JP2580506B2 - Manufacturing method of heat resistant packing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a method for producing a heat-resistant packing used in applications requiring low radiation, high temperature and high pressure, such as valves and pumps for nuclear power and thermal power generation. About.

(Prior art) Conventionally, a practical method of packing used for the above-mentioned applications is to use a fiber such as asbestos as a base material and fill the voids with an auxiliary material such as rubber or oil finger to maintain the sealing property. A method of using asbestos-based packing alone, for example, as shown in FIG. 4, several layers of expanded graphite packing 4 are stacked, and the outer periphery of a core obtained by mixing and molding asbestos and a heat-resistant lubricating agent from both ends is covered with a Monel wire-containing asbestos yarn. A method of sandwiching with an asbestos braided packing 9 in which a double bag is knitted and whose surface is baked with graphite is known.

(Problems to be Solved by the Invention) However, in recent years, the carcinogenicity of asbestos has become a problem on a global scale, and it is necessary to promptly improve the ratio of non-asbestos to packing. When the temperature is high, the volume of the auxiliary material is reduced, and appears as stress relaxation or a decrease in sealing performance, requiring maintenance such as tightening,
Eventually, the heat resistance is insufficient and oils and fats may ooze during use. In addition, there is a problem that after the oil or fat is removed, the packing becomes hard, and it is difficult to remove the packing from the stuffing box or the shaft at the time of replacement. In addition, petroleum-based packing has a problem in using it as a nuclear gland packing because halogen such as Cl elutes during use.

On the other hand, according to the method shown in FIG. 4, the leakage of liquid can be eliminated by the good sealing property of the expanded graphite packing 4, but the asbestos braided packing is used and the expanded graphite packing is not used alone. When the packing is set, the expanded graphite can be deformed by tightening with the packing retainer (also called gland), so if the tightening pressure is high, the gland and the mating material should be separated from the shaft or packing case from a slight gap. It has the drawback of easily oozing, and the expanded graphite packing easily adheres to the shaft and separates and tears off during replacement, which takes time to clean the stuffing box. This is because it has disadvantages such as danger of being exposed.

An object of the present invention is to solve the above-mentioned disadvantages and to provide a method for manufacturing a heat-resistant packing without using asbestos.

(Means for Solving the Problems) The present inventors have found a method for producing a heat-resistant packing that uses carbon fiber and expanded graphite, can be replaced with gypsum-based packing, has no outflow of oils and fats, and is easy to replace.

The present invention is characterized in that carbon fibers around a rod-shaped molded body formed by adding carbon fibers to expanded graphite are braided, molded, the molded product is impregnated with an organic substance, and then fired to carbonize the organic substance. After braiding the organic fibers around a rod-shaped molded body formed by adding carbon fibers to expanded graphite and a method of manufacturing a heat-resistant packing to be formed, then forming and firing to carbonize the organic fibers or bake the organic fibers. The present invention relates to a method for producing a heat-resistant packing, which comprises carbonizing and then molding.

In the present invention, the type of expanded graphite, that is, the starting material, the production method, and the like are not limited. The carbon fibers to be added to expanded graphite are preferably soft and include graphite fibers, and the organic fibers are carbonized to such an extent that some organic substances remain. Fiber (semi-carbonized fiber)
Alternatively, it may be added in the form of short fiber, long fiber, cloth, mesh, felt or the like.

The molded article is molded after adding short fibers of carbon fibers to expanded graphite particles and mixing. Expanded graphite sheet and carbon fiber long fiber,
The rod-shaped body is formed by means such as laminating and forming a cloth, mesh, or felt, and the sectional shape thereof is not particularly limited, such as a square, a circle, and an ellipse.

The carbon fibers for the braid provided around the molded body include graphite fibers and the above-mentioned semi-carbonized fibers, and are long fibers. The method of braiding is performed by bag knitting or the like, but there is no particular limitation, and double knitting, triple knitting, or the like may be used.

For packing that does not require total carbon quality, use Monel wire or SU
S lines may be mixed in for reinforcement.

The packing material is obtained by bundling one compact or a plurality of compacts and braiding carbon fibers around the bundle.

The heat-resistant packing is obtained by placing the above packing material in a mold and molding it into a desired shape and size by a known method, impregnating the molded product with a thermosetting resin, an organic substance such as tar pitch, and then carbonizing the organic substance. Can be Further, the rod-shaped molded body is braided with organic fibers that become carbonized carbon fibers such as PAN fibers, phenolic resin fibers, and the like. The braided body may be fired and then molded to form a heat-resistant packing.

(Example) An example of the present invention will be described below.

Example 1 A natural scale graphite powder produced from Madakascal having a peak at 42 mesh was immersed in a mixed solution of concentrated sulfuric acid and concentrated nitric acid for 1 hour, filtered, washed with water, and dried at 130 ° C. Then add this powder to 1000
The mixture was rapidly heated at 10 ° C. for 10 seconds to obtain expanded graphite particles in which the C axis of graphite expanded 200 times. Next, the expanded graphite particles were subjected to pressure molding to obtain an expanded graphite sheet having a bulk density of 0.3 g / cm ³ and a thickness of 0.9 mm.
This expanded graphite sheet was cut into a square of 20 cm, and carbon fibers (CF-1601 manufactured by Nippon Kainol Co., Ltd.) cut to a length of 20 cm were lined up evenly in the vertical direction without any gap. The expanded graphite sheet is layered on top of this, and the carbon fibers are further arranged on this side in the horizontal direction. Similarly, five layers of carbon fibers are alternately arranged between the expanded graphite sheets, and the outside is always expanded graphite sheet. 11 layers in total so that
A compact having a thickness of 8 mm was obtained by compression molding.

Next, the molded body was cut into a width of 8 mm to form a rod. As shown in FIG. 1, around the rod-shaped molded body 1, low elastic carbon fibers (CFY-0204-3, manufactured by Nippon Kainol Co., Ltd.) were applied. The braided body 2 was provided by double bag knitting to obtain a packing material. The packing material is placed in a mold and molded under pressure. The molding is impregnated with furfuryl alcohol precondensate (Hitafuran VF-302, manufactured by Hitachi Chemical Co., Ltd.), and then heated to 800 ° C. in a nitrogen stream. The furfuryl alcohol precondensate was carbonized to obtain a gland packing 3 shown in FIG. 2 having an outer shape × inner diameter × height of 48 × 30 × 9 (mm). The above-mentioned heat treatment causes the low-boiling components in the furfuryl alcohol-treated condensate to evaporate and the remaining components to be carbonized. Adhesion between graphite and carbon fiber was improved.

Thereafter, as shown in FIG. 3, an expanded graphite packing (manufactured by Nippon Pillar Industry Co., Ltd.) is provided around the shaft 5 in the shaft sealing member.
# 6610) 4 layers are stacked, and the gland packing 3 is arranged on the upper and lower sides, and the gland 6 is pressed from above the upper gland packing 3, and the gland 6 is screwed into the packing case 8.
And the shaft was sealed. A leak test showed that there was no leakage of the liquid and good sealing properties could be maintained. Further, the gland packing 3 did not adhere to the shaft 5 and the packing case 8 or bleed out from the gap between the shaft and the packing case 8, and was easily pulled out from the packing case 8.

Example 2 A phenolic resin fiber (Kainol fiber, manufactured by Nippon Kainol Co., Ltd., kainol fiber) was double-knitted around the rod-shaped molded body obtained in Example 1 to form a braided body to obtain a packing material. In the same manner as in Example 1, the mold was placed in a mold, placed in a furnace after molding, gradually heated in a non-oxidizing atmosphere, and calcined at 1000 ° C. to obtain a gland packing. When a leakage test was performed using the obtained gland packing in the same manner as in Example 1, good results were obtained as in Example 1.

The following test was performed on the packing obtained in Example 1 and the asbestos packing (comparative example) in order to confirm the heat resistance, load stability, and dissolution property in water of the heat-resistant packing of the present invention.

(1) Heat resistance test The packing was heated to 400 ° C. in the atmosphere, and the relationship between the passage of time and the weight loss rate was determined. As a result, as shown in FIG. 5, the packing of Example 1 hardly loses weight.

(2) Load stability test A tightening load of 400k is applied by the gland 6 in Fig. 3.
g / cm ² , and the load cell was used to investigate the change in the clamping surface pressure over time at room temperature. As shown in FIG. 6, the packing of Example 1 was able to maintain the initial tightening contact pressure for 100 hours.

(3) Dissolution test When packing is immersed in pure water at room temperature for 24 hours (A
Method) and when immersed in pure water at 90 ° C. for 30 minutes (method B), the elution amount (ppm) of chloride ions and the like was measured. The results are shown in Table 1.

From Table 1, the packing of Example 1 shows no elution of chloride ions or the like.

(Effect of the Invention) The heat-resistant packing of the present invention does not adhere or deform to the shaft like the packing of expanded graphite alone, and is easy to replace. Further, unlike the asbestos packing, there is no outflow of oils and fats and solidification due to the outflow, so that heat resistance is high and maintenance such as tightening becomes unnecessary.

Further, according to the present invention, since the all-carbonaceous packing has radiation resistance, there is little danger in replacement work and it is extremely useful for nuclear power.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating the structure of a packing material in an embodiment of the present invention, FIG. 2 is a perspective view of a gland packing obtained by the embodiment of the present invention, and FIG. FIG. 4 is a sectional view showing how to use the conventional packing, FIG. 5 and FIG.
The figure is a graph showing the relationship between the weight loss rate and time and the relationship between the tightening surface pressure and time. DESCRIPTION OF SYMBOLS 1... Molded article 2... Braided body 3... Gland packing 4... Expanded graphite packing 5... Shaft, 6... Ground 7...

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-29854 (JP, A) JP-A-55-112841 (JP, A) JP-A-60-84476 (JP, A) JP-A-60-84 127284 (JP, A) JP-A-2-73881 (JP, A) Japanese Utility Model Application Sho 56-160360 (JP, U) Japanese Patent Publication No. 57-56512 (JP, B2)

Claims (2)

(57) [Claims] The present invention relates to a method in which carbon fibers around a rod-like molded body formed by adding carbon fibers to expanded graphite are braided, molded, impregnated with an organic substance, and then fired to carbonize the organic substance. Characteristic heat-resistant packing manufacturing method. 2. An organic fiber is braided around a rod-shaped molded body formed by adding carbon fiber of expanded graphite, and then molded and fired to carbonize the organic fiber, or fired to carbonize the organic fiber, Then, a method for producing a heat-resistant packing, characterized by forming.