JP7162343B2 - Leakage prevention device for flange joints - Google Patents

Description

The present invention relates to a device for preventing fluid leakage at a flange joint of a fluid pipe.

At the flange joint of the fluid pipe, the fluid may leak from the gap between the flanges due to external force such as an earthquake or aging. Patent Documents 1 and 2 by the applicant of the present application propose leakage prevention devices for preventing such fluid leakage in advance or for preventing and stopping fluid leakage that has already occurred. This device includes a belt-shaped packing arranged in a ring so as to cover the flange joint, and a ring-shaped fixture externally fitted to the flange joint via the packing. The packing is formed into an annular shape by bonding its circumferential ends (see FIG. 5 of Patent Document 1, for example).

However, since it is necessary to bond such a packing at the construction site, there is a problem that it takes time and effort to attach the packing. Moreover, since the circumferential end portion of the once-bonded packing cannot be easily peeled off, if the packing is bonded in a distorted state by an unskilled worker, it will be difficult to re-bond. Moreover, even if the packing is properly adhered, the dimensional tolerance of the outer diameter and thickness of the flanges is relatively large, and/or the pair of flanges are connected while being radially displaced from each other. As a result, the packing may not be in close contact with the outer peripheral surface of the flange, resulting in a decrease in sealing performance.

JP 2013-204636 A Design registration No. 1305825

SUMMARY OF THE INVENTION It is an object of the present invention to provide a leakage prevention device for a flange joint that allows easy attachment of a packing and has excellent sealing performance.

A leakage prevention device for a flange joint according to the present invention includes a belt-shaped packing arranged in an annular shape so as to cover the flange joint of a fluid pipe, and an annular packing fitted onto the flange joint through the packing. A leak prevention device for a flange joint, comprising: a split portion formed in at least one location in the circumferential direction of the packing; and a first end portion and a second end portion joined to each other at the split portion. , the first end is formed with a first inclined surface that is inclined with respect to the radial direction and faces radially outward, and the second end is formed with a first inclined surface that is inclined with respect to the radial direction A second slanted surface facing radially inward is formed so as to overlap and be in close contact with the first slanted surface. According to this configuration, the end portions of the packing need not be adhered to each other, so the packing can be easily attached. Moreover, by allowing the first inclined surface and the second inclined surface to slide against each other, the flange is less susceptible to dimensional tolerances and radial misalignment, and the packing is brought into close contact with the outer peripheral surface of the flange to improve sealing performance. be able to.

The inner peripheral surface of the packing is provided with a ridge that protrudes radially inward and extends in the circumferential direction, and the first slanted surface and the second slanted surface each include an end surface of the ridge. preferably. According to such a configuration, the end face of the ridge at the first end and the end face of the ridge at the second end overlap each other in the radial direction and are in close contact with each other, thereby improving the sealing performance.

The first inclined surface forms an acute angle with the inner peripheral surface of the packing, forms an obtuse angle with the outer peripheral surface of the packing, and the second inclined surface forms an obtuse angle with the inner peripheral surface of the packing. and form an acute angle with the outer peripheral surface of the packing. Thereby, a wide contact area between the first and second inclined surfaces can be ensured, and the sealing performance can be effectively improved.

Preferably, the first end is free from the fixture and the second end is fixed to the fixture. According to such a configuration, in a state in which the packing is positioned with respect to the fixture, the first inclined surface can be overlapped with the second inclined surface so as to be in close contact with the second inclined surface. can be slid along.

The fixture includes a plurality of split pieces connected in a circumferential direction, including a first split piece and a second split piece adjacent to the first split piece, and the first end portion or the second split piece It is preferable that two ends protrude from the ends of the first split piece and are arranged radially inward of the second split piece. As a result, the first and second inclined surfaces are brought into firm contact with each other on the radially inner side of the second split piece, and the sealing performance can be improved.

Between the outer peripheral surface of the packing and the inner peripheral surface of the fixture that is in contact with the outer peripheral surface of the packing, there is formed an uneven portion that engages with each other. It may be configured to prevent deviation. As a result, it is possible to prevent deterioration of the sealing performance due to axial positional deviation of the packing with respect to the fixture.

Between the first slanted surface and the second slanted surface, a recessed and recessed portion that engages with each other is formed so as to prevent the axial positional displacement of the second end portion with respect to the first end portion. may be configured to As a result, it is possible to prevent deterioration of the sealing performance due to axial positional deviation between the ends of the packing.

Front view of the leak prevention device attached to the flange joint FIG. 2 is a side view of the leak prevention device of FIG. 1; AA sectional view of FIG. Cross-sectional view of packing and fittings Exploded view of the leak prevention device A three-sided view of a piece of packing that constitutes the packing. Dihedral view showing first and second ends joined together at a split Dihedral view showing first and second ends joined together at a split Dihedral view showing first and second ends joined together at a split Perspective view showing how the leakage prevention device is attached to the flange joint Perspective view showing how the leakage prevention device is attached to the flange joint Sectional drawing of the packing in another embodiment, and a fixture A two-sided view of a packing piece in another embodiment

An embodiment of the present invention will be described with reference to the drawings.

1 to 3 show a flange joint portion 10 in which water pipes P1 and P2, which are fluid pipes, are flange-joined to each other. The water pipes P1 and P2 are made of, for example, ductile cast iron. In the flange joint portion 10, a pair of flanges 11 and 12 formed at the ends of the water pipes P1 and P2 are fastened by fasteners 20. As shown in FIG. The fasteners 20 are attached at a plurality of locations (four locations in this embodiment) in the circumferential direction. As shown in FIG. 3, an annular gasket 13 is interposed between the pair of flanges 11 and 12, but the present invention is not limited to this. Between the flanges 11 and 12, a gap 14 is formed that opens radially outward (peripheral side).

The fastener 20 includes a bolt 21 inserted through the bolt holes of the flanges 11 and 12 and a nut 22 screwed onto the bolt 21. The head of the bolt 21 and the nut 22 hold the flanges 11 and 12 together. is sandwiched. The fixture 20 further includes sealing materials 23a and 23b for sealing gaps between bolt holes, metal water stop rings 24a and 24b covering them, and spacers 25a and 25a for adjusting the positions of the bolt 21 and nut 22. 25b. The sealing members 23a and 23b are each formed with a fin portion that fits into the bolt hole. The configuration of the fixture 20 is not limited to this. For example, the nut 22 may be replaced with a cap nut (cap nut), and the water stop ring 24b and the spacer 25b may be omitted.

In the flange joint portion 10 of the water pipes P1 and P2, water may leak from the gap 14 when the flanges 11 and 12 are separated from each other due to an external force such as an earthquake or the influence of aging. Therefore, the leakage prevention device 1 is attached to the flange joint portion 10 in order to prevent water leakage from the gap 14 in advance or to prevent water leakage that has already occurred. If the flanges 11 and 12 are spaced apart from each other, water leakage from those bolt holes is also a concern. can prevent and stop water leakage.

The leakage prevention device 1 includes a belt-like packing 3 arranged in an annular shape so as to cover the flange joint portion 10 , and an annular fitting 4 fitted onto the flange joint portion 10 via the packing 3 . The packing 3 seals the gap 14 along the circumferential direction, and the fixture 4 presses the packing 3 against the outer peripheral surfaces of the flanges 11 and 12 . The packing 3 is made of an elastic material such as rubber. The fixture 4 is made of a material harder than the packing 3, preferably a metallic material such as ductile cast iron.

As shown in FIGS. 3 and 4 , the packing 3 has an outer peripheral surface facing the inner peripheral surface (bottom surface 41 a described later) of the fixture 4 and an inner peripheral surface facing the outer peripheral surfaces of the flanges 11 and 12 . A plurality (three in this embodiment) of protrusions 32 to 34 are provided on the inner peripheral surface of the packing 3 so as to protrude radially inward (inner peripheral side) and extend in the circumferential direction. A groove portion 41 extending along the circumferential direction is provided on the inner peripheral surface of the fixture 4 so as to open radially inward. The groove portion 41 has a bottom surface 41a and a pair of inner wall surfaces 41b extending radially inward from both axial ends of the bottom surface 41a. The pair of inner wall surfaces 41b face the side surface of the packing 3 with a minute gap therebetween, but the invention is not limited to this.

In this embodiment, the packing 3 includes a belt-like main body 31 including an outer peripheral surface, a central ridge 32 that closes the gap 14, and a central ridge 32 that closes the gap 14. A pair of protrusions 33 and 34 are provided in close contact with each other. Each of the ridges 32-34 has a semicircular cross-sectional shape. The radius of curvature of the semicircle of the center ridge 32 is larger than the radii of curvature of the semicircles of the ridges 33 and 34 on both sides, and the amount of protrusion thereof is relatively large. That is, the thickness T1 of the ridge 32 is greater than the thickness T2 of the ridges 33 and 34 . Since the flat portion 3f is formed between the ridge 32 and the ridges 33 and 34, interference between the ridges is suppressed even if the packing 3 is strongly compressed. The width W2 of the packing 3 is larger than the width W1 of the flange joint portion 10 (see FIG. 3). The cross-sectional shape of the packing 3 is not limited to this, and various modifications can be adopted.

As shown in FIG. 5, the fixture 4 includes a plurality of split pieces including a split piece 4A (corresponding to a first split piece) and a split piece 4B (corresponding to a second split piece) adjacent to the split piece 4A. are connected in the circumferential direction. A plurality of (two in this embodiment) divided pieces 4A and 4B constituting the fixture 4 are connected to each other by fasteners 42 attached to the divided portion 4S. The fastener 42 has a bolt 43 inserted through an extension 45 projecting in the left-right direction in FIG. The fixture 4 is reduced in diameter as the fastener 42 is tightened, and presses the packing 3 toward the outer peripheral surfaces of the flanges 11 and 12 .

As can be seen from FIG. 2 and FIG. 10, which will be described later, the end of the split piece 4A and the end of the split piece 4B facing the end of the split piece 4A are formed in a comb shape. , and they have complementary shapes that can be fitted to each other. The condition of these fittings (degree of meshing) changes according to the diameter dimension of the flanges 11 and 12 and the tightening of the fastener 42 . According to such a configuration, it is possible to suppress relative positional deviation between the split pieces 4A and the split pieces 4B in the axial direction. Also, if the split piece 4A or the split piece 4B is oriented in the opposite direction, the ends of the comb tooth shape will not fit together, so that they cannot be connected in a wrong combination.

The packing 3 includes a split portion 3S formed at least in one place in the circumferential direction, and an end portion 3E1 (corresponding to a first end portion) and an end portion 3E2 (corresponding to a second end portion) joined to each other at the split portion 3S. ) and In the present embodiment, split portions 3S are formed at two locations in the circumferential direction of the packing 3, and the packing 3 is split into two according to the number of splits of the fixture 4. As shown in FIG. The packing 3 is composed of a plurality of (in this embodiment, two) packing pieces 3P extending in an arc shape along the circumferential direction, and these packing pieces 3P are connected in the circumferential direction to form an annular shape (see FIG. 1). The end portions 3E1 and 3E2 form end portions of the packing piece 3P in the circumferential direction. Both ends 3E1 and 3E2 are formed in a tapered shape with thickness gradually decreasing.

As shown in FIGS. 5 and 6, the end portion 3E1 is formed with an inclined surface 3T1 (corresponding to a first inclined surface) that is inclined with respect to the radial direction and faces radially outward. The end portion 3E2 is formed with an inclined surface 3T2 (corresponding to a second inclined surface) that is inclined with respect to the radial direction, faces radially inward, and overlaps and closely contacts the inclined surface 3T1. The end portion 3E1 of the packing piece 3P is joined to the end portion 3E2 of the adjacent packing piece 3P, and the inclined surface 3T1 overlaps the inclined surface 3T2 in the radial direction. When the fastener 42 is tightened to reduce the diameter of the fixture 4, the diameter of the packing 3 is reduced while the inclined surfaces 3T1 and 3T2 slide against each other. hits hard.

According to such a configuration, since the end portion 3E1 and the end portion 3E2 are firmly joined to each other as described above, the bonding operation for forming the packing 3 into a ring shape can be eliminated. Therefore, it is not necessary to apply an adhesive to both the inclined surface 3T1 and the inclined surface 3T2, and the ends 3E1 and 3E2 can be joined without adhesion. As a result, it becomes unnecessary to bond the ends of the packing 3 to each other at the construction site, and the packing 3 can be easily attached. Moreover, since the inner diameter of the packing 3 can be finely adjusted by sliding the inclined surfaces 3T1 and 3T2, the flanges 11 and 12 are less susceptible to dimensional tolerances and radial misalignment. Sealing performance can be improved by bringing the packing 3 into close contact.

FIGS. 7-9 show the ends 3E1 and 3E2 respectively joined together at the split 3S. When the outer peripheral length of the flanges 11 and 12 is substantially the same as the effective length of the packing 3, the inclined surfaces 3T1 and 3T2 are brought into contact with each other without positional deviation as shown in FIG. The end faces of the ridges 32-34 at the end 3E1 match the end faces of the ridges 32-34 at the end 3E2. In addition, the inner peripheral surface of the packing piece 3P is arranged flush with the inner peripheral surface of the adjacent packing piece 3P (within the same plane). The effective length of the packing 3 is the designed inner peripheral length of the annularly shaped packing 3 and corresponds to the sum of the inner peripheral lengths of the packing pieces 3P constituting the packing 3 .

When the outer diameters of the flanges 11 and 12 are relatively small and the outer peripheral length of the flanges 11 and 12 is smaller than the effective length of the packing 3, the tip of the end portion 3E1 is positioned inside the end portion 3E2 as shown in FIG. A portion X1 that overlaps the peripheral surface and a portion X2 that the tip of the end portion 3E2 overlaps the outer peripheral surface of the end portion 3E1 are formed. However, since the inclined surface 3T1 and the inclined surface 3T2 can slide on each other, there is little concern that these portions X1 and X2 will be excessively compressed. Moreover, since the packing 3 is compressed from the radially outer side by the fitting 4, these portions X1 and X2 do not adversely affect the sealing performance (water stoppage).

When the outer diameters of the flanges 11 and 12 are relatively large and the outer peripheral length of the flanges 11 and 12 is longer than the effective length of the packing 3, the tip of the end portion 3E1 is positioned inside the end portion 3E2 as shown in FIG. A thin portion Y1 that does not reach the peripheral surface and a thin portion Y2 that the tip of the end portion 3E2 does not reach the outer peripheral surface of the end portion 3E1 are formed. However, since the degree of thinness at these portions Y1 and Y2 is very small, the fitting 4 compresses the packing 3 from the outside in the radial direction, thereby obtaining sufficient sealing performance. However, in order to secure the compression amount of the packing 3, it is preferable to be in the state shown in FIGS.

In this embodiment, the inclined surface 3T1 and the inclined surface 3T2 each include the end surfaces of the ridges 32-34. Therefore, in the divided portion 3S, the end surfaces of the projections 32 to 34 at the end portion 3E1 and the end surfaces of the projections 32 to 34 at the end portion 3E2 overlap each other in the radial direction and adhere to each other, thereby improving the sealing performance. The ratio of the thickness of the overlapping portion of the inclined surface 3T1 and the inclined surface 3T2 to the maximum thickness T1 (see FIG. 4) of the packing 3 is preferably 80% or more, more preferably 90% or more. 100% is most preferred. Moreover, when thickness increases, 120% or less is preferable and 110% or less is more preferable. The inclined surface 3T1 is preferably formed from the outer peripheral surface to the inner peripheral surface of the packing 3 . The inclined surface 3T2 is also similar to this. A maximum thickness T1 of the packing 3 is, for example, 15 to 25 mm.

In this embodiment, the inclined surface 3T1 forms an acute angle with the inner peripheral surface of the packing 3 and forms an obtuse angle with the outer peripheral surface of the packing 3 . The inclined surface 3T2 forms an obtuse angle with the inner peripheral surface of the packing 3 and forms an acute angle with the outer peripheral surface of the packing 3 . Both the angles θ1 and θ3 are less than 90 degrees, for example, 15 to 45 degrees. Both the angles θ2 and θ4 are greater than 90 degrees, for example, 135 to 165 degrees. As a result, a large contact area between the inclined surfaces 3T1 and 3T2 can be ensured, and the sealing performance can be effectively improved. Each of the angles θ1 to θ4 is measured with the packing 3 placed on a flat surface and extended linearly.

In this embodiment, in each packing piece 3, the end 3E1 is not fixed to the fixture 4, and the end 3E2 is fixed to the fixture 4. As shown in FIG. The end portion 3E2 is fixed to the fixture 4 by adhesion. Adhesive is applied to the outer peripheral surface of the end portion 3E2, for example, the region 35 including the tip of the end portion 3E2, and is attached to the bottom surface 41a of the groove portion 41 of the fixture 4. FIG. If the packing 3 is adhered to the fixture 4 in advance at a factory or the like, labor at the construction site can be saved. Since the end portion 3E1 is not glued, it can move freely with respect to the fixture 4. According to such a configuration, in a state in which the packing 3 is positioned with respect to the fixture 4, the inclined surface 3T1 can be brought into close contact with the inclined surface 3T2 by overlapping the inclined surface 3T1 along the circumferential direction with respect to the inclined surface 3T2. It can be slid.

As described above, the fixture 4 is configured by connecting the split piece 4A and the adjacent split piece 4B in the circumferential direction. As shown in FIGS. 1 and 5, the end portion 3E1 of the packing 3 protrudes from the end portion of the split piece 4A and is arranged radially inward of the split piece 4B. More specifically, the end portion 3E1 of the packing piece 3P attached to the split piece 4A straddles the split portion 4S to reach the split piece 4B, and is joined to the end portion 3E2 in the groove portion 41 of the split piece 4B. It is The same applies to the end portion 3E1 of the packing piece 3P attached to the split piece 4B. Therefore, the inclined surfaces 3T1 and 3T2 can be brought into close contact with each other not in the dividing portion 4S of the fixture 4 but in the groove portion 41, thereby improving the sealing performance. Although it is possible to protrude the end portion 3E2, it is preferable to protrude the end portion 3E1 from the viewpoint of workability during installation.

An example of the procedure for installing the leakage prevention device 1 in order to prevent water leakage occurring in the existing flange joint portion 10 will be briefly described. First, as shown in FIG. 10, the bolts 21 of the fasteners 20 are removed from the flanges 11 and 12 to weaken the momentum of water leaking out from the gap 14 . For safety, it is preferable to remove only one bolt 21 . Next, as shown in FIG. 11, the split pieces 4A and 4B are put on the flanges 11 and 12 from the radially outer side, and they are connected by the fastener 42, and the fixture 4 is externally fitted to the flange joint portion 10. . After that, the flange surface indicated by the shaded area in FIG.

The packing piece 3P held by each of the split pieces 4A and 4B is pressed against the outer peripheral surfaces of the flanges 11 and 12 by fitting the fitting 4 onto the outside. At that time, the central ridge 32 having a relatively large amount of protrusion abuts against the edges of the flanges 11 and 12 to block the opening of the gap 14. Adhere to the outer surface. Also, the end portion 3E1 of the packing piece 3P is joined to the end portion 3E2 of the adjacent packing piece 3P, thereby forming the packing 3 into an annular shape. Since the end portion 3E1 and the end portion 3E2 are joined by non-adhesion, no adhesive is required for forming the packing 3 into a ring shape.

When the end portion 3E1 is joined to the end portion 3E2, the end portion 3E1 projecting from the end portion of the split piece 4A enters the groove portion 41 of the split piece 4B, and the inclined surface 3T1 and the inclined surface 3T2 overlap and adhere to each other. . The end portion 3E1 that has entered the groove portion 41 of the split piece 4B is guided by the pair of inner wall surfaces 41b, so that the end portion 3E1 is joined to the end portion 3E2 without being twisted. Moreover, since the end portion 3E2 is adhered to the fixture 4, the inclined surface 3T1 can be slid appropriately with respect to the inclined surface 3T2. Similarly, the end portion 3E1 protruding from the end portion of the split piece 4B enters the groove portion 41 of the split piece 4A, and the inclined surfaces 3T1 and 3T2 overlap each other and adhere to each other.

When a water leakage confirmation test (water pressure test) was actually performed using a leakage prevention device having a configuration similar to that of the present embodiment, it was found that even though the ends of the packing were not glued together, the It was confirmed that water leakage did not occur from the flange joint even when water pressure was applied. In addition, the test was conducted under various adverse conditions, such as misalignment of the packing in the axial direction with respect to the flange, intentionally loosening the fastener at one split part of the fixture (unilateral tightening), etc. Good results were obtained in all cases.

In this embodiment, the outer peripheral surface of the packing 3 and the inner peripheral surface of the fixture 4 are formed flat. It is also possible to prevent axial displacement of the packing 3 with respect to the mounting fixture 4 by forming an uneven portion that engages with the inner peripheral surface (bottom surface 41a) of the mounting fixture 4 that is in contact with the outer peripheral surface. . In the example of FIG. 12, a protrusion 36 protruding radially outward is formed on the outer peripheral surface of the packing 3, and a concave portion 46 recessed radially outward is formed on the bottom surface 41a. You can also reverse the relationship. When the bottom surface 41a is provided with a convex portion, the effect of pressing the ridge 32 toward the flanges 11 and 12 is also obtained. The cross-sectional shape of such uneven portions is not limited to a triangle.

In the present embodiment, the inclined surface 3T1 and the inclined surface 3T2 are formed flat, but the present invention is not limited to this. For example, as shown in FIG. An uneven portion may be formed to prevent the end portion 3E2 from axially displacing with respect to the end portion 3E1. In the example of FIG. 13, the inclined surface 3T1 is formed with a concave portion 37 recessed radially inward, and the inclined surface 3T2 is formed with a convex portion 38 protruding radially inward. can be reversed. Further, for example, it is desirable to make the size of the convex portion 38 smaller than that of the concave portion 37 so as to ensure the sliding of the inclined surfaces 3T1 and 3T2.

In the present embodiment, an example in which the fixture 4 is divided into two is shown, but it is not limited to this, and may be divided into three or more. It is preferable that the packing 3 is divided into the same number as the mounting fixture 4 , so that each of the packing pieces forming the packing 3 can be attached to each of the dividing sections forming the mounting fixture 4 . Further, in the present embodiment, an example is shown in which the dividing portions are formed at a plurality of positions in the circumferential direction of the packing 3, but the dividing portion may be formed at one position in the circumferential direction.

In this embodiment, a water pipe is used as an example of a fluid pipe, but the present invention is not limited to this, and can be applied to fluid pipes used for fluids such as various liquids and gases other than water.

The present invention is by no means limited to the above-described embodiments, and various modifications and improvements are possible without departing from the scope of the present invention.

1 leakage prevention device 3 packing 3P packing piece 3E1 end (first end)
3E2 end (second end)
3S Divided portion 3T1 Inclined surface (first inclined surface)
3T2 inclined surface (second inclined surface)
4 Attachment 4A Split piece 4B Split piece 4S Split part 10 Flange joint part 11 Flange 12 Flange 32 Ridge 33 Ridge 34 Ridge 41 Split part 42 Fastener P1 Water pipe (an example of a fluid pipe)
P2 water pipe (an example of a fluid pipe)

Claims (7)

A leakage prevention device for a flange joint comprising: a band-shaped packing arranged in an annular shape so as to cover a flange joint of a fluid pipe; and an annular fixture fitted onto the flange joint through the packing ,
The packing is circumferentialin multiple placeshaving a split formed thereon and a first end and a second end joined together at the split;
The first end is formed with a first inclined surface that is inclined with respect to the radial direction and faces radially outward,
The second end is formed with a second inclined surface that is inclined with respect to the radial direction, faces radially inward, and overlaps and closely contacts the first inclined surface.cage,
wherein the first end is unfixed to the fixture and the second end is adhesively fixed to the fixture;
The packing is composed of a plurality of packing pieces extending in an arc along the circumferential direction,
The fixture is configured by connecting a plurality of divided pieces in a circumferential direction, and the packing piece is attached to each of the plurality of divided pieces,
The first end protrudes from the end of one of the circumferentially adjacent split pieces and is arranged radially inside the other split piece. A leakage prevention device for a flange joint, characterized by: The inner peripheral surface of the packing is provided with a ridge that protrudes radially inward and extends in the circumferential direction,
2. A leakage prevention device for a flange joint according to claim 1, wherein said first inclined surface and said second inclined surface each include an end surface of said ridge. the first inclined surface forms an acute angle with respect to the inner peripheral surface of the packing and forms an obtuse angle with respect to the outer peripheral surface of the packing;
3. The leakage prevention device for a flange joint according to claim 1, wherein the second inclined surface forms an obtuse angle with respect to the inner peripheral surface of the packing and forms an acute angle with respect to the outer peripheral surface of the packing. The leakage prevention device for a flange joint according to any one of claims 1 to 3, wherein the packing is divided into the same number as the number of divisions of the fitting. Between the outer peripheral surface of the packing and the inner peripheral surface of the fixture that is in contact with the outer peripheral surface of the packing, there is formed an uneven portion that engages with each other. The leakage prevention device for a flange joint according to any one of claims 1 to 4 , which is configured to prevent displacement. Between the first slanted surface and the second slanted surface, a recessed and recessed portion that engages with each other is formed so as to prevent the axial positional displacement of the second end portion with respect to the first end portion. The leakage prevention device for a flange joint portion according to any one of claims 1 to 5 , wherein the leakage prevention device is configured as As the uneven portion, a concave portion formed on one of the first inclined surface and the second end portion and a convex portion formed on the other are formed,
7. The leakage prevention device for a flange joint according to claim 6, wherein the size of the projection is smaller than the size of the recess so that the first inclined surface and the second end can slide on each other.

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