JPH0449424Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] This invention relates to a self-closing gland packing valve that automatically compensates for the tightening surface pressure of the gland packing using the internal pressure of the valve. This prevents it from expanding due to [Prior Art] Conventional general gland packing valves have a structure where the lower end of the gland packing (the side closest to the internal fluid) is effective in sealing the valve stem that passes through the valve box.
In response to the frequent leakage of internal fluid, especially in high-temperature/high-pressure valves, due to the lack of surface pressure at A self-closing gland packing valve (Japanese Patent Application Laid-Open No. 1983-1992) is constructed by sandwiching a gland packing between a packing holder fitted externally on a valve stem, and elastically biasing the packing holder with a disc spring or the like. 19482), the performance of this type of gland packing valve was dramatically improved. [Problems to be solved by the invention] However, the self-closing gland packing valve described above, especially in actual use under high-temperature and high-pressure fluids, has problems such as internal fluid leakage starting after the number of openings and closings is limited to around 200 times. Having discovered the problem, the inventors of the present invention conducted further experiments and research, and found that the cause of the problem was, in particular, that the inside of the bonnet expanded thermally and the circumferential pressure of the gland packing decreased.
Furthermore, it has been found that fatigue of the gland packing that rubs against the inner wall of the bonnet is accelerated. [Means for solving the problem] Therefore, the inventors of the present invention fitted a packing guide made of a material with a small coefficient of thermal expansion to the inner wall of a bonnet, etc., while integrally protruding a flange near the lower end. A self-closing gland packing in which a valve stem with a valve body attached thereto is inserted into the packing guide, and a gland packing inserted through the valve stem is sandwiched between the flange and an elastically biased packing holder. By providing a valve, the above-mentioned problems are completely solved. [Function] In the proposed gland packing valve with the above configuration, the valve stem is pushed up by the internal fluid pressure acting on the lower surface of the flange of the valve body and valve stem, and the gland packing is pinched between the flange and the packing retainer, so that the internal The special effect is that while the surface pressure on the packing side near the fluid is highest, the packing guide fitted to the inner wall surface of the bonnet near the gland packing reliably prevents diameter expansion due to thermal expansion of that part. It is something that plays. [Example] Hereinafter, the structure of the present invention will be described in more detail based on an example shown in the drawings. Seat 3 is made of the same material as the valve case 1 and is seal-welded to the upper part of the valve case. 4 is 17-7PH steel (SUS630) tightly fitted to the inner periphery of the valve case 1 and bonnet 3. A cylindrical packing guide consisting of
Reference numeral 5 denotes a valve stem made of 17-7PH steel (SUS630) having a flange 6 integrally protruded near its lower end, and the flange 6 and a valve body 7 attached directly below the flange.
is slidable along the inner wall of the packing guide 4. Reference numeral 8 denotes a ring-shaped gland packing that is inserted into the valve stem 5, and is made of graphite or the like. Adapter packings 9 are attached to the top and bottom of the gland to prevent the fitting from protruding, and the outer circumferential surfaces of these gland fittings are attached to the inner wall of the packing guide 4. It is a close-knit one. Reference numeral 10 denotes a packing holder which is fitted onto the valve stem 5, and is designed to pinch the gland packing 8 between it and the flange 6 by the elasticity of a disc spring 11 provided at its upper end. Furthermore, 12 is a sleeve that is externally fitted and screwed onto substantially the upper half of the packing holder 10, and is connected to the yoke 1 through a bushing 13.
By rotating a handle 15 supported by the valve body 4 and fixed to the upper end of the handle 15 in the forward and reverse directions, the valve body 7 can be raised and lowered together with the gland packing 8 and the packing retainer 10 via the valve stem 5. . 1
Reference numerals 6 and 17 indicate a locking plate and its guide groove provided to prevent the packing presser 10 from rotating together with the sleeve 12 when the handle 15 is rotated. Therefore, the self-closing gland packing valve of the present invention has a bonnet 3 near the gland packing 8.
Even if the bonnet is heated to a high temperature by fluid, the packing guide 4 made of a material with a small coefficient of thermal expansion fitted to the inner periphery of the bonnet reliably prevents the inner diameter from expanding due to the expansion of this part. , the surface pressure between the outer peripheral surface of the gland packing 8 and the inner wall of the packing guide 4 can be maintained constant. Therefore, when opening and closing the valve, leakage of the internal fluid can be reliably prevented, and the gland packing 8 and the packing guide 4 can be smoothly slid, allowing the valve rod 4 to move up and down smoothly. 8 fatigue can be significantly suppressed. Furthermore, when the valve is fully opened or partially opened, only the valve stem 5 is pushed up by the internal fluid pressure acting on the lower surface of the flange 6 of the valve body 7 and the valve stem 5, so the gland packing 8 is pushed up between the flange 6 and the packing retainer 10. It is compressed and a occlusion effect corresponding to the internal pressure is obtained. In this case, the surface pressure on the lower end side of the gland packing 8, that is, on the side closest to the internal fluid that is most effective for sealing, is the highest. It goes without saying that the material of the packing guide 4 is not limited to 17-7PH steel (SUS630), but may be stellite-based as long as it has a small coefficient of thermal expansion. Regarding the performance of the above-mentioned self-closing gland-packing valve (proposed valve), the number of valve openings and closings between the conventional general valve and the self-closing gland-packing valve (conventional valve) developed earlier by the applicant was determined. The results of the tests conducted on the amount of leakage are shown in the table below.

[Table] According to the above table, good results were obtained in that the leakage amount of the valve of this invention was 1/10 that of the above-mentioned general valve and 1/2 that of the conventional valve. In addition, the number of times the valve opens and closes when leakage begins is explained in the second section.
As seen in the transition curve in the figure, the above general valve is 50
In contrast to the 200th test with the conventional valve, leakage was not observed with the proposed valve until after the 700th test.
In addition, a significant difference was observed in the cumulative leakage amount as the number of valve openings and closings increased. The above mock test is based on a natural circulation boric acid water test loop, pressure: 157Kg/cm ² , temperature: 300
The test was carried out under the following conditions: °C and diluted alcohol concentration: 1500 ppm. [Effects of the invention] As described above, according to the self-closing gland packing valve of the present invention, a packing guide with a small coefficient of thermal expansion is fitted onto the inner wall of the bonnet on which the gland packing slides, and its inner diameter is expanded. The superior performance of the gland packing is due to the fact that the circumferential pressure between the gland packing and the gland packing is prevented from decreasing, and the sealing effect due to self-pressure is obtained on the packing side closest to the fluid that is most effective for sealing. Sealing performance can be obtained for a long period of time. In addition, the gland packing supported by the valve stem and flange can be taken out together, greatly reducing the effort required to disassemble the valve and replace the packing. It is effective.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional perspective view of the self-closing gland packing valve according to the present invention, and FIG. 2 is a graph showing a transition curve of the number of times leakage starts and the cumulative amount of leakage for each valve. In the diagram, 1...valve box, 2...valve seat, 3...bonnet, 4...packing guide, 5...valve stem, 6
...flange, 7...valve body, 8...gland packing, 9...adapter packing, 10...packing holder, 11...disc spring.

Claims (1)

[Scope of utility model registration request] A packing guide 4 with a small coefficient of thermal expansion is fitted onto the inner wall of the bonnet 3, etc., while a flange 6 is integrally protruded near the lower end, and a valve stem 5 with a valve body 7 attached thereto is inserted into the packing guide 4. A self-closing gland packing valve characterized in that a gland packing 8 inserted through the valve stem 5 is sandwiched between the flange 6 and a resiliently biased packing holder 10.