JPS6081404A - Steam control valve for steam turbine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a steam control valve for a steam turbine.

[Prior art and its problems]

A steam control valve in a steam turbine has an important function of controlling the steam flow of the steam turbine, which uses high-temperature, high-pressure steam as energy. Therefore, in order for this valve to operate quickly and reliably at all times, it is required that the valve stem and the gland part that supports it so that it can slide in the axial direction always engage smoothly. Ru.

Fig. 1 and Fig. 2 show conventional embodiments, Fig. 1 is a configuration diagram of the main part of the steam control valve of the steam turbine, and Fig. 2 is a diagram of the main part of the steam control valve of the steam turbine.
It is a detailed view of the P section shown in the figure. 20 is the main part of the steam control valve of the steam coupin. This steam control valve 20 has a valve casing 1 equipped with an inlet and an outlet 4 (not shown), and a valve body 3a is attached to a valve stand 2 which is fastened to the valve Kuhn 1 with a bolt 8 in its axial direction. It is slidably held in place. The hole in the penetrating part of the valve stem 3 of the valve stand 2, the so-called ground part 14, is formed in order from the steam chamber 17 side to the top.
Grand bushing 6, asbestos-based presser/g 13a
7. A plurality of asbestos-based hacks for preventing steam leakage provided in a length range of 5 to 6 times the outer diameter of the valve stem 3. It is composed of an asbestos-based retainer ring 13b and a bush 5. The lower end of the gland bushing 6 and the upper end of the bushing 5 are connected to the valve stand 2, respectively.
Ring nut 1 that screws into the threaded part provided on the inner diameter side of
5 and Plan-5. The valve stem 3 is supported by a gland blank 6 and a bush 5, and is sealed by the plurality of asbestos gaskets 7 to prevent steam from leaking from the steam chamber 17 to the outside air. Further, the valve stem 3 is moved to the other end of the lever 10 by transmitting the force from the servo motor 16 to the end of the lever 10 which is attached with a bolt 18 to the operating shaft 9 supported on the valve stand 2. It slides in the axial direction via a connecting rod 11 supported by a swivel bearing 19 to control the amount of steam flowing to a steam turbine (not shown).

In the above configuration, the asbestos-based packing 7 is made by hardening asbestos and graphite with a certain type of binder, and the asbestos-based retaining ring 13a,
13b is a braided packing whose main component is asbestos fiber, and it is said that production of asbestos will soon be discontinued due to pollution problems, and asbestos-based packing 7
However, when operated under high-temperature steam, the binder and, at high temperatures, the asbestos crystallized water vaporized, resulting in weight loss, and over time, the tightening effect became less effective, leading to steam leaks and accidents. Therefore, it is necessary to replace all the gaskets 7 with new ones during periodic inspections, which increases maintenance costs.In addition, the gasket 7 is an inexpensive alternative to asbestos and has excellent reliability under high temperature and high pressure. It was necessary to develop materials.

[Purpose of the invention]

In view of the above points, the present invention eliminates troubles caused by retightening and steam leakage during operation, reduces the number of gaskets used, and constantly maintains the connection between the valve stem and the gland that supports the valve stem. The purpose of the present invention is to provide an asbestos-free steam control valve for a steam turbine that maintains smooth operation, is inexpensive, and has high reliability under high temperature and high pressure conditions.

[Key points of the invention]

According to the present invention, the outer circumferential surface of the valve stem is connected to the inner circumferential surface of the valve stem penetrating portion of the valve stand in the ground region between the valve stem of the steam control valve and the valve stem penetrating portion of the valve stand. A plurality of highly compressible ring-shaped gelatin fibers and kin are provided to airtightly seal the pores, and a presser ring made of graphite having a higher density than the graphite packing is provided at both axial end regions of the gelafiber and kin. This can be achieved by providing

[Embodiments of the Invention]' The present invention will be described in detail below based on drawings showing embodiments. 3 to 5 show embodiments of the present invention;
The figure shows a detailed view of the P part shown in Fig. 1, Fig. 4 shows the shape of the highly compressible graphite packing shown in Fig. 3, and Fig. 5 shows the shape of the graphite presser ring. Components that are the same as those shown in FIGS. 1 and 2 are given the same reference numerals, and their explanations will be omitted.

The hole in the penetrating part of the valve stem 3 of the valve stand 2, the so-called crand part 14, is formed in order from the steam chamber 17 side to the top by a gland push-piece 6, a plurality of spacing rings 21°, a graphite retaining ring n, and a plurality of high-pressure rings. Compressible Graphidopa, Kin22. Furthermore, a graphite retainer ring n similar to the above-mentioned
and a bushing 5. The lower end portion of the gland bush 6 and the upper end portions of the gland bushing 6 and the no.

) 15 and a screw bush 12. The valve stem 3 is supported by a gland bush 6 and a bush 5, and is sealed by a plurality of highly compressible graphite pads 22 to prevent steam from leaking from the steam chamber 17 to the outside air.

This highly compressible graphite pad 22 is formed into a ring shape with a rectangular cross-section as shown in FIG. , the inner diameter d is slightly larger than the outer diameter of the valve stem 3, for example, when the outer diameter of the valve stem is 20 mm and the inner diameter of the valve stand through hole is 40 mm, a highly compressible graphoid pad,
The inner diameter d of the kin 22 is 0.1 to 0.25 rxtn (D
It is large in the range o, small in the range of outer diameter DViO,025 to 0.05, the axial thickness tl is loIIIm, and the density is about 1.4 ji/cr3. Then, the valve stem 3 of the valve stand 2 is assembled into the gland part 14 in a range of 2 to 3 times the size of the valve stem 3, and is compressed by tightening it through the screw pin 12. Airtightly seal the inner periphery of the hole of the through-hole and the outer periphery of the valve stem 3,
No retightening during operation or steam leakage,
Moreover, the sliding movement of the valve stem 3 in the axial direction is maintained smoothly.

The highly compressible graphite packing 22 is made by cutting an expanded natural graphite sheet (trade name: Grafoil) into appropriate dimensions, winding it up, and molding it into a ring shape using a mold. /cr
By applying a tightening surface pressure of about rL2, elasticity with a compression ratio of about 5% can be obtained, and the land portion 14 can be solened with a low tightening force. In addition, this highly compressible graphoid pad kin 22 has high airtightness, does not lose weight or creep due to aging or heating, and does not cause stress relaxation. Furthermore, physical property changes such as embrittlement do not occur even at low temperatures. Therefore, there is no need to retighten the valve during operation, it can withstand long-term use, and it can fully serve the purpose with a range of 2 to 3 times the outer diameter of the valve stem 3, which is about half that of conventional asbestos-based gaskets. can be reached.

On the other hand, the presser ring n is of the same type as the highly compressible graphite packing 22, but has a higher sealing area of about 1.717 cm3 than the graphite packing 22, and has a rectangular cross-sectional shape as shown in FIG. It is formed into a ring shape by roasting it. The outer and inner diameter dimensions are set to match the inner diameter of the through hole of the valve stand and the outer diameter of the valve rod 3, and the highly compressible graphite packing 22 is uniformly compressed from both ends. However, it is difficult to distinguish between the highly compressible graphite packing 22 and the graphite retaining ring n from their appearance, so the axial thickness is For example, as shown in the figure, the axial thickness t2 of the presser ring 23 is smaller than the axial thickness tl of the highly compressible graphite packing 22. Therefore, it is possible to assemble the packing correctly without making any mistakes at the time of on-site assembly, and it is possible to make it asbestos-free.

〔Effect of the invention〕

As described above, the present invention provides a ground area between the valve stem of the steam control valve and the valve stem penetrating portion of the valve stand, the outer circumferential surface of the valve stem and the inner circumference of the valve stem penetrating portion of the valve stand. A plurality of highly compressible ring-shaped graphite packings are provided to tightly seal the surfaces, and presser rings made of graphite having a higher density than the graphite packings are provided at both axial end regions of the graphite packings. In particular, it eliminates troubles due to re-tightening and steam leakage during operation, reduces the number of I-couples used, and always maintains smooth engagement between the valve stem and the gland that supports the valve stem. It is possible to provide an inexpensive steam control valve for a steam turbine that is asbestos-free and has high faT M properties under high temperature and high pressure.

[Brief explanation of drawings]

1 and 2 show conventional embodiments, FIG. 1 is a configuration diagram of the main part of the steam control valve of a steam turbine, FIG. 2 is a detailed view of the P section shown in FIG. 1, and FIGS. FIG. 5 shows an embodiment of the present invention, FIG. 3 is a detailed view of the main part thereof, FIG. 4 is a detailed view of the highly compressible succiphite packing shown in FIG.
The figure is a detailed view of the graphite retainer ring shown in FIG. 3. . 2... Valve stand, 3... Valve stem, 22 Compressible graphite packing, % Graphite retaining ring. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1) A plurality of glands are provided in a gland area between the valve stem and the valve stem penetration part of the valve stand, which hermetically seals the outer peripheral surface of the valve stem and the inner circumferential surface of the valve stem penetration part of the valve stand. Steam control of a steam turbine characterized in that a highly compressible ring-shaped graphite packing is provided, and presser rings made of graphite having a higher density than the graphite packing are provided in both axial end regions of the graphite packing. valve.