed. . In FIG. 1, only one bolt 5 and one nut 6 are illustrated, but two or more bolts 5 and nuts 6 may be used.

In addition, pipe materials such as STPG (JIS G 3454) and SGP (JIS G 3452) are used for pipes for transferring water, air, steam, etc., and their outer diameters are 50A to 350A. It has become mainstream. Therefore, the present inventors analyzed the design factors that affect the sealing performance of the loose flange type flare pipe joint by finite element method analysis (FEA) assuming 100A SGP piping.

As a result, the inventors focused on the angle θ [°] of the end face 9 of the flare portion 2 with respect to the central axis 8 of the steel pipe 1 shown in FIG. 2 (hereinafter referred to as “flare end face angle θ”). . FIG. 3 shows the relationship between the flare end face angle θ and the surface pressure distribution generated at the abutting portion of the loose flange type flare fitting. FIG. 3 shows that a loose flange type flare pipe joint having various flare end face angles θ is fastened with bolts 5 and nuts 6 and is generated in the gasket 3 of the abutting portion when a bending load equivalent to 80 MPa is applied. The relationship between the contact surface pressure and the position where this contact surface pressure is generated (position [mm] from the gasket inner diameter) is shown.

From the analysis result by FEA shown in FIG. 3, it can be seen that as the flare end face angle θ decreases, the surface pressure generated in the gasket 3 when a bending load is applied increases. Therefore, when a bending load or a tensile load is applied, it is considered that the sealing performance of the joint improves as the flare portion end face angle θ decreases.

Therefore, a flare steel pipe 1 with various flare end face angles θ was manufactured, and an evaluation test of the sealing performance of the joint was performed.
First, the ends of two 100A (outer diameter 114.3 mm, wall thickness 4.5 mm)

SGP steel pipes

1a and 1b were flared to form flared

portions

2a and 2b. The

flanges

4a and 4b are brought into contact with the

flare portions

2a and 2b, both the

flare portions

2a and 2b are brought into contact with each other via the gasket 3, and the

flanges

4a and 4b are fastened with bolts 5 and nuts 6 to form a loose flange flare pipe. It was a joint.

Next, the loose flange type flare pipe fitting was filled with 1 MPa of air, and a load load (leakage load) was observed when a sudden drop in air pressure was observed while applying a tensile axial force. The leakage load was divided by the tube yield strength of the steel pipe, and the sealability index α [%] was calculated. In addition, the pipe body yield strength was measured by taking a test piece from a steel pipe of the same lot as the steel pipe 1 in which the flare portion 2 was formed, and performing a tensile test.

FIG. 4 shows the relationship between the sealability index α and the flare end face angle θ obtained by the above evaluation test. From this, it can be seen that as the flare end face angle θ decreases, the sealability index α increases and the sealability is improved. In particular, when the flare end face angle θ is less than 89 °, the sealability index α is 80% or more, and it was proved that the load resistance characteristic of the sealability is improved. However, when the flare end face angle θ was less than 87 °, the gasket 3 was damaged when the joint was fastened or when an axial force was applied. It can be presumed that this is because the contact surface pressure is excessively increased locally and exceeds the load resistance of the gasket 3.

As described above, the flare end face angle θ should be 87 ° or more and 89 ° or less in order to prevent gas sealing up to an axial force of 80% or more with respect to the yield load of the tube by the actual pipe test and to prevent the gasket 3 from being damaged. It was confirmed that it was important to control the value. Further, according to the result of FIG. 4, when the flare end face angle θ is 88 ° or less, the sealing performance index α is 90% or more. Therefore, the flare end face angle θ is set to 87 ° to 88 °. The sealing performance can be further improved.

In addition, about the processing method which forms the flare part 2 in the edge part of the steel pipe 1 concerning this embodiment, this is not limited, For example, as shown in FIG. 5, the steel pipe 1 and the cone 7 (conical roller) It is preferable to employ a method in which the contact is made by rotating and relatively rotating and revolving relatively. By this method, if the angle between the axis of the cone 7 and the axis of the steel pipe 1 is gradually increased, the flare end face angle θ can be gradually increased, and the flare end face angle θ can be accurately controlled. Can do.

Next, as an example of the present invention, an experiment for evaluating the sealing property index α when the flare end face angle θ is changed in various steel pipes 1 will be described.

In this experiment, first, end portions of various SGP steel pipes 1 were subjected to a flange processing by the method shown in FIG. And this flare part end surface angle (theta) (FIG. 2) was measured.

Loose flanges

4a and 4b were brought into contact with the

flare portions

2a and 2b using two

steel pipes

1a and 1b having the same flare portion end face angle θ as a set. Then, the end faces 9 and 9 of the

flare portions

2a and 2b were brought into contact with each other with the gasket 3 interposed therebetween, and fastened with bolts 5 and nuts 6 to produce a loose flange type flare pipe joint. As shown in Table 1, the SGP steel pipe used in the test is a forged steel pipe and an electric resistance steel pipe having a size of 65A to 200A. In addition, from these steel pipes, tensile test pieces were separately collected and the yield strength was measured.

In this experiment, “general-purpose NA joint seal TOMBO No. 1995” manufactured by NICHIAS Corporation was used as the gasket 3. The gasket 3 is a non-asbestos joint seal in which an inorganic fiber, an aramid fiber, an inorganic filler, and an oil-resistant synthetic rubber are blended as a binder. The dimensions of the gasket 3 are as follows. The applicable standards are JIS F0602HJ and ASTM 104F712100-B5E12M5. The gasket 3 is an example used in this experiment, and the gasket 3 of the present invention is not limited to this example.
(I) Steel pipe of size 65A: gasket 3 outer diameter 124 mm, inner diameter 77 mm, thickness 3 mm
(Ii) Steel pipe of size 100A: gasket 3 outer diameter 159 mm, inner diameter 115 mm, thickness 3 mm
(Iii) Steel pipe of size 200A: gasket 3 outer diameter 270 mm, inner diameter 218 mm, thickness 3 mm

The loose flange type flare pipe joint was filled with 1 MPa of air, and then the load (leakage load) when the pressure suddenly decreased was obtained while applying a tensile axial force. This leak load was divided by the yield load of the tube, and the sealability index α [%] was evaluated. The experimental results are shown in Table 1 below.

In Examples 1 to 12, θ was within the range of the present invention (87 ° to 89 °), and α was 80% or more. On the other hand, in Comparative Examples 1 to 4, 6 to 10, and 13 to 16, since θ was too large, α was less than 80%. In Comparative Examples 5, 11, 12, and 17, where the flare end face angle θ is too small, the gasket 3 was damaged when the joint was fastened or when a tensile load was applied.

Therefore, according to such experimental results, when the flare end face angle θ is greater than 89 °, the sealability index α is less than 80% and the desired sealing performance cannot be obtained. On the other hand, if θ is less than 87 °, the gasket 3 is damaged. For this reason, neither case is suitable. On the other hand, when the flare end face angle θ is 87 ° or more and 89 ° or less, the sealing property index α is 80% or more, and a suitable sealing property can be exhibited even when an excessive external force is applied to the joint. And it was proved that the gasket 3 was not damaged.

The loose flange type flare pipe joint according to the present embodiment has been described in detail above. According to the present embodiment, by adjusting the flare end face angle θ of the steel pipe 1 to an appropriate angle (87 ° to 89 °), the contact surface pressure with respect to the gasket 3 interposed between the flare portions 2 abutted against each other can be reduced. Can be raised appropriately. Therefore, even when an excessive tensile load, bending load, or the like is applied to the joint during an earthquake or the like, it is possible to ensure the sealing performance of the joint and prevent leakage of the transfer fluid in the pipe.

Further, in the loose flange type flare pipe joint according to the present embodiment, in order to improve the sealing performance of the joint portion of the steel pipe 1, it is only necessary to adjust the flare portion end face angle θ when the flare portion 2 is tapped. Good. Therefore, unlike Patent Document 6, it is not necessary to change the tool during the forming process in order to form the tapered flare portion. Therefore, the fluffing process of the flare part 2 can be simplified.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

The loose flange type flare pipe joint of the present invention can be sealed without leakage of the transfer fluid in the pipe even when an excessive tensile load, bending load or the like is applied. For this reason, it can be applied to the site where sufficient earthquake resistance is required. In addition, even when high-temperature fluid such as steam is passed through the pipe, the transfer fluid in the pipe leaks even when the joint is subjected to axial stress or bending stress due to thermal expansion and contraction. It can be used as a joint for piping through which high-temperature fluid passes.

Claims

A flare portion formed at each end of two steel pipes, and a loose flange abutting on each of the flare portions,
A loose flange type flare pipe joint, wherein an angle θ [°] of an end face of the flare portion with respect to a central axis of the steel pipe is 87 ° to 89 °.
Forming the flare portion in which the angle θ [°] of the end surface of the flare portion with respect to the central axis of the steel pipe is 87 ° to 89 ° by subjecting the end portion of the steel pipe to a process;
Abutting the flare portions formed respectively on the ends of the two steel pipes;
A method of joining steel pipes using a loose-flange type flare pipe joint, comprising the steps of: mechanically fastening the abutted flare portions with two loose flanges.