A secondary filter spindle sealing device and method for a nuclear power plant

Abstract

The present invention relates to the technical field of nuclear power plant maintenance, commissioning and operation, and particularly relates to a main shaft sealing device and method for a secondary filter in a nuclear power plant. The main shaft sealing device for the secondary filter in the nuclear power plant comprises: a compressed air system, a first isolation valve, a first pressure reducing valve, and a sealing branch connected in sequence; the sealing branch comprises a second isolation valve, a second pressure reducing valve, an oil tank device, a third isolation valve, and a main shaft sealing interface of the secondary filter connected in sequence through pipelines. The sealing method is as follows: when the main shaft of the secondary filter operates, when the main shaft sealing device of the secondary filter operates, the first isolation valve, the second isolation valve, and the third isolation valve are all in an open state, and at the same time, by adjusting the first pressure reducing valve and the second pressure reducing valve, the pressure of the oil tank device is made higher than the pressure of the seawater medium. The present invention is used to strengthen the dynamic seal of the main shaft, play a role in isolation sealing and heat dissipation lubrication, and improve the sealing reliability of the main shaft of the secondary filter.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant maintenance, commissioning and operation, and particularly relates to a main shaft sealing device and method for a secondary strainer in a nuclear power plant. Background Art

[0002] The secondary strainer is a key and sensitive device in the circulating water system (CRF) of a nuclear power plant. There are 8 circulating water secondary strainers in Units 1 and 2 of Fuqing Nuclear Power Plant. During the daily operation of the secondary strainer, the main shaft seal fails many times, seawater enters the interior, resulting in corrosion and damage of the transmission components, the function of the secondary strainer fails, seriously threatening the safe and stable operation of the condenser and the steam turbine unit, and finally forced to reduce power for maintenance.

[0003] The circulating water secondary strainer has a diameter of DN2600 and a length of 2800 mm, and is horizontally installed in the circulating water pipeline through a flange. Its operating principle is as follows: The drive motor is connected to the first-stage reduction gearbox, and the power is transmitted to the second-stage reduction gearbox (hereinafter referred to as the second-stage reduction gearbox) through a universal joint drive shaft, converting the vertical drive into a horizontal drive. After being transmitted by the main shaft assembly, the backwashing bucket is driven to rotate 360°, and the backwashing bucket sweeps across the entire filter screen surface for a full backwash. The entire main shaft assembly is immersed in seawater. Among them, three O-rings are used between the rotating shaft and the sealing chamber. The rotating shaft is in a rotating state during operation, and the three O-rings at this position are dynamic seals. During long-term operation, the O-rings are worn and leaked with the rotating shaft. After seawater enters the interior of the main shaft assembly, on the one hand, it causes rust and corrosion of the bearing balls and raceways; on the other hand, a large amount of silt and other impurities enter the bearing balls and raceways, damaging the bearing lubrication and causing the bearing to jam. The combined effect of the two finally leads to the failure of the secondary strainer drive, and it is necessary to be forced to reduce power for maintenance. Therefore, it is urgent to solve the above-mentioned shortcomings in the prior art. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a main shaft sealing device and method for a secondary strainer in a nuclear power plant, which is used to strengthen the dynamic seal of the main shaft, play a role in isolation sealing and heat dissipation lubrication, and improve the reliability of the main shaft seal of the secondary strainer.

[0005] The present invention provides a main shaft sealing device for a secondary strainer in a nuclear power plant, including: a compressed air system, a first isolation valve, a first pressure reducing valve, and a sealing branch connected in sequence;

[0006] The sealing branch includes a second isolation valve, a second pressure reducing valve, an oil tank device, a third isolation valve, and a main shaft sealing interface of the secondary strainer connected in sequence through pipelines.

[0007] Preferably, a pressure gauge is installed on the oil tank device.

[0008] Preferably, the medium inside the oil tank device is glycerol, and the medium liquid level occupies 1 / 2 - 2 / 3 of the space of the oil tank.

[0009] Preferably, it includes 2 to 4 sealing branches.

[0010] The secondary filter main shaft seal interface is respectively connected to the sealing grooves between every two of the three O-ring seals of the secondary filter rotating shaft.

[0011] Preferably, the compressed air system is a compressed air system that has passed the on-site acceptance test.

[0012] The present invention also provides a method for sealing the main shaft of a secondary filter in a nuclear power plant, including the following steps:

[0013] Step 1: Connect the secondary filter main shaft seal interface in the secondary filter main shaft seal device described above to the sealing groove between the three O-ring seals of the secondary filter rotating shaft; fill the sealing groove with the medium;

[0014] Step 2: Operate the secondary filter main shaft. When the secondary filter main shaft seal device is operating, the first isolation valve, the second isolation valve, and the third isolation valve are all in the open state. At the same time, by adjusting the first pressure reducing valve and the second pressure reducing valve, make the pressure of the oil tank device higher than the pressure of the seawater medium;

[0015] When a failure occurs in the oil tank device or the pressure reducing valve, isolate and repair by closing at least one of the first isolation valve, the second isolation valve, and the third isolation valve.

[0016] Preferably, the pressure of the oil tank device is 0.15 to 0.25 MPa.

[0017] Preferably, in Step 2, the pressure of the seawater medium is 0.11 MPa.

[0018] Preferably, a pressure gauge is connected to the oil tank device. By directly reading the oil tank pressure and according to the pressure change in the sealing groove, timely adjust the flow rate of the medium filled into the sealing groove;

[0019] The medium inside the oil tank device is glycerol.

[0020] Preferably, in Step 1, the secondary filter main shaft seal device in the nuclear power plant includes 2 sealing branches.

[0021] The secondary filter main shaft seal interface is respectively connected to the sealing grooves between every two of the three O-ring seals of the secondary filter rotating shaft.

[0022] Compared with the prior art, for a main shaft sealing device and method of a secondary filter in a nuclear power plant of the present invention, a medium is injected into the sealing grooves between two O-ring seals, so that the medium pressure at the sealing part is higher than the seawater pressure, isolating the seawater outside and preventing the seawater from entering the inside of the main shaft assembly, playing a role in strengthening the seal. When operating normally, the medium fills the space between the rotating shaft O-ring seals, which can play a role in heat dissipation and lubrication for the sealing rings. This device also effectively solves the problem of frequent failure of the dynamic seal of the main shaft, improving the seal reliability and the operation reliability of the secondary filter equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It shows a schematic structural diagram of a main shaft sealing device of a secondary filter in a nuclear power plant;

[0024] Figure 2 It shows a schematic structural diagram of the main shaft seal of the secondary filter;

[0025] In the figure,

[0026] 1 - Compressed air system, 2 - First isolation valve, 3 - First pressure reducing valve, 4 - Second isolation valve, 5 - Second pressure reducing valve, 6 - Oil tank device, 7 - Third isolation valve, 8 - Main shaft sealing interface of the secondary filter, 9 - Pressure gauge, 10 - Pipeline, 11 - O-ring seal, 12 - Main shaft. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] To further understand the present invention, the implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the present invention.

[0028] An embodiment of the present invention discloses a main shaft sealing device for a secondary filter in a nuclear power plant, as shown in Figure 1 and 2 shown, including: a compressed air system 1, a first isolation valve 2, and a sealing branch connected in sequence;

[0029] The sealing branch includes a first pressure reducing valve 3, a second isolation valve 4, a second pressure reducing valve 5, an oil tank device 6, a third isolation valve 7, and a main shaft sealing interface 8 of the secondary filter connected in sequence through a pipeline 10.

[0030] The oil tank device 6 is installed with a pressure gauge 9.

[0031] The medium inside the oil tank device 6 is glycerol, and the medium liquid level occupies 1 / 2 - 2 / 3 of the space of the oil tank, that is, there is 1 / 3 - 1 / 2 space left above the inside of the oil tank device.

[0032] The number of sealing branches is 1 - 4,

[0033] When there are 2 to 4 sealing branches, the secondary filter screen main shaft sealing interfaces of each sealing branch are respectively connected to the sealing grooves between every two of the three O-ring seals 11 on the secondary filter rotating shaft.

[0034] The compressed air system is a compressed air system that has passed the Site Acceptance Test (SAT).

[0035] An embodiment of the present invention also discloses a method for sealing the main shaft of a secondary filter screen in a nuclear power plant, including the following steps:

[0036] Step 1: Connect the secondary filter screen main shaft sealing interface in the secondary filter screen main shaft sealing device of the above technical solution to the sealing groove between the three O-ring seals 11 on the secondary filter rotating shaft; fill the sealing groove with the medium.

[0037] The secondary filter screen main shaft sealing device in the nuclear power plant includes 2, 3, or 4 sealing branches.

[0038] The secondary filter screen main shaft sealing interfaces are respectively connected to the sealing grooves between every two of the three O-ring seals 11 on the secondary filter rotating shaft.

[0039] A pressure gauge 9 is connected to the fuel tank device, and the medium inside the fuel tank device is glycerol.

[0040] Step 2: Operate the secondary filter screen main shaft 12. When the secondary filter screen main shaft sealing device is operating, the first isolation valve 2, the second isolation valve 4, and the third isolation valve 7 are all in the open state. At the same time, by adjusting the first pressure reducing valve 3 and the second pressure reducing valve 5, the pressure of the fuel tank device 6 is made higher than the seawater medium pressure.

[0041] The seawater medium pressure is 0.11 MPa. Therefore, the pressure of the fuel tank device is controlled to be 0.15 - 0.25 MPa.

[0042] By directly reading the pressure of the fuel tank device 6 and according to the pressure change in the sealing groove, the flow rate of the medium filled into the sealing groove is adjusted in a timely manner.

[0043] When the fuel tank device 6 or the pressure reducing valve fails, at least one of the first isolation valve 2, the second isolation valve 4, and the third isolation valve 7 is closed for isolation and maintenance.

[0044] The effects of the secondary filter screen main shaft sealing device are as follows: 1) When the O-ring seal on the rotating shaft fails, since the pressure of the glycerol medium inside the fuel tank device is higher than the seawater pressure, it can isolate the seawater outside and prevent the seawater from entering the inside of the main shaft assembly, playing a role in strengthening the seal; 2) When operating normally, the space between the O-rings on the rotating shaft is filled with glycerol medium, which can play a role in heat dissipation and lubrication for the O-ring seals. 3) This device effectively solves the problem of frequent failure of the current dynamic seal of the main shaft, improves the sealing reliability, and improves the operating reliability of the secondary filter screen equipment.

[0045] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0046] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A main shaft sealing device for the secondary filter of a nuclear power plant, characterized in that, Comprising: A compressed air system, a first isolation valve, a first pressure reducing valve, and a sealing branch connected in sequence; The sealing branch includes a second isolation valve, a second pressure reducing valve, an oil tank device, a third isolation valve, and a secondary filter spindle seal interface connected in sequence through pipelines; The internal medium of the oil tank device is glycerol; The secondary filter spindle seal interface is respectively connected to the sealing grooves between every two of the three O-ring seals of the secondary filter rotating shaft; The pressure of the oil tank device is higher than the pressure of the seawater medium; When operating normally, the O-ring seals of the rotating shaft are filled with glycerol medium.

2. The main shaft sealing device of the secondary filter in a nuclear power plant according to claim 1, wherein A pressure gauge is installed on the oil tank device.

3. The main shaft sealing device of the secondary filter in a nuclear power plant according to claim 2, characterized in that, The medium liquid level occupies 1 / 2 to 2 / 3 of the space of the oil tank.

4. The secondary filter spindle sealing device of a nuclear power plant according to claim 1, characterized in that Including 2 to 4 sealing branches.

5. The main shaft sealing device of the secondary filter in a nuclear power plant according to claim 1, characterized in that The compressed air system is a compressed air system that has passed the on-site acceptance test.

6. A main shaft sealing method for the secondary filter of a nuclear power plant, characterized in that, Including the following steps: Step 1: Connect the secondary filter spindle seal interface in the secondary filter spindle seal device of claim 1 to the sealing groove between the three O-ring seals of the secondary filter rotating shaft; fill the sealing groove with the medium; Step 2: Operate the secondary filter spindle. When the secondary filter spindle seal device is operating, the first isolation valve, the second isolation valve, and the third isolation valve are all in the open state. At the same time, by adjusting the first pressure reducing valve and the second pressure reducing valve, the pressure of the oil tank device is made higher than the pressure of the seawater medium; When a failure occurs in the oil tank device or the pressure reducing valve, isolation and repair are carried out by closing at least one of the first isolation valve, the second isolation valve, and the third isolation valve.

7. The main shaft sealing method of the secondary filter in a nuclear power plant according to claim 6, characterized in that, The pressure of the oil tank device is 0.15 to 0.25 MPa.

8. The method for sealing the main shaft of the secondary filter in a nuclear power plant according to claim 6, characterized in that, In step 2, the pressure of the seawater medium is 0.11 MPa.

9. The method for sealing the main shaft of the secondary filter in a nuclear power plant according to claim 6, characterized in that, A pressure gauge is connected to the oil tank device. By directly reading the oil tank pressure and according to the pressure change in the sealing groove, the flow rate of the medium filled into the sealing groove is adjusted in a timely manner.

10. The method for sealing the main shaft of the secondary filter in a nuclear power plant according to claim 6, characterized in that, In step 1, the secondary filter spindle seal device in the nuclear power plant secondary filter spindle seal device includes 2 sealing branches.

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