Valve rod sealing structure capable of being maintained on line under pressure

Abstract

The utility model belongs to the technical field of valve rod sealing, and particularly relates to a valve rod sealing structure capable of being maintained on line under pressure, which comprises a valve body with a valve rod hole and a valve rod penetrating through the valve body, and an annular flange of the valve rod is matched with the valve body in an axial limiting mode to prevent the valve rod from moving outwards under medium pressure. The valve rod hole is a stepped hole, and the upper section hole, the filler and the filler gland form a first sealing part; and an elastic sealing ring is arranged between the lower section hole and the valve rod to form a second sealing part, so that medium leakage can be effectively prevented. According to the structure, when the first sealing part needs to be maintained, the annular flange and the valve body form a stopping block to prevent the valve rod from moving outwards, and meanwhile the elastic sealing ring of the second sealing part prevents media from leaking in the axial direction of the valve rod. Compared with a traditional structure, pressure of a valve cavity and a pipeline section does not need to be emptied, maintenance convenience and efficiency are remarkably improved, and maintenance cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of valve stem seals, in particular to a valve stem seal structure capable of being maintained online under pressure. Background Art

[0002] In the industrial sector, valves, as key control components in fluid delivery systems, are widely used in industries such as petrochemicals, electric power, and natural gas. The valve stem seal is a core component that ensures valve sealing and prevents media leakage. Its performance is directly related to the safety and stability of the system. Currently, the mainstream valve stem seal structure uses compression packing (such as graphite packing) to achieve sealing. The packing is compressed by gland bolts to fill the gap between the valve stem and the stuffing box, thereby blocking the media leakage path.

[0003] The valve stem seal structure is susceptible to problems such as packing wear and aging that affect its sealing performance, so regular maintenance or replacement of sealing components is required. In most operating conditions, the gland must be loosened when repairing or replacing the packing seal. At this time, the packing sealing force is lost, and the limiting effect on the valve stem is reduced. The pressure of the medium inside the valve will act on the valve stem, which can easily cause a "valve stem blowout" accident. Therefore, the pressure in the valve cavity and pipeline section must be released in advance to eliminate the thrust of the medium at the bottom of the valve stem, or to reduce the thrust.

[0004] However, in some special working conditions, such as oil pipelines and natural gas transportation, this maintenance method has certain disadvantages: the pressure relief shutdown process is time-consuming and labor-intensive, which will lead to transportation interruptions and cause large economic losses. In the industry, some researchers have proposed a sealing structure that can be repaired online under pressure to solve the above problems. For example, by adding an external sealing sleeve, online leak plugging can be achieved, thereby reducing pressure relief shutdowns. However, the external sealing sleeve structure needs to be additionally equipped with hydraulic clamping devices, multi-layer seals and other components, resulting in a complex overall structure, cumbersome disassembly and assembly, and difficulty in achieving the needs of rapid maintenance or replacement. Therefore, how to provide a valve stem sealing structure with a simple structure that can be quickly repaired under pressure conditions is a technical problem that needs to be solved urgently in this field. Utility Model Content

[0005] The purpose of the present utility model is to provide a valve stem sealing structure that can be maintained online under pressure, so as to solve the defects or deficiencies in the prior art and provide at least the advantages to be described later.

[0006] In order to achieve these objectives, the present application provides the following technical solutions: a valve stem sealing structure that can be maintained online under pressure, comprising: a valve body having a valve stem hole; a valve stem inserted into the valve stem hole, on which an annular flange is formed, and the annular flange cooperates with the axial limit of the valve body to prevent the valve stem from moving outward under the action of the medium pressure; the valve stem hole is a stepped hole, comprising an upper hole and a lower hole; the upper hole cooperates with the packing and the packing cover to form a first sealing part; an elastic sealing ring is embedded between the lower hole and the valve stem, and a second sealing part is formed between the annular flange and the upper hole to prevent the medium from leaking from the lower hole to one end of the upper hole.

[0007] As a preferred embodiment, a friction-reducing pad is provided between the annular flange and the valve body to reduce damage to the annular flange and make the valve stem rotation operation smoother.

[0008] As a preferred embodiment, a groove matching the annular flange is formed on the valve body, the inner diameter of the groove matches the outer diameter of the annular flange, and the annular flange tightly abuts in the groove to form a better inverted sealing structure.

[0009] As a preferred embodiment, a first annular groove is provided on the valve stem, and the elastic sealing ring is arranged in the first annular groove to ensure that the elastic sealing ring maintains circumferential positioning during the rotation of the valve stem and prevents the elastic sealing ring from being displaced when the medium pressure fluctuates or the valve stem is frequently opened and closed.

[0010] As a preferred embodiment, the sealing ring is an O-type fluororubber sealing ring, which can withstand high temperatures and adapt to various temperature environments, ensuring that the valve stem sealing structure can maintain a sealing effect in a complex media environment.

[0011] As a preferred embodiment, the packing gland and the valve body are connected by bolts. The tightness of the packing can be adjusted by changing the screw-in depth of the bolts, and the packing can be replaced under pressure. During maintenance under pressure, the packing pressure can be gradually released by loosening the bolts.

[0012] As a preferred embodiment, in the sealing structure of the packing, the packing is a plurality of conical graphite packings stacked on each other. The conical graphite packing helps to form a wedge-shaped extrusion with the valve stem and the inner wall of the stuffing box under the axial pressure of the packing cover. The higher the pressure, the tighter the fit, so as to ensure the sealing effect.

[0013] As a preferred embodiment, the annular flange is constructed as a split ring, which consists of two half rings. A second annular groove is provided on the valve stem. The two half rings of the split ring are respectively installed in the second annular groove from both sides of the valve stem and spliced into a complete ring. The split ring cooperates with the axial limit of the valve body to prevent the valve stem from moving outward under the action of the medium pressure.

[0014] As a preferred embodiment, the annular flange is integrally formed with the valve stem.

[0015] As a preferred embodiment, the valve body includes an upper valve body and a lower valve body, the valve stem is installed from the top of the valve body, and the end cover of the upper valve body is pressed on the annular flange of the valve stem to prevent the valve stem from moving outward under the action of the medium pressure.

[0016] Compared to existing technologies, this application offers the following advantages: The valve stem seal structure provided by this application allows for online maintenance under pressure. When the packing seal (first sealing portion) requires repair or replacement, the annular flange and the valve body form an axial stop, preventing the valve stem from moving outward under medium pressure. The elastic sealing ring (second sealing portion) embedded in the lower bore effectively blocks axial leakage of the valve cavity medium toward the upper bore along the valve stem. Compared to traditional structures, this design eliminates the need to vent the valve cavity and pipeline medium pressure; worn packing can be replaced online simply by loosening the packing gland, improving the convenience and efficiency of packing maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic diagram of a valve stem sealing structure capable of online maintenance under pressure in Example 1 of the present application;

[0019] Figure 2 This is a schematic diagram of a valve stem sealing structure capable of online maintenance under pressure according to Example 2 of the present application;

[0020] Figure 3 This is a schematic diagram of a valve stem sealing structure capable of online maintenance under pressure in Example 3 of the present application;

[0021] Markings in the figure: 1-valve body; 2-valve stem hole; 3-valve stem; 4-annular flange; 5-upper section hole; 6-lower section hole; 7-packing; 8-packing gland; 9-elastic sealing ring; 10-limiting groove; 11-friction reducing pad; 12-first annular groove; 13-second annular groove; 14-upper valve body; 15-lower valve body; 41-half ring. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] Example 1, see Figure 1 This embodiment 1 provides a valve stem sealing structure that can be repaired online under pressure, including: a valve body 1 with a valve stem hole 2; a valve stem 3 passing through the valve stem hole 2, and having an annular flange 4 formed on the valve stem; the valve stem hole 2 is a stepped hole, including an upper hole 5 and a lower hole 6.

[0024] exist Figure 1 In the structure shown, the matching parts of the valve body 1 and the valve stem 3 are integrally formed, without any separate parts; therefore, the valve stem 3 is installed from the inside of the valve body 1, and the outer diameter of the annular flange 4 is larger than the inner diameter of the lower hole 6 to form an effective axial limit for the valve stem 3.

[0025] Among them, the upper hole 5 cooperates with the packing 7 and the packing cover 8 to form a first sealing part; an elastic sealing ring 9 is embedded between the lower hole 6 and the valve stem 3 to form a second sealing part between the annular flange 4 and the upper hole 5. The second sealing part can prevent the medium in the valve cavity from entering the first sealing part before failure.

[0026] When the first sealing part and the packing 7 therein need to be repaired or replaced, this embodiment 1 can abut against the valve body 1 through the annular flange 4 to ensure that the valve stem 3 is not blown out by the medium pressure, and the elastic sealing ring 9 in the second sealing part plays a sealing role to prevent the medium from leaking axially along the valve stem to the upper hole 5.

[0027] Therefore, the present application can replace the packing 7 online without venting the valve cavity medium and pipeline medium pressure. The worn packing 7 can be replaced by simply loosening the packing cover 8. It is convenient for maintenance and effectively improves maintenance efficiency.

[0028] As a preferred embodiment, see Figure 1 The valve body 1 is further provided with a limiting groove 10, the inner diameter of which matches the outer diameter of the annular flange 4, and the annular flange 4 abuts against the limiting groove 10, so that the annular flange 4 can contact the valve body 1 to form an optimal inverted sealing structure;

[0029] Specifically, the inverted sealing structure means that when the valve stem 3 abuts the valve body 1 outward under the action of the medium pressure, the annular flange 4 contacts the valve body 1 or the step surface of the inner wall of the valve body, forming a self-tightening metal seal from the inside to the outside; generally, the greater the medium pressure, the tighter the sealing surface fits and the better the sealing effect.

[0030] In this embodiment 1, the annular flange 4 can form a primary seal through the inverted seal, which facilitates the online maintenance or replacement of the packing under pressure; in addition, in some special circumstances, such as when the rotating part of the valve stem 3 catches fire, resulting in the failure of the non-metallic sealing material, the inverted sealing structure can reduce the leakage of the medium from the valve stem 3.

[0031] As a preferred embodiment, a friction-reducing pad 11 is provided between the annular flange 4 and the valve body 1. Exemplarily, the friction-reducing pad 11 may be a thrust bearing, which is used to reduce the friction resistance between the annular flange 4 and the valve body 1, reduce the wear of the annular flange 4, and make the rotation operation of the valve stem 3 smoother.

[0032] As a preferred embodiment, a first annular groove 12 is provided on the valve stem 3, and the first annular groove 12 is correspondingly configured in the lower hole 6. The elastic sealing ring 9 is arranged in the first annular groove 12 to ensure that the elastic sealing ring 9 maintains circumferential positioning during the rotation of the valve stem 3 and forms a stable sealing surface with the inner wall of the lower hole 6; by embedding the elastic sealing ring 9 into the first annular groove 12 of the valve stem 3, the elastic sealing ring 9 can be prevented from being displaced when the medium pressure fluctuates or the valve stem 3 is frequently opened and closed, thereby ensuring the reliability of the second sealing part.

[0033] Furthermore, the elastic sealing ring 9 forms an interference fit with the inner wall of the lower hole 6 and the bottom surface of the first annular groove 12. During installation, the sealing ring is pre-extruded and deformed to form an initial seal, thereby limiting the displacement of the sealing ring and preventing it from squeezing into the gap between the valve stem 3 and the valve body 1 under the action of the medium pressure, causing sealing failure. Furthermore, the elastic sealing ring 9 is an O-type fluororubber sealing ring, such as a VITON fluororubber ring, which can withstand high temperatures and adapt to various temperature environments, ensuring that the valve stem sealing structure can maintain a sealing effect even in complex media environments.

[0034] As a preferred embodiment, the packing gland 8 is connected to the valve body 1 by bolts (not shown in the figure). The tightness of the packing 7 can be adjusted by changing the screw-in depth of the bolts. During the operation of the valve, as the sealing performance of the packing 7 decreases due to wear, the packing 7 can be squeezed by tightening the bolts, causing the packing 7 to produce axial displacement and squeeze the valve stem 3, thereby ensuring the sealing effect of the first sealing part. During pressurized maintenance, the pressure on the packing 7 can be gradually released by loosening the bolts, making it easy to replace the worn packing 7.

[0035] Furthermore, in the first sealing portion, the packing 7 is a plurality of conical graphite packings stacked on each other. The conical graphite packing helps to form a wedge-shaped extrusion with the valve stem 3 and the inner wall of the upper hole 5 under the axial pressure of the packing cover 8. The higher the pressure, the tighter the fit to ensure the sealing effect. In addition, during pressure maintenance, the conical graphite packing facilitates automatic positioning of the new packing 7 through the conical surface when it is installed.

[0036] Example 2, see Figure 2 The difference between this embodiment 2 and embodiment 1 is that the valve body includes an upper valve body 14 and a lower valve body 15, and the upper valve body 14 and the lower valve body 15 are connected by bolts (not shown in the figure), and a sealing ring is provided between the upper valve body 14 and the lower valve body 15 to ensure sealing.

[0037] Compared with Example 1, in this Example 2, the valve stem 3 can be installed from above the valve body 1. By pressing the end cover of the upper valve body 14 onto the annular flange 4 of the valve stem 3, a limiting structure is formed to prevent the valve stem 3 from moving outward under the action of the medium pressure.

[0038] Compared with Example 1, in Example 2, the valve stem 3 is installed from the top of the valve body. Compared with the method of assembling the valve stem 3 from the inside, there is no need to limit the length of the valve stem 3. Specifically:

[0039] For a commonly used valve body structure, the valve stem 3 is usually installed through the side opening of the valve body. The length of the valve stem 3 is often limited by the internal space size of the valve body. In order not to affect the assembly, the valve stem 3 is usually designed to be shorter.

[0040] However, a valve stem 3 that is too short sometimes cannot meet the space requirements for connecting the drive device and installing additional accessories such as the position indicator, or can only sacrifice the anti-movement performance of the valve stem, thereby limiting the functional scalability of the valve.

[0041] In addition, in some special working conditions, such as low temperature environment, there are often requirements for the length of the valve stem 3. A longer valve stem 3 is needed to form an effective thermal insulation buffer distance between the valve cavity and the external operating mechanism.

[0042] Therefore, the valve stem sealing structure of Example 2 eliminates the spatial limitation of the valve stem length by the traditional side installation method through the upper installation method, thereby improving the versatility of the valve stem sealing structure of the present application and enabling it to adapt to more working conditions and application scenarios.

[0043] However, it should be noted that although designing the valve body as an upper valve body 14, a lower valve body 15 or a plurality of separate structures can realize the installation of the valve stem 3 from above and remove the length restriction, this split design also adds additional valve body sealing surfaces or connection points, which to some extent increases the potential leakage risk and processing costs.

[0044] Therefore, the valve stem sealing method disclosed in Example 1 of the present application is more suitable for high-pressure working conditions with extremely high requirements for sealing reliability due to its stronger valve body integrity and fewer potential leakage points; while the valve stem sealing method disclosed in Example 2 is more suitable for working conditions that require a longer valve stem 3, are easy to maintain, or have specific requirements for the length of the valve stem 3, especially in application scenarios with medium and low pressures or relatively higher tolerance for leakage risks.

[0045] Example 3, see Figure 3 The difference between this embodiment 3 and embodiment 1 is that the annular flange 4 is constructed as a split ring, which is spliced by two half rings 41; a second annular groove 13 is provided on the valve stem 3, and the two half rings 41 are embedded in the second annular groove 13 and abut against the valve body 1 or the friction-reducing pad to prevent the valve stem 3 from moving outward under the action of the medium pressure.

[0046] Compared with Example 1, in this Example 3, after the valve stem 3 is installed from the top of the valve body, the half ring 41 of the split ring is installed into the second annular groove 13 from the inside of the valve body 1 and the lower end of the valve stem 3. Compared with the method of assembling the valve stem 3 from the inside, there is no need to limit the length of the valve stem 3; at the same time, when the annular flange 4 fails due to wear, corrosion or sealing, it is only necessary to disassemble and replace the split ring, and there is no need to replace the entire valve stem 3 as a whole.

[0047] Compared to Example 2, Example 3 eliminates the length restriction on the valve stem 3 without adding any additional valve body sealing surfaces or connection points, thus reducing potential leakage risks. However, the annular flange 4 adopts a split-ring structure and is assembled on the valve stem 3 rather than being integrally formed, which results in a relatively weak reverse sealing performance.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A valve stem sealing structure capable of online maintenance under pressure, characterized in that: include: a valve body having a valve stem hole; The valve stem is inserted into the valve stem hole and is formed with an annular flange. The annular flange cooperates with the axial limit of the valve body to prevent the valve stem from moving outward under the action of the medium pressure. The valve stem hole is a stepped hole, including an upper hole and a lower hole; The upper hole cooperates with the packing and the packing gland to form a first sealing portion; An elastic sealing ring is embedded between the lower hole and the valve stem, forming a second sealing portion between the annular flange and the upper hole to prevent the medium from leaking from the lower hole to the upper hole.

2. The valve stem sealing structure capable of online maintenance under pressure according to claim 1 is characterized in that: A friction-reducing pad is abutted between the annular flange and the valve body.

3. The valve stem sealing structure capable of online maintenance under pressure according to claim 1 is characterized in that: A limiting groove is formed on the valve body, the inner diameter of the limiting groove matches the outer diameter of the annular flange, and the annular flange abuts against the limiting groove.

4. The valve stem sealing structure capable of online maintenance under pressure according to claim 1 is characterized in that: A first annular groove is formed on the valve stem, and the elastic sealing ring is arranged in the first annular groove.

5. The valve stem sealing structure capable of online maintenance under pressure according to claim 1 is characterized in that: The sealing ring is an O-type fluororubber sealing ring.

6. The valve stem sealing structure capable of online maintenance under pressure according to claim 1 is characterized in that: The packing gland is connected to the valve body with bolts. The packing tightness can be adjusted by changing the screw-in depth of the bolts and the packing can be replaced under pressure.

7. The valve stem sealing structure capable of online maintenance under pressure according to claim 6, characterized in that: In the sealing structure of the packing, the packing is a plurality of conical graphite packings stacked on each other.

8. The valve stem sealing structure capable of online maintenance under pressure according to claim 1, characterized in that: The annular flange is constructed as a split ring, including two half rings; a second annular groove is provided on the valve stem, and the two half rings of the split ring are respectively installed in the second annular groove from both sides of the valve stem and spliced into a complete ring. The split ring is matched with the axial limit of the valve body to prevent the valve stem from moving outward under the action of the medium pressure.

9. The valve stem sealing structure capable of online maintenance under pressure according to claim 1, characterized in that: The annular flange is integrally formed with the valve stem.

10. The valve stem sealing structure capable of online maintenance under pressure according to claim 8 or 9, characterized in that: The valve body includes an upper valve body and a lower valve body. The valve stem is installed from the top of the valve body. The end cover of the upper valve body is pressed on the annular flange of the valve stem to prevent the valve stem from moving outward under the action of the medium pressure.

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