A regulating valve stem gap seal structure

Abstract

The application relates to a regulating valve valve rod gap sealing structure, which comprises a valve cover 3, a valve shell 4, a valve disc 5, a valve seat 6, a valve rod 2 and a sleeve 1, the valve cover 3 is installed on the valve shell 4, the valve seat 6 is installed in the valve shell 4, the valve disc 5 is arranged above the valve seat 6, the top of the valve disc 5 is located in the valve cover 3, the sleeve 1 is fixed in the valve cover 3, the valve rod 2 penetrates through the sleeve 1 and extends into the valve disc 5, the valve rod 2 is in a structure of being thin at the top and thick at the bottom, the valve disc 5 is provided with a middle protrusion, the lower part of the valve rod 2 is matched with the middle protrusion so as to drive the valve disc 5 to move, and the inside of the sleeve is provided with a sawtooth-shaped thread 1A. The standard thread on the inside of the sleeve and the outside of the valve rod is machined by using a tap under the premise of reducing machining cost and not influencing the strength of the valve rod, the labyrinth sealing effect is realized, and the gas leakage loss is reduced.

Description

Technical Field

[0001] The present invention relates to a valve, specifically a valve stem gap sealing structure. Background Technology

[0002] Control valves are an essential component of steam turbines, and their economy and safety are crucial for the efficient and stable operation of steam turbines.

[0003] When the steam turbine operates under varying conditions, the regulating valve stem is controlled by a hydraulic motor, moving axially within the sleeve and driving the valve disc to adjust the valve's flow area. A gap exists between the valve stem and the sleeve, allowing high-temperature, high-pressure steam inside the valve to leak through this gap. This not only causes losses but also poses safety hazards, ultimately affecting the valve's economic efficiency and safety.

[0004] Reducing the valve stem diameter and the clearance between it and the sleeve is one way to reduce steam leakage from the valve stem clearance. However, if the valve stem diameter is too small, the valve stem strength will decrease, and during long-term operation, valve stem bending and breakage are likely to occur. If the clearance is too small, valve stem jamming is likely to occur, especially during unit start-up, shutdown, or changes in operating conditions.

[0005] Adding a sealing structure between the valve stem and the sleeve is another way to reduce steam leakage from the valve stem clearance. However, the sleeve is a single-circle structure with a small inner diameter, making it very difficult to insert or machine steam seal teeth on its inner side. The valve stem is also relatively thin, and inserting or machining steam seal teeth on its outer side would severely affect its strength.

[0006] Reducing the pressure in the unloading chamber is also a direct way to reduce air leakage. Reducing the pressure in the unloading chamber reduces flow loss, which in turn reduces the leakage gas velocity. Summary of the Invention

[0007] The purpose of this invention is to provide a valve stem clearance sealing structure for a regulating valve that can effectively reduce steam leakage in the valve stem clearance and reduce valve losses.

[0008] The objective of this invention is achieved as follows:

[0009] The present invention provides a valve stem gap sealing structure for a regulating valve, characterized in that: it includes a valve cover (3), a valve shell (4), a valve disc (5), a valve seat (6), a valve stem (2), and a sleeve (1). The valve cover (3) is installed on the valve shell (4), the valve seat (6) is installed inside the valve shell (4), the valve disc (5) is provided above the valve seat, the top of the valve disc (5) is located inside the valve cover (3), the sleeve (1) is fixed inside the valve cover (3), the valve stem (2) passes through the sleeve (1) and extends into the valve disc (5), the valve stem (2) has a structure that is thinner at the top and thicker at the bottom, the valve disc (5) is provided with a central protrusion, the lower part of the valve stem (2) cooperates with the central protrusion to drive the valve disc (5) to move, and the inner side of the sleeve is provided with a sawtooth thread (1A).

[0010] The present invention may also include:

[0011] 1. A fine thread (2A) is provided on the outer side of the valve stem (2). The sawtooth thread (1A) and the fine thread (2A) form a continuous chamber. The valve stem (2) and the sleeve (1) form a valve stem gap (7). The chamber and the valve stem gap (7) form a labyrinth seal.

[0012] 2. The sawtooth thread (1A) on the inside of the sleeve and the fine thread (2A) on the outside of the valve stem adopt opposite directions of rotation.

[0013] 3. The sawtooth thread (1A) of the sleeve does not completely penetrate the sleeve, leaving an unthreaded section at the bottom 2mm.

[0014] 4. The sawtooth thread (1A) on the inner side of the sleeve and the fine thread (2A) on the outer side of the valve stem are both standard threads.

[0015] 5. A sealing ring (9) is provided above the valve disc (5), and an elastic metal (8) is provided between the sealing ring (9) and the valve cover (3) above it.

[0016] 6. An unloading chamber (10) is formed between the valve disc (5), valve stem (2), and valve cover (3). A valve inlet is opened on the side of the valve body (4), and a valve outlet is opened below the valve body (4). When the valve stem (2) is lifted, the valve disc (5) is lifted upward, the elastic metal (8) is squeezed, and the sealing ring (9) contacts the valve disc (5), thereby isolating the unloading chamber from the valve inlet and the valve outlet.

[0017] 7. The length of the sawtooth thread (1A) is less than the length of the fine thread (2A).

[0018] 8. The tooth angle α of the sawtooth thread (1A) is 30°.

[0019] 9. The thread angle β of the fine thread (2A) is 30°.

[0020] The advantages of this invention are as follows: the sawtooth thread on the inner side of the sleeve and the fine thread on the outer side of the valve stem together form multiple continuous chambers. The steam leakage in the valve stem gap generates vortices within these chambers, hindering axial steam flow and significantly reducing leakage. The sawtooth thread on the inner side of the sleeve and the fine thread on the outer side of the valve stem have opposite directions of rotation, disrupting the circumferential flow of steam and further reducing leakage in the valve stem gap, thus improving valve economy. The threads on both the sleeve and the valve stem are machined in one step using a tap, a mature and low-cost process. Thanks to the valve stem gap sealing structure of this invention, steam leakage in the valve stem gap is effectively controlled, allowing for an appropriate increase in valve stem diameter and gap, reducing the risk of valve stem bending or jamming, and further enhancing valve safety. Furthermore, the valve stem gap sealing structure of this invention can be simplified according to actual conditions, i.e., retaining the sawtooth thread structure on the inner side of the sleeve and eliminating the fine thread structure on the outer side of the valve stem. This achieves a certain sealing effect while reducing machining workload, resulting in low cost and no impact on the valve stem structure, making it particularly suitable for valve modification. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention;

[0022] Figure 2 This is a schematic diagram of the sealing structure;

[0023] Figure 3 A schematic diagram of the sawtooth thread structure on the inner side of the sleeve;

[0024] Figure 4 A schematic diagram of the fine thread structure on the outer side of the valve stem;

[0025] Figure 5 Detailed drawing of the sawtooth thread for the sealing structure;

[0026] Figure 6 Detailed drawing of fine thread for sealing structure.

[0027] Reference numerals: Sleeve 1; Valve stem 2; Valve cover 3; Valve body 4; Valve disc 5; Valve seat 6; Valve stem clearance 7; Elastic metal 8; Sealing ring 9; Unloading chamber 10. Detailed Implementation

[0028] The invention will now be described in more detail with reference to the accompanying drawings:

[0029] Combination Figure 1-6 See Figure 1The diagram shows the regulating valve and valve stem gap sealing structure of the present invention. The regulating valve includes a sleeve 1, valve stem 2, valve cover 3, valve body 4, valve disc 5, and valve seat 6. During valve regulation, the valve stem 2, controlled by a hydraulic motor, moves axially within the sleeve 1, causing the valve disc 5 to move and thus changing the flow area between the valve disc 5 and the valve seat 6. A gap exists between the sleeve 1 and the valve stem 2, referred to as the valve stem gap 7. High-temperature, high-pressure steam flow inside the valve leaks through the valve stem gap 7, causing energy loss. 8 is an elastic metal. After the valve stem is raised to a certain extent, the elastic metal 8 is compressed, and the sealing ring 9 contacts the upper part of the valve disc, thus isolating the main flow from the unloading chamber 10. The unloading chamber does not receive replenishment from the main flow, and its pressure decreases as the valve stem leaks.

[0030] See Figure 2 The diagram shown is a schematic of the sealing structure of the present invention. It consists of a sawtooth thread 1A on the inner side of the sleeve 1 and a fine thread 2A on the outer side of the valve stem 2. The length of the sawtooth thread is L1, and the length of the fine thread is L2, wherein L2 > L1.

[0031] See Figure 3 and Figure 4 The diagram shows a sawtooth thread structure on the inner side of the sleeve and a fine thread structure on the outer side of the valve stem, both of which are standard threads, and their directions of rotation are opposite.

[0032] See Figure 5 The diagram shows a detailed view of the sawtooth thread of the sealing structure of the present invention. The vertical surface of the tooth is located on the steam inlet side of the valve stem gap leakage, and the inclined surface is located on the steam outlet side of the valve stem gap leakage. The pitch is H1, and the size of H1 depends on the actual situation of the valve. The tooth angle is α, and α is recommended to be 30°.

[0033] See Figure 6 The diagram shown is a detailed drawing of the fine thread of the sealing structure of the present invention. The pitch is H2, and the size of H2 depends on the actual situation of the valve. The thread angle is β, and it is recommended that β be 30°.

[0034] The working principle of this invention is as follows: the sawtooth thread 1A on the inner side of the sleeve 1 and the fine thread 2A on the outer side of the valve stem 2 together form multiple continuous chambers. The leakage steam flow in the valve stem gap 7 generates vortices within these chambers, hindering the axial flow of the steam and significantly reducing leakage. The sawtooth thread 1A on the inner side of the sleeve 1 and the fine thread 2A on the outer side of the valve stem 2 have opposite directions of rotation, disrupting the circumferential flow of the steam, further reducing leakage in the valve stem gap 7 and improving valve economy. Both the sawtooth thread 1A and the fine thread 2A are formed in one step using a tap, a mature process with low cost.

[0035] This invention has the following characteristics:

[0036] (1) The sawtooth thread on the inner side of the sleeve and the fine thread on the outer side of the valve stem form multiple continuous chambers. The steam leakage in the valve stem gap generates vortices in the chambers, which hinders the axial flow of the steam and significantly reduces the amount of steam leakage in the valve stem gap.

[0037] (2) The inclined surface of the sawtooth thread guides the steam flow to the bottom of the chamber, which intensifies the steam flow vortex at the bottom of the chamber and makes the steam flow tortuous and multi-directional, further reducing the amount of steam leakage in the valve stem gap.

[0038] (3) The sawtooth thread on the inner side of the sleeve and the fine thread on the outer side of the valve stem have opposite directions of rotation, which disrupts the circumferential flow of steam and reduces the steam velocity.

[0039] (4) The sawtooth thread on the inner side of the sleeve and the fine thread on the outer side of the valve stem are both standard threads, which can be formed by tapping in one go. The process is mature and the cost is low.

[0040] (5) The sleeve thread does not completely penetrate the sleeve, and a threadless section is retained at the bottom 2mm. This can reduce the area of ​​the gap between the chamber and the valve stem and prevent swirling from forming at the beginning.

[0041] (6) Thanks to the valve stem gap sealing structure of the present invention, the leakage of steam in the valve stem gap is effectively controlled, the valve stem diameter and gap can be appropriately increased, the risk of valve stem bending or jamming is reduced, and the safety of the valve is further improved.

[0042] (7) The valve stem gap sealing structure of the present invention can be simplified according to the actual situation, that is, the sawtooth thread structure on the inner side of the sleeve is retained, and the fine thread structure on the outer side of the valve stem is cancelled. While achieving a certain sealing effect, the amount of processing is reduced, the cost is low and the valve stem structure is not affected at all, which is especially suitable for valve modification.

[0043] (8) Add a sealing structure to the unloading chamber to greatly reduce the pressure in the unloading chamber during valve operation and reduce air leakage loss.

[0044] Overall, the valve stem gap sealing structure of this invention can increase steam flow vortex, making the flow tortuous and multi-directional, hindering the axial and circumferential flow of steam within the gap, effectively reducing steam leakage in the valve stem gap, reducing valve losses, and is easy to process and has a low cost.

Claims

1. A valve stem clearance sealing structure for a regulating valve, characterized in that: The valve includes a valve cover (3), a valve body (4), a valve disc (5), a valve seat (6), a valve stem (2), and a sleeve (1). The valve cover (3) is installed on the valve body (4), and the valve seat (6) is installed inside the valve body (4). The valve disc (5) is set above the valve seat, and the top of the valve disc (5) is located inside the valve cover (3). The sleeve (1) is fixed inside the valve cover (3). The valve stem (2) passes through the sleeve (1) and extends into the valve disc (5). The valve stem (2) has a structure that is thinner at the top and thicker at the bottom. The valve disc (5) has a central protrusion, and the lower part of the valve stem (2) matches the central protrusion. This drives the valve disc (5) to move. The inner side of the sleeve is provided with a sawtooth thread (1A); the outer side of the valve stem (2) is provided with a fine thread (2A). The sawtooth thread (1A) and the fine thread (2A) form a continuous chamber. The valve stem (2) and the sleeve (1) form a valve stem gap (7). The chamber and the valve stem gap (7) form a labyrinth seal. The sawtooth thread (1A) on the inner side of the sleeve and the fine thread (2A) on the outer side of the valve stem adopt opposite directions of rotation. The length of the sawtooth thread (1A) is less than the length of the fine thread (2A).

2. The valve stem clearance sealing structure of a regulating valve according to claim 1, characterized in that: The serrated thread (1A) of the sleeve does not completely penetrate the sleeve, leaving an unthreaded section at the bottom 2mm.

3. The valve stem clearance sealing structure of a regulating valve according to claim 1, characterized in that: The sawtooth thread (1A) on the inside of the sleeve and the fine thread (2A) on the outside of the valve stem are both standard threads.

4. The valve stem clearance sealing structure of a regulating valve according to claim 1, characterized in that: A sealing ring (9) is provided above the valve disc (5), and an elastic metal (8) is provided between the sealing ring (9) and the valve cover (3) above it.

5. The valve stem clearance sealing structure of a regulating valve according to claim 4, characterized in that: An unloading chamber (10) is formed between the valve disc (5), valve stem (2), and valve cover (3). A valve inlet is opened on the side of the valve body (4), and a valve outlet is opened below the valve body (4). When the valve stem (2) is lifted, the valve disc (5) is lifted upward, the elastic metal (8) is squeezed, and the sealing ring (9) contacts the valve disc (5), thereby isolating the unloading chamber from the valve inlet and the valve outlet.

6. The valve stem clearance sealing structure of a regulating valve according to claim 1, characterized in that: The tooth angle α of the sawtooth thread (1A) is 30°.

7. The valve stem clearance sealing structure of a regulating valve according to claim 1, characterized in that: The thread angle β of the fine thread (2A) is 30°.

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