JP4918461B2 - gasket - Google Patents

Description

  The present invention relates to a gasket used for applications that require long-term seal stability in severe use environments such as piping joints (JIS or JPI standard flanges, etc.) and equipment joints (valve bonnets, etc.).

  2. Description of the Related Art Conventionally, a structure in which an expanded graphite sheet is laminated and bonded as a sealing material on both surfaces of a concentric corrugated metal sheet is known. This conventional structure has been achieved by using a thin metal plate with concentric corrugations in the core material, which has previously been a flat metal plate or a metal plate that has been processed into discontinuous irregularities or sawtooth irregularities. The slight compression rate is dramatically increased, and high deformation followability (followability with respect to the flange surface accuracy) that can be used even for a glass lining flange with distortion or undulation is secured. Also, the expanded graphite sheet is used for the sealing material as before, and both surfaces that come into contact with the flange are formed of the expanded graphite sheet. The expanded graphite sheet has high fluidity and ensures excellent conformability to the flange. Yes.

  The mechanism by which such a conventional structure exerts a sealing action will be described with reference to the compression deformation process of the conventional structure shown in FIGS. In the figure, 1 is a thin metal plate with a concentric corrugation that is a core material, 2 and 3 are expanded graphite sheets laminated and bonded to both surfaces of the metal thin plate 1, 4 and 5 are flanges, and T is the gasket thickness.

  In the free state before tightening in FIG. 6 (A), the metal thin plate 1 has the original wave pitch P and wave height T1 / 2 (peak height T1), and the expanded graphite sheets 2 and 3 are also uniform throughout. The gap 4 is formed between the valley 1a of the thin metal plate 1 and the expanded graphite sheets 2 and 3.

  In the tightened state in which the low tightening load is applied as shown in FIG. 6 (B), the metal sheet 1 is compressed in the thickness direction between the opposed flanges 5 and 6, and the wave pitch P is increased while the wave height T1 / 2 is reduced. However, it also stretches and deforms in the surface direction (inner and outer diameter directions) while compressively deforming in the thickness direction. The expanded graphite sheets 2 and 3 are compressed in the thickness direction at the crest 1 b of the metal thin plate 1, but are not compressed at the trough 1 a of the metal thin plate 1. For this reason, the conventional structure ensures a high tightening surface pressure locally at the peak portion 1b of the thin metal plate 1 and exhibits sealing performance. At this time, the expanded graphite sheets 2 and 3 are not deformed due to the high fluidity and follow the change in the position of the crest 1b of the metal thin plate 1, and are reduced while the thickness T2 is reduced by the crest 1b of the metal thin plate 1. 1 is increased at the valley 1a, and a part of the gap 4 is filled.

  In the tightening state in which a high tightening load is applied in FIG. 6C, the metal sheet 1 is further compressed in the thickness direction between the opposing flanges 5 and 6, and the metal sheet 1 further reduces the wave height T1 / 2 while reducing the wave pitch P1 / 2. Is further expanded and further deformed in the plane direction while further compressively deforming in the thickness direction to a state close to a flat plate. At this time, the expanded graphite sheets 2 and 3 are formed by further reducing the thickness T2 at the peak portion 1b of the metal thin plate 1 without further deforming and destroying the position change of the peak portion 1b of the metal thin plate 1 due to its high fluidity. It further increases at the valley 1a of the thin plate 1 and finally fills the entire gap 4. For this reason, in the conventional structure, the expanded graphite sheets 2 and 3 are compressed in the thickness direction even in the valley portion 1a of the metal thin plate 1, and the tightening surface pressure is secured over the entire surface of the peak portion 1b and the valley portion 1a of the metal thin plate 1. Demonstrates stable sealing performance.

Note that a conventional structure in which an expanded graphite sheet is laminated and bonded to both surfaces of a thin metal plate having a concentric corrugated shape is known, for example, in a gasket described in Patent Document 1.
Japanese Utility Model Publication No. 5-92574

  The conventional structure uses an expanded graphite sheet as a sealing material, and thus can be used for a non-oxidizing fluid having a temperature of 400 ° C. or lower, but is difficult to use for an oxidizing fluid. Then, when a PTFE sheet was used as a sealing material, it was found that there were the following problems. The PTFE sheet is a sealing material that can be used for most acidic / alkaline fluids having a temperature of 260 ° C. or lower.

  In other words, a thin metal plate with concentric corrugations is used as the core material, so it is difficult to secure the tightening surface pressure over the entire surface at low tightening load, and the seal stability at low tightening load is poor. When an applied load is applied, the PTFE sheet is significantly lower in fluidity than the expanded graphite sheet, and therefore breaks and leaks. If a sufficiently thick PTFE sheet is used, the destruction of the sheet can be avoided, but penetration leakage occurs in the PTFE sheet at a low tightening load, and the sealing performance cannot be ensured. Such a sufficiently thick PTFE sheet is also expensive.

The present invention has been made in view of the above problems, with the purpose to realize a gasket formed by laminating against wearing PTFE sheet on both surfaces of the metal thin plate with a concentric waveform is the central core material, the It is to solve such problems and to secure a stable sealing performance for a long period of time at a low to high tightening load.

In order to achieve the above object, a gasket according to claim 1 is characterized in that a concentric corrugated metal sheet is filled with a PTFE powder sealing material in a valley, and both surfaces of the metal sheet have a sealing property of 0 thickness. A PTFE sheet having a thickness of 25 mm or more and 0.50 mm or less is laminated and adhered.

The gasket of claim 2, in gasket according to claim 1, at a density tightening surface pressure in the valleys of the sheet metal is lower than the tightening surface pressure of the ridge portions of the sheet metal, the PTFE powder The sealing material is filled in the valleys of the thin metal plate.

The gasket according to claim 1 or 2 can be compressed with a conventional low tightening load by filling the valley portion of the metal thin plate, which has been a conventional gap, with PTFE powder sealing material and filling the valley from the beginning. compressing the PTFE sheet in the valleys never been a thin metal plate, it is possible to secure a fastening surface pressure over the entire surface in a load with a low tightening, stable sealing performance from the load with a low tightening is obtained. Further, it is possible to suppress the deformation amount of the PTFE sheet, on less liquid PTFE sheet is not broken even if a load with high fastening, thinner thickness 0.25mm or 0.50mm less PTFE Sea use of the door becomes possible, there is no concern that caused the penetration leakage in the PTFE sheet in the load with low-tightening.

Further, since the sealing material on both sides of the sheet metal is disposed in two layers, even if PTFE sheet which is outside of the sealing material was broken, but may be sealed by PTFE powder is an inner sealant, the seal Increased reliability .

  Furthermore, since the sealing material filled in the valleys of the metal thin plate is powder and has both high compressibility and high fluidity, the deformation of the metal thin plate is not hindered and the deformation followability of the gasket is not impaired. It is difficult to generate a gap in the valley portion of the metal thin plate, and the clamping surface pressure can be stably secured in the portion. The powder sealing material is inexpensive and can be used without waste at a high yield and is economical.

As in the gasket according to claim 2 , the PTFE powder sealing material is applied to the valley of the metal sheet at a density such that the clamping surface pressure at the valley of the metal sheet is lower than the clamping surface pressure at the peak of the metal sheet. By filling the portion, the tightening surface pressure distribution is not uniform and the tightening surface pressure does not decrease, so that the minimum tightening force required for sealing does not increase.

According to the gasket of claim 1, 2, realizing a gasket formed by laminating against wear following PTFE sheet thickness 0.25mm or 0.50mm on both surfaces of the metal thin plate with a concentric waveform is the central core member In addition, it is possible to ensure a long-term stable sealing performance at low to high tightening loads.

According to the gasket of the second aspect , the strength of the required joint portion of the equipment / pipe is not increased in use, and there is no need for a review of the design and modification of the equipment / device.

  Hereinafter, embodiments of a gasket according to the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a gasket according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the structure of the gasket according to an embodiment of the present invention.

  A gasket 10 shown in FIGS. 1 and 2 is an annular ring having sealing properties on both front and back surfaces of an annular thin metal plate (hereinafter referred to as “corrugated thin metal plate”) 11 having a concentric corrugation as a core material. The PTFE sheets 12 and 13 are laminated and bonded to each other, and the portion that is the conventional gap 4 (see FIG. 6) (between the valley 11a of the corrugated metal sheet 11 and the PTFE sheets 12 and 13) The PTFE sheets 12 and 13 in the trough portion 11a of the corrugated metal sheet 11 that could not be compressed by the applied load are compressed, and the tightening surface pressure is ensured over the entire surface at a low tightening load, and the stable sealing performance from the low tightening load is achieved. In addition, the deformation amount of the PTFE sheets 12 and 13 is suppressed, the PTFE sheets 12 and 13 having low fluidity are not broken even when a high tightening load is applied, and the thinner PTFE sheets 12 and 13 In order to prevent the occurrence of permeation leakage in the PTFE sheets 12 and 13 at a low tightening load, a powder sealing material (hereinafter referred to as “filler”) 14 is filled, The portion that has been the conventional gap 4 is filled with the filler 14 from the beginning. Therefore, the gasket 10 has a structure in which the filler 14 as the sealing material and the PTFE sheets 12 and 13 are arranged in two layers on the front and back sides of the corrugated metal sheet 11.

  Here, the inner peripheral edge and the outer peripheral edge of the corrugated metal thin plate 11 are located on one plane including the apex of each peak portion 11b projecting to one side of the corrugated metal thin plate 11 (the lower side in FIG. 2). Circular flat portions 11c and 11d are formed. Further, the outer shape of the front and back surfaces of the corrugated metal thin plate 11 after the filler 14 is filled in the valley portion 11a is the surface of the flat portions 11c and 11d whose outer surfaces (upper side in FIG. 2) are located on the same plane. Is a three-dimensional shape that rises into a trapezoid with a low profile, and the outer shape of the back surface (the lower side in FIG. 2) is a planar shape in which the back surfaces of the flat portions 11c and 11d located on the same plane are connected by a flat surface. It has become. Then, the PTFE sheet 12 on the surface side of the corrugated metal sheet 11 has a three-dimensional surface on the surface of the corrugated metal sheet 11 ranging from the end of the flat part 11c on the inner peripheral side to the end of the flat part 11d on the outer peripheral side. The PTFE sheet 13 on the back side of the corrugated metal sheet 11 is laminated and adhered along the outer shape of the shape, and extends from the end of the flat part 11c on the inner peripheral side of the corrugated metal sheet 11 to the end of the flat part 11d on the outer peripheral side. The corrugated metal thin plate 11 is laminated and adhered along the outer shape of the planar shape on the back surface. The inner peripheral edges of the PTFE sheets 12 and 13 protrude in the inner diameter direction from the end of the flat portion 11c on the inner peripheral side of the corrugated metal sheet 11, and the flat portion 11c on the inner peripheral side from the end of the flat portion 11c. It is stuck and fixed within the thickness of. The outer peripheral edges of the PTFE sheets 12 and 13 protrude in the outer diameter direction from the end of the flat portion 11d on the outer peripheral side of the corrugated metal sheet 11, and the thickness of the flat portion 11d on the outer peripheral side from the end of the flat portion 11d. It is stuck and fixed inside.

The gasket 10 is manufactured by holding the corrugated metal sheet 11, which is a press-molded product, in a substantially horizontal posture, filling the valleys 11 a on the upper surface side of the corrugated metal sheet 11 with the filler 14, and then forming the corrugated metal sheet 11. One PTFE sheet 12 is laminated and bonded to the upper surface (surface) via an adhesive (not shown). Next, the corrugated metal sheet 11 is turned upside down, and the filling material 14 is filled in the valleys 11a on the upper surface side of the corrugated metal sheet 11, and then the other PTFE sheet 13 is bonded to the upper surface (back surface) of the corrugated metal sheet 11 (not shown). completing the laminating adhesive through the agent monitor, by fixing alignment bonded to the inner peripheral edge between the outer peripheral edge between the PTFE sheets 12 and 13.

  At this time, the filling surface pressure is lower than the density of the PTFE sheets 12 and 13 so that the tightening surface pressure in the valley portion 11a of the corrugated metal sheet 11 is lower than the tightening surface pressure in the peak portion 11b of the corrugated metal sheet 11. It is important to fill the valleys 11 of the corrugated metal sheet 11 with the material 14. By filling the filler 14 with such a density, in the gasket 10, the filler 14 (low density) and the PTFE sheets 12 and 13 (high density), which are sealing materials having different densities, are formed on both the front and back surfaces of the corrugated metal sheet 11. ) Are arranged in two layers inside and outside.

  FIG. 3 is a cross-sectional view showing the structure of a gasket according to another embodiment of the present invention. In addition, the plane of the gasket which concerns on this embodiment is the same as the plane shown in FIG. Further, the structure of the gasket according to the present embodiment is the same as the structure of the gasket 10 shown in FIG. 2 except for the PTFE sheet.

  The gasket 20 shown in FIG. 3 is obtained by continuously covering both front and back surfaces and inner periphery of the corrugated metal thin plate 11 with an integrally formed PTFE molded body 21 manufactured by cutting an annular PTFE flat plate. . This PTFE molded body 21 includes annular sheet portions 21a and 21b that are opposed in the thickness direction, and a short cylindrical connecting portion 21c that is integrally formed between the inner peripheral side edges of the sheet portions 21a and 21b. A core storage space 21e having an opening 21d on the outer periphery is formed inside the connecting portions 21c and the sheet portions 21a and 21b. The corrugated metal thin plate 11 is mounted in the core housing space 21e, and the front and back both sides of the corrugated metal thin plate 11 from the upper and lower ends of the connecting portion 21c rising immediately inside the flat portion 11c on the inner peripheral side of the corrugated metal thin plate 11 Sheet portions 21a and 21b are extended.

  The gasket 20 is manufactured by holding the PTFE molded body 21 in a horizontal position, lifting one sheet portion 21a on the upper surface side on the same cylindrical surface as the connecting portion 21c, and forming the corrugated metal thin plate 11 from above into a cylindrical sheet. After being fitted to the outside of the connecting portion 21 c through the portion 21 a, the filling material 14 is filled into each trough portion 11 a on the upper surface side of the corrugated metal thin plate 11. Next, the cylindrical sheet portion 21a is returned to the original, and laminated and bonded to the upper surface (front surface) of the corrugated metal thin plate 11 via an adhesive (not shown). Next, the corrugated metal thin plate 11 is turned over, and the other sheet portion 21b on the upper surface side is raised on the same cylindrical surface as the connecting portion 21c, and then the filler 14 is applied to each trough portion 11a on the upper surface side of the corrugated metal thin plate 11. Fill. Next, the cylindrical sheet portion 21b is returned to its original position, and is completed by laminating and bonding the upper surface (back surface) of the corrugated metal thin plate 11 with an adhesive (not shown). In this case, it is important that the filling material 14 is filled in the valley portion 11 of the corrugated metal sheet 11 with a lower density than the density of the PTFE molded body 21 in the same manner as the gasket 10. .

  In the case of the gasket 20, a gap is formed in the inner corner of the inner periphery (between the flat portion 11c of the corrugated metal thin plate 11 and the inner peripheral edge of one sheet portion 21a). The material 14 is filled to fill the gap.

  Since the gaskets 10 and 20 configured as described above have the same mechanism for exerting a sealing action, description will be given with reference to the compression deformation process of the gaskets 10 and 20 shown in FIGS. .

  In FIG. 4, 50 and 60 are flanges of equipment and piping, and t is the gasket thickness.

  In the free state before tightening in FIG. 4 (A), the corrugated metal sheet 11 has the original wave pitch p and wave height t1 / 2 (peak height t1), and the PTFE sheets 12 and 13 and the PTFE molded body 21 The sheet portions 21a and 21b also have a uniform original thickness t2 as a whole, and in the portion (between the trough portion 11a of the corrugated metal thin plate 11 and the PTFE sheets 12 and 13 and the PTFE molded body 21) that has been the conventional gap 4, The filler 14 is filled.

  In the tightened state in which the low tightening load shown in FIG. 4B is applied, the gaskets 10 and 20 are compressed in the thickness direction between the opposing flanges 50 and 60, and the corrugated metal sheet 11 reduces the wave height t1 / 2. While expanding the wave pitch p, it is also deformed in the surface direction (inner / outer diameter direction) while compressively deforming in the thickness direction. The PTFE sheets 12 and 13 and the sheet portions 21 a and 21 b of the PTFE molded body 21 are compressed in the thickness direction by the crests 11 b of the corrugated metal thin plate 11, and the trough 11 a of the corrugated metal thin plate 11 is filled with the filler 14. As a result, the corrugated metal sheet 11 is compressed even in the valley 11a, and the tightening surface pressure is secured over the entire surface of the crest 11b and the valley 11a of the corrugated metal sheet 11 to exhibit stable sealing performance.

  4C, the gaskets 10 and 20 are further compressed in the thickness direction between the opposing flanges 50 and 60, and the corrugated metal sheet 11 further increases the wave height t1 / 2. The wave pitch p is further enlarged while being reduced, and further stretched and deformed in the surface direction while further compressively deforming in the thickness direction to a state close to a flat plate. The PTFE sheets 12 and 13 and the sheet portions 21 a and 21 b of the PTFE molded body 21 are further compressed in the thickness direction by the crest portions 11 b of the corrugated metal thin plate 11, and the filler 14 is formed in the trough portions 11 a of the corrugated metal thin plate 11. Since it is filled, it is further compressed even in the valley 11a of the corrugated metal sheet 11, ensuring a higher clamping surface pressure on the entire surface of the crest 11b and the valley 11a of the corrugated metal sheet 11, and a low clamping load. Continue to maintain the stable sealing performance obtained in.

  Thus, in each gasket 10 and 20, since the filling material 14 is filled in the valley portion 11a of the corrugated metal thin plate 11 which has been the gap 4 in the past and the portion is buried from the beginning, it can be compressed with the conventional low tightening load. Since the PTFE sheets 12 and 13 and the sheet portions 21a and 21b of the PTFE molded body 21 in the trough portion 11a of the corrugated metal sheet 11 that have not been present can be compressed, and the tightening surface pressure can be secured over the entire surface at a low tightening load, Stable sealing performance can be obtained from low tightening load. Therefore, it is possible to ensure a long-term stable sealing performance at low to high tightening loads.

Moreover, in each gasket 10 and 20, since the filling material 14 is filled in the trough part 11a of the corrugated metal thin plate 11 which was the space | gap 4 conventionally, and this part is buried from the beginning, PTFE sheets 12 and 13 and PTFE molded object 21 are filled. There order to suppress the deformation of an attempt to fill the valley portion 11a of the corrugated metal sheet 11 by its fluidity and thickness t 2, the amount of deformation of the seat portions 21a and 21b of the PTFE sheet 12 and 13 and PTFE molded body 21 Very small. For this reason, the PTFE sheets 12 and 13 and the PTFE molded body 21 having low fluidity are not broken even when a high tightening load is applied, and the thinner PTFE sheets 12 and 13 and the PTFE molded body 21 can be used. There is no concern that penetration leakage will occur in the PTFE sheets 12 and 13 and the PTFE molded body 21 in the tightening load.

  Moreover, in each gasket 10 and 20, the filler 14 which is a sealing material, and the PTFE sheets 12 and 13 and the sheet portions 21a and 21b of the PTFE molded body 21 are arranged in two layers on the front and back surfaces of the corrugated metal sheet 11. Since it has a structure, even if the PTFE sheets 12 and 13 and the PTFE molded body 21 which are the outer sealing materials are broken, the sealing can be performed by the filler 14 which is the inner sealing material, and the reliability of the sealing is improved. high. The same material or a combination of different materials can be used as the material of the filler 14 as the inner sealing material and the PTFE sheets 12 and 13 and the PTFE molded body 21 as the outer sealing material.

  Moreover, in each gasket 10 and 20, since the filler 14 with which the trough part 11a of the corrugated metal sheet 11 is filled is a powder and has both high compressibility and high fluidity, the trough part 11a of the corrugated metal sheet 11 is obtained. Since the corrugated metal sheet 11 is compressed and flows in the valley portion 11a of the corrugated metal sheet 11 with good followability, the deformation of the corrugated metal sheet 11 is not disturbed and the deformation followability of the gaskets 10 and 20 is not impaired. It is difficult to generate a gap in the valley portion 11a of the corrugated metal sheet 11, and the tightening surface pressure can be stably secured in the portion. The powder filler 14 is inexpensive and can be used without waste at a high yield and is economical.

  Further, in each gasket 10, 20, the filling material 14 is filled in the valley portion 11 of the corrugated metal sheet 11 at a density lower than the density of the PTFE sheets 12 and 13 and the PTFE molded body 21. In this case, the tightening surface pressure at the valley portion 11a of the corrugated metal sheet 11 is lower than the tightening surface pressure at the peak portion 11b of the corrugated metal sheet 11, and the tightening surface pressure distribution is not uniform and the tightening surface pressure is increased. Since it does not decrease, there is no increase in the minimum tightening force required for sealing. Therefore, in use, the required strength of the joints of equipment and piping does not increase, and there is no need for a review of the design and modification of facilities and equipment.

  As described above, each of the gaskets 10 and 20 ensures compatibility with the PTFE sheets 12 and 13 and the PTFE molded body 21 having low fluidity, and the use of the PTFE sheets 12 and 13 and the PTFE molded body 21 is realized. Therefore, it can be used for most acidic / alkaline fluids having a temperature of 260 ° C. or lower. In this application, PTFE powder, graphite-based powder such as expanded graphite and flake graphite, or inorganic powder such as mica, talc, and vermiculite can be used as the filler 14.

  Further, the corrugated metal sheet 11 can be used for the above applications as long as it is a metal sheet such as copper, iron, mild steel, stainless steel, and aluminum in consideration of the temperature of the internal fluid and the corrosion resistance with the internal fluid. is there.

Hereinafter, examples of the gasket according to the present invention will be described.
Corrugated metal sheet 11 (material: stainless steel [316L], sheet thickness: 0.55 mm, wave pitch p: 3.2 mm, wave height t1 / 2: 0.5 mm [mountain height t1: 1.1 mm] 1), porous PTFE sheets (thickness t2: 0.5 mm) are used as the PTFE sheets 12 and 13, and PTFE powder (average particle size: 50 μm) is used as the filler 14, FIG. A gasket (hereinafter referred to as “Example”) as shown in FIG.

As a comparative example of the example, a gasket having the same structure as the example (hereinafter referred to as “comparative example” ) was prepared except that the filler 14 was not filled.

  FIG. 5 shows the sealing characteristics of the example and the comparative example. FIG. 5 shows a helium gas seal test at room temperature for the example and the comparative example, and the seal characteristics are compared. In FIG. 5, the example is superior in sealing performance at a low to high tightening load (surface pressure) as compared with the comparative example. Further, in the comparative example, the PTFE sheets 12 and 13 were broken and leaked at a high tightening load. Thereby, by filling the valley portion 11a of the corrugated metal sheet 11 that has been the conventional gap 4 with the filler 14 and filling the portion from the beginning, it is possible to secure a stable sealing performance for a long period of time with a low to high tightening load. Thus, it was confirmed that the PTFE sheets 12 and 13 and the PTFE molded body 21 made of a material having low fluidity can be used in a high tightening load.

  Table 1 below shows the relationship between the thickness and the sealing performance of the PTFE sheets 12 and 13 (porous PTFE sheets) of Examples and Comparative Examples.

  Table 1 shows a comparison of sealing performance for each thickness by performing a helium gas seal test while changing the thickness of the PTFE sheets 12 and 13 for the examples and comparative examples. In Table 1, stable sealing performance was obtained with the PTFE sheets 12 and 13 having a thickness t2 that was much thinner than that of the comparative example. Thereby, it is possible to use the thinner PTFE sheets 12 and 13 and the PTFE molded body 21 by filling the valley portion 11a of the corrugated metal thin plate 11 which has been the conventional gap 4 with the sub seal material 14 and filling the portion from the beginning. It was confirmed that

It is a top view of the gasket concerning the embodiment of the present invention. It is sectional drawing which shows the structure of the gasket which concerns on embodiment of this invention. It is sectional drawing which shows the structure of the gasket which concerns on other embodiment of this invention. It is a figure which shows the compression deformation process of the gasket which concerns on embodiment of this invention and other embodiment. It is a line graph which shows the sealing characteristic of the Example and comparative example of this invention. It is a figure which shows the compression deformation process of the conventional gasket structure.

10,20 Gasket 11 Corrugated metal sheet (metal sheet)
11a Valley 11b Mountain 12,13 PTFE sheet 14 Filler (sealant)
21 PTFE molded body

Claims (2)

A concentric corrugated metal sheet is filled with a tetrafluoroethylene resin (hereinafter referred to as “PTFE”) powder sealing material in the valleys, and the thickness of the metal sheet is 0.25 mm or more. A gasket characterized by laminating and bonding PTFE sheets of 0.50 mm or less . The PTFE powder sealing material is filled in the valley of the metal thin plate at a density such that the clamping surface pressure in the valley of the metal thin plate is lower than the clamping surface pressure in the peak of the metal thin plate. The gasket according to 1 .

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