A secondary filter device with double cantilever structure

Abstract

The present invention belongs to the technical field of nuclear power equipment, and specifically relates to a secondary filter device with a double cantilever structure. The partition plate evenly divides the filter cylinder into intervals, and each interval is equipped with a mesh, which is connected to the partition plate. The mesh divides the filter cylinder into two parts: the water inlet side and the water outlet side; the main shaft package is arranged at the center of the filter cylinder, passes through the mesh and the partition plate, and is fixed to the partition plate through the mounting flange. The main shaft in the main shaft package extends out of the partition plate on the water inlet side, and two symmetrically arranged sewage buckets are installed on the main shaft. One end of the main shaft package on the water outlet side is connected to the reducer through a coupling; the bevel gear side of the reducer is connected to the motor outside the filter cylinder through a transmission shaft, and two circles of support ribs are installed on the water inlet side of the mesh, and the support ribs on this side are fixed to the partition plate; two circles of support ribs are also installed on the water outlet side of the mesh, and the support ribs on this side are fixed to the partition plate; the sewage pipe passes through the filter cylinder. The present invention improves the operating reliability of the secondary filter supporting the million-kilowatt nuclear power unit.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear power equipment, and in particular relates to a secondary filter device with a double cantilever structure. Background Art

[0002] The function of the secondary filter is to filter impurities in the circulating water, ensure that the circulating water that meets the requirements enters the water side of the condenser heat transfer tube, and cools the exhaust steam of the steam turbine. Failure of the secondary filter will affect the safety of the unit's cold source, and will cause the unit to reduce power or shut down. Therefore, the reliability of the secondary filter is related to the safe and stable operation of the unit. However, the failure rate of the secondary filter equipment supporting the million-kilowatt nuclear power unit is relatively high, and it is urgently needed to be redesigned to reduce the failure rate and improve the operational reliability.

[0003] At present, the secondary filters of million-kilowatt nuclear power units all adopt a single cantilever structure design. The common problems of the secondary filter devices with this structure are mainly:

[0004] 1. The spindle seal is seriously worn and water has entered the spindle;

[0005] 2. Failure of the secondary filter transmission component causes jamming;

[0006] 3. The reducer flange bolts and spring pins are broken;

[0007] 4. The reducer falls off and the filter cannot work;

[0008] 5. Partial wear of the reducer bevel gear;

[0009] 6. The mesh is damaged;

[0010] 7. The wear-resistant plate of the sewage hopper is severely worn.

[0011] A detailed analysis and research was conducted on the fault defects of the current secondary filter equipment, pointing out that the single cantilever structure secondary filter equipment supporting the million-kilowatt nuclear power unit has inherent defects in design: under the pressure difference of the filter, the unilateral force of the sewage hopper causes the bolts of the reducer housing to be subjected to excessive shear force, resulting in bolt breakage. After the bolt breaks, the reducer falls under the action of gravity, resulting in failure of the transmission shaft system. Under the pressure difference of the filter, the sewage hopper will be subjected to a force, the magnitude of which is related to the magnitude of the pressure difference of the filter and the area of ​​the sewage hopper. This force will be applied to the main shaft package through the sewage hopper arm to form an external torque, which causes the main shaft to move toward the sewage hopper side, thereby pressing the main shaft against the sealing ring on the sewage hopper side, aggravating the wear of the main shaft package sealing ring. At the same time, the sun gear and planetary gear of the reducer will be displaced in the opposite direction of the sewage hopper, causing the bevel gear on the sun gear side of the reducer to swing a lot, resulting in poor meshing between the bevel gears, thus causing bevel gear wear.

[0012] As the power of the random unit increases, the flow rate of circulating water increases, the diameter of the secondary filter increases, the length and area of ​​the sewage hopper increase, and the external torque acting on the main shaft increases more. Therefore, the sewage hopper design with a single cantilever structure still used in the million-kilowatt nuclear power unit can no longer meet the safe and reliable operation of the secondary filter equipment. It is urgently necessary to make design improvements to reduce the failure rate and improve operational reliability. Summary of the invention

[0013] The purpose of the present invention is to provide a double-cantilever structure secondary filter device to overcome the various shortcomings of existing secondary filter equipment, improve the operating reliability of the secondary filter supporting the million-kilowatt nuclear power unit, and reduce the failure rate.

[0014] In order to achieve the above object, the technical solution adopted by the present invention is:

[0015] A double cantilever structure secondary filter device, 24 partition plates are arranged in the middle position of the filter cylinder, the partition plates evenly divide the filter cylinder into 24 intervals, each interval is installed with a mesh, the mesh is connected to the partition plates, and the 24 meshes divide the filter cylinder into two parts: the water inlet side and the water outlet side; the main shaft package includes a thrust bearing, a sealing ring, a coupling, and a main shaft. The main shaft is installed on the thrust bearing, one end of the main shaft is connected to the coupling, and the other end is provided with a sealing ring; the main shaft package is arranged in the center of the filter cylinder, passes through the mesh and the partition plates, and passes The mounting flange is fixed on the partition plate, the main shaft in the main shaft package extends out of the partition plate on the water inlet side, and two symmetrically arranged sewage buckets are installed on the main shaft, and one end of the main shaft package on the water outlet side is connected to the reducer through a coupling; the bevel gear side of the reducer is connected to the motor outside the filter cylinder through a transmission shaft, and two circles of supporting ribs are installed on the water inlet side of the mesh, and the supporting ribs on this side are fixed on the partition plate; two circles of supporting ribs are also installed on the water outlet side of the mesh, and the supporting ribs on this side are fixed on the partition plate; the part where the sewage pipe passes through the filter cylinder is connected by sealing welding.

[0016] The partition plate is welded to the filter cylinder.

[0017] The mesh sheet is connected to the partition plate by bolts.

[0018] The reducer and the main shaft package are arranged in a reducer sealing cover.

[0019] A wear-resistant plate is installed at the contact position between the sewage hopper and the support ring formed by the support rib plate.

[0020] The two circles of supporting ribs installed on the water inlet side are fixed to the partition plate in the form of bolt connection.

[0021] The two circles of supporting ribs installed on the water outlet side are fixed to the partition plate by welding.

[0022] The transmission shaft is arranged in the transmission shaft sealing cover, one end of the transmission shaft sealing cover is connected to the reducer sealing cover by a flange, the other end of the transmission shaft sealing cover passes through the filter cylinder, and is connected by sealing welding at the position passing through the filter cylinder. The transmission shaft sealing cover is made of a Φ108mm pipe.

[0023] The filter cylinder is rolled from a steel plate with a diameter of 22 mm, a diameter of 2600 mm, and a length of 2200 mm; the sewage pipe is made of a 377 mm pipe.

[0024] When the pressure difference of the filter is high, backwashing is automatically performed. At this time, the motor runs and drives the reducer to work through the transmission shaft. The reducer drives the main shaft package to run through the coupling. The main shaft package drives the sewage bucket to rotate in intervals in sequence. When the sewage bucket rotates to a certain compartment interval and stops, the water in this compartment area changes direction under the action of the pressure difference, and flows back from the filter into the sewage pipe, flushing the surface of the filter mesh in the sewage discharge area, flushing the debris out of the filter, and discharging it through the sewage pipe, completing the cleaning and sewage discharge process of one compartment, realizing automatic cleaning and sewage discharge of the filter. When the sewage bucket rotates to another compartment interval, the above sewage discharge process is repeated, and so on.

[0025] The beneficial effects achieved by the present invention are:

[0026] The present invention aims to improve the operating reliability of the secondary filter screen of a million-kilowatt nuclear power unit and reduce the failure rate. The main advantages are as follows:

[0027] (1) Greatly improve the working reliability of the reducer

[0028] Because the sewage hoppers are arranged symmetrically and the areas of the two sewage hoppers are exactly the same, the external forces generated by the pressure difference of the filter screen are just balanced, that is, the force generated by the pressure difference of the filter screen acts completely on the thrust bearing, and the reducer flange bolts no longer have shear force, which can avoid the occurrence of reducer flange bolt breakage failure. The shear force at the reducer flange will be greatly reduced and can be completely eliminated in theory. In addition, two spring pins are added to the reducer flange to improve the shear resistance, and the bolts are changed from the original M8 to M10 to improve the bearing capacity of the bolts, which greatly improves the reliability of the reducer.

[0029] (2) Extend the service life of the spindle package and sealing ring

[0030] The double-cantilever symmetrical sewage hopper layout is adopted. The force generated by the pressure difference of the filter screen acts completely on the thrust bearing. The main shaft will not deviate to the sewage hopper side. The main shaft is in the center position and will no longer be tightly pressed on the sealing ring on the sewage hopper side, which reduces the wear of the main shaft package and the sealing ring and extends the service life of the main shaft package and the sealing ring.

[0031] (3) Reduce the wear of the reducer bevel gear

[0032] Due to the symmetrical arrangement of the sewage hopper, the main shaft will not produce radial displacement, so the sun gear shaft and the reducer bevel gear will not produce large swings, the two bevel gears can achieve normal meshing, and the wear problem of the reducer bevel gear can be greatly improved.

[0033] (4) Reduce the probability of mesh damage and improve the reliability of the mesh

[0034] After increasing the number of compartments from 16 to 24, the arc length of the mesh is reduced to 67% of the original, and the rigidity and support strength of the mesh will be improved to a certain extent. The original design of the mesh did not have a support plate on the water-facing surface. During the backwashing stage and normal operation stage, the mesh was subjected to positive and reverse alternating stress, resulting in fatigue fracture of the mesh. The improved secondary filter not only has mesh support reinforcement ribs installed on the backwater surface, but also has support reinforcement ribs designed on the water-facing surface to improve the mesh's ability to resist fatigue fracture. The mesh thickness is increased from 2mm to 3mm, and the mesh's bearing capacity is improved. Therefore, after the improvement, the mesh reliability will be greatly improved.

[0035] (5) Improve the wear resistance of wear-resistant plates

[0036] Due to the symmetrical arrangement of the sewage hopper, the forces of the pressure difference on the surface of the sewage hopper are balanced, the main shaft will not produce radial displacement, and theoretically a certain design gap can be maintained between the wear-resistant plate and the grid, which greatly reduces the risk of wear of the wear-resistant plate and improves the reliability of the wear-resistant plate. Considering that the sewage hopper may be deformed to a certain extent during operation, resulting in friction between the wear-resistant plate and the grid, wear-resistant ceramics are embedded on the surface of the wear-resistant plate to improve the wear resistance, extend the life of the wear-resistant plate, and improve the reliability of the wear-resistant plate.

[0037] The scheme of the present invention is simple and feasible, can reduce the failure rate of the secondary filter, and only improves the internal component structure of the secondary filter, all external interfaces and foundations remain unchanged, and subsequent changes to the operating unit are simple and convenient to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a cross-sectional view of the secondary filter screen with a double cantilever structure;

[0039] Figure 2 This is the water inlet side view of the double cantilever structure secondary filter;

[0040] Figure 3 This is the water outlet side view of the secondary filter with double cantilever structure;

[0041] Figure 4 This is a schematic diagram of the force on the main shaft of the secondary filter with a double cantilever structure;

[0042] In the figure: 1. filter cylinder; 2. mesh; 3. sewage hopper; 4. sewage pipe; 5. wear-resistant plate; 6. main shaft package; 7. reducer; 8. transmission shaft; 9. motor; 10. supporting rib plate; 11. partition plate; 12. reducer sealing cover; 13. transmission shaft sealing cover. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Considering that the unbalanced force of the filter pressure difference on the sewage bucket is the root cause of wear and bolt breakage, the improved design must balance the unbalanced force of the sewage bucket components caused by the filter pressure difference, reduce the unbalanced external torque borne by the main shaft, and reduce the external force generated by the filter pressure difference at the reducer flange. The double-cantilever structure secondary filter device with two symmetrical sewage buckets can balance the unbalanced force caused by the filter pressure difference. During operation, the secondary filter main shaft will not deviate to the sewage bucket side, which can overcome the various shortcomings of the existing secondary filter equipment, improve the operating reliability of the secondary filter, and reduce the failure rate. This double-cantilever structure secondary filter device is Figure 1 , 2 , as shown in Figure 3.

[0045] Compared with the original design drawings of the single cantilever secondary filter of Fuqing Nuclear Power Units 3 and 4, this double cantilever secondary filter device has undergone a lot of improvements. The main improvements are as follows:

[0046] (1) The number of compartments in the secondary filter cylinder is changed from the current 16 to 24;

[0047] (2) The number of sewage hoppers will be increased from one to two and arranged symmetrically, with the two sewage hoppers sharing a sewage pipe;

[0048] (3) Two circles of supporting ribs are added on the water inlet and outlet sides of the middle part of the secondary filter mesh;

[0049] (4) The mesh thickness of the secondary filter is increased from 2mm to 3mm to improve the structural strength of the mesh;

[0050] (5) The bolt specification at the reducer flange was changed from the original design M8 to M10 to improve the bolt bearing capacity;

[0051] (6) Add two spring pins at the flange of the reducer to improve the shear resistance;

[0052] (7) Wear-resistant ceramics are embedded in the wear-resistant plate to improve the wear resistance.

[0053] like Figure 1 , 2As shown in FIG. 3 , the double-cantilever structure secondary filter device of the present invention comprises: a filter cylinder 1, a mesh 2, a sewage hopper 3, a sewage pipe 4, a wear-resistant plate 5, a main shaft package 6, a reducer 7, a transmission shaft 8, a motor 9, a supporting rib plate 10, a partition plate 11, a reducer sealing cover 12, and a transmission shaft sealing cover 13.

[0054] The device is designed with 24 partition plates 11, which are arranged in the middle position of the filter cylinder 1 and connected to the filter cylinder 1 by welding. The partition plate 11 divides the filter cylinder 1 into 24 compartments evenly, and each compartment is installed with a mesh 2, which is bolted to the partition plate 11. The 24 meshes divide the filter cylinder 1 into two parts: the water inlet side and the water outlet side. The main shaft package 6 includes thrust bearings, sealing rings, mounting flanges, couplings, main shafts and other components. The main shaft is installed on the thrust bearing, one end of the main shaft is connected to the coupling, and the other end is provided with a sealing ring. The main shaft package 6 is arranged in the center of the filter cylinder 1, passes through the mesh 2 and the partition plate 11, and is fixed to the partition plate 11 through the mounting flange. The main shaft in the main shaft package extends out of the partition plate 11 on the water inlet side of the filter, and two symmetrically arranged sewage buckets 3 are installed on the main shaft. One end of the main shaft package 6 on the water outlet side is connected to the reducer 7 through a coupling. The reducer 7 includes components such as planetary gears, sun gears, bevel gears and mounting flanges. The bevel gear side of the reducer 7 is connected to the motor 9 outside the filter cylinder through the transmission shaft 8. The reducer 7 and the main shaft package 6 are arranged in the sealing cover 12. The contact part of the support ring formed by the sewage hopper 3 and the support rib plate 10 is installed with a wear-resistant plate 5 of wear-resistant material. Two circles of support rib plates 10 are installed on the water inlet side of the mesh 2, and the support rib plates 10 on this side are fixed to the partition plate 11 in the form of bolt connection; two circles of support rib plates 10 are also installed on the water outlet side of the mesh 2, and the support rib plates 10 on this side are fixed to the partition plate 11 in the form of welding to improve the support strength of the mesh. The transmission shaft 8 is arranged in the transmission shaft sealing cover 13, one end of the transmission shaft sealing cover 13 is connected to the reducer sealing cover 12 by a flange, and the other end of the transmission shaft sealing cover 13 passes through the filter cylinder 1, and is connected in the form of sealing welding at the part passing through the filter cylinder 1. The transmission shaft sealing cover 13 is made of a Φ108mm pipe. The filter cylinder 1 is rolled with a steel plate with a diameter of 22 mm, a diameter of 2600 mm, and a length of 2200 mm. The sewage pipe 4 is made of a 377 mm pipe. The sewage pipe 4 collects the filter impurities collected by the sewage hopper and discharges them to the outside of the filter cylinder 1. The sewage pipe 4 passes through the filter cylinder 1 and is connected by sealing welding.

[0055] Working process of the filter: When the pressure difference of the filter is high, it will automatically backwash. At this time, the drive motor 9 will run, and the reducer 7 will work through the transmission shaft 8. The reducer will drive the main shaft package 6 to run through the coupling. The main shaft package 6 will drive the sewage bucket 3 to rotate in intervals. When the sewage bucket 3 rotates to a certain compartment interval and stops, the water in this compartment area changes direction under the action of the pressure difference, and flows back from the filter into the sewage pipe 4, flushing the surface of the filter mesh 2 in the sewage discharge area, flushing the debris out of the filter, and discharging through the sewage pipe 4, completing the cleaning and sewage discharge process of a compartment, and realizing automatic cleaning and sewage discharge of the filter. When the sewage bucket rotates to another compartment interval, the above sewage discharge process is repeated, and so on.

[0056] This double-cantilever secondary filter is improved on the basis of the single-cantilever secondary filter, and the internal component structure of the single-cantilever secondary filter is comprehensively improved. The sewage hopper is changed from a single-cantilever sewage hopper to two symmetrically arranged double-arm structures. The force generated by the filter pressure difference can be basically balanced, and the impact on the shaft system is minimal; the number of compartments in the secondary filter cylinder is changed from the current 16 to 24, and supporting ribs are added on the water inlet side of the mesh. The mesh thickness is increased to 3mm. These measures can improve the load-bearing and fatigue resistance of the mesh; wear-resistant ceramics are inlaid on the wear-resistant plate to improve wear resistance; 2 spring pins are added at the reducer flange to improve shear resistance; the bolt specification at the reducer flange is changed from the original design M8 to M10 to improve the bolt load-bearing capacity.

[0057] Calculation of shaft force of the secondary filter with double cantilever structure: Since the sewage hoppers are arranged symmetrically and the areas of the two sewage hoppers are exactly the same, the external forces generated by the pressure difference of the filter are just balanced with each other. The force generated by the pressure difference of the filter is completely applied to the thrust bearing, and the reducer flange bolts are no longer subject to shear force, which can avoid the occurrence of reducer flange bolt breakage failure. Due to the symmetrical arrangement of the sewage hoppers, the main shaft will not produce radial displacement, so the sun gear shaft and the reducer bevel gear will not produce large swings, the two bevel gears can achieve normal meshing, and the wear problem of the reducer bevel gear can be greatly improved. Since the main shaft will not produce radial displacement, the main shaft is in the center position and will no longer be pressed tightly against the sealing grid ring on the sewage hopper side, which greatly improves the wear of the main shaft pack sealing ring and increases the service life of the main shaft pack. For details of the shaft force analysis diagram, see Figure 4 shown.

[0058] In summary, the use of the double cantilever structure secondary filter designed by this patent can eliminate the breakage of the reducer flange bolt, reduce the wear of the reduction bevel gear, reduce the wear of the main shaft seal ring, reduce the wear of the dirt hopper wear plate, prevent the filter mesh from being damaged, reduce the failure rate of the secondary filter, and greatly improve the operating reliability of the secondary filter. With the increase of unit capacity, this double cantilever structure secondary filter will be widely used in engineering.

Claims

1. A double cantilever structure secondary filter device, characterized in that: 24 partition plates are arranged in the middle of the filter cylinder. The partition plates evenly divide the filter cylinder into 24 compartments. A mesh is installed in each compartment. The mesh is connected to the partition plates. The 24 meshes divide the filter cylinder into two parts: the water inlet side and the water outlet side. The main shaft package includes a thrust bearing, a sealing ring, a coupling, and a main shaft. The main shaft is installed on the thrust bearing. One end of the main shaft is connected to the coupling, and the other end is provided with a sealing ring. The main shaft package is arranged in the center of the filter cylinder, passes through the mesh and the partition plates, and is fixed to the filter cylinder through the mounting flange. On the partition plate, the main shaft in the main shaft package extends out of the partition plate on the water inlet side, and two symmetrically arranged sewage buckets are installed on the main shaft. One end of the main shaft package on the water outlet side is connected to the reducer through a coupling; the bevel gear side of the reducer is connected to the motor outside the filter cylinder through a transmission shaft, and two circles of supporting ribs are installed on the water inlet side of the mesh, and the supporting ribs on this side are fixed on the partition plate; two circles of supporting ribs are also installed on the water outlet side of the mesh, and the supporting ribs on this side are fixed on the partition plate; the part where the sewage pipe passes through the filter cylinder is connected by sealing welding.

2. The double cantilever structure secondary filter device according to claim 1, characterized in that: The partition plate is welded to the filter cylinder.

3. The double cantilever structure secondary filter device according to claim 1, characterized in that: The mesh sheet is connected to the partition plate by bolts.

4. The double cantilever structure secondary filter device according to claim 1, characterized in that: The reducer and the main shaft package are arranged in a reducer sealing cover.

5. The double cantilever structure secondary filter device according to claim 1, characterized in that: A wear-resistant plate is installed at the contact position between the sewage hopper and the support ring formed by the support rib plate.

6. The double cantilever structure secondary filter device according to claim 1, characterized in that: The two circles of supporting ribs installed on the water inlet side are fixed to the partition plate in the form of bolt connection.

7. The double cantilever structure secondary filter device according to claim 1, characterized in that: The two circles of supporting ribs installed on the water outlet side are fixed to the partition plate by welding.

8. The double cantilever structure secondary filter device according to claim 4, characterized in that: The transmission shaft is arranged in the transmission shaft sealing cover, one end of the transmission shaft sealing cover is connected to the reducer sealing cover by a flange, the other end of the transmission shaft sealing cover passes through the filter cylinder, and is connected by sealing welding at the position passing through the filter cylinder. The transmission shaft sealing cover is made of a Φ108mm pipe.

9. The double cantilever structure secondary filter device according to claim 1, characterized in that: The filter cylinder is rolled from a steel plate with a diameter of 22 mm, a diameter of 2600 mm, and a length of 2200 mm; the sewage pipe is made of a 377 mm pipe.

10. The double cantilever structure secondary filter device according to claim 1, characterized in that: When the pressure difference of the filter is high, backwashing is automatically performed. At this time, the motor runs and drives the reducer to work through the transmission shaft. The reducer drives the main shaft package to run through the coupling. The main shaft package drives the sewage bucket to rotate in intervals in sequence. When the sewage bucket rotates to a certain compartment interval and stops, the water in this compartment area changes direction under the action of the pressure difference, and flows back from the filter into the sewage pipe, flushing the surface of the filter mesh in the sewage discharge area, flushing the debris out of the filter, and discharging it through the sewage pipe, completing the cleaning and sewage discharge process of one compartment, realizing automatic cleaning and sewage discharge of the filter. When the sewage bucket rotates to another compartment interval, the above sewage discharge process is repeated.

Images