JPH10299903A - Ring gland packing and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent permeating leakage from between the layers of expansion graphite packing formed by a tape molding system by arranging expansion graphite and fluororesin alternately in spiral or concentric circle shape. SOLUTION: At the time of manufacturing a ring gland packing 3 used to prevent fluid leakage from a valve stem or the like, expansion graphite tapes 1 and fluororesin tapes 2 are overlapped in the state of the tips of the fluororesin tapes 2 being folded, and wound to an inner die of a molding die and then spirally wound and put in an outer die of the molding die for pressing to obtain the required ring gland packing 3. The fluororesin tapes 2 are therefore filled between the layers of the expansion graphite tapes 1 so as to eliminate leakage from between the layers. The ring gland packing with the face 2b of the fluororesin tape 2 exposed to the inner peripheral surface has the effect of reducing required torque at the time of rotating a shaft by the low sliding property of fluororesin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a ring-shaped gland packing which is loaded into a stuffing box of a device such as a valve and used for preventing leakage of fluid from a valve stem.

[0002]

2. Description of the Related Art Conventionally, as a packing used to prevent leakage from a valve stem or a rotating shaft (hereinafter referred to as a shaft), heat-resistant fibers such as asbestos fiber and carbon fiber are knitted, sack-knitted or latticed. A so-called braided packing which is braided into a braid or the like and impregnated with a lubricant or the like or subjected to a surface treatment has been often used. Such packings are still widely used today because of their excellent heat resistance, chemical resistance, wear resistance, etc., but recently, small leaks have become a problem due to increased awareness of environmental issues. Thus, packing using expanded graphite having high sealing properties as a main material (hereinafter referred to as expanded graphite-based packing) has been used.

[0003] There are various types of the expanded graphite-based packing, and the most common type is called a tape mold type, and a tape-shaped material obtained by slitting an expanded graphite sheet into a predetermined width is used for forming metal. This is a ring-shaped gland packing obtained by spirally or concentrically arranging in a mold, and then press-molding this vertically.

Another molding method is called a lamination method, in which a predetermined number of ring-shaped materials obtained by punching an expanded graphite sheet into a ring shape are laminated in a molding die, and this is press-formed in the longitudinal direction. There are methods, and many other methods are known, such as a method combining these methods.

[0005]

However, among the conventional expanded graphite-based packings, the ring-shaped gland packing formed by the tape mold method has a small size formed between the expanded graphite tapes 1 as shown in FIG. There is a disadvantage that leakage of the fluid f occurs from a gap (layer), and in a ring-shaped gland packing formed by a lamination method, as shown in FIG. 6, the pressure in the radial direction when a tightening load is applied to the packing. (Side pressure) is small, and the packing itself is less deformed in the radial direction and the adhesion to the shaft is weak. Therefore, it is unavoidable that a small gap is generated between the gland packing and the shaft. The fluid has not yet been sealed.

An object of the present invention has been made in view of the above problems, and it is possible to effectively prevent the leakage of the expanded graphite-based packing formed by the tape molding method from between the layers, and it is easy and inexpensive to manufacture. The present invention is to provide a ring-shaped gland packing which can be manufactured at a time.

[0007]

According to a first aspect of the present invention, there is provided a ring-shaped gland packing in which expanded graphite and fluororesin are alternately arranged in a spiral or concentric manner. .

[0008] The invention of claim 2 is the gist of the invention of claim 1, wherein the width of the fluororesin tape is smaller than the width of the expanded graphite tape.

According to a third aspect of the present invention, in the first or second aspect, the surface of the fluororesin is exposed on the inner peripheral surface of the ring-shaped gland packing.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a ring-shaped gland packing, comprising disposing spirally or concentrically a tape made of expanded graphite and a tape made of a fluororesin, placing the tape in a molding die and extending the tape vertically. The gist is to perform pressure molding.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, for example, as shown in FIG.
The expanded graphite tape 1 and a fluororesin tape 2 having a thickness of 0.1 mm and a width of 13 mm are overlapped with each other so that the tip of the fluororesin tape 2 is folded back, and this is wound around an inner die of a molding die. This is a ring-shaped gland packing as shown in FIG. 1 which is spirally wound, placed in an outer mold of a molding die, and pressure molded. Also, as shown in FIG.
An expanded graphite tape 1 having a width of 8 mm and a width of 16 mm and a fluororesin tape 2 having a narrower width are superimposed such that the leading end of the tape 1 becomes an expanded graphite tape 1, and the spirally wound tape is similarly wound. And a ring-shaped gland packing as shown in FIG.

The present inventors have made intensive studies to reduce the minute gaps (interlayers) formed between the expanded graphite tapes of the expanded graphite ring-shaped gland packing formed by the tape molding method. We considered increasing the molding density of the expanded graphite ring-shaped gland packing. However, even if it was increased to 2.0 g / cm ^3, which is considered to be the upper limit density of the expanded graphite ring-shaped gland packing, the fluid was completely sealed. Did not reach.

Next, a liquid sealing material was applied to the surface of the expanded graphite sheet in advance, and then a ring-shaped gland packing made of expanded graphite was formed by a conventional tape molding method. The sealing material protrudes from between the layers, causing a problem of poor appearance.

Therefore, the present inventors conducted further studies,
Overlay the fluoroplastic tape on the expanded graphite tape,
After this was spirally wound, a ring-shaped gland packing was formed by press-molding in a vertical direction with a molding die, and a fluororesin tape was filled between the layers of the expanded graphite tape. It was found that there was almost no leakage. In addition, it has been found that the one in which the surface 2b of the fluororesin tape is exposed on the inner peripheral surface as shown in FIG. 1 also has the effect of reducing the torque required when rotating the shaft due to the low sliding property of the fluororesin. .

[0015]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Example 1 An expanded graphite tape having a thickness of 0.38 mm and a width of 16 mm and a tape made of unfired ethylene tetrafluoride resin having a thickness of 0.1 mm and a width of 13 mm (Naflon seal tape manufactured by Nichias Co., Ltd.) are shown in FIG. As shown in the figure, about 10 mm of the tip of the unfired tetrafluoroethylene resin tape is folded back and overlapped, wound around the inner mold of the molding die, and then spirally wound to form a molding die. A ring shape (inner diameter 26) as shown in FIG.
mm, outer diameter 42 mm, height 8 mm). [Example 2] Instead of the unfired ethylene tetrafluoride resin tape of Example 1, a graphite tetrafluoride ethylene resin tape (GFO manufactured by Gore-Tex Corp.) having a thickness of 0.1 mm and a width of 13 mm was used. In the same manner as in Example 1, a ring-shaped (inner diameter 26 mm, outer diameter 42 mm, height 8 mm) gland packing was obtained. Example 3 A tape made of expanded graphite tape having a thickness of 0.1 mm and a width of 13 mm (Naflon seal tape manufactured by Nichias Co., Ltd.) was applied to an expanded graphite tape having a thickness of 0.38 mm and a width of 16 mm. As shown in the figure, the tip is about 100mm
Are superimposed to form an expanded graphite tape 1 and molded in the same manner as in Example 1 to obtain a ring-shaped (inner diameter 26 mm, outer diameter 42 mm, height 8 mm) gland packing as shown in FIG. . [Comparative Example 1] An expanded graphite tape having a thickness of 0.38 mm and a width of 16 mm was spirally wound, and then formed into a ring shape (inner diameter: 26 mm, outer diameter: 42 m) by pressing in a vertical direction with a molding die.
m, height 8 mm).

The ring-shaped gland packings P of Examples 1 to 3 and Comparative Example 1 are applied to a tester 4 of the applicant's standard shown in FIG.
(Stem diameter 26 mm, stuffing box inner diameter 42 m
m, stuffing box depth 150 mm), and tightened with a surface pressure of 300 kgf / cm ^2. The tester 4 was heated at room temperature for 7 days and further at 260 ° C. for 16 hours, and then allowed to cool to room temperature Cycle for 7 days,
The amount of leakage when helium gas H of 21 kgf / cm ² was loaded was measured. Table 1 shows the average amount of leakage for 7 days at normal temperature and during the heating cycle. In FIG. 7, 5
Is a shaft, 6 is a packing holder, 7 is a fastening bolt, 8 is a lantern ring, 9 is a gas pressurizing port, and 10 is a gas outlet.

[0017]

[Table 1]

As shown in Table 1, Examples 1 to 3 according to the present invention were used.
It was confirmed that the ring-shaped gland packing obtained in No. 3 had significantly less leakage at room temperature and after heating than the ring gland packing made of expanded graphite of Comparative Example 1. In addition, although all of the examples in this example are used without using a surface treatment agent or the like, depending on the purpose of use, mineral oil-based lubricants such as turbine oil or the like normally used for packing before and after ring molding, silicon oil, Lubricants such as fluorine oil and paraffin wax and solid lubricants such as molybdenum disulfide and boron nitride may be treated.

[0019]

As described above, the ring-shaped gland packing according to the present invention is formed by minute gaps generated between layers of the expanded graphite sheet due to the fluororesin, as compared with the conventional expanded gland-made ring gland packing. Clearly, there is no leakage and very good sealability is maintained.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view of one embodiment of a ring-shaped gland packing of the present invention.

FIG. 2 is a sectional perspective view of another embodiment of the ring-shaped gland packing of the present invention.

FIG. 3 is a schematic diagram showing an initial state of manufacture of an embodiment of the ring-shaped gland packing of the present invention.

FIG. 4 is a schematic view showing an initial state of manufacture of another embodiment of the ring-shaped gland packing of the present invention.

FIG. 5 is a sectional perspective view of a conventional expanded graphite ring-shaped gland packing.

FIG. 6 is a sectional perspective view of another conventional expanded graphite ring gland packing.

FIG. 7 is a cross-sectional view of the testing machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Expansive graphite tape 2 Fluororesin tape 2a Folded part 2b Inner peripheral surface 3 Ring-shaped gland packing f Fluid H Helium gas P Test gland packing 4 Test machine main body 5 Shaft 6 Packing holder 7 Tightening bolt 8 Lantern ring 9 Gas supply Pressure port 10 Gas outlet

Claims (4)

[Claims] 1. A ring-shaped gland packing in which expanded graphite and fluororesin are alternately arranged in a spiral or concentric manner. 2. The ring-shaped gland packing according to claim 1, wherein the width of the fluororesin tape is smaller than the width of the expanded graphite tape. 3. The fluororesin surface is exposed on the inner peripheral surface of the ring-shaped gland packing.
Or the ring-shaped gland packing of 2. 4. A ring-shaped gland packing characterized in that an expandable graphite tape and a fluororesin tape are spirally or concentrically arranged, and then placed in a molding die and pressure-formed in the vertical direction. Manufacturing method.