A front pump structure for a large boiler feed pump set

Abstract

A pre-pump structure for a large boiler feed water pump group belongs to the technical field of pre-pumps. The present invention includes a pump shaft and a pump body sleeved on the outside of the pump shaft, and is characterized in that the pump body is divided into a first sub-pump body and a second sub-pump body in the horizontal radial direction and fastened together, and the two sides of the pump body are respectively connected with a first pump cover and a second pump cover of the same structure, and the first pump cover and the second pump cover are respectively inserted into the two ends of the pump shaft, and the outside of the first pump cover is connected to a drive end bearing component, and the pump shaft passes through the bearing end bearing component and cooperates with the drive end bearing component, and the outside of the second pump cover is connected to a non-drive end bearing component, and the pump shaft extends into the non-drive end bearing component and cooperates with the non-drive end bearing component. The present invention can be interchangeable with existing pre-pumps that are widely used in power plants, and can solve the problems of high bearing temperature and impeller "gnawing on the shaft".

Description

Technical Field

[0001] The invention belongs to the technical field of pre-pumps, and in particular relates to a pre-pump structure for a large boiler feed water pump group. Background Art

[0002] In large-capacity subcritical, supercritical, or ultra-supercritical coal-fired power or nuclear power units (e.g., 1000MW, 1036MW, 1250MW, etc.), steam-driven or electric-driven boiler feedwater pumps require a pre-pump. This pre-pump is located at the front end of the boiler feedwater pump inlet and its function is to prevent cavitation in the boiler feedwater pump. It is typically driven by an electric motor.

[0003] During startup of large-capacity coal-fired or nuclear power units, conventional steam pumps are often preferred over electric pumps as the main feedwater pump. High-temperature, high-pressure steam is used to drive the steam turbine, which in turn drives the steam pump. This allows the steam pump to be fully activated during startup, eliminating the need for a motor (with a power rating of at least 10,000 kW) to drive the electric pump, saving significant plant electricity. However, since a fore-stage pump is used to fill the boiler, the steam pump outlet valve is fully closed, and water is supplied through the booster stage pipeline. Under these operating conditions, the flow rate through the fore-stage pump is far less than the rated operating flow rate required by normal steam pumps, and the flow rate range varies significantly (<30% of Q). This results in significant shaft strain on the fore-stage pump, placing a significant strain on the non-drive-end thrust bearing. During normal operation, the non-drive-end bearing temperature often reaches as high as 65-70°C, requiring external cooling by connecting a cooling water pipe to the bearing compartment, significantly complicating maintenance.

[0004] In the existing split-case pre-mounted pump, the impeller and shaft are fitted with a sliding fit, and the clearance is above 0.1 mm. Due to the large outer diameter and heavy weight of the double-suction impeller, when the operating conditions fluctuate or become unstable, the impeller is subjected to the combined impact of the axial and radial forces. Although the sleeve that locks the impeller has a locking washer and nut, it will loosen and back off soon after operation, causing the impeller to "gnaw on the shaft" or break.

[0005] The existing technology has a problem of leakage in the horizontal split surface of the split-center pre-pump. For example, during on-site maintenance of the SQ300-670 pre-pump used in power plants, the upper half of the pump cover was removed without the rotor in place, and the gap in the split surface was measured. It was found that the split surface of the upper pump cover was tight around the edges, but arched in the middle. This was mainly because the water temperature in the deaerator was already high when the pre-pump was filled with water. The hot water directly passed through the inlet valve of the pre-pump and reached the pre-pump. The pre-pump was subjected to thermal shock, and the temperature of the inner wall was higher than that of the outer wall, resulting in the metal expansion of the inner wall being blocked and plastic deformation. After the temperature of the outer wall rose, the permanent deformation of the arched middle occurred, resulting in the horizontal split-center surface not being a complete plane, causing the high-pressure asbestos pads on the joint surface to leak frequently.

[0006] In the prior art, the position of the pre-pump, the driving motor and the transmission end of the pre-pump cannot be changed or adjusted. When the position of the driving motor is adjusted by 180 degrees, the pre-pump needs to be replaced, which increases the cost.

[0007] In addition, the SQ300-670 pre-pump, which is widely used in power plants, has a horizontally split upper pump cover and lower pump body flow passage with poor manufacturing technology, and the suction flow passages on both sides are poorly symmetrical, which aggravates the stability of the rotor, resulting in high bearing temperature, rotor shaking and shaft stringing, and gradually developing into the impeller locking nut being stripped and loose, and the impeller "gnawing on the shaft" and other problems. Summary of the Invention

[0008] The present invention is aimed at the above-mentioned problems, makes up for the deficiencies of the existing technology, and provides a pre-pump structure for a large boiler feed water pump group; the present invention can be interchangeable with the existing pre-pumps widely used in power plants, and can solve the problems of high bearing temperature and impeller "gnawing" of the shaft.

[0009] To achieve the above objectives, the present invention adopts the following technical solutions.

[0010] The present invention provides a front pump structure for a large boiler feed water pump group, comprising a pump shaft and a pump body sleeved on the outside of the pump shaft, characterized in that the pump body is divided into a first sub-pump body and a second sub-pump body in the horizontal radial direction and buckled together, a first pump cover and a second pump cover of the same structure are connected to the two sides of the pump body respectively, the first pump cover and the second pump cover are respectively inserted into the two ends of the pump shaft, a driving end bearing component is connected to the outside of the first pump cover, the pump shaft passes through the bearing end bearing component and cooperates with the driving end bearing component, and a non-driving end bearing component is connected to the outside of the second pump cover. The pump shaft extends into the non-drive end bearing component and cooperates with the non-drive end bearing component. A cold carrier coil is provided in the non-drive end bearing component. The non-drive end bearing component is provided with a carrier inlet interface connected to the cold carrier coil inlet and a carrier outlet interface connected to the cold carrier coil outlet. The pump shaft is connected to an impeller, and the impeller is located in the middle of the pump body. Locking sleeves are connected and fixed on both sides of the impeller on the pump shaft, and the outer circle of the locking sleeve is provided with an annular labyrinth groove. The pump inlet and pump outlet are horizontally provided on both sides below the center line of the pump body.

[0011] Furthermore, the first pump cover and the second pump cover are both connected to an annular support, the first pump cover is connected to the driving end bearing component through its annular support, and the second pump cover is connected to the non-driving end bearing component through its annular support, and two windows are relatively opened on the annular support.

[0012] Furthermore, the first pump cover and the second pump cover are both provided with a suction channel, the suction channel is annular and connected to the inlet of the impeller, a partition tongue is provided on the inner wall of the suction channel, the side section of the partition tongue is in the shape of a "mountain", and the inner wall of the suction channel is provided with two diversion baffles on the opposite side of the partition tongue, the side section of the diversion baffle is arc-shaped, and the two ends of the diversion baffle are circular.

[0013] Furthermore, a Q-shaped annular cavity is provided in each of the first pump cover and the second pump cover, an end plate is provided in the Q-shaped annular cavity, and the first pump cover and the second pump cover are connected and fixed to the corresponding end plates.

[0014] Furthermore, rectangular grooves are evenly distributed in an annular shape on the end of the locking sleeve, and the two locking sleeves are both threadedly connected to the pump shaft, and the threads of the two locking sleeves connected to the pump shaft have opposite rotation directions.

[0015] Furthermore, the locking sleeve is further provided with a screw hole, which can be connected to the pump shaft by a fixing screw passing through the screw hole, thereby further fixing the locking sleeve on the pump shaft.

[0016] Furthermore, the drive-end bearing component includes a drive-end bearing shell and a first sliding bearing, the first sliding bearing is connected to and fixed on the inner wall of the drive-end bearing shell, the pump shaft is cooperatively connected with the sliding bearing, and the sliding bearing can support the pump shaft, and the drive-end bearing shell is also provided with a water-cooling jacket.

[0017] Furthermore, the non-drive end bearing component includes a non-drive end bearing shell, a second sliding bearing, and a rolling bearing group. The second sliding bearing is connected and fixed to the inner wall of the non-drive end bearing shell. The pump shaft is connected to the second sliding bearing in a cooperative manner, and the second sliding bearing can support the pump shaft. The rolling bearing group is also fixed in the non-drive end bearing shell. The rolling bearing group is connected to the end of the pump shaft in a cooperative manner. A lubricating oil chamber is provided in the non-drive bearing shell, the cold carrier coil is provided in the lubricating oil chamber, and the carrier inlet interface and the carrier outlet interface are provided on the non-drive end bearing shell.

[0018] Furthermore, the pump body is provided with a flow channel, and the pump body is provided with a bend pipe and an exhaust valve at the highest point of the flow channel. A support is provided at the center position of the pump body, and the support is connected to a pump support fixing seat. A thermal expansion positioning guide block is provided at the lower part of the pump body, and a guide block seat is provided to cooperate with the thermal expansion positioning guide block.

[0019] Furthermore, axial seals are provided between the pump shaft and the first pump cover, and between the pump shaft and the second pump cover.

[0020] Beneficial effects of the present invention.

[0021] According to the present invention, when the driving motor is rotated 180° for installation, the installation position of the pump body does not change, so the positions of the pump inlet and the pump outlet do not change. There is no need to replace the entire pre-pump, which saves usage costs; the pump body is radially divided into upper and lower parts, and there is no leakage sealing surface when there is no left and right center division, which ensures the safe operation of the pre-pump and reduces maintenance costs and spare parts consumption; the heat exchange effect of the cold carrier coil is better than that of the water cooling jacket, and the structure of the cold carrier coil is more suitable for natural circulation cooling of lubricating oil; the annular labyrinth groove structure of the locking sleeve can not only increase the throttling effect, reduce axial leakage of the conveying medium, improve the hydraulic volumetric efficiency of the pump, and reduce the non-contact area between the throttling gaps, but also enable some solid particles in the liquid to enter the groove, reduce the risk of "shaft gnawing" due to blockage, and increase operation safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] Figure 1 It is a schematic diagram of the front cross-sectional structure of the present invention.

[0024] Figure 2 For the present invention Figure 1 Schematic diagram of the K-direction side view structure.

[0025] Figure 3 It is a schematic diagram of the front cross-sectional structure of the first pump cover (second pump cover) of the present invention.

[0026] Figure 4 For the present invention Figure 3 AA cross-sectional diagram of .

[0027] Figure 5 For the present invention Figure 3 BB cross-section diagram.

[0028] Figure 6 It is a schematic diagram of the front cross-sectional structure of the locking sleeve of the present invention.

[0029] Figure 7 It is a side structural schematic diagram of the locking sleeve of the present invention.

[0030] Markings in the figure: 1 is the pump shaft, 2 is the first sub-pump body, 3 is the second sub-pump body, 4 is the first pump cover, 5 is the second pump cover, 6 is the cold carrier coil, 7 is the carrier inlet interface, 8 is the carrier outlet interface, 9 is the impeller, 10 is the locking sleeve, 11 is the annular labyrinth groove, 12 is the pump inlet, 13 is the pump outlet, 14 is the annular support, 15 is the window, 16 is the suction flow channel, 17 is the partition tongue, 18 is the diversion partition, 19 is the Q-shaped annular cavity, 2 0 is the end plate, 21 is the rectangular groove, 22 is the screw hole, 23 is the drive end bearing shell, 24 is the first sliding bearing, 25 is the water cooling jacket, 26 is the non-drive end bearing shell, 27 is the second sliding bearing, 28 is the rolling bearing group, 29 is the lubricating oil chamber, 30 is the spit flow channel, 31 is the elbow, 32 is the exhaust valve, 33 is the support, 34 is the pump support fixing seat, 35 is the thermal expansion positioning guide block, 36 is the guide block seat, and 37 is the axial seal. DETAILED DESCRIPTION

[0031] As shown in the accompanying drawings, this embodiment provides a pre-pump structure for a large boiler feed water pump group, including a pump shaft 1 and a pump body sleeved on the outside of the pump shaft 1. The pump body is divided into a first sub-pump body 2 and a second sub-pump body 3 along the horizontal radial direction and connected together. Compared with the traditional structure, there is no leakage surface on the center dividing surface, so the operation is safer.

[0032] The two sides of the pump body are respectively connected to the first pump cover 4 and the second pump cover 5 with the same structure. The first pump cover 4 and the second pump cover 5 are respectively inserted into the two ends of the pump shaft 1. Axial seals 37 are provided between the pump shaft 1 and the first pump cover 4 and between the pump shaft 1 and the second pump cover 5.

[0033] The pump shaft 1 is connected to an impeller 9, which is located in the middle of the pump body. The impeller 9 is connected to the pump shaft 1 through a standard flat key.

[0034] The first pump cover 4 and the second pump cover 5 are both provided with a suction channel 16. The suction channel 16 is annular and connected to the inlet of the impeller 9. It is a flow section from the pump inlet 12 to the front of the impeller 9. Its function is to ensure that the liquid flow enters the impeller 9 evenly, reduce losses, and improve the efficiency and anti-cavitation performance of the pump. The suction channel 16 will affect the flow state of the liquid flow, thereby affecting the efficiency of the pump, especially the cavitation performance of the pump.

[0035] A baffle 17 is provided on the inner wall of the suction channel 16. Its side profile is shaped like a mountain. Two diverter baffles 18 are also provided on the inner wall of the suction channel 16, opposite the baffle 17. These baffles 18 have an arc-shaped side profile and rounded ends. These baffles 17 and 18 are part of the suction channel 16, and their shape can influence the flow distribution at the inlet of the pump impeller 9, thereby affecting the impeller's suction performance and the pump's external characteristics.

[0036] A Q-shaped annular cavity 19 is provided in each of the first pump cover 4 and the second pump cover 5 . An end plate 20 is provided in the Q-shaped annular cavity 19 . The first pump cover 4 and the second pump cover 5 are connected and fixed to their corresponding end plates 20 .

[0037] The first pump cover 4 and the second pump cover 5 are both connected to an annular support 3314 , and two windows 15 are formed on the annular support 3314 in opposite directions.

[0038] The first pump cover 4 is connected to the drive-end bearing component through its annular support 14. The drive-end bearing component includes a drive-end bearing shell 23 and a first sliding bearing 24. The first sliding bearing 24 is connected and fixed to the inner wall of the drive-end bearing shell 23. The pump shaft 1 is connected to the sliding bearing and can support the pump shaft 1. The drive-end bearing shell 23 is also provided with a water-cooling jacket 25. The pump shaft 1 passes through the drive-end bearing shell 23 of the bearing-end bearing component.

[0039] The second pump cover 5 is connected to the non-drive end bearing component via its annular support 14. The non-drive end bearing component includes a non-drive end bearing shell 26, a second sliding bearing 27, and a rolling bearing group 28. The second sliding bearing 27 is connected and fixed to the inner wall of the non-drive end bearing shell 26. The pump shaft 1 is cooperatively connected to the second sliding bearing 27 and can support the pump shaft 1. The rolling bearing group 28 is also fixed in the non-drive end bearing shell 26. The pump shaft 1 extends into the non-drive end bearing shell 26. The rolling bearing group 28 is cooperatively connected to the end of the pump shaft 1. A lubricating oil chamber 29 is provided in the non-drive end bearing shell. A cold carrier coil 6 is provided in the lubricating oil chamber 29. A carrier inlet interface 7 and a carrier outlet interface 8 are provided on the non-drive end bearing shell 26. The carrier inlet interface 7 is connected to the inlet of the cold carrier coil 6, and the carrier outlet interface 8 is connected to the outlet of the cold carrier coil 6.

[0040] The heat exchange effect of the cold carrier coil 6 is better than that of the traditional water cooling jacket, and the structure of the cold carrier coil 6 is more suitable for natural circulation cooling of the lubricating oil, which solves the problem of high bearing temperature, reduces maintenance workload and shutdown times, and improves operational reliability.

[0041] Locking sleeves 10 are attached and fixed to both sides of the impeller 9 on the pump shaft 1. Both locking sleeves 10 are threadedly connected to the pump shaft 1, and the threads of the two locking sleeves 10 connected to the pump shaft 1 are rotated in opposite directions. This ensures that the two locking sleeves 10 do not loosen when the pump shaft 1 rotates, otherwise they will easily loosen and fall off. Rectangular grooves 21 are evenly distributed around the ends of the locking sleeves 10 to facilitate installation and removal.

[0042] A screw hole 22 is also provided on the locking sleeve 10. After the locking sleeve 10 is threadedly connected, fine-tuning is performed to ensure that the outlet of the impeller 9 is consistent with the flow channel center of the pump body. The locking sleeve 10 is connected to the pump shaft 1 by passing the fixing screw through the screw hole 22 to further fix the locking sleeve 10 on the pump shaft 1 to further prevent the locking sleeve 10 from loosening.

[0043] The outer circle of the locking sleeve 10 is provided with an annular labyrinth groove 11. The functions of the labyrinth groove are: first, to increase the throttling effect, reduce axial leakage of the conveying medium, and improve the hydraulic volumetric efficiency of the pump; second, to reduce the non-contact area between the throttling gaps, and at the same time enable some solid particles in the liquid to enter the groove, reduce the risk of "gnawing the shaft" and increase the safety of operation.

[0044] The pump inlet 12 and pump outlet 13 are horizontally located on either side of the pump body's centerline. When the pump shaft 1 is rotated 180° for assembly, the drive-end and non-drive-end bearing components are rotated 180° for assembly, while the pump body, first pump cover 4, and second pump cover 5 remain in their positions. Therefore, if the driver needs to be rotated 180° for installation in special circumstances, the pump inlet 12 and pump outlet 13 remain unchanged, as the pump body's installation position remains unchanged. There's no need to completely replace the pre-pump; simply rotate the pump shaft 1 180°, and reassemble the drive-end and non-drive-end bearing components. This allows for interchangeable dimensions with the power plant's existing horizontally split-case pre-pumps, saving operational costs.

[0045] The pump body is provided with a discharge channel 30, and a bend pipe 31 and an exhaust valve 32 are provided at the highest point of the discharge channel 30. A support 33 is provided at the center of the pump body, and the support 33 is connected to a pump support fixing seat 34. A thermal expansion positioning guide block 35 is provided at the lower part of the pump body, and a guide block seat 36 is provided to cooperate with the thermal expansion positioning guide block 35.

[0046] It can be understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Ordinary technicians in this field should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the scope of protection of the present invention.

Claims

1. A pre-pump structure for a large boiler feed water pump group, comprising a pump shaft (1) and a pump body sleeved outside the pump shaft (1), characterized in that: The pump body is divided into a first sub-pump body (2) and a second sub-pump body (3) along the horizontal radial direction and buckled together. The two sides of the pump body are respectively connected with a first pump cover (4) and a second pump cover (5) of the same structure. The first pump cover (4) and the second pump cover (5) are respectively inserted into the two ends of the pump shaft (1). The outer side of the first pump cover (4) is connected with a drive end bearing component. The pump shaft (1) passes through the bearing end bearing component and matches the drive end bearing component. The outer side of the second pump cover (5) is connected with a non-drive end bearing component. The pump shaft (1) extends into the non-drive end bearing component and matches the non-drive end bearing component. The non-drive end bearing component is provided with a cold carrier coil (6), the non-drive end bearing component is provided with a carrier inlet interface (7) communicating with the inlet of the cold carrier coil (6) and a carrier outlet interface (8) communicating with the outlet of the cold carrier coil (6), the pump shaft (1) is connected with an impeller (9), the impeller (9) is located in the middle of the pump body, the pump shaft (1) is connected and fixed with locking sleeves (10) on both sides of the impeller (9), the outer circle of the locking sleeve (10) is provided with an annular labyrinth groove (11), and the pump inlet (12) and the pump outlet (13) are horizontally provided on both sides below the center line of the pump body; The drive-end bearing component comprises a drive-end bearing shell (23) and a first sliding bearing (24), wherein the first sliding bearing (24) is connected to and fixed on the inner wall of the drive-end bearing shell (23), the pump shaft (1) is cooperatively connected to the sliding bearing, and the sliding bearing is capable of supporting the pump shaft (1), and the drive-end bearing shell (23) is further provided with a water-cooling jacket (25); The non-drive end bearing component comprises a non-drive end bearing shell (26), a second sliding bearing (27), and a rolling bearing group (28). The second sliding bearing (27) is connected to and fixed on the inner wall of the non-drive end bearing shell (26). The pump shaft (1) is connected in cooperation with the second sliding bearing (27), and the second sliding bearing (27) can support the pump shaft (1). The rolling bearing group (28) is also fixed in the non-drive end bearing shell (26). The rolling bearing group (28) is connected in cooperation with the end of the pump shaft (1). A lubricating oil cavity (29) is provided in the non-drive end bearing shell (26). The cold carrier coil (6) is provided in the lubricating oil cavity (29). The carrier inlet interface (7) and the carrier outlet interface (8) are provided on the non-drive end bearing shell (26).

2. A front pump structure for a large boiler feed water pump group according to claim 1, characterized in that: The first pump cover (4) and the second pump cover (5) are both connected to an annular support (14), the first pump cover (4) is connected to the drive end bearing component through the annular support (14), and the second pump cover (5) is connected to the non-drive end bearing component through the annular support (14), and two windows (15) are provided on the annular support (14) in opposite directions.

3. A pre-pump structure for a large boiler feed water pump group according to claim 1, characterized in that: The first pump cover (4) and the second pump cover (5) are both provided with a suction channel (16), the suction channel (16) is annular and communicates with the inlet of the impeller (9), a partition tongue (17) is provided on the inner wall of the suction channel (16), the side section of the partition tongue (17) is in the shape of a "mountain", and the inner wall of the suction channel (16) is provided with two diversion baffles (18) on the opposite side of the partition tongue (17), the side section of the diversion baffle (18) is in the shape of an arc, and the two ends of the diversion baffle (18) are circular.

4. A front pump structure for a large boiler feed water pump group according to claim 1, characterized in that: A Q-shaped annular cavity (19) is provided in each of the first pump cover (4) and the second pump cover (5), an end plate (20) is provided in the Q-shaped annular cavity (19), and the first pump cover (4) and the second pump cover (5) are connected and fixed to the corresponding end plates (20).

5. The front pump structure for a large boiler feed water pump group according to claim 1, characterized in that: The ends of the locking sleeves (10) are evenly distributed with rectangular grooves (21) in an annular pattern. Both locking sleeves (10) are threadedly connected to the pump shaft (1), and the threads of the two locking sleeves (10) connected to the pump shaft (1) have opposite rotation directions.

6. A front pump structure for a large boiler feed water pump group according to claim 5, characterized in that: The locking sleeve (10) is further provided with a screw hole (22), which can be connected to the pump shaft (1) by passing a fixing screw through the screw hole (22), thereby further fixing the locking sleeve (10) on the pump shaft (1).

7. The pre-pump structure for a large boiler feed water pump group according to claim 1, characterized in that: The pump body is provided with a discharge channel (30), and a bend pipe (31) and an exhaust valve (32) are provided at the highest point of the discharge channel (30). A support (33) is provided at the center of the pump body, and the support (33) is connected to a pump support fixing seat (34). A thermal expansion positioning guide block (35) is provided at the lower part of the pump body, and a guide block seat (36) is provided to cooperate with the thermal expansion positioning guide block (35).

8. The front pump structure for a large boiler feed water pump group according to claim 1, characterized in that: Axial seals (37) are provided between the pump shaft (1) and the first pump cover (4), and between the pump shaft (1) and the second pump cover (5).

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