JPH04341661A - Spiral-wound gasket - Google Patents

Abstract

PURPOSE:To improve the extent of productivity by enabling it to secure excellent heating resistance and sealing performance, while making any buckling at the action of high clamping surface pressure preventable, and especially, reducing the forming man-hours of a spiral form, in a spiral-wound gasket which has held a filler in a spiral-wound form with a section-waveform metal band plate. CONSTITUTION:An inner circumferential forming part 2A of filler 2 held in a spiral form is composed of an inorganic filler 21 using an inorganic material excepting asbestos for a base material and an expansion graphite filler 22 being subjected to lap winding together with the former, and then an outer circumferential forming part 2B is constituted of this filler 22.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is made by stacking a metal band plate with a corrugated cross-section and a band-shaped filler material and winding them in a spiral shape several times, for example, to connect a pipe for an automobile exhaust pipe. It is applied to various piping joints that seal fluids such as water, oil, steam, and gas, such as by being sandwiched between flanges formed at each pipe end to seal the inside and outside of the pipe. This relates to a spiral wound gasket.

0002

2. Description of the Related Art Conventional spirally wound gaskets of this type have generally been made by overlapping and winding a metal strip with a corrugated cross section and asbestos fibers. In other words, the above-mentioned asbestos fibers are easier to form into paper than other inorganic fibers, and serve as fillers with excellent shape retention, so spiral-wound gaskets made using these fibers have excellent mechanical properties, flexibility, and resilience. It was widely used for its excellent heat resistance and sealability.

[0003] However, recently, the above-mentioned asbestos fibers are
Its use is discouraged because inhaling the large amount of dust generated during handling can cause lung cancer, and asbestos disease can occur when the dust settles on the skin.

[0004] For this reason, there has been a demand for the development of filler materials other than the above-mentioned asbestos fibers, and for example, as shown in Fig. 3, a spiral-wound gasket using only expanded graphite 22 as a filler has been developed. There is.

[0005]

[Problems to be Solved by the Invention] The spirally wound gasket molded using the filler material 22 made only of expanded graphite can withstand a tightening surface pressure of about 350 kgf/cm2 at all temperatures from room temperature to 800°C. It is an alternative to spiral-wound gaskets using asbestos fiber fillers because it maintains superior compression and recovery rates under the conditions compared to those using asbestos fiber fillers, and in particular exhibits superior sealing performance. This is something that is attracting attention.

[0006] However, the above conventional product
It has been confirmed that when an abnormal tightening surface pressure of about gf/cm2 is applied, the compression ratio becomes abnormally high due to buckling, and the recovery ratio decreases.Therefore, this conventional product has limited applications. There's a problem.

Under these circumstances, the present applicant has already proposed that the inner peripheral forming portion 2A of the filler held in a spiral shape is made of an inorganic filler 21 whose base material is an inorganic material other than asbestos, as shown in FIG. The present invention proposes a spiral gasket in which the filler outer periphery forming portion 2B is made of expanded graphite filler 22. The proposed spiral-wound gasket secures sealing performance with the expanded graphite filler 22 in the filler's outer periphery forming part 2B, while tightening due to the high compression rigidity and high friction coefficient of the inorganic filler 21 in the filler's inner periphery forming part 2A. It has the advantage that buckling is less likely to occur even under abnormally high surface pressure loads.

However, in the above structure, as shown in FIG. 15 in the spiral forming process, both metal strips 1 and 21 are first removed from a spool (not shown) wound with the metal strip 1 and the inorganic filler 21. After winding a predetermined number of turns around the winding core 10 while being fed out, an expanded graphite filler-wrapped spool (not shown) is set in place of the inorganic filler-wrapped spool, and the expanded graphite filler 22 is fed out together with the metal strip 1 from this spool. However, it must be wound around the inner peripheral forming portion 2A of the inorganic filler 21. That is, the molding time was extremely long due to the replacement of the spool.

The present invention was made in view of the above-mentioned circumstances, and provides a spiral-wound gasket that can ensure excellent heat resistance and sealing performance, prevent buckling, and has good productivity. The purpose is to

0010

[Means for Solving the Problems] In order to achieve the above object, the spirally wound gasket according to the present invention has an inner periphery forming part of the filler held in the spiral shape, which is made of an inorganic material excluding asbestos as a base material. It consists of an inorganic filler and an expanded graphite filler wrapped around the inorganic filler, and is characterized in that the outer circumferential portion of the filler is made of the expanded graphite filler.

[0011]

[Operation] The spiral gasket configured as described above has a friction coefficient of 0.25 or more between the compressive rigidity of the inorganic filler forming the inner periphery of the spiral filler and the flange seating surface of the piping. This prevents buckling due to tightening pressure, and excellent sealing performance can be ensured by the expanded graphite filler forming the outer periphery of the filler. Furthermore, when the sealing fluid is a high-temperature oxidizing gas, the inorganic filler prevents oxidation of the expanded graphite filler due to the heat insulating effect. In particular, when forming into a spiral shape, the metal strip, the inorganic filler, and the expanded graphite filler are wound around the winding core a predetermined number of times, and once the inorganic filler has been supplied, the metal strip and the expanded graphite filler are supplied as is. Since it is only necessary to wind it, there is no need to replace the expanded graphite filler-wound spool during molding, and it is possible to shorten the molding process time.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view of a spiral-wound gasket according to the present invention, in which a filler 2 is held in a spiral shape by a metal strip 1. As shown in FIG. 2, the metal strip 1 has a corrugated cross section. On the other hand, the filler 2 is composed of an inner circumferential forming part 2A and an outer circumferential forming part 2B, and each of these forming parts 2A and 2B is continuous and has a spiral shape.

The inner periphery forming portion 2A is composed of an inorganic filler 21 whose base material is an inorganic material other than asbestos, and an expanded graphite filler 22 wrapped around the inorganic filler 21. , an inorganic powder, a binder, etc., and when the inorganic filler 21 is wound, the expanded graphite filler 22 is rolled up in a superimposed manner.

[0015] As the inorganic fiber, one or more types of glass fiber, ceramic fiber, mineral fiber, etc. can be used. The content of this inorganic fiber is desirably 5 to 40% by weight of the entire inorganic filler. That is, if the content of inorganic fiber is less than 5% by weight, it becomes difficult to obtain the resiliency required as a filler for a spiral-wound gasket. Furthermore, if the content exceeds 40% by weight, the porosity of the filler increases, resulting in a decrease in sealing performance, and the fibers tend to break during tightening, reducing the strength of the filler.

[0016] As the inorganic powder, talc, kaolin, sepiolite, vermiculite, mica, volasnite, etc. are used alone or in combination. The content of this inorganic powder is 35 to 95% by weight of the entire inorganic filler.
It is desirable to do so. That is, if the content of the inorganic powder is less than 35% by weight, the plugging effect of the inorganic powder decreases, and the filler becomes weak against tightening. Moreover, when the content exceeds 95% by weight, the flexibility of the filler decreases and the sealing performance deteriorates.

[0017] As the binder, natural rubber, synthetic rubber, latex and various pulps are used. The content of this binder is desirably 25% by weight or less of the total inorganic funuilla. That is, if this binder is contained in an amount exceeding 25% by weight, the heat resistance of the inorganic filler will be significantly reduced.

The thickness of the inorganic filler 21 made of the above-mentioned inorganic fiber, inorganic powder, and binder is 0.
It is preferable to set it as 1-1.2 mm. That is, if the thickness of the inorganic filler 21 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 21. Also, the thickness is 1
．． If it exceeds 2 mm, the compressive rigidity and restorability of the metal strip 1 will be inhibited, making it impossible to obtain suitable compressive rigidity, restoring property, and strength as a filler.

The bulk density of the inorganic filler 21 is preferably in the range of 0.6 to 1.1 g/cm 2 . That is, the bulk density is 0.6 g/cm2
If it is less than that, the inorganic filler 21 will not have adequate compressive rigidity or restorability, and the value of the inorganic filler 21 in this respect will be diminished. In addition, the bulk density is 1.1g/
If the inorganic filler exceeds cm2, the compression rigidity will become too high and the sealing performance will deteriorate.

Furthermore, it is necessary that the inorganic filler 21 has a composition such that the coefficient of friction with the flange seating surface of the pipe is 0.25 or more. That is, when the friction coefficient is less than 0.25, when a tightening pressure is applied to the spiral-wound gasket, the gap between the gasket inner periphery formed by the metal strip 1 and the inorganic filler 21 and the piping flange This causes slippage and flattening of the entire spiral-wound gasket, that is, abnormal compression occurs. Therefore, if the coefficient of friction is less than 0.25, there is a risk that the spiral gasket will be abnormally compressed during tightening, particularly when tightening with abnormal tightening pressure, and will become irrecoverable. In such a state, the sealing body leaks in a spiral trajectory through the gap created between the metal strip 1 and the filler 2.

Next, the outer periphery forming portion 2B of the filler 2 will be explained. This outer periphery forming portion 2B is made of expanded graphite filler 22, and in the case of the embodiment shown in FIG. 1, it occupies a portion of three turns of the spiral filler 2 wound six times. In addition, in the spirally wound gasket according to the present invention, it is sufficient that the outer circumferential forming portion 2B occupies at least one turn or more of the filler 2 wound a plurality of times. The reason why the outer periphery forming portion 2B occupies one or more turns is to ensure that the expanded graphite filler 22 prevents leakage in the axial direction in the spiral gasket over the entire circumference. It is.

[0022] At the same time, the volume content of the outer periphery forming portion 2B, that is, the expanded graphite filler 22, is 70% or less of the entire filler. This is because when the volume content of the expanded graphite filler 22 exceeds 70%, the filler 2
This is because even if the other parts of the gasket are made of the above-mentioned inorganic filler, sufficient compressive rigidity cannot be obtained for the entire spiral-wound gasket.

The process for forming such a spiral gasket is generally as follows. That is, as shown in FIG. 5, a metal strip 1 wound around a spool (not shown),
The expanded graphite filler 22 and the inorganic filler 21 are unwound from the spool and wound around the winding core 10 a predetermined number of times to form the inner peripheral forming portion 2A of the filler 2. At this point, the supply of the inorganic filler 21 is finished, but the metal strip 1 and the expanded graphite filler 22 are fed out as they are and wound a predetermined number of times on the inner circumference forming part 2A of the filler 2. Form 2B.

[0024] The spirally wound gasket constructed as described above secures the necessary compressive rigidity and restorability by the inorganic filler 21 forming the inner periphery forming portion 2A of the filler 2 and the metal strip 1. It maintains its shape as a shaped gasket. That is, as a result, the expanded graphite filler 22 forming the outer periphery forming portion 2B of the filler 2 also maintains the required shape at all times. Therefore, this spiral-wound gasket is attached to each flange A of pipe A and pipe B, as shown in FIG. 6, for example.
When the expanded graphite filler 2 is sandwiched between the tubes A and B1 and seals the joint between these tubes A and B, the expanded graphite filler 2 does not lose its shape due to buckling even if the bolt C is tightened too strongly.
Utilizes the heat resistance and sealing performance of 2 to demonstrate reliable sealing ability.

[0025] At the same time, the volume content of the outer periphery forming portion 2B, that is, the expanded graphite filler 22, is 70% or less of the entire filler 2. This is because if the volume content of the expanded graphite filler 22 exceeds 70%, even if the other parts of the filler 2 are made of an inorganic material as described above, sufficient compression rigidity cannot be obtained for the entire spiral-wound gasket. It's for a reason. Further, the sealing fluid may be, for example, 6
In the case of oxidizing gas at 00° C., the inorganic filler 21 prevents leakage from the inner circumferential side to the outer circumferential side, and also suppresses oxidation of the expanded graphite filler 22 to prevent its deterioration.

In particular, in the spiral forming process, the expanded graphite filler 22 can be shared by the inner circumferential forming part 2A and the outer circumferential forming part 2B, so that the metal strip 1, the inorganic filler 21, and the expanded graphite filler 22 can be used in common. If a wound supply spool is prepared, the metal strip 1 and the expanded graphite filler 22 can be continuously fed out after the inner periphery forming part 2 is formed to form the outer periphery forming part 2B. In other words, there is no need to replace the supply spool midway, and the molding time can be shortened.

Note that D in the figure is a metal outer ring that is fitted onto the spiral gasket and helps maintain its shape.

Next, we will discuss the embodiments of the spiral-wound gasket according to the present invention shown in FIGS. 1 and 2, and a comparative product 1 using only the expanded graphite filler 22 as the filler 2, as shown in FIG.
Furthermore, as shown in FIG. 4, the compression/restitution test results and the sealing test results of a comparative product 2 in which the inner circumferential forming part 2A of the filler 2 is composed of an inorganic filler 21 and the outer circumferential forming part 2B is composed of an expanded graphite filler 22 are shown. show.

In the embodiment of the present invention, the composition and blending ratio of the inorganic filler 21 in the inner peripheral forming portion 2A of the filler 2 are as shown in FIG. 9, and the expanded graphite filler 22 is as shown in FIG. It is. In this case, the thickness of the inorganic filler 21 and the expanded graphite filler 22 in the inner peripheral forming portion 2A of the filler 2 is 0.4 mm, and the bulk density is 0.7.
g/cm3, friction coefficient with flanges A and B is 0.26
It is. Further, the thickness of the expanded graphite filler 22 of the outer peripheral forming portion 2B of the filler 2 is 0.4 mm, and the bulk density is 1.1 g/
cm3.

[0030] Furthermore, the composition and blending ratio of the filler (expanded graphite filler) of comparative product 1 are as shown in FIG. are as shown in FIGS. 9 and 10, respectively.

[0031] The following compression and decompression tests were conducted using the above-mentioned practical product, comparative product 1, and comparative product 2. FIG. 7 is a front view showing the compression/decompression test apparatus, and M is a test sample such as the tested product or comparative products 1 and 2. The sample M is set in a hydraulic press P with being sandwiched between two flanges F, F, so that a tightening force can be applied to the sample M. G is a dial gauge that measures the amount of compression and restoration. Using such a test device, a tightening surface pressure of 35
FIG. 11 shows the compressive deformation rates of each sample, which were held for 1 minute under 0 kgf/cm2 and 1000 kgf/cm2, and then measured using a dial gauge G. Also, in this Figure 11, the tightening surface pressure is 1000 kgf/c.
The recovery rate of each sample after applying m2 and the change in inner diameter and amount of deformation of each sample (spiral gasket) measured with a caliper before and after the test are also shown.

As is clear from the results shown in FIG. 11, the product implementing the present invention has a clamping surface pressure of 350 kgf/c, which corresponds to the Y value shown in "JIS 8243 Structure of Pressure Vessel".
m2, the compression ratio is the same as Comparative Product 2 and smaller than Comparative Product 1. And the tightening surface pressure 1 which can be called abnormal pressure
At 000 kgf/cm2, the compressibility of Comparative Product 1 and the amount of deformation of the inner diameter of the gasket were large and buckling occurred, whereas the compressibility of the product implementing the present invention was significantly improved to the same level as Comparative Product 2. is kept small. In addition, the recovery rate at a tightening surface pressure of 1000 kgf/cm2 was much higher for the implemented product than for comparison product 1;
It is slightly larger than . Furthermore, the amount of change in the inner diameter of each sample before and after the test was as small as that of Comparative Product 2 in the product implementing the present invention. That is, the inorganic filler 21 of the inner periphery forming portion 2A has high compression rigidity and has a large friction coefficient, so that the product according to the present invention can handle up to 1000 kgf.
It can be seen that almost no buckling occurs compared to Comparative Product 1 even when an abnormally large tightening surface pressure of /cm2 is applied.

FIG. 8 is a configuration diagram showing the sealing test device, in which F is a flange and S is a tightening bolt.
Nut, PM is a pressure gauge, V is a valve, and WP is a water pressure pump. Then, tighten the sample M with the tightening bolt and nut S.
After tightening with a surface pressure of 350 kgf/cm2, water sent from the water pressure pump WP is sent into the inner circumferential side of the sample M through the feed passage F1 provided through the lower flange F. A pressure is applied to M. For the tightening bolts and nuts S, the relationship between the tightening torque and the generated bolt axial force is measured in advance.

[0034] Using the apparatus shown in Fig. 8 as described above, the test product and comparative products 1 and 2 were heated in an electric furnace at 350°C for 24 hours before heating, and after being allowed to cool naturally, a sealing test was conducted on each product. . The results are shown in FIG.

As is clear from the results shown in FIG. 12, each sample could be sealed at 140 kgf/cm2 before heating, but the product of the present invention specifically used only the expanded graphite filler 22 as the filler. Like Comparative Product 1, it maintains significantly high sealing ability after heating. This is because the inorganic filler 21 in the inner periphery forming part 2A maintains its shape even in a high temperature atmosphere and has a small amount of heat loss, so the heat resistance of the expanded graphite filler 22 in the outer periphery forming part 2B can be effectively utilized. be done.

FIG. 13 compares characteristic a of the hermetic leakage gas test results of the product implementing the present invention with characteristic b of comparative product 2.
Shown below. It was found that the product implementing the present invention had characteristics equivalent to those of Comparative Product 2. Further, the results of the water pressure test at room temperature and under heating for the product implementing the present invention are shown in FIG. 14 in comparison with the test results for Comparative Product 2 and the product containing asbestos (reference product). It was found that the products implementing the present invention can exhibit superior water pressure resistance performance than conventional products.

As described above, the product implementing the present invention can shorten the spiral forming time, and has superior strength when excessive tightening surface pressure is applied, compared to comparative product 1 using only the expanded graphite filler 22. It is strengthened to the same extent as comparative product 2, which uses inorganic filler 21 and expanded graphite filler 22, and has the same high sealing ability as comparative products 1 and 2 after long-term heating. It can be seen that it has good performance.

[0038] Similar effects can be expected not only with the above-described embodiment but also with other spiral-wound gaskets according to the present invention.

[0039]

[Effects of the Invention] As is clear from the above description, the spiral-wound gasket according to the present invention not only provides excellent sealing performance and heat resistance equivalent to those using expanded graphite filler, but also has an unusual The strength is improved so that buckling does not easily occur even when tightening pressure is applied, and the spiral shape is particularly strong compared to a filler in which the inner periphery is made of inorganic filler and the outer periphery is made of expanded graphite filler. In addition to being easy to mold, the molding time can be shortened and productivity can be improved.

[Brief explanation of drawings]

FIG. 1 is a front view of a spiral-wound gasket according to an embodiment of the invention.

FIG. 2 is a sectional view of the same spiral-wound gasket.

FIG. 3 is a sectional view of a gasket of comparative product 1.

FIG. 4 is a sectional view of a gasket of comparative product 2.

FIG. 5 is an explanatory diagram of the spiral forming process of the spiral-wound gasket of the present invention.

FIG. 6 is an explanatory diagram of how the same spiral-wound gasket is used.

FIG. 7 is a front view of the compression/decompression test device.

FIG. 8 is a front view of the sealing test device.

FIG. 9 is a table showing the formulation of inorganic fillers.

FIG. 10 is a table showing the formulation of expanded graphite filler.

FIG. 11 is a table showing compression/decompression test results.

FIG. 12 is a table showing sealing test results.

FIG. 13 is a characteristic diagram showing the results of an airtight leakage test.

FIG. 14 is a diagram showing the results of a water pressure test at room temperature and under heating.

FIG. 15 is an explanatory diagram of the spiral forming process of comparative product 2.

[Explanation of symbols]

1 Metal strip 2 Filler 2A Inner periphery forming part 2B Outer periphery forming part 21 Inorganic filler 22 Expanded graphite filler

Claims (1)

[Claims] 1. A spiral gasket in which a filler is held in a spiral shape by a metal band plate having a corrugated cross section, wherein the inner circumferential portion of the filler held in the spiral shape is made of inorganic material other than asbestos. 1. A spirally wound gasket comprising an inorganic filler as a base material and an expanded graphite filler wound over the inorganic filler, the outer periphery of the filler being formed of the expanded graphite filler.