A nuclear power plant drum screen backwash pump

Abstract

The present application relates to the field of backwash pump, especially to a drum-shaped filter screen backwash pump for nuclear power plant. The backwash pump comprises a pump rotor system connected with a motor rotor; the pump rotor system comprises a shaft, an upper impeller and a lower impeller; the shaft and an intermediate water guide bearing are provided with a sheath pipe, the upper part of the sheath pipe extends to the lower end of the shaft seal, and the lower part ends in a bearing hole seat inside the upper flow guide; an external injection pipe injects water into the sheath through the shaft seal; the upper flow guide is provided with a precise bearing seat hole, an upper water guide bearing is installed in interference fit, and the upper water guide bearing is connected with a lower flow guide, the lower flow guide is connected with a pump suction inlet; a thrust bearing is located at the upper end of the shaft, is pressed into a bearing chamber and is axially locked; the pump shaft is provided with a central hole, a top injection hole and a bottom discharge hole, forming an internal flushing circuit; the multi-stage water guide bearing and the shaft sleeve form a friction pair, supplemented by a skeleton oil seal to prevent leakage. The present application reduces vibration, improves reliability and reduces maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of backwash pumps, and more particularly to a backwash pump for a drum-shaped filter screen in a nuclear power plant. Background Technology

[0002] The seawater circulating water system is an extremely important cooling source system for nuclear power plants and a key system for ensuring the safe and stable operation of nuclear power plants. The system inputs seawater through the water intake head, and after passing through the water conveyance tunnel, gates, trash racks, and drum filters, the seawater is pressurized by the circulating water pumps and supplied to the condenser and auxiliary cooling water system. Finally, the seawater is discharged into the sea through drainage channels, siphon wells, shield tunnel discharge pipes, and drainage outlets.

[0003] To remove fine debris from seawater and ensure the normal operation of subsequent equipment, a drum filter is installed after the trash rack. During operation, debris continuously accumulates on the drum filter, causing blockages. If this debris is not removed promptly, it will affect the normal operation of the drum filter. Therefore, a backwashing system is provided for the drum filter. The backwashing system consists of a backwash pump, flushing pipelines, and nozzles. The backwash pump draws in seawater, pressurizes it, and sends it to the nozzles, which are located outside the drum filter. The nozzles flush the drum filter from the outside in. The flushing water containing debris enters the backwash water collection hopper inside the drum filter, and then is discharged through a ditch into a slag pit, and finally into the sea.

[0004] The drum-type filter backwash pump is a vertical deep well pump with a shaft system consisting of nine shafts: one pump shaft, seven intermediate shafts, and one upper shaft. The total length of the shaft system is 13.7m. Since its operation, it has frequently experienced serious defects such as high vibration, broken shaft seal water pipes, large packing leakage, severe wear of the water guide bearings, and high motor bearing temperatures. It is disassembled on average once a month, with each disassembly and spare parts repair costing 200,000 yuan. Its design flaws are mainly manifested in four aspects:

[0005] 1. The pump set has large radial oscillation, and the bushing and Sailon bearing are severely worn, resulting in excessive vibration of the pump set and frequent defects such as water leakage from the packing.

[0006] 2. Improper processing of Sailong bearings led to an excessively large clearance dimension during actual assembly, which is one of the reasons for the large radial oscillation of the pump unit.

[0007] 3. Cooling water is injected into the shaft seal and each water-guided bearing through external water pipes. The cooling water pipes are 13m long, thin and without rigid support. They often break under long-term vibration, resulting in the bearings having no cooling water and lubricating water, and aging and failing rapidly after dry grinding.

[0008] 4. The cooling water of the pump shaft water guide bearing is designed to be open. After the cooling water enters the water guide bearing, it is not sealed but flows directly into the seawater. Because the pump shaft water guide bearing is at the end of the cooling water and is in an open state, the cooling water pressure is insufficient. Seawater mud and sand will enter the bearing, causing severe wear of the pump shaft water guide bearing and resulting in large vibration of the pump unit.

[0009] 5. The main material of the pump set's flow-through components is 316L stainless steel, while some components are made of copper alloy. According to the characteristics of the seawater quality in Hangzhou Bay, 316L stainless steel cannot meet the requirements. The flow-through components are severely corroded, and the impeller, guide tube, and other components must be replaced each time the pump is disassembled, resulting in high maintenance costs.

[0010] 6. The motor shares the upper shaft of the pump, and the motor bearings bear the weight of the entire pump rotor. Therefore, defects such as high motor bearing temperature and abnormal noise are frequently reported.

[0011] Therefore, it is necessary to optimize and improve the design to solve problems such as high defect rate and high maintenance cost of backwash pumps. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide a backwash pump for a drum-shaped filter in a nuclear power plant, which reduces vibration, improves reliability, and reduces maintenance costs.

[0013] This invention provides a backwashing pump for a drum filter in a nuclear power plant, comprising:

[0014] The pump rotor system is connected to the motor rotor via a flexible pin coupling;

[0015] The pump rotor system includes a shaft, an upper impeller, and a lower impeller;

[0016] The shaft includes an upper shaft, an intermediate shaft, and a pump shaft connected sequentially from top to bottom;

[0017] A shaft seal is provided in the middle of the upper shaft;

[0018] The shaft and the intermediate water guide bearing are fitted with a protective sleeve. The upper part of the protective sleeve extends to the lower end of the shaft seal, and the lower part ends in the bearing hole seat inside the upper water guide.

[0019] An external injection tube enters through the shaft seal and injects into the protective sleeve;

[0020] The upper guide tube has a precision bearing seat hole machined inside, and the upper water guide bearing is installed with an interference fit.

[0021] The lower part of the upper guide fluid is connected to the lower guide fluid;

[0022] The lower part of the guide tube is connected to the pump inlet;

[0023] The thrust bearing is located at the upper end of the upper shaft. The thrust bearing is press-fitted into the bearing housing with an interference fit. The outer ring of the thrust bearing is axially locked by the steps of the bearing housing and the end cover.

[0024] The intermediate water guide bearing is sleeved on the intermediate shaft;

[0025] The upper water guide bearing is sleeved on the upper end of the pump shaft and forms a friction pair with the upper shaft sleeve; before the outer ring of the bearing is pressed into the upper guide bearing, the inner ring is clearance-fitted with the upper shaft sleeve, and a skeleton oil seal is installed at the lower end;

[0026] The lower guide bearing is sleeved on the lower end of the pump shaft and mates with the lower shaft sleeve; both the upper and lower ends of the lower guide bearing and the lower shaft sleeve are equipped with skeleton oil seals.

[0027] A radial horizontal injection hole is provided at the top of the pump shaft;

[0028] The pump shaft is drilled with a central hole that runs through its entire length along the axial direction.

[0029] The bottom of the pump shaft is provided with a radial horizontal discharge hole.

[0030] In one specific embodiment of the present invention, the flexible pin coupling includes an upper half coupling and a lower half coupling, which are connected by a pin.

[0031] In one specific embodiment of the present invention, the shaft seal includes a stuffing box, packing, and a packing gland;

[0032] A stuffing box is fitted in the middle of the upper shaft. The stuffing box and the upper shaft are filled with packing. The packing is pressed together by a packing gland to achieve a shaft seal.

[0033] In one specific embodiment of the present invention, a connecting pipe is also included, one end of which is connected to the pump base and the other end is connected to the fluid guide shell.

[0034] In one specific embodiment of the present invention, the connecting pipe is composed of several sub-connecting pipes spliced ​​together, and different connecting pipes are connected by flanges. A water guide bearing bracket is installed between the flanges, and the intermediate water guide bearing is installed inside the water guide bearing bracket.

[0035] In one specific embodiment of the present invention, the sheath tube is supported by a water-conducting bearing bracket.

[0036] In one specific embodiment of the present invention, the gap between the intermediate water guide bearing and the intermediate bushing is 0.2 to 0.25 mm; the gap between the upper water guide bearing and the upper bushing is 0.2 to 0.25 mm; and the gap between the lower water guide bearing and the lower bushing is 0.2 to 0.25 mm.

[0037] In one specific embodiment of the present invention, the motor is fixed to the motor support by bolts, and the motor support is fastened to the pump base; the motor has an independent motor shaft and bearing system.

[0038] In one specific embodiment of the present invention, the upper impeller is pressed against the pump shaft shoulder by the pump shaft lower sleeve, the lower impeller, and the upper impeller locking nut, close to the upper guide fluid;

[0039] The lower impeller is fixed to the bottom of the pump shaft by the lower impeller locking nut, near the lower guide tube.

[0040] In one specific embodiment of the present invention, the pump shaft is designed with a stepped shoulder, and the impeller hub end face is in close contact with the shoulder to achieve precise axial positioning.

[0041] Compared with the prior art, the nuclear power plant drum filter backwashing pump of the present invention has the following beneficial effects:

[0042] (1) The motor and pump have independent shaft systems and thrust bearings, and each bears its own axial force. The motor bearing no longer bears the weight of the entire pump rotor, which solves the problems of high motor bearing temperature and abnormal noise.

[0043] (2) The cooling water system of the water-guided bearing has been optimized. The water supply for the shaft seal and the water supply for the water-guided bearing share the same external water supply pipeline. The cooling water is introduced from the water supply for the shaft seal, enters the shaft seal cooling packing upwards, and enters the protective sleeve downwards. The cooling water enters the water-guided bearing in sequence for cooling. The long and thin external bearing cooling water pipe is eliminated, which avoids the problem of bearing cooling water pipe breaking due to vibration.

[0044] (3) The pump shaft water guide bearing cooling water system adopts a unique closed design. To address the problem that the water supply from the protective sleeve cannot directly enter the pump shaft water guide bearing, a hole is opened in the center of the pump shaft. The cooling water flows into the pump shaft water guide bearing through this hole. The pump shaft water guide bearing is sealed at the top and bottom to prevent the cooling water from opening. At the same time, the lubricating water pressure of the pump shaft water guide bearing is guaranteed. This prevents seawater from entering the pump water guide bearing in reverse due to low cooling water pressure. In addition, the closed design prevents fresh water from flowing into seawater, thus saving precious fresh water resources.

[0045] After testing and verification, the backwash pump of this invention exhibits excellent vibration, only about 0.7-1.1 mm / s, which is far superior to the 3.5-5.5 mm / s vibration of existing backwash pumps; the packing seal leakage is small, reduced from the original 5-10 l / h to 1-2 l / h; the motor bearing temperature is normal and there is no abnormal noise; the reliability is greatly improved, and serious defects such as high vibration, shaft seal water pipe breakage, large packing leakage, severe wear of water guide bearing, and high motor bearing temperature no longer occur. Attached Figure Description

[0046] Figure 1A schematic diagram showing the structure of a backwash pump for a drum filter in a nuclear power plant;

[0047] Figure 2 A schematic diagram showing the structure of the backwash pump head section;

[0048] Figure 3 A schematic diagram showing the structure of the pump shaft section;

[0049] Figure 4 This is a magnified view of the externally injected water.

[0050] Figure 5 This is a magnified view of water being injected into the pump shaft.

[0051] Figure 6 This is a magnified view of the water being injected into the guide bearing.

[0052] Wherein: 1-Motor; 2-Bolt; 3-Motor support; 4-Upper coupling; 5-Pin; 6-Lower coupling; 7-Thrust bearing; 8-Bearing housing; 9-Stuffing gland; 10-Stuffing; 11-Gland bolt; 12-Stuffing box; 13-External water injection pipe; 14-Pump base; 15-Sheath pipe; 16-Upper shaft; 17-Connecting pipe; 18-Key; 19-Shaft sleeve; 20-Compression coupling; 21-Fastening screw; 22-Bracket flange Bolt; 23-Water guide bearing bracket; 24-Intermediate water guide bearing; 25-Intermediate shaft; 26-Upper shaft sleeve; 27-Flange; 28-Horizontal injection hole; 29-Pump shaft; 30-Center hole; 31-Upper water guide bearing; 32-Skeleton oil seal; 33-Upper guide fluid; 34-Upper impeller; 35-Horizontal discharge hole; 36-Lower shaft sleeve; 37-Lower impeller; 38-Lower water guide bearing; 39-Lower guide fluid; 40-Pump suction inlet; 41-Inlet filter screen. Detailed Implementation

[0053] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0054] An embodiment of the present invention discloses a backwashing pump for a drum filter in a nuclear power plant, such as... Figures 1-6 As shown, it includes:

[0055] Motor 1 is fixed to motor support 3 by bolts 2; motor 1 has an independent motor shaft and bearing system.

[0056] The motor support 3 is fastened to the pump base 14;

[0057] The pump rotor system is connected to the motor rotor via a flexible pin coupling, which includes an upper coupling 4 and a lower coupling 6, and the upper coupling 4 and the lower coupling 6 are connected by a pin 5.

[0058] The pump rotor system includes a shaft, an upper impeller 34, and a lower impeller 37;

[0059] The shaft includes an upper shaft 16, an intermediate shaft 25, and a pump shaft 29 connected sequentially from top to bottom. The different shafts are specifically connected by a ferrule coupling 20, which consists of two half-half rings and is fixed to the shaft by a bushing 19, a key 18, and a fastening screw 21.

[0060] The upper impeller 34 is pressed against the shoulder of the pump shaft 29 by the lower shaft sleeve 36, the lower impeller 37, and the lower impeller locking nut, near the upper guide fluid 33.

[0061] The lower impeller 37 is fixed to the bottom of the pump shaft 29 by the lower impeller locking nut, near the lower guide fluid 39.

[0062] The pump shaft 29 is designed with a stepped shoulder, and the impeller hub end face is in close contact with the shoulder to achieve precise axial positioning.

[0063] A stuffing box 12 is fitted in the middle of the upper shaft 16. The stuffing box 12 and the upper shaft 16 are filled with packing 10. The packing 10 is pressed by the packing gland 9 to achieve shaft sealing. The packing gland 9 is pressed by the gland bolts 11, and the degree of pressing is adjustable.

[0064] The external water injection pipe 13 is connected to the sheath pipe 15 through the inside of the stuffing box 12, and the stuffing box 12 is equipped with a cooling packing.

[0065] Clean water enters through the external injection pipe 13, then flows upward into the cooling packing to cool the packing 10; it then flows downward into the sheath pipe 15, and then reaches the intermediate water guide bearing 24 and the upper water guide bearing 31 to lubricate and cool each water guide bearing.

[0066] The top of the pump shaft 29 is provided with a radial horizontal injection hole 28;

[0067] The pump shaft 29 is drilled with a central hole 30 that runs through the entire length along the axial direction;

[0068] The bottom of the pump shaft 29 is provided with a radial horizontal discharge hole 35;

[0069] After the clean water reaches the pump shaft 29, it enters the drain guide bearing 38 through the horizontal injection hole 28, the pump shaft center hole 30 and the horizontal discharge hole 35.

[0070] The connecting pipe 17 is composed of several sub-connecting pipes spliced ​​together. One end of the connecting pipe 17 is connected to the pump base 14, and the other end is connected to the outer shell of the fluid guide 33; specifically, it includes 6 to 10 sub-connecting pipes.

[0071] Different sub-connecting pipes are welded to flange 27 respectively, and water guide bearing brackets 23 are installed between flanges that are close to each other. The flanges are fastened together by bracket flange bolts 22.

[0072] The shaft and the intermediate water guide bearing 24 are fitted with a protective sleeve 15, which is supported by the water guide bearing bracket 23.

[0073] The upper part of the sheath tube 15 extends to the lower end of the stuffing box 12, and the lower part ends in the bearing hole seat inside the upper guide tube 33;

[0074] The sheath tube 15 isolates the clean cooling water from the seawater medium, ensuring that the water guide bearing is cooled and lubricated by clean cooling water, while the seawater medium is discharged along the channel between the sheath tube 15 and the connecting pipe 17.

[0075] The sheath tube 15 is composed of several sub-tubes connected together. Preferably, there are 6 to 10 sub-tubes.

[0076] The upper guide fluid 33 has a precision bearing seat hole machined inside, and the upper water guide bearing 31 is installed with an interference fit.

[0077] The lower part of the upper guide fluid 33 is connected to the lower guide fluid 39;

[0078] The lower guide tube 39 is connected to the pump suction port 40 and the inlet filter screen 41.

[0079] The thrust bearing 7 is located at the upper end of the upper shaft 16. The thrust bearing 7 is pressed into the bearing chamber 8 with an interference fit. The outer ring of the thrust bearing 7 is axially locked by the step and end cover of the bearing chamber 8.

[0080] The thrust bearings 7 are used in pairs to bear all axial loads; their radial force is borne by several intermediate water guide bearings 24, upper water guide bearings 31 and lower water guide bearings 38.

[0081] The bearing housing 8 houses the thrust bearing 7, provides lubrication for the workpiece, and serves as an intermediate carrier for the transmission of axial force.

[0082] The bearing housing 8 flange is fastened to the machined surface at the bottom of the motor support 3 by bolts;

[0083] The intermediate water guide bearing 24 is installed inside the water guide bearing bracket 23 and is sleeved on the intermediate shaft 25.

[0084] The upper water guide bearing 31 is sleeved on the upper end of the pump shaft 29 and forms a friction pair with the upper shaft sleeve 26. Before the outer ring of the bearing is pressed into the upper guide fluid 33, the inner ring is clearance-fitted with the upper shaft sleeve 26. The lower end is provided with a skeleton oil seal 32 to prevent cooling water leakage and seawater intrusion.

[0085] The lower water guide bearing 38 is sleeved on the lower end of the pump shaft 29 and cooperates with the lower shaft sleeve 36, close to the lower impeller 37; both the upper and lower ends of the lower water guide bearing 38 and the lower shaft sleeve 36 are provided with skeleton oil seals 32 for sealing to prevent the injection water from losing pressure and seawater from entering.

[0086] All three types of water-guided bearings mentioned above are made of high-molecular wear-resistant materials. The clearance between the water-guided bearing and the bushing is 0.2 to 0.25 mm, which enhances the rigidity of the water-guided bearing and reduces shaft vibration.

[0087] The water guide bearing is made of a high-molecular wear-resistant composite material, which is superior to Sailong bearings; the matrix of the high-molecular wear-resistant material is modified acrylic rubber as the matrix, with added reinforcing fiber aramid as the reinforcing agent, and graphite as the solid lubricant.

[0088] All flow-through components are made of 2205 duplex steel, ensuring high corrosion resistance in seawater media, superior to 316L steel. The backwash pump is a vertical long-shaft deep well pump. Its working principle is as follows: seawater enters the impeller after being filtered through the inlet filter screen. After being pressurized by two stages of impellers, it is transported to the pump outlet through the chamber between the connecting pipe and the sheath pipe, and then enters the nozzle to flush the debris from the drum filter screen. The backwash pump is designed with multiple shafts, each with a water-guided bearing. The water-guided bearings are supplied with clean water from an external source and adopt a unique closed-loop design, ensuring that the cooling and lubricating water of the water-guided bearings maintains pressure and preventing seawater impurities from entering, thus ensuring their normal function. Vertical long-shaft deep well pumps, due to their long shafts and significant oscillation, commonly suffer from wear caused by excessive vibration. Therefore, multi-stage water-guided bearings are required to support the pump rotor. However, seawater contains a large amount of silt and other impurities, which can easily enter the water-guided bearings, causing wear and affecting their function. This, in turn, leads to severe wear and cracking of the pump rotor due to excessive vibration. This design improvement employs a unique closed-loop design, ensuring that the cooling and lubricating water for the water-guided bearings maintains pressure while preventing seawater impurities from entering, thus guaranteeing their normal function.

[0089] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0090] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A backwashing pump for a drum-shaped filter screen in a nuclear power plant, characterized in that, include: The pump rotor system is connected to the motor rotor via a flexible pin coupling; The pump rotor system includes a shaft, an upper impeller, and a lower impeller; The shaft includes an upper shaft, an intermediate shaft, and a pump shaft connected sequentially from top to bottom; A shaft seal is installed in the middle of the upper shaft; The shaft and the intermediate water guide bearing are fitted with a protective sleeve. The upper part of the protective sleeve extends to the lower end of the shaft seal, and the lower part ends in the bearing hole seat inside the upper water guide. An external injection tube enters through the shaft seal and injects into the protective sleeve; The upper guide tube has a precision bearing seat hole machined inside, and the upper water guide bearing is installed with an interference fit. The lower part of the upper guide fluid is connected to the lower guide fluid; The lower part of the guide tube is connected to the pump inlet; The thrust bearing is located at the upper end of the upper shaft. The thrust bearing is press-fitted into the bearing housing with an interference fit. The outer ring of the thrust bearing is axially locked by the steps of the bearing housing and the end cover. The intermediate water guide bearing is sleeved on the intermediate shaft; The upper water guide bearing is sleeved on the upper end of the pump shaft and forms a friction pair with the upper shaft sleeve; before the outer ring of the bearing is pressed into the upper guide bearing, the inner ring is clearance-fitted with the upper shaft sleeve, and a skeleton oil seal is installed at the lower end; The lower guide bearing is sleeved on the lower end of the pump shaft and mates with the lower shaft sleeve; both the upper and lower ends of the lower guide bearing and the lower shaft sleeve are equipped with skeleton oil seals. A radial horizontal injection hole is provided at the top of the pump shaft; The pump shaft is drilled with a central hole that runs through its entire length along the axial direction. The bottom of the pump shaft is provided with a radial horizontal discharge hole; The clearance between the intermediate water guide bearing and the intermediate bushing is 0.2 to 0.25 mm; the clearance between the upper water guide bearing and the upper bushing is 0.2 to 0.25 mm; and the clearance between the lower water guide bearing and the lower bushing is 0.2 to 0.25 mm.

2. The nuclear power plant drum filter backwashing pump according to claim 1, characterized in that, The flexible pin coupling includes an upper coupling and a lower coupling, which are connected by a pin.

3. The nuclear power plant drum filter backwashing pump according to claim 1, characterized in that, The shaft seal includes a stuffing box, packing, and a packing gland; A stuffing box is fitted in the middle of the upper shaft. The stuffing box and the upper shaft are filled with packing. The packing is pressed together by a packing gland to achieve a shaft seal.

4. The nuclear power plant drum filter backwashing pump according to claim 1, characterized in that, It also includes a connecting pipe, one end of which is connected to the pump base and the other end is connected to the fluid guide shell.

5. The nuclear power plant drum filter backwashing pump according to claim 4, characterized in that, The connecting pipe is composed of several sub-connecting pipes spliced ​​together. Different connecting pipes are connected by flanges, and water guide bearing brackets are installed between the flanges. The intermediate water guide bearing is installed inside the water guide bearing bracket.

6. The nuclear power plant drum filter backwashing pump according to claim 5, characterized in that, The sheath tube is supported by a water-conducting bearing bracket.

7. The nuclear power plant drum filter backwashing pump according to claim 1, characterized in that, The motor is fixed to the motor support by bolts, and the motor support is fastened to the pump base; the motor has an independent motor shaft and bearing system.

8. The nuclear power plant drum filter backwashing pump according to claim 1, characterized in that, The upper impeller is pressed against the pump shaft shoulder by the pump shaft lower sleeve, the lower impeller, and the upper impeller locking nut, near the upper guide fluid; The lower impeller is fixed to the bottom of the pump shaft by the lower impeller locking nut, near the lower guide tube.

9. The nuclear power plant drum filter backwashing pump according to claim 8, characterized in that, The pump shaft is designed with a stepped shoulder, and the impeller hub end face is in close contact with the shoulder to achieve precise axial positioning.

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