JPS5943435B2 - ben - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve having a novel valve seat or valve body.

The valve seat and valve body are important components of a valve, and are required to have the following properties.

(a) It must have appropriate flexibility, compression ratio, and compression recovery ratio to maintain sealing between the valve seat and the valve body.

(b) It must have a low coefficient of friction to ensure smooth rotation or sliding between the valve seat and valve body.

(c) Must have enough strength to withstand compression between the valve body, valve seat, and valve body.

(d) be stable over a wide temperature range;

(e) Be resistant to fluid passing through the valve.

(f) It is easy to mold the valve seat and valve body.

These properties required for valve seats and valve bodies are applicable to various types of valves, such as ball valves, butterfly valves, plug valves,
Common to gate valves, globe valves, check valves, etc.

A typical ball valve among these valves includes a spherical valve body (ball) positioned between two opposing annular valve seats.

Conventional conventional ball valves have a valve seat molded from a polymeric material such as polytetrafluoroethylene (PTFE).

PTFE satisfies conditions (a), (b), and (e) above, but is insufficient in other conditions, and there are no practical problems when the valve is used under normal temperature conditions. However, if this valve is to be operated at low temperatures (such as when flowing liquid nitrogen) or when flowing fluids at high temperatures (for example, over 200°C), leakage may occur due to the high coefficient of expansion of PTFE. This may occur.

Furthermore, PTFE sublimates when heated to a temperature of 100° C. or higher, which is the temperature at which fires occur.

In addition, PTFE may cause cold flow due to pressure, making it difficult to maintain sealing properties, and the
cIIL level is an acceptable range.

On the other hand, an improved method of filling PTFE with asbestos, glass fiber, or carbon has been carried out, but the heat resistance is only slightly improved.

Alternatively, a metal valve seat has been proposed, but it has problems with sealing performance and the allowable leakage amount is about 0.01% of the flow rate when fully open.

Furthermore, carbon and graphite have also been proposed;
Although it has good heat resistance, it is easily damaged by compressive stress.

The above problem with the valve seat of a ball valve also occurs with the O-ring part or valve seat of the valve body of a butterfly valve, the plug or valve seat of a plug valve, and the valve body of a gate valve, globe valve, or check valve. It is a question of obtaining.

The object of the present invention is to provide a valve seat or a valve body having the properties (a) to (f) above, which have been impossible to satisfy with the materials used for conventional valve seats or valve bodies. An object of the present invention is to provide a valve having the following features.

That is, the present invention is based on a graphite composite having a specific gravity of 1.1 or more obtained by blending expanded graphite with at least one kind selected from inorganic binders such as boric acid and aluminum phosphate as a binder, and then compression molding the mixture. The object is to provide a valve having a valve seat or valve body consisting of:

Hereinafter, the present invention will be explained in more detail with reference to the drawings, taking a ball valve as an example.

Referring to FIG. 1, a valve chamber 1 is formed by valve bodies 2 and 3, and a rotatable ball valve body 4 is located within the valve chamber 1.

Annular recesses 5 and 6 are provided at the inner ends of the valve bodies 2 and 3, and valve seats 7 and 8 are located in the recesses 5 and 6, respectively.

Valve bodies 2 and 3 are provided with passages 910 forming the inlet and outlet passages of the valves.

The rotatable ball valve body 4 also has a passage 11.

This passage 11 is connected to the passage 9, when the valve is in the open state.
10 to form the flow path of the valve.

The ball valve body 4 has a groove 12 and receives the tip of the valve stem 13.

The valve stem 13 is attached to the valve body 2 with a backing 14 and a backing press ring 15, and a band lever 16 and an indicator 17 are attached to the upper part.

By rotating the band lever 16 by 90 degrees, the ball valve body 4 is rotated and the flow path is opened and closed.

In order to make perfect contact with the ball valve body 4, the valve seat is placed in the second position.
The valve seat 7.8 is formed into the shape shown in the figure or other shapes, and as shown in FIG. and keep it sealed.

The valve seat and valve body used in the present invention are obtained by blending expanded graphite with at least one kind of inorganic binder selected from boric acid, aluminum phosphate, etc. as a binder, and then compression molding the mixture, which has a specific gravity of 1.1. It consists of the above graphite composite.

This graphite composite can be used, for example, in Japanese Patent Application No. 48-27149 (
It can be manufactured by the method described in Japanese Patent Application Laid-Open No. 49-115095).

Compression molding of expanded graphite using the binder described above provides the following advantages.

Even with the same molding pressure, a molded product with higher density can be obtained than when only expanded graphite is compressed.

That is, it has excellent compressive strength.

A valve seat made of a compression molded body of expanded graphite alone is prone to cracking and peeling, but this graphite composite can not only completely eliminate these defects, but is also impermeable.

The valve seat and valve body made of this graphite composite have a small coefficient of thermal expansion, are stable in shape and size over a wide temperature range of -250°C to 3600°C, do not cause any change in characteristics, and do not undergo rapid heating. There is no problem with this.

Furthermore, the valve seat and valve body made of this graphite composite 75) have excellent self-lubricating properties and excellent corrosion resistance against acids, alkalis, organic compounds, and the like.

In addition, other physical properties of this graphite composite can be controlled by specifying the specific gravity, and the reason why the specific gravity is set to 1.1 or more is because if the specific gravity is less than this, problems will occur in terms of strength and other properties. It is from.

The specific gravity is preferably 1.5 or more.

A specific gravity of 1.5 or more can be achieved by appropriately adjusting the blending ratio of expanded graphite and binder, temperature, pressure, time, etc. during compression molding. 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, the pressure is 50 kg/cIIF, or more,
More preferably, it is 100 to 700 kg/crIL.

The outline of the production of expanded graphite used in producing the valve seat according to the present invention is as follows.

First, in the production of expanded graphite, when natural graphite, pyrolytic graphite, and quiche graphite are treated with sulfuric acid, sodium nitrate, potassium permanganate, or a mixture of oxidizing agents of sulfuric acid and nitric acid, bromine, halides, etc., interlayer A compound is formed.

In general, substances that have a structure in which the crystal lattice is not dense and have many voids have the property of absorbing various other molecules into the voids.

Graphite has a unique layered structure, with very strong bonds within the plane of the carbon atoms, forming a dense layer plane, but weak bonds in the direction perpendicular to the layer plane, leaving relatively wide spaces between the layers. I'm leaving it behind.

Therefore, other reactive substances can enter between the graphite layers and form bonds with the carbon planes, forming a crystalline compound without losing the layered structure of carbon, which is called an intercalation compound.

Graphite particles with this intercalation compound formed are heated to high temperature (for example, 1
By heat treatment at 200° C.), the intercalation compound generates gas pressure, thereby expanding the graphite interlayers.

In this case, assuming that the direction perpendicular to the layer plane is the C direction, the expanded graphite used in this application has a dimension in the C direction that is 10 times or more that of the original particle.

That is, expanded graphite particles are obtained by expanding the interlayer space.

Boric acid is used dissolved in a solvent such as methanol, ethanol, acetone, water, etc., and the amount used is preferably 1:20% by weight based on the expanded graphite.

If it is less than 1% by weight, the effect will not be significant, and if it is more than 20% by weight, the concentration of expanded graphite will be diluted, which is not preferable.

The amount of solvent used is sufficient to saturate boric acid at room temperature.

To remove the solvent, either natural drying or heat drying may be used, but it is preferable to perform natural evaporation, followed by gentle heating, and then heat the mixture above the boiling point of the solvent while stirring to completely drive out the solvent. .

The pressure during pressure molding is not limited as long as it is 50 kg or more, but it is appropriate to use a hot press machine at 50 kg to 250 kg/cIIL.

The heating temperature is at least 600°C or higher, preferably 1.0°C.
00-2,400°C is suitable.

After molding, the monoaluminum phosphate is heat-treated at 500°C or higher, preferably 600 to 1,000°C.

The present invention will be explained in more detail below using actual cases and comparative examples.

Example 1 Expanded graphite was manufactured as follows.

Natural graphite (-24 to +48 mesh 70 to 90%) 1
00g to 5007rLl of concentrated sulfuric acid and 50g of sodium nitrate.
react in a mixed solution.

The reaction time was approximately 16 hours.

The acid-treated natural graphite particles are washed with sufficient water.

Next, the water-washed particles are dried at 100° C. to evaporate water.

The dried particles were subjected to heat treatment at a heat treatment temperature of 1300° C. and a heat treatment time of 5 to 10 seconds.

As a result, particles expanded to about 300 times the original size of the graphite particles in the C direction were obtained.

A 50% methanol solution of boric acid was mixed with 100 parts by weight of this expanded graphite so that the amount of boric acid added was 7 parts by weight, and compression molding was performed at a molding pressure of 200 kg/i, a temperature of 1300°C, and a time of 10 minutes to obtain a valve seat. Ta.

Example 2 A 50% aqueous solution of primary aluminum phosphate was added to 100 parts by weight of the expanded graphite obtained in Example 1 so that the added amount of primary aluminum phosphate was 5 parts by weight, and a molding pressure of 200 kg was applied.
/cr? A valve seat was obtained by compression molding using L and then heat treatment at 600°C for 2 hours.

Comparative Example 1 A graphite composite was obtained in the same manner as in Example 1, but its specific gravity was 1.0.

Comparative Examples 2 and 3 As conventional products, PTFE (Comparative Example 2) and PTFE containing 30% graphite (Comparative Example 3) were tested for comparison.

Comparative Example 4 50 parts by weight of natural graphite powder crushed to a particle size of 74μ or less and 50 parts by weight of pitch coke powder were mixed, 20 parts by weight of a 50% by weight aqueous solution of monoaluminum phosphate as a binder, and a hardening agent (amorphous active After adding 3 parts by weight of each alumina and kneading them at room temperature in a Warner type mixer, they were put into a mold to form a molded body at a molding pressure of 50 kg/cytt, air-dried for 4 days, and fired in a kiln at a maximum temperature of 1100°C to phosphorus. A graphite composite containing 8% by weight of acid aluminum component was obtained.

The table below shows the results of measuring the mechanical characteristics required for the valve seat for the above-mentioned actual example and comparative example.

As is clear from the table, the product of the present invention is superior to the conventional product.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a ball valve showing an embodiment of the present invention;
Fig. 2 is a partial sectional view of the valve seat used in the ball valve of Fig. 1, and Fig. 3 shows the relationship between the valve seat and the ball valve body when assembled in the ball valve of Fig. 1. FIG. 7... Valve seat, 4... Ball valve body.

Claims (1)

[Claims] 1. A graphite composite with a specific gravity of 1.1 or more obtained by blending expanded graphite that has expanded 10 times or more in the C-axis direction of protons with at least one of boric acid and aluminum phosphate as an inorganic binder, and then compression molding it. A valve with a valve seat or valve body consisting of a body.