Mechanical sealing structure for nuclear power pump

Abstract

The invention provides a nuclear power pump mechanical sealing structure which comprises a fastener, an O-shaped ring, a corrugated pipe, a movable ring and a static ring, the movable ring is installed in the corrugated pipe to transmit torque and achieve sealing, the O-shaped ring is installed in the corrugated pipe to seal a movable ring assembly and a pump shaft, and the static ring is installed in the corrugated pipe to seal the movable ring assembly and the pump shaft. The fastening piece is pre-installed in the corrugated pipe and screwed down after the corrugated pipe is installed on the pump shaft, and the static ring abuts against the moving ring. The low-leakage valve is long in service life and meets the requirement for low leakage. The steel has good tensile strength, fatigue strength and creep resistance.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical seals for nuclear power pumps, and in particular to a mechanical seal structure for nuclear power pumps. Background Art

[0002] At present, the emergency diesel engine fuel system of nuclear power plants is an emergency power generation equipment newly added after the Fukushima accident. It requires small space, compact layout, high reliability, and can be put into use at any time when not in use during normal times. It also requires a long replacement cycle for wearing parts. The mechanical seals of the pump equipment are also required to have a short axial size to save installation space. At present, most of them use rubber bellows mechanical seal technology, which relies on a large spring + rubber bellows combination to achieve torque transmission and provide elastic force to fit the end faces of the dynamic and static rings.

[0003] However, traditional rubber bellows are prone to aging, and often have problems such as bellows rupture and large spring fatigue failure. They are generally used for no more than 2 years, which does not meet the current nuclear power use requirements of at least 4-6 years. Summary of the invention

[0004] The purpose of the present invention is to provide a mechanical seal structure for a nuclear power pump, which solves the problems of easy aging and rupture of traditional rubber bellows mechanical seals, frequent fatigue failure of large springs and short service life.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A mechanical seal structure for a nuclear power pump comprises a fastener, an O-ring, a bellows, a dynamic ring and a static ring, wherein the dynamic ring is installed inside the bellows to transmit torque and achieve sealing, the O-ring is installed inside the bellows to seal the dynamic ring assembly and the pump shaft, the fastener is pre-installed inside the bellows and is tightened after the bellows is installed to the pump shaft, and the static ring is arranged against the dynamic ring.

[0007] Furthermore, the fastener is a set screw.

[0008] Furthermore, the dynamic ring is installed inside the bellows by interference fit.

[0009] Furthermore, the stationary ring is installed on the pump cavity through interference fit by means of a sealing gasket, so that the stationary ring is fixed and sealed and the torque is transmitted through the interference fit of the sealing gasket.

[0010] Furthermore, the sealing gasket is L-shaped or O-shaped and is made of fluororubber.

[0011] Furthermore, an annular groove is provided on the outer side of the static ring, and a static ring sealing ring is arranged in the annular groove.

[0012] Furthermore, the bellows is a hydraulic metal bellows, and the trough of the hydraulic metal bellows is an arc structure.

[0013] Furthermore, the hydraulic metal bellows is manufactured by micro-plasma welding technology and is made of Inconel718 material.

[0014] Furthermore, the stationary ring is made of pressureless sintered silicon carbide, and the dynamic ring is made of graphite, so that the dynamic ring and the stationary ring have good matching performance.

[0015] Furthermore, the O-ring is made of fluororubber.

[0016] Compared with the prior art, the mechanical seal structure for nuclear power pump provided by the present invention has the following beneficial effects:

[0017] The invention has excellent tensile strength, fatigue strength, creep strength, high and low temperature stability, reduces friction with the shaft end, improves floating performance, improves torsion resistance, expands the applicable temperature range, extends the service life of the product, and meets the host's requirements for long life and low leakage of the seal. 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 mechanical seal structure for a nuclear power pump provided by the present invention;

[0020] Figure 2 This is a schematic diagram of another mechanical seal structure for a nuclear power pump provided by the present invention.

[0021] Description of reference numerals:

[0022] 1-Fastener; 2-O-ring; 3-Bellows; 4-Dynamic ring; 5-Static ring; 6-Sealing gasket; 7-Static ring sealing ring. DETAILED DESCRIPTION

[0023] The following is further explained in detail through specific implementation methods.

[0024] like Figure 1As shown, the present invention provides a mechanical seal structure for a nuclear power pump, which is a highly reliable, compact, and long-life metal bellows mechanical seal, including a fastener 1, an O-ring 2, a bellows 3, a dynamic ring 4, a static ring 5, and a sealing gasket 6. The fastener 1 is a set screw.

[0025] The dynamic ring 4 is installed inside the bellows 3 by using an interference fit process to transmit torque and achieve sealing. The O-ring 2 is installed inside the bellows 3 to achieve sealing between the dynamic ring assembly and the pump shaft. The set screw is pre-installed inside the bellows 3, and after the bellows 3 is installed on the pump shaft, the set screw is tightened and fixed on the pump shaft to achieve transmission of the pump shaft torque.

[0026] The stationary ring 5 is arranged close to the dynamic ring 4, and the stationary ring 5 is installed on the pump cavity through the interference fit of the sealing gasket 6 to achieve the fixation and sealing of the stationary ring 5, and transmit the torque through the interference fit of the sealing gasket 6. Figure 2 As shown, an annular groove is provided on the outer side of the stationary ring 5 , a stationary ring sealing ring 7 is arranged in the annular groove, and a sealing gasket 6 is no longer arranged on the outer side of the stationary ring 5 .

[0027] Preferably, the bellows 3 is a hydraulic metal bellows, the trough of which is an arc structure, so that impurities in the medium are not easily deposited on the inner side of the bellows, and the bellows 3 rotates with the axis, which is conducive to the discharge of impurities with centrifugal force. The hydraulic metal bellows adopts a wave structure, which makes the elastic force more uniform and has a certain pressure resistance.

[0028] Hydraulic metal bellows are manufactured by micro-plasma welding, which has the advantages of low energy and concentration, and is especially suitable for welding ultra-thin parts. In addition, its energy concentration improves welding efficiency, so under the combined effect of protective gas and high-efficiency welding, the weld is less oxidized or has no oxidation.

[0029] Hydraulic metal bellows are made of Inconel718 material, which enhances the welding performance and can maintain high tensile strength, fatigue strength and creep strength at high and low temperatures.

[0030] The stationary ring 5 is made of pressureless sintered silicon carbide, which is the hardest and most corrosion-resistant sealing material among silicon carbide and can withstand almost all corrosive media.

[0031] The moving ring 4 is made of graphite, which has good performance when paired with silicon carbide (stationary ring 5). Preferably, the moving ring 4 adopts a square cross-section structure, which is conducive to transmitting torque and enhancing strength. The parts material part uses graphite as a soft ring material. Graphite material is a commonly used material in friction pairs and has many excellent properties: good thermal conductivity, low linear expansion coefficient, good corrosion resistance and excellent self-lubrication.

[0032] The O-ring 2 is made of fluororubber, which is resistant to fuel, acid and alkali, and has the characteristics of ozone resistance, weather resistance and good aging resistance. The O-ring 2 is installed inside the bellows 3 to achieve the sealing of the dynamic ring assembly and the pump shaft.

[0033] Preferably, the O-ring 2 is installed inside the bellows 3 through a metal bellows seat, and after the metal bellows seat and the metal bellows are welded, a sealing boundary is formed and torque is transmitted.

[0034] The sealing gasket 6 is L-shaped or O-shaped and is made of fluororubber. It realizes the sealing between the stationary ring and the pump chamber and prevents the stationary ring assembly from rotating with the moving ring.

[0035] The single-end bellows mechanical seal structure of the present invention is suitable for the working conditions of the fuel booster pump medium temperature of 60° C. and the sealing chamber pressure of 10 bar, and meets the requirements of low leakage and long service life.

[0036] As a first embodiment, when the pump shaft diameter is φ32, the working height of the mechanical seal structure for the nuclear power pump is set to 28.5 cm, the height is set to 35±0.5 cm, the radial diameter is set to 46.4 cm, and the radial dimension of the sealing gasket 6 is set to φ48.

[0037] As a second embodiment, when the pump shaft diameter is φ40, the working height of the mechanical seal structure for the nuclear power pump is set to 30 cm, the height is set to 39±0.5 cm, the radial diameter is set to 55.5 cm, and the radial dimension of the sealing gasket 6 is set to φ58 cm.

[0038] As a third embodiment, when the pump shaft diameter is φ25.4, the working height of the mechanical seal structure for the nuclear power pump is set to 25.1 cm, the height is set to 36.4±0.5 cm, the radial diameter is set to 41.5 cm, and the radial dimension of the sealing gasket 6 is set to φ40.8 cm.

[0039] 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 mechanical seal structure for a nuclear power pump, characterized in that: The invention comprises a fastener (1), an O-ring (2), a bellows (3), a dynamic ring (4) and a static ring (5); the dynamic ring (4) is installed inside the bellows (3) to transmit torque and achieve sealing; the O-ring (2) is installed inside the bellows (3) to seal the dynamic ring assembly and the pump shaft; the fastener (1) is pre-installed inside the bellows (3) and is tightened after the bellows (3) is installed on the pump shaft; and the static ring (5) is arranged against the dynamic ring (4).

2. The mechanical seal structure for a nuclear power pump according to claim 1, characterized in that: The fastener (1) is a set screw.

3. The mechanical seal structure for a nuclear power pump according to claim 1, characterized in that: The dynamic ring (4) is installed inside the bellows (3) by interference fit.

4. The mechanical seal structure for a nuclear power pump according to claim 1, characterized in that: The stationary ring (5) is interference-mounted on the pump cavity through a sealing gasket (6), thereby achieving fixation and sealing of the stationary ring (5) and transmitting torque through the interference-mounted installation of the sealing gasket (6).

5. The mechanical seal structure for a nuclear power pump according to claim 4, characterized in that: The sealing gasket (6) is L-shaped or O-shaped and is made of fluororubber.

6. The mechanical seal structure for a nuclear power pump according to claim 1, characterized in that: An annular groove is provided on the outer side of the static ring (5), and a static ring sealing ring (7) is arranged in the annular groove.

7. The mechanical seal structure for a nuclear power pump according to claim 1, characterized in that: The bellows (3) is a hydraulic metal bellows, and the wave trough of the hydraulic metal bellows is an arc structure.

8. The mechanical seal structure for a nuclear power pump according to claim 7, characterized in that: The hydraulic metal bellows is manufactured by micro-plasma welding technology and is made of Inconel718 material.

9. The mechanical seal structure for a nuclear power pump according to claim 1, characterized in that: The stationary ring (5) is made of pressureless sintered silicon carbide, and the dynamic ring (4) is made of graphite, so that the dynamic ring (4) and the stationary ring (5) have good pairing performance.

10. The mechanical seal structure for a nuclear power pump according to claim 1, characterized in that: The O-ring (2) is made of fluororubber.

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