A chamber structure for improving the flow condition of low-pressure leakage flow of a mechanical seal at the last stage of a nuclear main pump

Abstract

The application discloses a chamber structure for improving flow condition of low-pressure leakage flow of a mechanical seal of a last stage of a nuclear main pump, which comprises a mechanical seal dynamic ring and a mechanical seal static ring, the mechanical seal dynamic ring is located at the lower part of the mechanical seal static ring, the mechanical seal dynamic ring and the mechanical seal static ring are arranged in the inside of a shaft sleeve, the outside of the shaft sleeve is a pump shaft, a low-pressure leakage flow chamber is formed between the mechanical seal dynamic ring and the mechanical seal static ring, a static ring guide sleeve is sleeved on the mechanical seal static ring, a spring is arranged between the top of the mechanical seal static ring and the static ring guide sleeve, an O-shaped ring is arranged between the side surface of the mechanical seal static ring and the static ring guide sleeve, and a groove is arranged on the pump shaft side of the static ring guide sleeve. The chamber structure has the beneficial effects that (1) the increased right-angled trapezoidal groove design can increase the water storage capacity of the ascending section, and effectively inhibits the formation of the gas-water mixed flow condition caused by high-speed rotation.

Description

TECHNICAL FIELD

[0001] The application belongs to the last stage mechanical seal of the main pump, and particularly relates to a chamber structure for improving the flow condition of low-pressure leakage flow of the last stage mechanical seal of the nuclear main pump. BACKGROUND

[0002] The reactor coolant pump (main pump) of a nuclear power plant is a key sensitive equipment of the nuclear power plant and is the heart of the nuclear power plant. Since the mechanical seal of the fluid dynamic pressure type main pump of the nuclear power plant is put into use, a plurality of times of the events of the high low-pressure leakage flow of the main pump mechanical seal, the pressure drop before the third stage seal and even 0 have occurred in a few years. The events cause the shutdown of the nuclear power plant, the shutdown of the reactor for maintenance or repair of the main line, and serious influence on the nuclear safety and economic benefits of the nuclear power plant. Therefore, how to avoid the leakage of the main pump mechanical seal and ensure the safe and stable operation of the main pump becomes a problem to be solved. SUMMARY

[0003] The application aims to provide a chamber structure for improving the flow condition of low-pressure leakage flow of the last stage mechanical seal of the nuclear main pump, which can effectively improve the use environment of the O ring of the mechanical seal, thereby improving the reliability of the mechanical seal and the pump set.

[0004] The technical scheme of the application is as follows: a chamber structure for improving the flow condition of low-pressure leakage flow of the last stage mechanical seal of the nuclear main pump, comprising a mechanical seal dynamic ring and a mechanical seal static ring, the mechanical seal dynamic ring is located at the lower part of the mechanical seal static ring, the mechanical seal dynamic ring and the mechanical seal static ring are arranged in the inside of a shaft sleeve, the outside of the shaft sleeve is a pump shaft, a low-pressure leakage flow chamber is formed between the mechanical seal dynamic ring and the mechanical seal static ring, a static ring guide sleeve is sleeved on the mechanical seal static ring, a spring is arranged between the top of the mechanical seal static ring and the static ring guide sleeve, an O ring is arranged between the side surface of the mechanical seal static ring and the static ring guide sleeve, and a groove is arranged on the pump shaft side of the static ring guide sleeve.

[0005] The groove is annular.

[0006] The cross section of the groove is a right-angled trapezoid.

[0007] The acute angle of the inclined edge of the groove is 40-60°, and the inclined surface faces downward.

[0008] The application has the following beneficial effects:

[0009] (1) The increased right-angled trapezoidal groove design can increase the water storage capacity of the rising section and effectively inhibit the formation of the gas-water mixed flow condition caused by high-speed rotation.

[0010] (2) the design of the upper inclined edge of the groove can convert the centrifugal force generated by the high-speed rotating fluid into downward punching force, and the open design of the upper part of the chamber can slightly and limitedly increase the pressure of the low-pressure leakage chamber, thereby increasing the boiling point of the fluid in the chamber, avoiding the occurrence of local bubble nucleation boiling, and inhibiting the bluing of the shaft sleeve. Meanwhile, the use environment of the O-ring can be improved, and the followability can be improved, thereby avoiding the jamming of the static ring. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 A chamber structure for improving the flow condition of low-pressure leakage flow of a nuclear main pump final stage mechanical seal is provided.

[0012] In the figure, 1 is a mechanical seal dynamic ring, 2 is a mechanical seal static ring, 3 is a static ring guide sleeve, 4 is a spring, 5 is a low-pressure leakage flow chamber, 6 is a pump shaft, 7 is a shaft sleeve, 8 is an O-ring, and 9 is a groove. DETAILED DESCRIPTION

[0013] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0014] The dynamic and static ring distribution in the chamber structure for improving the flow condition of low-pressure leakage flow of a nuclear main pump final stage mechanical seal provided by the application is that the dynamic ring is placed below and the static ring is placed above, the dynamic ring rotates at high speed together with the shaft sleeve and the pump shaft, the spring is arranged between the static ring and the static ring guide sleeve, the sealing force between the dynamic ring and the static ring is stabilized and the possible dynamic and static wear is compensated, the static ring and the static ring guide sleeve will have axial relative movement during the axial movement of the pump shaft during the pump operation, and the two are sealed by the O-ring. When the O-ring is installed for the first time, an appropriate amount of silicone grease needs to be applied on the O-ring. The low-pressure leakage flow of the mechanical seal is at normal pressure, and the air will be contacted at a position about 130 mm away from the sealing surface. In the narrow annular channel where the leakage flow rises, the air will be mixed with water to form extremely turbulent flow condition due to the high-speed rotation of the shaft sleeve, and the high temperature of the shaft sleeve makes the flow condition in the chamber very poor, which causes the surface of the shaft sleeve to be blued due to alternating thermal stress, and even more, the performance of the O-ring and the silicone grease is reduced, the followability of the O-ring is greatly reduced, and the static ring is jammed.

[0015] As Figure 1As shown, a chamber structure for improving the flow condition of low-pressure leakage flow of the last stage mechanical seal of a nuclear main pump, comprising a mechanical seal dynamic ring 1 and a mechanical seal static ring 2, the mechanical seal dynamic ring 1 is located below the mechanical seal static ring 2, the mechanical seal dynamic ring 1 and the mechanical seal static ring 2 are arranged inside a shaft sleeve 7, the outside of the shaft sleeve 7 is a pump shaft 6, a low-pressure leakage flow chamber 5 is formed between the mechanical seal dynamic ring 1 and the mechanical seal static ring 2, a static ring guide sleeve 3 is sleeved on the mechanical seal static ring 2, a spring 4 is installed between the top of the mechanical seal static ring 2 and the static ring guide sleeve 3, an O-ring 8 is arranged between the side surface of the mechanical seal static ring 2 and the static ring guide sleeve 3, an annular right-angled trapezoidal groove 9 is arranged on the pump shaft side of the static ring guide sleeve 3, the cross-sectional shape of the groove is suggested to be a right-angled trapezoid, but is not limited to a right-angled trapezoid, and as shown Figure 1 As shown, the groove 9 is annular, the cross-section of the groove 9 is a right-angled trapezoid, there is a distance of at least 5 mm between the maximum diameter of the groove 9 and the spring hole, the acute angle of the inclined side is 40-60°, and the inclined surface is downward.

[0016] The static ring guide sleeve 3 is positioned and static with the sealing chamber, the inner wall and the outer wall of the shaft sleeve form a low-pressure leakage chamber; the spring 4 provides compensation force for the mechanical seal static ring; the low-pressure leakage flow chamber 5 has normal pressure and small gap, and the temperature at this position is several degrees higher than the saturated temperature of water.

[0017] The mechanical seal dynamic ring 1, the shaft sleeve 7 and the pump shaft 6 rotate at a high speed with the rated speed of the pump, and other components are static. The leakage flow flows into the low-pressure leakage flow chamber 5 from the sealing surface between the dynamic ring and the static ring, and flows upward along the narrow gap between the shaft sleeve 7 and the static components and through the groove 9.

[0018] The cross-section of the groove 9 is Figure 1 As shown, the right-angled trapezoid, the design of the upper inclined side of the trapezoid can convert the centrifugal force of the high-speed rotating fluid into downward ram pressure, and the open design of the upper part of the chamber can slightly and limitedly increase the pressure of the low-pressure leakage flow chamber 5, can increase the water storage capacity of the rising section, and effectively suppresses the formation of gas-water mixed flow condition caused by high-speed rotation. Thus, the boiling point of the fluid in the chamber is improved, local nucleate boiling is avoided, and the bluing of the shaft sleeve is inhibited. At the same time, the gas content of the low-pressure leakage flow chamber 5 is reduced, the use environment of the O-ring 8 is improved, the follow-up performance is improved, and the jamming of the static ring 2 is avoided. The right short side of the groove 9 needs to leave a certain thickness between the spring 4 chamber, and a certain distance is reserved between the lower side and the original right-angled bend, so as to ensure the structural strength of the static ring guide sleeve 3.

[0019] The present patent is not limited to a specific cross-sectional type, and the general principle is:

[0020] 1. There is a certain space to increase the water storage capacity of the rising section of the low-pressure leakage chamber;

[0021] 2. The method of making the liquid rotating at a high speed produce downward centrifugal force by cross-sectional structure design, the inclined surface is downward, and the acute angle is preferably 40-60°.

[0022] 3. Do not affect the structural strength of the static ring guide sleeve 4, especially the maximum diameter of the trapezoidal groove needs to be kept a certain distance from the spring hole, and the lower right angle needs to be kept 1 cm away from the corner of the guide sleeve.

[0023] This design will not affect the operation and operation of the original related system. It has an optimization effect on the flow of the low-pressure leakage chamber and an improvement effect on the performance of the mechanical seal.

Claims

1. A chamber structure for improving the flow condition of low pressure leakage flow of the mechanical seal of the last stage of a nuclear main pump, characterized in that: The mechanical seal dynamic ring is located below the mechanical seal static ring, the mechanical seal dynamic ring and the mechanical seal static ring are arranged in the shaft sleeve, the outside of the shaft sleeve is the pump shaft, a low-pressure leakage flow chamber is formed between the mechanical seal dynamic ring and the mechanical seal static ring, the static ring guide sleeve is sleeved on the mechanical seal static ring, the spring is arranged between the top of the mechanical seal static ring and the static ring guide sleeve, the O-shaped ring is arranged between the side surface of the mechanical seal static ring and the static ring guide sleeve, and the recess is arranged on the pump shaft side of the static ring guide sleeve. The recess is annular. The cross section of the recess is a right-angled trapezoid. The acute angle of the inclined edge of the recess is 40-60 degrees, and the inclined surface faces downward.

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