Mechanical sealing structure for waste heat removal pump

Abstract

The invention provides a mechanical sealing structure for a waste heat removal pump, which comprises a shaft sleeve, a first spiral sleeve is mounted on the shaft sleeve, a second spiral sleeve is screwed on the first spiral sleeve to form a double-spiral structure, and a labyrinth sealing structure is arranged on the outer side of the first spiral sleeve; the second spiral sleeve is installed on a gland, and a mechanical sealing piece is installed between the shaft sleeve and the gland. The auxiliary sealing ring is not prone to aging, an elastic element is not prone to fatigue, a liquid film on the mechanical sealing end face is not prone to gasification, the sealing ring cannot be damaged due to gasification, and therefore the stability of mechanical sealing operation is guaranteed. The sealing ring is not prone to thermal deformation, so that the flatness of the end face of the sealing ring cannot be changed, and the stability of the mechanical sealing leakage rate is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical seals for a waste heat removal pump in a primary circuit of a nuclear power plant, and in particular to a mechanical seal structure for a waste heat removal pump. Background Art

[0002] The residual heat removal pump is a nuclear secondary pump in the primary circuit system and an important component of the residual heat removal system. It is located in the containment and allows the primary circuit coolant to flow through the heat exchanger of the residual heat removal system to remove the residual heat and thereby obtain or maintain a cold shutdown state.

[0003] The waste heat removal pump is responsible for cooling the waste heat of the core. When the hot reactor is shut down, the waste heat removal pump starts to operate, and the water temperature of the primary circuit directly reaches 180°C. As an important equipment in a nuclear power plant, the mechanical seal is one of the key components of the waste heat removal pump, which is used to limit the leakage of reactor coolant. It is also the most easily damaged component on the waste heat removal pump. A slight deviation in operation can cause abnormal leakage and even lead to an emergency shutdown of the reactor, threatening the safe production of the nuclear power plant and causing huge economic losses. Summary of the invention

[0004] The purpose of the present invention is to provide a mechanical seal structure for a waste heat discharge pump, which solves the problems of the existing mechanical seal structure for a waste heat discharge pump in that the liquid film on the mechanical seal end face is easily vaporized at a high temperature of 180°C, the sealing ring is easily thermally deformed and thermally cracked, the auxiliary sealing ring is easily aged, and the elastic element is easily fatigued.

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

[0006] A mechanical seal structure for a waste heat discharge pump comprises a shaft sleeve, on which a first spiral sleeve is mounted, on which a second spiral sleeve is screwed to form a double spiral structure, a labyrinth seal structure is arranged on the outer side of the first spiral sleeve; the second spiral sleeve is mounted on a gland, and a mechanical seal is mounted between the shaft sleeve and the gland.

[0007] As an practicable method, the labyrinth sealing structure is a structure in which a plurality of annular sealing teeth are arranged in sequence around the rotating shaft, and a series of intercepting gaps and expansion cavities are formed between the teeth. When the sealing medium passes through the gaps of the tortuous labyrinth, a throttling effect is generated under the hydraulic friction effect and the flow contraction effect to achieve leakage prevention.

[0008] As an practicable manner, the first spiral sleeve is mounted on the shaft sleeve by a first screw.

[0009] As an practicable manner, the second spiral sleeve is mounted on the gland by a second screw.

[0010] As an implementable manner, an annular groove is provided on the inner side of the shaft sleeve, and a first O-ring is arranged in the annular groove.

[0011] As an practicable manner, two parallel annular grooves are formed on the inner side of the shaft sleeve, and one of the first O-rings is disposed in each of the annular grooves.

[0012] As an practicable manner, the first O-ring is an EPDM rubber sealing ring.

[0013] As an implementable manner, a sealing ring is arranged between the mechanical seal and the gland, the gland is provided with a sealing groove, the sealing groove faces the mechanical seal, and the sealing ring is installed in the sealing groove.

[0014] As an implementable manner, the right side of the gland is positioned and fixed by a positioning block, and a first bolt fixedly connects the positioning block to the gland.

[0015] As an implementable manner, a rectangular groove is provided on the inner wall of the gland, and a throttling ring and a clamping ring are installed in the rectangular groove.

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

[0017] The auxiliary sealing ring of the present invention is not easy to age, the elastic element is not easy to fatigue, the liquid film on the end face of the mechanical seal is not easy to gasify, and the sealing ring will not be damaged due to gasification, thereby ensuring the stability of the mechanical seal operation. The sealing ring is not easy to be thermally deformed, so the flatness of the end face of the sealing ring will not change, ensuring the stability of the mechanical seal leakage. 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 waste heat removal pump provided by the present invention;

[0020] Figure 2 A maze diagram of a mechanical seal for a waste heat removal pump provided by the present invention;

[0021] Figure 3 A diagram of two sealing rings of a mechanical seal for a waste heat removal pump provided by the present invention;

[0022] Figure 4This is a partial enlarged view of the spring-external mechanical seal structure provided by the present invention.

[0023] Description of reference numerals:

[0024] 1-first spiral sleeve; 2-first screw; 3-spring washer; 4-first O-ring; 5-sleeve; 6-second spiral sleeve; 7-second screw; 8-mechanical seal; 9-pressure cover; 10-first bolt; 11-positioning block; 12-clamping ring; 13-throttling ring; 14-second bolt; 15-second O-ring; 16-threaded pin. DETAILED DESCRIPTION

[0025] The following is further explained in detail through specific implementation methods.

[0026] like Figure 1 As shown, the present invention provides a mechanical seal structure for a waste heat removal pump, including a shaft sleeve 5, a first spiral sleeve 1, a second spiral sleeve 6, a mechanical seal 8, a gland 9, a positioning block 11, a clamping ring 12 and a throttling ring 13.

[0027] The first spiral sleeve 1 (spiral sleeve FR) is mounted on the shaft sleeve 5 by means of the first screw 2, and the second spiral sleeve 6 is on the outer side of the first spiral sleeve 1. The spring washer 3 is arranged between the first screw 2 and the shaft sleeve 5. The second spiral sleeve 6 is mounted on the gland 9 by means of the second screw 7 ( Figure 1 The left side of the middle pressure cover 9).

[0028] like Figure 1 and Figure 2 As shown, the first spiral sleeve 1 and the second spiral sleeve 6 form a double spiral structure, so that the sealing fluid circulates and reduces the temperature of the sealing ring end surface. A labyrinth sealing structure is arranged on the outer side of the first spiral sleeve 1. The mechanical seal is effectively isolated from the high-temperature medium through the labyrinth sealing structure, thereby minimizing the influence of the high-temperature medium on the mechanical seal. Therefore, the problem caused by high temperature is solved by the above design, that is, the medium reactor coolant temperature of the waste heat removal pump can reach 180°C.

[0029] Specifically, Figure 2 As shown in the figure, the labyrinth seal is a plurality of annular sealing teeth arranged in sequence around the rotating shaft, and a series of intercepting gaps and expansion cavities are formed between the teeth. When the sealing medium passes through the gaps of the tortuous labyrinth, a throttling effect is produced under the hydraulic friction effect (when the leaking medium flows in the labyrinth, the friction generated by the viscosity of the medium slows down the flow velocity and reduces the leakage) and the flow stream contraction effect (when the leaking medium passes through the labyrinth slit, it will shrink due to the influence of inertia, and the cross-section of the flow stream will be reduced), thereby achieving the purpose of preventing leakage.

[0030] An annular groove is provided on the inner side of the shaft sleeve 5, and a first O-ring 4 is arranged in the annular groove. Preferably, two parallel annular grooves are provided on the inner side of the shaft sleeve 5, and a first O-ring 4 is arranged in each annular groove.

[0031] The mechanical seal 8 is arranged between the gland 9 and the shaft sleeve 5, a part of the structure of the mechanical seal 8 is compressed by the gland 9, and a sealing ring is arranged between the mechanical seal 8 and the gland 9. The gland 9 is provided with a sealing groove, the sealing groove faces the mechanical seal 8, and the sealing ring is installed in the sealing groove.

[0032] The right side of the gland 9 is positioned and fixed by the positioning block 11, and the first bolt 10 fixes the positioning block 11 to the gland 9. A rectangular groove is provided on the inner wall of the gland 9 near the positioning block 11, and a throttle ring 13 and a clamp ring 12 are installed in the rectangular groove. A gap is formed between the throttle ring 13 and the shaft sleeve 5, which can replace the sealing function for a short time when the seal fails. The clamp ring 12 ensures that the throttle ring 13 is not squeezed out by the medium.

[0033] The second bolt 14 fixes the gland 9 to the pump chamber. A sealing groove is provided on the left side of the gland 9, and a second O-ring 15 is arranged in the sealing groove.

[0034] The threaded pin 16 is installed on the shaft sleeve 5. When the shaft rotates, the shaft sleeve 5 and the threaded pin 16 are driven to rotate, and the threaded pin 16 drives the sealing ring to rotate.

[0035] Preferably, in order to further cool the end face of the mechanical seal ring and avoid dry friction, thermal deformation and thermal cracking of the friction pair, the present invention adopts the APIPLAN 23 scheme (flushing scheme of API682), in which the medium in the sealing cavity flows out of the sealing cavity through a double helix structure, passes through a heat exchanger and then returns to the sealing cavity, forming a self-closed cycle and a closed cooling circuit, thereby ensuring safe and reliable operation of the friction pair during the operation of the mechanical seal.

[0036] At a high temperature of 180°C, in order to prevent the auxiliary sealing ring from aging, cracking, hardening and losing elasticity, such as Figure 3 As shown, the first O-ring 4 uses a special EPDM rubber seal ring (the ordinary EPDM rubber seal ring can only withstand 120°C), which can still meet the sealing requirements after being exposed to radiation and high temperature. At the same time, two seal rings are used between the sleeve and the shaft to prevent leakage.

[0037] like Figure 4 As shown, in order to allow the spring to have sufficient elasticity to maintain the close fit of the sealing end face after long-term work, and to prevent the medium from corroding the spring and the high temperature of the medium from causing fatigue and creep effects on the spring, the present invention adopts a static, spring-external mechanical seal structure ( Figure 4 (Figure 2A and B)

[0038] 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 waste heat removal pump, characterized in that: The invention comprises a shaft sleeve (5), a first spiral sleeve (1) being mounted on the shaft sleeve (5), a second spiral sleeve (6) being screwed onto the first spiral sleeve (1) to form a double spiral structure, a labyrinth seal structure being arranged on the outer side of the first spiral sleeve (1); the second spiral sleeve (6) being mounted on a gland (9), and a mechanical seal (8) being mounted between the shaft sleeve (5) and the gland (9).

2. The mechanical seal structure for a waste heat removal pump according to claim 1, characterized in that: The labyrinth seal structure is a structure in which a plurality of annular sealing teeth are arranged in sequence around the rotating shaft, and a series of interception gaps and expansion cavities are formed between the teeth. When the sealing medium passes through the gaps of the tortuous labyrinth, a throttling effect is generated under the hydraulic friction effect and the flow contraction effect to achieve leakage prevention.

3. The mechanical seal structure for a waste heat removal pump according to claim 1 or 2, characterized in that: The first spiral sleeve (1) is mounted on the shaft sleeve (5) via a first screw (5).

4. The mechanical seal structure for a waste heat removal pump according to claim 1 or 2, characterized in that: The second spiral sleeve (6) is mounted on the gland (9) via a second screw (7).

5. The mechanical seal structure for a waste heat removal pump according to claim 1 or 2, characterized in that: An annular groove is provided on the inner side of the shaft sleeve (5), and a first O-ring (4) is arranged in the annular groove.

6. The mechanical seal structure for a waste heat removal pump according to claim 5, characterized in that: Two parallel annular grooves are provided on the inner side of the shaft sleeve (5), and one of the first O-rings (4) is arranged in each of the annular grooves.

7. The mechanical seal structure for a waste heat removal pump according to claim 6, characterized in that: The first O-ring (4) is an EPDM rubber sealing ring.

8. The mechanical seal structure for a waste heat removal pump according to claim 1, characterized in that: A sealing ring is arranged between the mechanical seal (8) and the gland (9); the gland (9) is provided with a sealing groove, the sealing groove faces the mechanical seal (8), and the sealing ring is installed in the sealing groove.

9. The mechanical seal structure for a waste heat removal pump according to claim 1, characterized in that: The right side of the gland (9) is positioned and fixed by a positioning block (11), and a first bolt (10) fixedly connects the positioning block (11) and the gland (9).

10. The mechanical seal structure for a waste heat removal pump according to claim 1, characterized in that: A rectangular groove is provided on the inner wall of the gland (9), and a throttling ring (13) and a clamping ring (12) are installed in the rectangular groove.

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