Patent Application
20220003317
The present invention relates to a metal gasket. More specifically, the present invention relates to a metal gasket which is used for connecting pipes to each other, for example, in a thermal electric power plant, a nuclear power plant, a steam engine of a steam turbine ship, a petroleum refining line, a petrochemical industry process line, a semiconductor manufacturing line, and the like.
As a metal gasket which is excellent in heat resistance, a hollow 0-ring metal gasket and a C-ring metal gasket have been proposed (see, for example, Patent Literature 1 and Patent Literature 2). These metal gaskets however have disadvantages such that a fastening force required for sealing flanges is so large. In order to reduce the fastening force of the metal gasket, it can be considered that a protrusion is formed on a seal surface of the metal gasket. When the metal gasket having the protrusion is provided between flanges, and the flanges are tightened, there is a possibility that sealability between the flanges is lowered, because the protrusion is destroyed by tightening the flanges. Also, it is difficult to accurately form the protrusion on the metal gasket. Moreover, since a stress is concentrated on the protrusion of the metal gasket when the flanges are tightened, the flanges may be damaged by the protrusion.
As a metal gasket which can be tightened with a small tightening force, and shows good sealability without providing a protrusion on the seal surface of the metal gasket, a metal gasket having a concave groove on an outer side wall or an inner side wall has been proposed (see, for example, Patent Literature 3). When the metal gasket is provided between flanges, and the flanges are tightened, a tightening force is reduced, and sealability is improved. However, when a thermal history is applied to the metal gasket, the sealability may be lowered.
Patent Literature 1: Japanese Patent Unexamined Publication No. H9-177976
Patent Literature 2: Japanese Patent Unexamined Publication No. H11-30333
Patent Literature 3: Japanese Patent Unexamined Publication No. 2003-156147
The present invention has been made in view of the above-mentioned prior art. An object of the present invention is to provide a metal gasket capable of ensuring sealability between flanges by fastening the flanges with a small fastening force, and capable of ensuring sealability between flanges even when a thermal history is applied to the metal gasket.
The present invention relates to:
(1) a metal gasket including a metal gasket body having a recessed circumferential groove on an outer peripheral surface, and an elastic body,
wherein the elastic body is inserted into the circumferential groove of the gasket body,
wherein an arc-shaped upper seal surface having an upward bulge is formed on a top surface of the gasket body in the vertical cross section of the metal gasket, in which the top surface comes into contact with a material to be sealed,
wherein an arc-shaped lower seal surface having a downward bulge is formed on a bottom surface of the gasket body in the vertical cross section of the metal gasket, in which the bottom surface comes into contact with a material to be sealed,
wherein an upper flat surface or an upper notched area is provided on the upper seal surface, and
wherein a lower flat surface or a lower notched area is provided on the lower seal surface;
(2) the metal gasket according to the above-mentioned item (1), wherein a surface hardness of the gasket body is 15 to 250 HV; and
(3) the metal gasket according to the above-mentioned item (1) or (2), wherein the gasket body is formed from a metal selected from the group consisting of aluminum, aluminum alloy, stainless steel, Inconel, carbon steel, lead, gold, silver, copper, nickel, tantalum, chromium molybdenum steel, Monel, titanium, and magnesium alloy.
According to the present invention, a metal gasket capable of ensuring sealability between flanges by fastening the flanges with a small fastening force, and capable of ensuring sealability between flanges even when a thermal history is applied to the metal gasket is provided.
As described above, the metal gasket according to the present invention is a metal gasket which includes a metal gasket body having a recessed circumferential groove on an outer peripheral surface, and an elastic body.
In the metal gasket according to the present invention, the elastic body is inserted into the circumferential groove of the gasket body. An arc-shaped upper seal surface having an upward bulge is formed on a top surface of the gasket body in the vertical cross section of the metal gasket, in which the top surface comes into contact with a material to be sealed. An arc-shaped lower seal surface having a downward bulge is formed on a bottom surface of the gasket body in the vertical cross section of the metal gasket, in which the bottom surface comes into contact with the material to be sealed. An upper flat surface or an upper notched area is provided on the upper seal surface. A lower flat surface or a lower notched area is provided on the lower seal surface.
Since the metal gasket according to the present invention has the above-mentioned configuration, the metal gasket exhibits excellent effects such as making it possible to ensure sealability between flanges by fastening the flanges with a small fastening force, and ensure sealability when a thermal history is received.
The metal gasket according to the present invention will be more specifically described below with reference to drawings. However, the present invention is not limited only to embodiments illustrated in the drawings.
The metal gasket 1 according to the present invention includes a gasket body 2 made of a metal, which has a recessed circumferential groove 3 on an outer peripheral surface thereof, and an elastic body 4, as shown in
In the embodiment shown in
The surface hardness (Vickers hardness) of the gasket body 2 is preferably 15 HV or more, and more preferably 19 HV or more, from the viewpoint of ensuring of sealability between flanges by fastening the flanges with a small fastening force. The surface hardness (Vickers hardness) of the gasket body 2 is preferably 250 HV or less, more preferably 220 HV or less, furthermore preferably 175 HV or less, and still furthermore preferably 170 HV or less, from the viewpoint of ensuring of sealability between flanges by fastening the flanges to each other with a small fastening force.
The material of gasket body 2 is preferably a metal selected from the group consisting of aluminum, aluminum alloy, stainless steel, Inconel, carbon steel, lead, gold, silver, copper, nickel, tantalum, chromium molybdenum steel, Monel, titanium and magnesium alloy, more preferably a metal selected from the group consisting of aluminum, aluminum alloy, stainless steel and Inconel, and furthermore preferably aluminum or stainless steel, from the viewpoint of ensuring of sealability between flanges by fastening the flanges with a small fastening force.
The aluminum alloy includes, for example, aluminum-iron alloy, aluminum-copper alloy, aluminum-manganese alloy, aluminum-magnesium alloy, aluminum-zinc alloy, aluminum-nickel alloy and the like, and the present invention is not limited only to those exemplified ones.
The stainless steel includes, for example, SUS304, SUS316, SUS430, SUS630, SUS631, SUS633, SUS420J2 and the like, and the present invention is not limited only to those exemplified ones.
A metal other than magnesium, which is used in the magnesium alloy includes, for example, lithium, calcium, aluminum, zinc, titanium, manganese, zirconium, yttrium, tantalum, neodymium, niobium and the like, and the present invention is not limited only to those exemplified ones.
The plane shape of the metal gasket 1 can be annular as shown in
The cross-sectional shape of the gasket body 2 in the X-X part shown in
In the metal gasket 1 according to the present invention, the arc-shaped upper seal surface 2a having an upward bulge is formed on the top surface of the gasket body 2, and the arc-shaped lower seal surface 2b having a downward bulge is formed on the bottom surface of the gasket body 2. The arc shape includes not only an arc shape of a true circle but also a concept including an arc of a vertically long elliptical shape, an arc of an oblong oval shape and an arc of a track elliptical shape, as well as the cross-sectional shape of the gasket body 2.
The gasket body 2 is described below with reference to
The upper notched area 5a is provided on the upper seal surface 2a of the gasket body 2 of the metal gasket 1 according to the present invention, and the lower notched area 5b is provided on the lower seal surface 2b of the gasket body 2.
The depth D of each of the upper notched area 5a and the lower notched area 5b cannot be absolutely determined, because the depth D differs depending on the material of the gasket body 2, the size of the gasket body 2 and the like. The depth D of each of the upper notched area 5a and the lower notched area 5b is preferably 0.1 to 3 mm, more preferably 0.3 to 2 mm, and furthermore preferably 0.5 to 1 mm, respectively, from the viewpoint of obtaining the metal gasket 1 which enables to ensure sealability between flanges by fastening the flanges with a small fastening force, and which enables to ensure sealability even when a thermal history is applied to the metal gasket 1. Incidentally, as shown in
The width W of each of the upper notched area 5a and the lower notched area 5b cannot be absolutely determined, because the width W differs depending on the material used for the gasket body 2, the size of the gasket body 2, and the like. The width W is preferably 0.1 to 3 mm, more preferably 0.3 to 2 mm, and furthermore preferably 0.5 to 1 mm, from the viewpoint of obtaining the metal gasket 1 which enables to ensure sealability between flanges by fastening the flanges with a small fastening force, and which enables to ensure sealability even when a thermal history is applied to the metal gasket 1. Incidentally, as shown in
It is preferred that each of the upper notched area 5a and the lower notched area 5b is a V-shaped notched area, respectively as shown in
In the upper notched area 5a and the lower notched area 5b, the bottom of the V-shaped notched area may have an acute angle as shown in
It is preferred that the deepest position of each of the upper notched area 5a and the lower notched area 5b in the horizontal direction of the metal gasket 1 exists between the innermost end P of the inner side wall of the circumferential groove 3 and the inlet part Q of the circumferential groove 3 as shown in
Incidentally, the upper notched area 5a and the lower notched area 5b can be provided not only on the upper seal surface 2a and the lower seal surface 2b respectively, but also on an upper wall (not shown in the figure) and a lower wall (not shown in the figure) inside the circumferential groove 3 for inserting an elastic body 4 which is described later as occasion demands.
The circumferential groove 3 for inserting the elastic body 4 is formed inside the gasket body 2. In the embodiments shown in
The minimum thickness of the inner side wall of the gasket body 2 at the innermost end P of the circumferential groove 3 cannot be absolutely determined, because the minimum thickness differs depending on uses of the metal gasket 1 according to the present invention, and the like. The minimum thickness of the inner side wall of the gasket body 2 at the innermost end P of the circumferential groove 3 is preferably 1 mm or more, more preferably 1.5 mm or more, and furthermore preferably 2 mm or more, from the viewpoint of obtaining the metal gasket 1 capable of ensuring sealability between flanges by fastening the flanges with a small fastening force, and ensuring sealability between flanges even when a thermal history is applied to the metal gasket 1. The maximum thickness of the gasket body 2 at the innermost end P of the circumferential groove 3 cannot be absolutely determined, because the maximum thickness differs depending on uses of the metal gasket 1 according to the present invention, and the like. The maximum thickness of the inner side wall of the gasket body 2 at the innermost end P of the circumferential groove 3 is preferably 15 mm or less, more preferably 10 mm or less, and furthermore preferably 5 mm or less, from the viewpoint of obtaining the metal gasket 1 capable of ensuring sealability between flanges by fastening the flanges with a small fastening force, and ensuring sealability between flanges even when a thermal history is applied to the metal gasket 1.
The inner surfaces (not shown in the figure) of the circumferential groove 3 of the gasket body 2 shown in
The width S of the opening of a circumferential groove 3 cannot be absolutely determined, because the width S differs depending on uses of the metal gasket 1 according to the present invention, and the like. It is preferred that the width S is 30 to 85% of the thickness T of the gasket body 2 of the metal gasket 1 shown in
The thickness T of the gasket body 2 cannot be absolutely determined, because the thickness T differs depending on uses of the metal gasket 1, and the like. It is preferred that the thickness T of the gasket body 2 is appropriately determined in accordance with uses of the metal gasket 1, and is usually 1.5 to 15 mm or so.
In
A value of the ratio of the depth A of the circumferential groove 3 of the gasket body 2 to the length B of the gasket body 2 in the horizontal direction (depth A of the circumferential groove/length B in horizontal direction) is preferably 0.1 or more, more preferably 0.2 or more, further preferably 0.3 or more, furthermore preferably 0.4 or more, and even more preferably 0.5 or more, from the viewpoint of ensuring sealability between flanges by fastening the flanges with a small fastening force. The value of the ratio is preferably 0.95 or less, more preferably 0.9 or less, further preferably 0.88 or less, and furthermore preferably 0.86 or less, from the viewpoint of increase in mechanical strength of the gasket body 2, and ensuring sealability between flanges by fastening the flanges with a small fastening force.
The elastic body 4 is arranged in the circumferential groove 3 of the gasket body 2 as shown in
The elastic body 4 has a shape corresponding to the internal shape of the circumferential groove 3 of the gasket body 2. The elastic body 4 shown in
The elastic body 4 may be arranged so that the whole inner part of the circumferential groove 3 of the gasket body 2 is filled with the elastic body 4. Alternatively, the elastic body 4 may be arranged in the circumferential groove 3 so that an edge 2c is formed at the inlet part Q of the circumferential groove 3 of the gasket body 2 as shown in
As another embodiment of the metal gasket 1 according to the present invention, the metal gasket 1 shown in
In the embodiments shown in
The upper flat surface 5c and the lower flat surface 5d may be provided to be parallel to the upper seal surface 2a and the lower seal surface 2b, respectively. Alternatively, the upper flat surface 5c and the lower flat surface 5d may be provided to be inclined with respect to the upper seal surface 2a and the lower seal surface 2b, respectively, as shown in
The metal gasket 1 according to the present invention being configured as described above can ensure sealability between flanges by fastening the flanges with a small fastening force, and can ensure sealability even when a thermal history is applied to the metal gasket 1. Accordingly, the metal gasket 1 according to the present invention can be suitably used for connecting pipes to each other in, for example, a thermal electric power plant, a nuclear power plant, a steam engine of a steam turbine ship, a petroleum refining line, a petrochemical industry process line, a semiconductor manufacturing line, and the like.
Next, an embodiment of the metal gasket according to the present invention will be more specifically described based on working examples. However, the present invention is not limited only to those working examples.
As a metal gasket body, a metal gasket body (surface hardness: 22 HV) made of aluminum, having a shape shown in
More specifically, in the metal gasket 1 shown in
A metal gasket 1 was manufactured by inserting an elastic body 4 made of fluorocarbon rubber, having a shape shown in
As the physical properties of the metal gasket 1 obtained in the above, necessary force for fastening, sealability, and sealability after thermal history were evaluated in accordance with the following methods. The results thereof are shown in Table 1.
(1) Necessary Force for Fastening
The necessary force for fastening was evaluated by using an evaluation test device 7 of a gasket shown in
A gasket 8 was provided between a test platen 9a and a test platen 9b, and moved distance of the test platen 9a was determined by means of a dial gauge while the gasket 8 was compressed. A compression ratio was determined in accordance with the equation:
[Compression ratio]=[(Initial height of gasket 8)−(Height of gasket 8 after compression)]÷[Initial height of gasket 8]×100.
When the compression ratio reached 17%, a compression load was determined, and the compression load was regarded as a necessary force for fastening. The necessary force for fastening was evaluated in accordance with the following evaluation criteria. Incidentally, the compressive load at which the compression ratio reached 17% means a compression load necessary for eliminating a gap between the gasket 8, and the test platens 9a, 9b (necessary force for fastening).
[Evaluation Criteria]
⊚: Necessary force for fastening (Compression load) is less than 50 kN/m.
◯: Necessary force for fastening (Compression load) is 50 kN/m or more, and less than 80 kN/m.
Δ: Necessary force for fastening (Compression load) is 80 kN/m or more, and less than 100 kN/m.
x: Necessary force for fastening (Compression load) is 100 kN/m or more.
(2) Sealability
When the sealability of a gasket was evaluated, the evaluation test device 7 of a gasket shown in
First of all, the gasket 8 was provided between the test platen 9a and the test platen 9b in the evaluation test device 7 for evaluating sealability, and a compression load of 25 kN/m was applied to the gasket 8. Thereafter, helium gas was injected from a nozzle 10a of a helium gas cylinder 10 to the evaluation test device 7, to fill the evaluation test device 7 with helium gas having atmospheric pressure.
Next, the pressure inside the gasket was reduced by means of a helium leak detector 11 until a degree of vacuum inside the gasket 8 was 0.1 Pa. When 5 minutes passed after the pressure inside the gasket 8 reached the above degree of vacuum, the leaked amount of helium gas flowed from the outside of the gasket 8 to a space inside the gasket 8 was determined.
The sealability was evaluated in accordance with the following evaluation criteria of sealability based on the leaked amount of helium gas as determined above.
[Evaluation Criteria]
⊚: Leaked amount of helium gas is less than 4×10−11 Pa·m3/s·m (detection limit).
◯: Leaked amount of helium gas is 4×10−11 Pa·m3/s·m or more, and less than 1×10−10 Pa·m3/s·m.
Δ: Leaked amount of helium gas is 1×10−10 Pa·m3/s·m or more, and less than 1×10−9 Pa·m3/s·m.
x: Leaked amount of helium gas is 1×10−9 Pa·m/s·m or more.
(3) Sealability after Thermal History
The gasket was placed in a thermostatic chamber having a temperature of 100° C., and heated at this temperature for 24 hours, to impart a thermal history to the gasket. Thereafter, the gasket was allowed to cool to room temperature, and taken out from the thermostatic chamber.
The gasket to which a thermal history was applied in the above was used, and sealability of the gasket was examined in the same manner as in the above. Whether or not the leakage amount of the helium gas was increased as compared to the leakage amount of the helium gas of the original gasket was confirmed, and sealability after thermal history was evaluated in accordance with the following evaluation criteria.
⊚: No increase of the leakage amount of helium gas is observed.
x: Increase of the leakage amount of the helium gas is observed.
(4) Comprehensive Evaluation
In the evaluation results of the necessary force for fastening, the sealability and the sealability after thermal history, the evaluation of ⊚ was counted as 100 points; the evaluation of ◯ was counted as 80 points; the evaluation of Δ was counted as 60 points; and the evaluation of x was counted as 0 point. The score of the necessary force for fastening, the sealability and the sealability after thermal history were summed to obtain total points, and the total points were listed in the column of comprehensive evaluation in Table 1.
Incidentally, when the evaluation of x was included in the evaluation results of the necessary force for fastening, the sealability and the sealability after thermal history, the evaluation of “Failure” was listed in the column of the comprehensive evaluation.
In Example 1, a gasket body in which the elastic body was not used was used as a metal gasket.
The necessary force for fastening, the sealability and the sealability after thermal history of the metal gasket were evaluated in the same manner as in Example 1. The results are shown in Table 1.
As a conventional gasket, an O-ring made of fluorocarbon rubber (manufactured by VALQUA, Ltd. under the product number of 4640) was used, and the necessary force for fastening, the sealability and the sealability after thermal history of the gasket were evaluated in the same manner as in Example 1. The results are shown in Table 1.
As a conventional metal gasket, a C-ring metal gasket including a spring (manufactured by VALQUA, Ltd. under the product number of 3645) was used, and the necessary force for fastening, the sealability and the sealability after thermal history of the gasket were evaluated in the same manner as in Example 1. The results are shown in Table 1.
As a conventional gasket, a hollow O-ring metal gasket made of stainless steel (SUS304) (manufactured by VALQUA, Ltd. under the product number of 3640) was used, and the necessary force for fastening, the sealability and the sealability after thermal history of the gasket were evaluated in the same manner as in Example 1. The results are shown in Table 1.
From the results shown in Table 1, the metal gasket obtained in Example 1 can eliminate the gap between the metal gasket and the test platen by a low tightening force of 35 kN/m. Accordingly, it can be seen that the metal gasket does not impart tightening marks to a flange even when a soft metal flange such as an aluminum flange is used in tightening, and therefore enhances sealability when the flange is used.
In addition, the metal gasket obtained in Example 1 is excellent in sealability, and there is no change in sealability after a thermal history was imparted to the metal gasket. Accordingly, it is considered that the metal gasket can be suitably used for connecting pipes to each other in a thermal electric power plant, a nuclear power plant, a steam engine of a steam turbine ship, a petroleum refining line, a petrochemical industry process line, a semiconductor manufacturing line, and the like.
On the other hand, it can be seen that the gasket used in each comparative example is inferior in any of the necessary force for fastening, the sealability and the sealability after thermal history of the gasket.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-191437 | Oct 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/037159 | 9/24/2019 | WO | 00 |
