JP2021055741A - Loose flange - Google Patents

Abstract

To provide a loose flange which is excellent in torque retention for a long time even when used in joint for a resin pipe.SOLUTION: A loose flange 30 is used to join pipes 10, 20 and includes: an annular core material 33 made of a metal; and a cover layer 34 covering the core material 33. The cover layer 34 contains a thermoplastic resin as a main component.SELECTED DRAWING: Figure 1

Description

The present invention relates to a loose flange used for joining pipes to each other, and more particularly to a loose flange suitable when at least one of the pipes is made of resin.

Generally, a flange is provided at the end of a pipe such as a factory pipe for joining with another pipe. As a type of flange, many loose flanges loosely fitted to the pipe are used (see Patent Document 1 and the like). The loose flange is locked to the flange portion (flare portion) of the stub end provided at the end of the pipe, and is joined with bolts and nuts facing the flange of the pipe to be joined.

Conventionally, most of pipes such as factory pipes are made of metal, and stub ends and loose flanges are also generally made of metal. By using metal, sufficient strength can be obtained against tightening torque and the like.
On the other hand, in recent years, advances in resin synthesis technology have improved mechanical strength, weather resistance, chemical resistance, earthquake resistance, and the like. In response to this, metal pipes are being replaced with resin pipes such as polyvinyl chloride and polyethylene in factory piping and the like.

Japanese Unexamined Patent Publication No. 5-280674

As a result of diligent research and study by the inventors, if bolting is performed with a standard tightening torque (T series) using a metal loose flange to join resin pipes such as polyethylene, the torque will decrease after a long period of time. However, it was found that water leakage may occur from the joints between pipes.
The present invention has been made based on such findings, and an object of the present invention is to provide a loose flange having excellent torque retention for a long period of time (for example, 30 years) even when used for joining resin pipes.

In order to solve the above problems, the present invention is a loose flange used for joining pipes to each other.
An annular core material made of metal and a coating layer covering the core material are provided, and the coating layer contains a thermoplastic resin as a main component.
According to the loose flange, the required tightening torque can be maintained for a long period of time even when used for joining resin pipes. As a result, it is possible to prevent or suppress the occurrence of water leakage or the like from the joints between the pipes.

The thickness of the coating layer is preferably 1 mm or more.
The thickness of the core material is preferably 3 mm or more.
It is preferable that the thermoplastic resin is a polyolefin resin and the coating layer contains 10% by mass or more of reinforcing fibers.

According to the present invention, it is possible to provide a loose flange having excellent long-term torque retention. Even when used for joining resin pipes, the required torque can be maintained for a long period of time.

FIG. 1 is a cross-sectional view taken along a pipe shaft showing a pipe joint structure according to an embodiment of the present invention in an assembled state. FIG. 2 is an exploded cross-sectional view of the pipe joint structure. FIG. 3 is a front sectional view showing a loose flange in the pipe joint structure along the line III-III of FIG. FIG. 4 is a cross-sectional view of the loose flange along line IV-IV of FIG. FIG. 5 is a front view showing the packing in the pipe joint structure along VV of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows, for example, a pipe joint structure 1 in a factory pipe. The pipe joint structure 1 is formed by bolting the first pipe 10 and the second pipe 20. The two pipes 10 and 20 are arranged so as to face each other on the same pipe axis.

The first pipe 10 and the second pipe 20 are made of resin. Hereinafter, the pipes 10 and 20 are appropriately referred to as "resin pipes 10 and 20". Examples of the materials of the resin tubes 10 and 20 include polyethylene, polyvinyl chloride, polypropylene and other synthetic resins. The resin pipes 10 and 20 may be pipes mainly made of resin, and may contain members other than resin, such as metal and reinforcing fibers.

As shown in FIG. 2, the first resin pipe 10 has a flange integrated type, and the second resin pipe 20 has a loose flange.
Specifically, the flange 13 is provided at the end of the resin pipe 10 facing the pipe 20. The flange 13 is made of a metal such as stainless steel or ordinary steel and is fixed to the resin pipe 10, but the flange 13 is not limited to this and may be made of the same resin as the resin pipe 10. A plurality of bolt holes 13b are formed in the flange 13 at intervals in the circumferential direction.

The resin tube 20 has a short tubular shape, but the present invention is not limited thereto. The resin pipe 20 may form a stub end. A resin pipe 20 may be connected as a stub end to the end of another pipe (not shown) by welding or the like.

An annular protrusions 21 and 22 projecting to the outer circumference and the inner circumference are formed in the middle portion of the resin pipe 20 in the tube axis direction.
A collar portion 23 (flare portion) is integrally formed at an end of the resin pipe 20 facing the pipe 10. The collar portion 23 has an annular shape and protrudes outward in the radial direction from the entire circumference of the facing end of the resin pipe 20. The end faces (left end faces in FIG. 2) of the flange portion 23 and the resin pipe 20 facing the pipe 10 on the connection partner side are flush with each other.

As shown in FIG. 2, a loose flange 30 is provided on the outer periphery of the resin pipe 20. As shown in FIG. 3, the loose flange 30 is formed in an annular plate shape having a center hole 31. A plurality of bolt holes 32 are formed in the loose flange 30 at intervals in the circumferential direction.
The outer diameter of the loose flange 30 is, for example, about 50 mm to 600 mm, but the present invention is not limited thereto.
The inner diameter of the loose flange 30 (diameter of the center hole 31) is, for example, about 30 mm to 400 m, but the present invention is not limited thereto.

As shown in FIG. 4, the loose flange 30 includes a core material 33 and a coating layer 34. The shape of the loose flange 30 is formed by the core material 33. The core material 33 is made of metal. Examples of the metal material of the core material 33 include cast iron, stainless steel, and ordinary steel.
The thickness of the core material 33 is preferably 3 mm or more, more preferably about 3 mm to 18 mm, and even more preferably about 6 mm to 12 mm.

The surface of the core material 33 is coated with the coating layer 34. The coating layer 34 covers all surfaces of the core material 33, that is, main surfaces on both sides, outer peripheral end surfaces, inner peripheral end surfaces, and inner peripheral surfaces of bolt holes and other holes. The core material 33 is buried inside the coating layer 34.
The thickness of the coating layer 34 is preferably 1 mm or more, more preferably about 1 mm to 10 mm, and even more preferably about 3 mm to 6 mm.

The coating layer 34 is made of a fiber reinforced resin. Specifically, the coating layer 34 contains a thermoplastic resin as a base material (main component) and reinforcing fibers as a reinforcing material.
The thermoplastic resin is preferably a polyolefin resin such as polypropylene or polyethylene.
The content ratio of the thermoplastic resin to the entire coating layer 34 is preferably 50% by mass or more, and more preferably about 70% by mass to 90% by mass.

The reinforcing fiber is preferably glass fiber.
The content ratio of the reinforcing fibers with respect to the entire coating layer 34 is preferably 10% by mass or more, and more preferably about 10% by mass to 30% by mass.

The loose flange 30 is loosely fitted in the resin pipe 20. As shown in FIG. 2, in the non-joined state between the pipes 10 and 20, the loose flange 30 can move in the pipe axial direction between the flange portion 23 and the annular protrusion 21 with respect to the resin pipe 20. And it is rotatable with respect to the resin tube 20. By rotation, the bolt holes 13b and 32 can be easily matched with each other.

As shown in FIG. 1, the loose flange 30 abuts on the flange portion 23 when the pipes 10 and 20 are joined to each other. Moreover, the loose flange 30 faces the flange 13. The bolt 40 is inserted into the bolt holes 13b and 32 of the flanges 13 and 30. By tightening the bolt 40 and the nut 41 screwed to the tip thereof, the flanges 13 and 30 and the resin pipes 10 and 20 are bolted together.

The tightening torque of the bolt 40 and the nut 41 is set to a value equivalent to the standard tightening torque when joining metal pipes to each other, but may be set to a value lower than the standard tightening torque.
As shown in FIGS. 1 and 2, an annular packing 50 is provided between the resin pipes 10 and 20. The material of the packing 50 is preferably ethylene propylene diene (EPDM) rubber. As shown in FIGS. 2 and 5, two large and small (plurality) annular convex portions 52 and 53 are formed on both sides of the packing 50, respectively. These annular protrusions 52 and 53 surround the central hole 51 and form a double circle concentric with the central hole 51.
The number of annular protrusions of the packing 50 is not limited to two, and may be three or more. Three or more annular convex portions having different diameters may be arranged so as to form multiple circles concentric with the central circle 51.

In the pipe joint structure 1, stress relaxation over a long period of time can be suppressed by using a loose flange 30 in which the metal core material 33 is coated with the resin coating layer 34 as the flange of one of the resin pipes 20. Therefore, the torque retention rate after a long period of time (for example, 30 years) is increased, and the required tightening torque can be maintained for a long period of time. As a result, it is possible to prevent or suppress the occurrence of water leakage or the like from the joints between the pipes 10 and 20 even after a long period of time.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the pipes 10 and 20 are not limited to resin pipes, and may be metal pipes such as stainless steel pipes and ordinary steel pipes. One of the tubes 10 and 20 may be a metal tube and the other may be a resin tube.
The reinforcing fiber of the coating layer 34 is not limited to glass fiber, but may be carbon fiber.
The coating layer 34 may be composed only of resin and may not contain reinforcing fibers.
The inner peripheral surface of the loose flange 30 may have a tapered shape that expands in diameter toward the flange portion 23. In accordance with this, the peripheral portion of the outer peripheral surface of the resin tube 20 may have a tapered shape in which the diameter of the portion near the flange portion 23 increases toward the flange portion 23.

An embodiment will be described. The present invention is not limited to the following examples.
In Example 1, a loose flange in which the core material was coated with a coating layer was manufactured.
The size of the core material was an outer diameter of 179 mm, an inner diameter of 101 mm, and a thickness of 12 mm. The material of the core material was SS400.
The entire surface of the core material was coated with a coating layer.
As the coating layer, a fiber reinforced plastic (GFPP) containing 70% by mass of polypropylene and 30% by mass of glass fiber was used.
The thickness of the coating layer was 3 mm.
The overall size of the loose flange was 185 mm in outer diameter, 95 mm in inner diameter, and 18 mm in thickness. The center diameter (twice the distance from the center of the loose flange to the center of the bolt hole 32) was 150 mm.

A bolt was tightened on the obtained loose flange, and a load corresponding to the standard tightening torque (60 Nm) of the bolt was applied to the loose flange by a universal testing machine manufactured by Shimadzu Corporation. The loading time was 3 hours.
The stress relaxation during loading was measured by the tester, and the residual torque after 30 years from the measurement result was calculated by curve approximation. Furthermore, the torque retention rate after 30 years was determined.
As a result, the residual torque after 30 years was 16.2 Nm and the torque retention rate was 27.0% with respect to the initial tightening torque of 60 Nm.

In Example 2, a loose flange was produced in which the thickness of the core material was 6 mm, the thickness of the coating layer was 6 mm, the total thickness was 18 mm, and the other parts were the same as in Example 1.
The obtained loose flange was evaluated in the same manner as in Example 1.
As a result, the residual torque after 30 years was 14.3 Nm and the torque retention rate was 23.8% with respect to the initial tightening torque of 60 Nm.

[Comparative Example 1]
In Comparative Example 1, a loose flange made of stainless steel (SUS304) having an outer diameter of 185 mm, an inner diameter of 95 mm, a center diameter of 150 mm, and a thickness of 18 mm was manufactured.
The obtained loose flange was evaluated in the same manner as in Example 1.
As a result, the residual torque after 30 years was 14.0 Nm and the torque retention rate was 23.3% with respect to the initial tightening torque of 60 Nm.

The results of Examples 1 and 2 and Comparative Examples are shown in Table 1.
It was confirmed that the loose flange in which the metal core material was coated with resin had excellent long-term torque retention as compared with the loose flange made of SUS.

As the third embodiment, bolts were tightened to the loose flange of the first embodiment, and 100 Nm was loaded by a universal testing machine manufactured by Shimadzu Corporation for 3 hours. After 3 hours, the amount of the bolt sunk into the coating layer of the loose flange was measured.
The amount of digging was 50 μm.

In Example 4, a loose flange was produced in which the coating layer was 80% by mass of polypropylene and 20% by mass of glass fiber, and other than that, it was the same as in Example 3.
The obtained loose flange was evaluated in the same manner as in Example 3.
The amount of digging was 121 μm.

In Example 5, a loose flange was produced in which the coating layer was 90% by mass of polypropylene and 10% by mass of glass fiber, and other than that, it was the same as in Example 3.
The obtained loose flange was evaluated in the same manner as in Example 3.
The amount of digging was 185 μm.

The results of Examples 3 to 5 are shown in Table 2.
From Examples 3 to 5, it was confirmed that as the glass fiber content of the coating layer increased, the amount of bolt penetration decreased. The amount of bolt digging affects the deterioration of creep resistance during long-term durability.

The present invention can be applied to, for example, pipe fittings in factory piping.

1 Pipe fitting structure 10 1st resin pipe 13 Flange 13b Bolt hole 20 2nd resin pipe 21 Ring protrusion 23 Flange 30 Loose flange 31 Center hole 32 Bolt hole 33 Core material 34 Coating layer 40 Bolt 41 Nut 50 Packing

Claims (4)

A loose flange used to join pipes together.
A loose flange comprising an annular core material made of metal and a coating layer covering the core material, wherein the coating layer contains a thermoplastic resin as a main component. The loose flange according to claim 1, wherein the coating layer has a thickness of 1 mm or more. The loose flange according to claim 1 or 2, wherein the core material has a thickness of 3 mm or more. The loose flange according to any one of claims 1 to 3, wherein the thermoplastic resin is a polyolefin resin, and the coating layer contains 10% by mass or more of reinforcing fibers.

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