Mechanical sealing structure of metal corrugated pipe for reheating valve

Abstract

The invention provides a metal corrugated pipe mechanical sealing structure for a reheat valve, which comprises a moving ring, a shaft sleeve, a spring, a corrugated pipe assembly and a static ring, the moving ring is sleeved on a valve rod and is matched with the valve rod for positioning, the shaft sleeve is connected on the valve rod through threads, the corrugated pipe assembly is arranged on a valve body, and the static ring is arranged on the shaft sleeve. An annular groove is formed in the side, facing the movable ring, of the corrugated pipe assembly, the static ring is arranged in the annular groove, the spring and the corrugated pipe assembly provide elastic force for the static ring so as to prevent the sealing end face from being opened due to quick opening, and the situation that the leakage amount exceeds the standard is avoided. The valve is suitable for the working conditions that the medium temperature of a reheat valve is 257 DEG C and the pressure of a sealing cavity is 9.59 bar, and the requirements for low leakage and long service life are met.

Description

Technical Field

[0001] The invention relates to the technical field of sealing for reheat valves in nuclear power plants, and in particular to a metal bellows mechanical sealing structure for reheat valves. Background Art

[0002] Many reheat steam valves and reheat regulating valves in use in nuclear power plants are important equipment on the secondary circuit of the power plant. Mechanical seals are key components of reheat steam valves and reheat regulating valves. Their function is to prevent superheated steam in the valve from leaking into the atmosphere from the gap between the valve stem and the valve body. The working conditions of the reheat valve are: medium temperature 257℃, seal chamber pressure 9.59bar. Mechanical seals must meet the requirements of low leakage and long life under this working condition. However, the existing mechanical seals have poor adaptability to the working environment and cannot meet the use requirements. Summary of the invention

[0003] The object of the present invention is to provide a metal bellows mechanical seal structure for a reheat valve, which solves the problem of poor mechanical seal effect of the existing reheat valve.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A metal bellows mechanical seal structure for a reheat valve comprises a dynamic ring, a sleeve, a spring, a bellows assembly and a static ring. The dynamic ring sleeve is arranged on a valve stem and cooperates with the valve stem for positioning. The sleeve is connected to the valve stem by threads. The bellows assembly is installed on a valve body. A ring groove is provided on the side of the bellows assembly facing the dynamic ring. The static ring is arranged in the ring groove. The spring and the bellows assembly provide elastic force for the static ring to prevent the sealing end face from opening due to rapid opening and to avoid excessive leakage.

[0006] As an practicable manner, the moving ring is driven by a driving pin on the valve stem.

[0007] As an practicable manner, the bushing is fixedly mounted on the valve stem by means of a set screw.

[0008] As an implementable manner, an adjustment pad is arranged between the shaft sleeve and the moving ring, and the shaft sleeve and the adjustment pad cooperate to perform axial positioning.

[0009] As an implementable manner, an anti-loosening washer is arranged on the set screw in the shaft sleeve to ensure that the set screw will not loosen due to external vibration and periodic cycle force during operation.

[0010] As an practicable manner, a first sealing gasket is disposed at a step transition between the dynamic ring and the valve stem to enhance sealing performance.

[0011] As an implementable manner, a second sealing gasket is disposed in a groove on the bellows assembly to achieve sealing between the valve body and the bellows assembly.

[0012] As an practicable manner, the stationary ring is made of wear-resistant graphite material.

[0013] As an practicable manner, the dynamic ring adopts a hard alloy spray coating.

[0014] As an practicable manner, the bellows assembly is made of Inconel718 material, and the spring is made of Hast.C material.

[0015] Compared with the prior art, the metal bellows mechanical seal structure for the reheat valve provided by the present invention has the following beneficial effects:

[0016] The present invention avoids the use of auxiliary seals that require micro-sliding, and the auxiliary seal gasket adopts a compression seal working state, which can be maintained for a long period. Ensuring the sealing end face fits, that is, ensuring the overall effect, is particularly suitable for working conditions with impact loads. The graphite, hard alloy and metal materials used are all suitable for the target working environment.

[0017] The present invention is suitable for the working conditions of a reheat valve medium temperature of 257° C. and a sealing chamber pressure of 9.59 bar, and meets the requirements of low leakage and long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of a metal bellows mechanical seal structure for a reheat valve provided by the present invention.

[0020] Description of reference numerals:

[0021] 1-steam shielding sleeve; 2-first sealing gasket; 3-moving ring; 4-connecting screw; 5-anti-loosening gasket; 6-setting screw; 7-second sealing gasket; 8-shaft sleeve; 9-spring; 10-metal bellows assembly; 11-static ring; 12-adjusting gasket. DETAILED DESCRIPTION

[0022] The following is further explained in detail through specific implementation methods.

[0023] like Figure 1As shown, the present invention provides a metal bellows mechanical seal structure for a reheat valve, which adopts a welded metal bellows structure, is arranged in a static manner, and includes two major parts: a rotating part and a static part. The present invention is suitable for the working conditions of a reheat valve medium temperature of 257°C and a sealing chamber pressure of 9.59 bar, and meets the requirements of low leakage and long life.

[0024] The rotating parts include a moving ring 3, a first sealing gasket 2, an adjusting gasket 12, a sleeve 8, a set screw 6, and an anti-loosening gasket 5. The moving ring 3 is sleeved on the valve stem, and the moving ring 3 cooperates with the valve stem for positioning. The driving pin on the valve stem is used for transmission. The sleeve 8 is clamped by the thread on the valve stem. The sleeve 8 and the adjusting gasket 12 cooperate for axial positioning. The adjusting gasket 12 is arranged between the sleeve 8 and the moving ring 3. The first sealing gasket 2 is arranged at the step transition between the moving ring 3 and the valve stem to enhance the sealing performance. The set screw 6 is used to prevent the sleeve 8 from loosening, and the set screw 6 fixes the sleeve 8 on the valve stem. The first sealing gasket 2 is used for sealing between the moving ring 3 and the valve stem. The anti-loosening gasket 5 is used to prevent the set screw on the sleeve 8 from loosening.

[0025] The stationary parts include a stationary ring 11, a bellows assembly 10, a spring 9, a steam shielding sleeve 1, a second sealing gasket 7, and a connecting bolt 4. The bellows assembly 10 is the most critical sealing component of the stationary parts. The bellows assembly 10 is fixed by the connecting bolt 4, and the second sealing gasket 7 realizes the sealing between the valve body and the bellows assembly 10. The bellows assembly 10 is arranged on one side of the dynamic ring 3. The bellows assembly 10 is provided with an annular groove on the side facing the dynamic ring 3. A stationary ring 11 is arranged between the bellows assembly 10 and the dynamic ring 3, and the stationary ring 11 is arranged in the annular groove. The bellows assembly 10 and the spring 9 provide sufficient elastic force for the stationary ring 11 to prevent the sealing end face from opening due to rapid opening and to avoid excessive leakage. The steam shielding sleeve 1 is used to prevent high-temperature steam from directly impacting the sealing end face. The spring 9 works in conjunction with the bellows and is installed on the end cover to squeeze the bellows assembly 10 toward the dynamic ring 3.

[0026] The stationary ring 11 is made of wear-resistant graphite material. Graphite material is a commonly used material in friction pairs. It has many excellent properties: good thermal conductivity, low linear expansion coefficient, good corrosion resistance and excellent self-lubrication.

[0027] The dynamic ring 3 uses a hard alloy spray coating. The combination of the two has good tribological properties.

[0028] The installation of the stationary ring 11 and the bellows assembly 10 adopts a non-inserted, inner and outer diameter clearance matching method, which effectively prevents external stress caused by temperature changes from causing deformation of the sealing end surface and affecting the sealing performance.

[0029] The metal bellows (bellows assembly 10) is made of Inconel718, and the spring 9 is made of Hast.C. Both materials have excellent temperature resistance and can maintain high tensile strength, fatigue strength, and creep resistance at high and low temperatures.

[0030] The present invention solves the problem of adaptability of mechanical seal materials to the working environment. The Inconel material used in the metal parts meets the requirements for long-term operation at 257°C. The performance will not change at this temperature, which will affect the use of the mechanical seal. The flexible graphite static seal ring used in the mechanical seal also needs to meet the requirements for long-term operation at 257°C. A reinforced metal skeleton is added to the flexible graphite to ensure that the seal can still maintain sufficient elasticity after long-term use.

[0031] The present invention solves the problem of mechanical seal closing force compensation. Since the medium of the mechanical seal is superheated steam, the steam viscosity is low and the permeability is strong under high temperature. In order to meet the performance requirements, the sealing end face must maintain a sufficiently large end face closing force. Under conventional design, the metal bellows alone cannot meet the design requirements. By adding a cylindrical helical spring, it provides thrust together with the metal bellows. Finally, the design requirements are met.

[0032] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A metal bellows mechanical seal structure for a reheat valve, characterized in that: The invention comprises a movable ring (3), a shaft sleeve (8), a spring (9), a bellows assembly (10), and a stationary ring (11); the movable ring (3) is sleeved on the valve stem and cooperates with the valve stem for positioning; the shaft sleeve (8) is connected to the valve stem by threads; the bellows assembly (10) is installed on the valve body; a ring groove is provided on the side of the bellows assembly (10) facing the movable ring (3); the stationary ring (11) is arranged in the ring groove; the spring (9) and the bellows assembly (10) provide elastic force for the stationary ring (11) to prevent the sealing end face from opening due to rapid opening and to avoid excessive leakage.

2. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: The moving ring (3) is driven by a driving pin on the valve stem.

3. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: The shaft sleeve (8) is fixedly mounted on the valve stem via a set screw (6).

4. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: An adjustment pad (12) is arranged between the shaft sleeve (8) and the movable ring (3), and the shaft sleeve (8) and the adjustment pad (12) cooperate to perform axial positioning.

5. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: The anti-loosening pad (5) is arranged in the shaft sleeve (8).

6. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: The first sealing gasket (2) is arranged at the step transition between the moving ring (3) and the valve stem to enhance the sealing performance.

7. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: The second sealing gasket (7) is arranged in a groove on the bellows assembly (10) to achieve sealing between the valve body and the bellows assembly (10).

8. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: The stationary ring (11) is made of wear-resistant graphite material.

9. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: The moving ring (3) is made of a hard alloy spray coating.

10. The metal bellows mechanical seal structure for a reheat valve according to claim 1, characterized in that: The bellows assembly (10) is made of Inconel 718 material, and the spring (9) is made of Hast. C material.

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