JPH086810B2 - Spiral wound gasket - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention comprises a metal band plate having a corrugated cross section and a band-shaped filler material, which are wound a plurality of times in a spiral shape in a state of being overlapped with each other. Various pipes for sealing fluids such as water, oil, steam, etc. that are used to seal the inside and outside of the pipe by being held between flanges formed at each pipe end at the pipe connection portion of an automobile exhaust pipe. The present invention relates to a spiral wound gasket applied to a joint.

[Prior Art] In the conventional spiral wound gasket of this type, a metal strip having a corrugated cross section and asbestos fibers are generally wound and wound.

That is, since the asbestos fiber is a filler that is easier to form on paper than other inorganic fibers and has excellent shape retention, the spiral wound gasket using this is extremely excellent in mechanical properties, flexibility, and restoration property. It has been widely used as a material having good heat resistance and sealing property.

However, recently, the asbestos fiber was found to cause lung cancer by inhaling a large amount of dust generated during handling, or cause asbestos disease in which the dust deposits on the skin, etc. Can be reserved.

Therefore, there has been a demand for the development of a filler material having an inorganic fiber other than the asbestos fiber as a base material. For example, in JP-A-61-225399, as a base material an inorganic fiber other than asbestos fiber, The use of a filler material blended with sepiolite in a spiral wound gasket is disclosed.

[Problems to be Solved by the Invention] A spiral wound gasket (hereinafter referred to as a conventional product) using a filler material disclosed in JP-A-61-225399 is disclosed in the above publication. As shown in the figure, under a general tightening surface pressure of about 200 kgf / cm ² , under all temperature conditions from room temperature to 800 ° C, the compression rate and restoration rate are superior to those using asbestos fiber as a filler. It is shown as a substitute for the spiral wound gasket using asbestos filler.

However, in the above conventional product, when an abnormal tightening surface pressure of about 1000 kgf / cm ² is applied, the compression ratio and the recovery ratio due to buckling become lower than those using an asbestos filler. It has been confirmed that, even after being heated for a long time (for example, 24 hours continuously), the sealing force is remarkably reduced as compared with the one using an asbestos filler.

As described above, the conventional product is not necessarily superior to the spiral wound gasket using the asbestos filler in all aspects, and there is a problem that the application is limited.

The present invention has been made in view of the above circumstances,
Not only can it solve hygiene problems like those using asbestos filler, but it can also exhibit excellent heat resistance and sealing properties when used in high-temperature atmospheres, as well as compressive rigidity and resilience. An object of the present invention is to provide a spiral wound gasket capable of ensuring a predetermined sealing performance without causing buckling even if it is sufficiently secured and an abnormal tightening surface pressure is applied.

[Means for Solving the Problem] In order to achieve the above object, a spiral wound gasket according to the present invention is a spiral wound gasket in which a filler is held in a spiral shape by a metal strip plate having a corrugated cross section. The inner circumference forming portion and the outer circumference forming portion of the filler which are held in a spiral shape are made of an inorganic filler having inorganic fibers excluding asbestos and inorganic powder excluding expanded graphite filler as a base material. The intermediate forming part excluding the peripheral forming part and the outer peripheral forming part is made of an expanded graphite filler, and is provided with a wound part of at least one circumference, and the volume content of the expanded graphite filler in the entire filler is 50% or less, and The friction coefficient between the inorganic filler and the metal strip is 0.25 or more.

[Operation] According to the spiral wound gasket of the present invention as described above,
Since asbestos is not used at all as a spiral wound filler, it does not cause hygiene problems like those using an asbestos filler, and of course the inner and outer peripheral parts of the spiral wound filler are As an inorganic filler based on an inorganic fiber except for and an inorganic powder excluding expanded graphite filler, by isolating the expanded graphite filler of the intermediate forming part from a high temperature oxidizing atmosphere,
Even when used in a high temperature oxidizing atmosphere, it is possible to prevent the expanded graphite filler from being oxidized and reduced in weight, and to sufficiently exhibit the excellent heat resistance and sealing property originally possessed by the expanded graphite filler. In addition, the compression rigidity decreases with the use of an inorganic filler that does not contain asbestos filler, but here the volume content of the filler of the expanded graphite filler is kept to 50% or less, and between the inorganic filler and the metal strip. By eliminating the problem of buckling of the metal strip due to the brittleness of expanded graphite by setting the friction coefficient of 0.25 or more, it becomes possible to give the inner and outer peripheral parts of the gasket a large compression rigidity and resilience. Even if a tightening surface pressure is applied, buckling does not occur and high sealing performance can be secured.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of a spiral wound gasket according to an embodiment of the present invention, in which a filler 2 is held in a spiral shape by a metal strip 1.

The metal strip 1 has a corrugated cross section, as shown in FIG.

On the other hand, the filler 2 includes an outer peripheral forming portion 2A, an intermediate forming portion 2B,
The inner circumference forming portion 2C is formed, and each of these forming portions has a continuous spiral shape.

Both the outer peripheral formation portion 2A and the inner peripheral formation portion 2C are made of an inorganic filler based on inorganic fibers excluding asbestos and inorganic powder excluding expanded graphite filler. That is, this inorganic filler is made by blending inorganic fibers, inorganic powder, binder and the like.

As the inorganic fiber, one kind or plural kinds of glass fiber, ceramic fiber and the like are used. The content of this inorganic fiber is preferably 5 to 40% by weight based on the whole inorganic filler. That is, if the content of the inorganic fibers is less than 5% by weight, it becomes difficult to obtain the resilience required for the filler of the spiral wound gasket. Also, the content is 40% by weight.
If it exceeds, the void ratio of the filler becomes high, so that the sealing property is deteriorated and the fiber is apt to be broken during tightening, and the strength of the filler is deteriorated.

As the inorganic powder, talc, kaolin, sepiolite, vermiculite, mica, wollastonite, etc. may be used alone or in combination. The content of the inorganic powder is preferably 35 to 95% by weight based on the whole inorganic filler. That is, when the content of the inorganic powder is less than 35% by weight, the filling effect of the inorganic powder is reduced and the filler becomes weak against tightening. Also, the content is 95% by weight
If it exceeds, the flexibility of the filler is lowered and the sealing force is deteriorated.

As the binder, natural rubber, synthetic rubber, latex and various pipes are used. The content of this binder is
It is desirable to be 25% by weight or less of the whole inorganic filler. That is, if the content of this binder exceeds 25% by weight, the heat resistance of the inorganic filler is significantly lowered.

The thickness of the inorganic filler formed by blending the inorganic fiber, the inorganic powder and the binder as described above is preferably 0.1 to 1.2 mm. If the thickness of the inorganic filler is less than 0.1 mm, the flexibility and elasticity of the filler will not be utilized regardless of the composition of the inorganic filler. In addition, if the thickness is a thick inorganic filler exceeding 1.2 mm,
The compression rigidity and the resilience of the metal strip 1 are impaired, and the compression rigidity, the resilience, and the strength suitable as filler cannot be obtained.

The inorganic filler also has a bulk density of 0.6 to 1.1 g /
It is preferably in the range of cm ³ . That is, when the bulk density is less than 0.6 g / cm ³ , the compression rigidity and the restoring property appropriate as the inorganic filler cannot be obtained, and the existence value of the inorganic filler on this aspect is reduced. In addition, the bulk density is 1.1 g / c
If the inorganic filler exceeds m ³ , the compression rigidity will be too high and the sealing performance will be deteriorated.

Furthermore, the inorganic filler must be composed so that the coefficient of friction with the metal strip is 0.25 or more. That is, when the coefficient of friction is less than 0.25,
When a tightening pressure is applied to the spiral wound gasket, slippage occurs between the metal strip 1 and the outer peripheral formation portion 2A or the inner peripheral formation portion 2C of the filler 2 formed of an inorganic filler, and the spiral wound gasket is formed. The entire flattening, that is, abnormal compression becomes possible. Therefore, the coefficient of friction is 0.25
If it is less than the above range, the spiral wound gasket may be abnormally compressed and become unrestorable when it is tightened, especially when tightened with an abnormal tightening pressure. In such a state, the metal strip 1
The sealing body draws a whirlpool locus and leaks through the gap formed between the filler 2 and the filler 2.

Next, the intermediate forming portion 2B of the filler 2 will be described.

The intermediate forming portion 2B is made of an expanded graphite filler, and in the case of the embodiment shown in FIG. 1, it occupies two winding portions of the spirally wound filler 2 wound six times. In the spiral wound gasket according to the present invention, the intermediate forming portion is
2B may occupy at least one winding portion of the filler 2 wound a plurality of times. In this way, the intermediate forming portion 2B occupies the winding portion of one round or more,
This is to prevent leakage in the axial direction of the spiral wound gasket over the entire circumference by the expanded graphite filler.

At the same time, the volume content of the intermediate forming portion 2B, that is, the expanded graphite filler is 50% of the entire filler 2.
It is said that This is because if the volume content of the expanded graphite filler exceeds 50%, sufficient compression rigidity cannot be obtained as the entire spiral wound gasket even if the other parts of the filler 2 are made of the inorganic filler as described above. Is.

The joint between the inorganic filler and the expanded graphite filler is
As shown in FIG. 1, a portion that overlaps with each other may be provided, or a state in which the ends are abutted with each other may be provided.

The spiral wound gasket constructed as described above is a spiral wound gasket that secures necessary compression rigidity and resilience by the inorganic filler forming the outer peripheral forming portion 2A and the inner peripheral forming portion 2C of the filler 2 and the metal strip plate 1. It retains its form as a gasket.
That is, by this, the expanded graphite filler forming the intermediate forming portion 2B of the filler 2 always holds the required shape. Therefore, this spiral wound gasket is sandwiched between the flanges A1 and B1 of the pipe A and the pipe B, for example, as shown in FIG. 3, to seal the connecting portion of these pipes A and B. Even if the bolt C is tightened too much, the shape of the expanded graphite filler is not deteriorated due to buckling, and the reliable sealing ability is exhibited by utilizing the heat resistance and sealing performance of the expanded graphite filler. In addition, D is a metal outer ring which is fitted onto the spiral wound gasket and contributes to maintain its shape.

Further, since the expanded graphite filler is cut off from direct contact with the outside air by the inorganic fillers of the outer peripheral formation portion 2A and the inner peripheral formation portion 2C, oxygen is introduced into the pipes A and B in FIG. 3 at high temperature and high pressure. Even when a gas with a high content is passed through, the oxidative loss of the expanded graphite filler hardly occurs due to the effect of isolating it from the high temperature oxidizing atmosphere, and the expanded graphite filler's original excellent sealing performance is demonstrated. Is possible.

Next, an embodiment of the spiral wound gasket according to the present invention,
The compression / restoration test result and the sealing test result of the comparative product 1 using only the inorganic filler as the filler and the comparative product 2 using the filler based on asbestos fiber are shown.

In the product of the present invention, the ratio of the inorganic filler forming the outer peripheral forming portion and the inner peripheral forming portion to the expanded graphite filler forming the intermediate forming portion of the filler is 3: 1. That is, the expanded graphite filler has a volume content of 25% of the entire filler. Further, the compounding ratio and the compounding ratio of the inorganic filler which occupy the remaining 75% are as shown in Table 1 below.

The inorganic filler shown in Table 1 has a thickness of 0.4 mm, a bulk density of 0.7 g / cm ³ , and a friction coefficient with a metal strip of 0.26. On the other hand, the expanded graphite filler has a thickness of 0.4 mm and a bulk density of 1.1 g / m ³
Is.

Next, the compounding ratio and the compounding ratio of the filler (inorganic filler) of Comparative Product 1 are as shown in Table 2 below.

The thickness of the filler shown in Table 2 is 0.4 mm and the bulk density is 0.7 g /
The coefficient of friction with the m ³ metal strip is 0.21.

Next, Table 3 shows the blends and blending ratios of the filler (asbestos filler) of Comparative Product 2.

The thickness of the filler shown in Table 3 is 0.4 mm and the bulk density is 0.9 g /
m ³ , the coefficient of friction with the metal strip is 0.21.

The following compression / restoration tests were performed using the above-described actual product, comparative product 1, and comparative product 2.

FIG. 4 is a front view showing a compression / decompression test device,
I is a test sample such as an actual product or a comparative product 1 or 2. The sample I is set in the hydraulic press machine P in a state of being sandwiched between the two flanges F, F, so that the tightening force can be applied. G is a dial cage for measuring the amount of compression and the amount of restoration. Using this test device, respectively and held for one minute while applying a tightening surface pressure 350 kgf / cm ² and 1000 kgf / cm ^2,
Table 4 shows the compressive deformation ratios of the respective samples measured by the dial gauge G after that. In addition, in Table 4, tightening surface pressure 1000kg
The restoration rate of each sample after applying f / cm ² and the change in inner diameter of each sample (spiral wound gasket) measured with a caliper before and after the test and the amount of deformation are also shown.

As is clear from Table 4, the products of the present invention are "JIS8
Even with a clamping surface pressure of 350 kgf / cm ² corresponding to the Y value shown in “243 Pressure Vessel Structure”, the compressibility is smaller than that of the other comparative products 1 and 2. Pressure
At 1000 kgf / cm ² , the compressibility is significantly smaller than that of Comparative products 1 and 2. Also, tightening pressure 1000 kg
The restoration rate at f / cm ² is much higher than that of the comparative products 1 and 2 in comparison. Further, the change amount of the inner diameter of each sample before and after the test is smaller in the product of the present invention than in the comparative products 1 and 2. That is, it can be seen that the product of the present invention hardly buckles as compared with the comparative products 1 and 2 even when an abnormally large tightening surface pressure of 1000 kgf / cm ² is applied.

FIG. 5 is a block diagram showing a sealing test device, where F is a flange, S is a tightening bolt nut, PM is a pressure gauge, V is a valve, and WP is a hydraulic pump. Then, after tightening the sample I with the tightening bolt nut S at the tightening surface pressure of 350 kgf / cm ² , the water sent from the water pressure pump WP is fed to the lower flange F.
The pressure is applied to the sample I by feeding it to the inner peripheral side of the sample I through the feed path F1 that penetrates through. For the tightening bolt nut S, the relationship between the tightening torque and the generated bolt axial force is measured in advance.

Using the apparatus shown in FIG. 5 as described above, the sealing test was performed on the product and the comparative products 1 and 2 before heating and after heating at 350 ° C. for 24 hours. The results are shown in Table 5.

As is clear from Table 5, each sample could be sealed at 140 kgf / cm ² before heating, but after heating, there was a significant difference in sealing ability between each sample. The product of the present invention retains a remarkably high sealing ability after heating, as compared with the comparative product 1 using only the inorganic filler as the filler. This is largely due to the high heat resistance of the expanded graphite filler as described above, but as can be seen by comparing Tables 1 and 2 above, in the product of the present invention, the inorganic filler was treated with an organic agent. It is considered that one of the causes is that no other filling material is used. Further, the product of the present invention exhibits a higher sealing ability after heating as compared with the comparative product 2 using an asbestos filler, and the comparative product 2 also has a heat resistance.
You can see that it is above.

As described above, the product of the present invention is a comparative product 1 using only the inorganic filler, in terms of the strength when an excessive tightening surface pressure is applied and the sealing ability after heating for a long time.
Not only that, it has higher performance than the comparative product 2 using asbestos filler.

Similar effects can be expected not only in the above-mentioned embodied products but also in other spiral wound gaskets according to the present invention.

[Effects of the Invention] As described above, according to the present invention, since asbestos is not used at all as a spiral wound filler, it is of course possible to avoid the problem of hygiene as in the case of using an asbestos filler. An inner circumference forming part and an outer circumference forming part of the spiral wound filler are inorganic fillers based on inorganic fibers excluding asbestos and inorganic powder excluding expanded graphite filler, and an intermediate forming part thereof is an expanded graphite filler. By doing so, it is possible to isolate the expanded graphite filler from the high temperature oxidizing atmosphere, and suppress the oxidation loss of the expanded graphite filler even when used in a high temperature oxidizing atmosphere, and it has the excellent properties originally possessed by the expanded graphite filler. The heat resistance and the sealing property can be sufficiently exhibited. Furthermore, the volume content of the expanded graphite filler as a whole is kept below 50%, and
The coefficient of friction between the inorganic filler and the metal strip is set to 0.25 or more to eliminate the problem of buckling of the metal strip due to the brittleness of expanded graphite, etc., so that compression with the use of an inorganic filler that does not include asbestos filler By suppressing the decrease in rigidity, the inner and outer peripheral parts of the gasket can have great compressive rigidity and resilience. Therefore, even if abnormal tightening surface pressure is applied, buckling does not occur and high sealing performance is achieved. There is an effect that it is possible to secure.

[Brief description of drawings]

FIG. 1 is a front view of a spiral wound gasket according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view taken along line II-II of FIG. 1, FIG. FIG. 5 is a front view of the test apparatus, and FIG. 5 is a front view of the sealing test apparatus. 1 …… Metal strip plate 2 …… Filler 2A …… Outer peripheral forming part 2B …… Intermediate forming part 2C …… Inner peripheral forming part

Claims (1)

[Claims] 1. A spiral wound gasket in which a filler is held in a spiral shape by a metal strip having a corrugated cross section, wherein the inner circumference forming portion and the outer circumference forming portion of the spirally held filler are asbestos. Inorganic fiber except for the inorganic fiber and the inorganic powder excluding the expanded graphite filler as a base material, the intermediate forming part excluding the inner peripheral forming part and the outer peripheral forming part of the filler is an expanded graphite filler, and at least It has a winding portion of one round or more, the volume content of the expanded graphite filler in the entire filler is 50% or less, and the friction coefficient between the inorganic filler and the metal strip is 0.25 or more, Spiral wound gasket.