A sealing device for a steam turbine valve stem

Abstract

A sealing device for a steam turbine valve stem, which relates to a sealing device. The present invention aims to solve the problems that the current gap between the valve stem and the sealing sleeve is too large, resulting in poor sealing effect, increasing the volume of the valve stem and the valve, and bringing inconvenience to the installation and maintenance of the steam inlet valve. After the valve stem of the present invention is heated, the gap with the hollow stepped sleeve gradually approaches 0, further reducing the gap between the valve stem and the hollow stepped sleeve during operation, improving the sealing effect of the valve stem, and at the same time ensuring that the valve stem and the hollow stepped sleeve will not jam during operation. Secondly, the annular groove, drain hole, groove and expansion joint of the present invention form a drain channel. As the valve stem moves axially, the hollow stepped sleeve can peel off the scale and oxide skin on the valve stem under the action of friction and discharge them through the drain channel, thereby avoiding the scale and oxide skin from wearing the surface of the valve stem. The present invention is used for the sealing of the steam turbine valve stem.

Description

Technical Field

[0001] The present invention relates to a sealing device, and particularly to a sealing device for a steam turbine valve stem, belonging to the technical field of steam turbine valve stem sealing. Background Art

[0002] The valve stem is an important component of the steam inlet valve of a steam turbine. The axial movement of the valve stem realizes the opening and closing of the valve. During actual operation, the operation or shutdown of the steam turbine is achieved by opening and closing the valve. When the valve stem leaks air, it is easy to cause problems such as heat energy loss, noise pollution, and safety hazards. Therefore, in order to ensure the stable operation of the steam turbine, it is particularly important to do a good job in the sealing treatment of the valve stem.

[0003] Currently, the steam inlet valve usually solves the sealing problem of the valve stem by installing a sealing sleeve on the valve stem. In actual application, a necessary gap is left between the inner diameter of the sealing sleeve and the outer diameter of the valve stem. On the one hand, it prevents the radial dimension of the valve stem from expanding due to temperature rise and exceeding the inner diameter of the sealing sleeve, thereby causing jamming between the two. On the other hand, it prevents scale or oxide scale on the surface of the valve stem from falling into the sealing sleeve, resulting in the gradual reduction of the gap between the two during long-term operation and causing wear on the surface of the valve stem.

[0004] The superposition of the above two factors makes the gap value between the outer diameter of the valve stem and the inner diameter of the sealing sleeve generally above 0.8 mm. Such a large gap results in a poor sealing effect. To ensure a good sealing effect, it is necessary to compensate by increasing the number of sealing sleeves and at the same time increasing the length of the valve stem. However, the above methods also increase the volume of the valve stem and the valve, bringing inconvenience to the installation and maintenance of the steam inlet valve.

[0005] In summary, how to propose a brand-new sealing device for the above technical problems has become an urgent problem to be solved by those skilled in the art at present. Summary of the Invention

[0006] The present invention aims at the above deficiencies of the prior art and further provides a sealing device for a steam turbine valve stem.

[0007] The technical solution of the present invention is: a sealing device for a steam turbine valve stem, including an end cover and an elastic sealing unit sequentially sleeved on the valve stem.

[0008] The end cover is connected to the valve body by bolts, and a sealing ring is installed on the end face of the end cover facing the valve body. The inner diameter of the end cover is in clearance fit with the outer diameter of the valve stem.

[0009] The elastic sealing unit arranged in the valve body includes a hollow stepped sleeve and two elastic collars.

[0010] The radial expansion coefficient of each elastic ferrule is not greater than that of the hollow stepped sleeve. The inner hole of the elastic ferrule is eccentrically arranged with the outer circumferential surface. A telescopic joint is axially opened at the thinnest part of the wall thickness of the elastic ferrule, and grooves are provided at the inner diameter edges of both end faces of the elastic ferrule.

[0011] The hollow stepped sleeve is a sleeve formed by buckling two docking flaps with the same structure, and the radial expansion coefficient of the hollow stepped sleeve is less than that of the valve stem; both elastic ferrules are sleeved on the small-diameter shaft section of the hollow stepped sleeve in an interference fit manner, and the length of the small-diameter shaft section of the hollow stepped sleeve is equal to the sum of the axial lengths of the two elastic ferrules.

[0012] An annular groove is circumferentially opened on the inner circumferential surface of the hollow stepped sleeve, and the inner circumferential surface of the hollow stepped sleeve is in clearance fit with the outer circumferential surface of the valve stem.

[0013] A sewage discharge hole is opened at the midpoint of the length of the small-diameter shaft section of the hollow stepped sleeve. The sewage discharge hole is communicated with the annular groove, and the axis of the sewage discharge hole is perpendicular to the buckling surface of the hollow stepped sleeve.

[0014] Furthermore, the clearance between the inner diameter of the hollow stepped sleeve and the outer diameter of the valve stem during initial cold-state installation is 0.15 mm.

[0015] Furthermore, both telescopic joints are perpendicular to the buckling surface of the hollow stepped sleeve.

[0016] Furthermore, the included angle between the two telescopic joints in the circumferential direction is 180°.

[0017] Furthermore, the radius of the sewage discharge hole is the same as the groove width of the groove.

[0018] Furthermore, the materials of the half sleeve and the elastic ferrule are both rubber.

[0019] The present invention has the following effects compared with the prior art:

[0020] 1. The end cover 2 of the present invention is arranged on the low-pressure side of the valve body 1, and a sealing ring 2-1 is installed on the end face of the end cover 2 facing the valve body 1; the elastic sealing unit is arranged on the high-pressure side of the valve body 1, and the clearance between the inner diameter of the hollow stepped sleeve 4 and the outer diameter of the valve stem 3 during initial cold-state installation is 0.15 mm.

[0021] When the temperature on the high-pressure side of the valve body 1 rises, the clearance between the valve stem 3 and the hollow stepped sleeve 4 gradually approaches 0 after the valve stem 3 is heated (when the radial dimension of the valve stem 3 expands to the maximum when heated, the clearance between the valve stem 3 and the hollow stepped sleeve 4 is 0), improving the sealing effect of the valve stem 3 and avoiding the situation of jamming of the valve stem 3 during operation.

[0022] 2. The two expansion joints 5-2 of the present invention are both perpendicular to the mating surface of the hollow stepped sleeve 4, and at the same time, the included angle between the two expansion joints 5-2 in the circumferential direction is 180°. In this way, when the hollow stepped sleeve 4 and the elastic ferrule 5 are assembled, the annular groove 4-1, the sewage discharge hole 4-2, the groove 5-1 and the expansion joint 5-2 form a sewage discharge channel. As the valve stem 3 axially moves, the hollow stepped sleeve 4 can peel off the scale and oxide skin on the valve stem 3 under the action of friction and discharge them through the sewage discharge channel, thereby avoiding the scale and oxide skin from wearing the surface of the valve stem 3.

[0023] 3. The structure of the present invention is simple and small in size. Using the present invention to seal the valve stem 3 can further reduce the volume of the valve stem and the valve, providing convenience for the installation and maintenance of the valve. Brief Description of the Drawings

[0024] Figure 1 is a sectional view of the present invention;

[0025] Figure 2 is an axonometric view of the hollow stepped sleeve 4 of the present invention;

[0026] Figure 3 is an axonometric view of the assembled hollow stepped sleeve 4 and elastic ferrule 5 of the present invention;

[0027] Figure 4 is a sectional view of the hollow stepped sleeve 4 of the present invention;

[0028] Figure 5 is an axonometric view of the elastic ferrule 5 of the present invention;

[0029] Figure 6 is Figure 1 a partial enlarged view of part I in

[0030] In the figure: 1, valve body; 2, end cover; 2-1, sealing ring; 3, valve stem; 4, hollow stepped sleeve; 4-1, annular groove; 4-2, sewage discharge hole; 5, elastic ferrule; 5-1, groove; 5-2, expansion joint. Detailed Embodiments

[0031] In order to make the object, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.

[0032] Detailed Embodiment 1: With reference to Figures 1 to 6 to illustrate this embodiment, a sealing device for a steam turbine valve stem in this embodiment includes an end cover 2 and an elastic sealing unit sequentially sleeved on the valve stem 3.

[0033] The end cover 2 is connected to the valve body 1 by bolts, and a sealing ring 2 - 1 is installed on the end surface of the end cover 2 facing the valve body 1 , and the inner diameter of the end cover 2 is clearance-matched with the outer diameter of the valve stem 3 .

[0034] The elastic sealing unit arranged in the valve body 1 includes a hollow step sleeve 4 and two elastic hoops 5; the radial expansion coefficient of each elastic hoop 5 is not greater than the radial expansion coefficient of the hollow step sleeve 4, the inner hole of the elastic hoop 5 is eccentrically arranged with respect to the outer circumferential surface, an expansion joint 5-2 is provided along the axial direction at the thinnest part of the wall thickness of the elastic hoop 5, and grooves 5-1 are provided at the inner diameter edges of the two end surfaces of the elastic hoop 5.

[0035] The hollow step sleeve 4 is a sleeve formed by two butt-jointed petals of the same structure, and the radial expansion coefficient of the hollow step sleeve 4 is smaller than the radial expansion coefficient of the valve stem 3; the two elastic hoops 5 are both mounted on the small-diameter shaft section of the hollow step sleeve 4 in an interference fit manner, and the length of the small-diameter shaft section of the hollow step sleeve 4 is equal to the sum of the axial lengths of the two elastic hoops 5.

[0036] An annular groove 4 - 1 is formed on the inner circumferential surface of the hollow step sleeve 4 along the circumferential direction, and the inner circumferential surface of the hollow step sleeve 4 is clearance-matched with the outer circumferential surface of the valve stem 3 .

[0037] A drain hole 4 - 2 is opened at half the length of the small diameter shaft section of the hollow step sleeve 4 , the drain hole 4 - 2 is connected to the annular groove 4 - 1 , and the axis of the drain hole 4 - 2 is perpendicular to the buckling surface of the hollow step sleeve 4 .

[0038] Specific implementation method 2: Combined with 1, this implementation method is described. In this implementation method, the inner diameter of the hollow step sleeve 4 has a clearance of 0.15 mm with the outer diameter of the valve stem 3 during initial cold installation. With this arrangement, according to the radial expansion coefficient of the valve stem 3 and the temperature to which the valve stem 3 is subjected, it is calculated that when the turbine is running, the radial dimension of the valve stem 3 expands to the maximum when heated, which is exactly the same as the inner diameter dimension of the hollow step sleeve 4, that is, at this time, the clearance between the valve stem 3 and the hollow step sleeve 4 is 0. Other components and connection methods are the same as those of the specific implementation method 1.

[0039] Specific implementation method three: Combination Figure 1 and Figure 3 To illustrate this embodiment, in this embodiment, both of the two expansion joints 5 - 2 are perpendicular to the fastening surface of the hollow step sleeve 4 ; further, the angle between the two expansion joints 5 - 2 in the circumferential direction is 180°.

[0040] With such arrangement, when the hollow step sleeve 4 is assembled with the elastic hoop 5, the annular groove 4-1, the drainage hole 4-2, the groove 5-1 and the expansion joint 5-2 form a drainage channel, which facilitates the discharge of scale and oxide skin attached to the outer circumferential surface of the valve stem 3 through the drainage channel.

[0041] Other compositions and connection methods are the same as those in the first or second specific implementation manner.

[0042] Specific implementation manner four: In combination with Figure 1 and Figure 6 describe this implementation manner. In this implementation manner, the radius of the sewage discharge hole 4-2 is the same as the groove width of the groove 5-1. Other compositions and connection methods are the same as those in the first, second, or third specific implementation manner.

[0043] Specific implementation manner five: In combination with Figures 1 to 6 describe this implementation manner. In this implementation manner, the materials of the semi-sleeve 4 and the elastic ferrule 5 are both rubber. Other compositions and connection methods are the same as those in the first, second, third, or fourth specific implementation manner.

[0044] Working principle

[0045] In combination with Figures 1 to 6 describe the working principle of the present invention:

[0046] The end cover 2 and the elastic sealing unit are sleeved on the valve stem 3 in sequence. The end cover 2 is connected to the valve body 1 by bolts, and a sealing ring 2-1 is installed on the end face of the end cover 2 facing the valve body 1. The elastic sealing unit is arranged inside the valve body 1.

[0047] The end cover 2 is arranged on the low-pressure side (i.e., the P1 side) of the valve body 1. The end cover 2 is connected to the valve body 1 by bolts, and a sealing ring 2-1 is installed on the end face of the end cover 2 facing the valve body 1. The inner diameter of the end cover 2 has a clearance fit with the outer diameter of the valve stem 3.

[0048] The elastic sealing unit is arranged on the high-pressure side (i.e., the P0 side, the initial end sealed by the valve stem 3) of the valve body 1. The clearance between the inner diameter of the hollow stepped sleeve 4 and the outer diameter of the valve stem 3 is 0.15 mm during the initial cold-state installation.

[0049] The radial expansion coefficient of the hollow stepped sleeve 4 is less than that of the valve stem 3, and the radial expansion coefficient of the elastic ferrule 5 is not greater than that of the hollow stepped sleeve 4; when the temperature on the P0 side of the valve body 1 rises, the clearance between the valve stem 3 and the hollow stepped sleeve 4 gradually approaches 0 (when the radial dimension of the valve stem 3 expands to the maximum when heated, the clearance between the valve stem 3 and the hollow stepped sleeve 4 is 0), ensuring that the valve stem 3 and the hollow stepped sleeve 4 will not get stuck during operation. With such a setting, the clearance between the valve stem 3 and the hollow stepped sleeve 4 during operation is further reduced, improving the sealing effect of the valve stem 3.

[0050] With the opening of the steam inlet valve, the valve stem 3 and the elastic sealing unit are pushed by the steam pressure to the low-pressure side (i.e., the P1 side) of the valve body 1 until the end face of the large-diameter shaft section of the hollow stepped sleeve 4 abuts tightly against the sealing ring 2-1. When the valve stem stops moving, under the action of the steam pressure difference (P0 > P1), the elastic sealing unit always fits tightly against the sealing ring 2-1, thereby achieving the sealing of the valve stem 3.

[0051] The hollow stepped sleeve 4 is a sleeve formed by buckling two docking flaps with the same structure. An annular groove 4-1 is formed on the inner circumferential surface of the hollow stepped sleeve 4 along the circumferential direction. A blowdown hole 4-2 is formed at half of the length of the small-diameter shaft section of the hollow stepped sleeve 4, and the blowdown hole 4-2 communicates with the annular groove 4-1.

[0052] The thinnest part of the wall thickness of the elastic ferrule 5 is provided with a telescopic joint 5-2 along the axial direction, and grooves 5-1 are provided at the inner diameter edges of both end faces of the elastic ferrule 5. The two elastic ferrules 5 are both sleeved on the small-diameter shaft section of the hollow stepped sleeve 4 in an interference fit manner, and the length of the small-diameter shaft section of the hollow stepped sleeve 4 is equal to the cumulative sum of the axial lengths of the two elastic ferrules 5.

[0053] When the hollow stepped sleeve 4 and the elastic ferrule 5 are assembled, the two telescopic joints 5-2 are both perpendicular to the buckling surface of the hollow stepped sleeve 4, and the included angle between the two telescopic joints 5-2 in the circumferential direction is 180°. In this way, after the hollow stepped sleeve 4 and the elastic ferrule 5 are assembled, the annular groove 4-1, the blowdown hole 4-2, the groove 5-1, and the telescopic joint 5-2 form a blowdown channel.

[0054] During the long-term use of the steam inlet valve, scale and oxide skin will adhere to the outer circumferential surface of the valve stem 3. With the axial movement of the valve stem 3, the hollow stepped sleeve 4 can peel off the scale and oxide skin on the valve stem 3 under the action of friction and discharge them through the blowdown channel, thereby avoiding the scale and oxide skin from wearing the surface of the valve stem 3.

[0055] The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the present invention. Any person skilled in the relevant art, without departing from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A sealing device for a steam turbine valve stem, characterized in that: It includes an end cover (2) and an elastic sealing unit sleeved on the valve stem (3) in sequence; The end cover (2) is connected to the valve body (1) by bolts, and a sealing ring (2-1) is installed on the end face of the end cover (2) facing the valve body (1). The inner diameter of the end cover (2) has a clearance fit with the outer diameter of the valve stem (3); The elastic sealing unit arranged in the valve body (1) includes a hollow stepped sleeve (4) and two elastic collars (5); The radial expansion coefficient of each elastic collar (5) is not greater than that of the hollow stepped sleeve (4). The inner hole of the elastic collar (5) is eccentrically arranged with the outer circumferential surface. A telescopic slit (5-2) is opened along the axial direction at the thinnest part of the wall thickness of the elastic collar (5). Both telescopic slits (5-2) are perpendicular to the fastening surface of the hollow stepped sleeve (4), and the included angle between the two telescopic slits (5-2) in the circumferential direction is 180°; Grooves (5-1) are provided at the inner diameter edges of both end faces of the elastic collar (5); The hollow stepped sleeve (4) is a sleeve formed by buckling two docking flaps with the same structure, and the radial expansion coefficient of the hollow stepped sleeve (4) is less than that of the valve stem (3). Both elastic collars (5) are sleeved on the small-diameter shaft section of the hollow stepped sleeve (4) in an interference fit manner, and the length of the small-diameter shaft section of the hollow stepped sleeve (4) is equal to the sum of the axial lengths of the two elastic collars (5); An annular groove (4-1) is opened along the circumferential direction on the inner circumferential surface of the hollow stepped sleeve (4), and the inner circumferential surface of the hollow stepped sleeve (4) has a clearance fit with the outer circumferential surface of the valve stem (3); A sewage discharge hole (4-2) is opened at the midpoint of the length of the small-diameter shaft section of the hollow stepped sleeve (4). The sewage discharge hole (4-2) is communicated with the annular groove (4-1), and the axis of the sewage discharge hole (4-2) is perpendicular to the fastening surface of the hollow stepped sleeve (4).

2. The sealing device for a steam turbine valve stem according to claim 1, characterized in that: The radius of the sewage discharge hole (4-2) is the same as the groove width of the groove (5-1).

3. The sealing device for a steam turbine valve stem according to claim 2, characterized in that: The width of the telescopic slit (5-2) is 1 mm.

4. A sealing device for a steam turbine valve stem according to claim 3, characterized in that: The materials of the hollow stepped sleeve (4) and the elastic collar (5) are both rubber.

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