Power plant feed water pump hydraulic screw seal control system

Abstract

The utility model relates to a kind of power plant feed water pump hydraulic screw seal control system belongs to water pump sealing control technical field.The utility model includes steam feed water pump, the first backwater pipeline is connected at the water outlet of the drive side hydraulic seal of the steam feed water pump, the second backwater pipeline is connected at the water outlet of the non-drive side hydraulic seal of the steam feed water pump, the first backwater pipeline and the second backwater pipeline are collectively gathered to backwater main pipeline, the backwater main pipeline one end is cleaning mouth, the other end is connected to the input end of multistage water seal ware, water seal ware backwater pipeline is led out from the output end of the multistage water seal ware to the input end of condenser, inlet main pipeline is led out from the output end of the condenser, the inlet main pipeline is branched into first sealing inlet pipeline and second sealing inlet pipeline in turn after passing through condensate pump, deaerator and filter.The utility model can timely and effectively prevent unnecessary unit non-stop from occurring;Can prevent the sudden rise or sudden drop of front pump outlet pressure.

Description

Technical Field

[0001] This invention belongs to the field of water pump sealing control technology, specifically relating to a hydraulic spiral sealing control system for power plant feedwater pumps. Background Technology

[0002] Currently, the main feedwater pumps in large-capacity (600MW and above) supercritical or ultra-supercritical power plants are mostly steam-driven, and their axial seals use a spiral shaft sleeve hydraulic seal (commonly known as a hydraulic seal). The sealing water for the hydraulic throttling shaft seal is condensate, with a pressure of 1.5–3.8 MPa. When the return water temperature exceeds 90℃, the main feedwater pump will be interlocked and adjusted. To ensure the safety of the feedwater pump's hydraulic seal, the sealing pump uses variable frequency speed regulation. However, to maintain a high sealing water pressure and thus ensure normal sealing water pressure and return water temperature, the sealing pump will operate at a high frequency for a long time, making deep frequency conversion impossible. Therefore, the power consumption of the sealing pump is relatively high.

[0003] In addition, the hydraulic spiral seal at the shaft end of the main feedwater pump in a thermal power plant or supercritical or ultra-supercritical unit is achieved by injecting condensate at a pressure higher than that inside the sealing chamber. This prevents the medium inside the main feedwater pump from leaking out through the shaft seal. To reduce working fluid loss, the condensate is recycled. To minimize the impact on the main unit vacuum and improve operational flexibility, the feedwater pump seal water return is not directly connected to the condenser, but is discharged to the condenser for recovery after passing through the seal water recovery system. The general flow of the seal water for the steam-driven feedwater pump in a thermal power plant or power plant is as follows: condensate in the condenser is pressurized by a variable frequency condenser pump and enters the main feedwater pump seal water system. After being filtered to remove impurities, the seal water temperature regulating valve controls the flow of seal water into the feedwater pump spiral shaft sleeve seal cooling system based on the seal water return temperature. The seal water return is then recycled back to the condenser. The current main feedwater pump of the unit has two return water paths. One path is discharged to the high and low back drain expansion tank for recycling through a water seal device, while the other path is discharged directly to the ditch for unpressurized return water, resulting in a large amount of condensate waste and increased operating costs.

[0004] Furthermore, the condensate control logic is as follows: the main regulating valve for the deaerator water supply maintains the deaerator water level at a set value based on the deaerator water level, deaerator inlet flow rate, and feedwater volume using a three-impulse adjustment. The condensate pump regulates the condensate pressure using either industrial frequency or variable frequency, with this pressure setpoint being a function of the load. However, the currently used sealing water system and condensate control logic rely on a temperature sensor installed on the inlet pipe before the pump sealing bushing to provide the sealing water temperature. This signal is transmitted to the DCS (temperature indicator controller), which processes the received data and then sends an action signal to the positioner (electric or pneumatic actuator) to control the opening of the TCV (temperature regulating valve). This regulates the temperature of the sealing water entering the hydraulic sealing bushing, ensuring it reaches the preset temperature before entering the sealing cavity to achieve a sealing effect. If the condensate system malfunctions, the condensate pump outlet pressure will suddenly drop. The regulating valve controlling the sealing water pressure has a certain lag, and the sealing water temperature will suddenly rise. Because the TCV regulating valve controlling the sealing water temperature has a certain lag, the sealing water temperature will suddenly rise, exceeding the predetermined limit temperature and triggering an alarm, causing the main feedwater pump to trip and stop, resulting in unnecessary unit shutdowns. Summary of the Invention

[0005] This invention addresses the aforementioned problems and overcomes the shortcomings of existing technologies by providing a hydraulic spiral seal control system for power plant feedwater pumps. This invention can effectively prevent unnecessary unit outages; the seal return water can be completely and effectively recycled with no external discharge, ensuring a clean and environmentally friendly production environment; it can prevent sudden increases or decreases in the outlet pressure of the booster pump, ensuring the safe operation and full life cycle of the main feedwater pump.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] This invention provides a hydraulic spiral seal control system for a power plant feedwater pump, characterized in that it includes a steam-driven feedwater pump. A first return water pipeline is connected to the hydraulic seal outlet on the drive side of the steam-driven feedwater pump, and a second return water pipeline is connected to the hydraulic seal outlet on the non-drive side of the steam-driven feedwater pump. The first and second return water pipelines converge into a return water header. One end of the return water header is a cleaning port, and the other end is connected to the input end of a multi-stage water seal device. A return water pipe is led out from the output end of the multi-stage water seal device. The water pipeline leads to the input end of the condenser, and a main inlet water pipeline is led out from the output end of the condenser. This main inlet water pipeline passes sequentially through the condensate pump, deaerator, and filter before branching into a first sealed inlet water pipeline and a second sealed inlet water pipeline. The first sealed inlet water pipeline is connected to the hydraulically sealed inlet on the drive side of the steam-driven feedwater pump, and the second sealed inlet water pipeline is connected to the hydraulically sealed inlet on the non-drive side of the steam-driven feedwater pump. A first differential pressure control valve is installed on both the first and second sealed inlet water pipelines. The system includes a first differential pressure control valve, a second differential pressure control valve, a first shut-off valve, and a second air inlet. A first sealing flushing differential pressure measuring pipeline branches off from the first sealing water inlet pipeline and connects to the inlet of the pre-pump. A second sealing flushing differential pressure measuring pipeline also branches off from the second sealing water inlet pipeline and connects to the inlet of the pre-pump. A first differential pressure transmitter is installed on the first sealing flushing differential pressure measuring pipeline, and a second differential pressure transmitter is installed on the second sealing flushing differential pressure measuring pipeline. A pressure transmitter is installed at the outlet of the pre-pump. A first temperature sensor is installed on the first return water pipeline, and a second temperature sensor is installed on the second return water pipeline. The first differential pressure transmitter, the second differential pressure transmitter, the pressure transmitter, the first temperature sensor, and the second temperature sensor are all connected to the central control room.

[0008] Furthermore, a gate valve is installed on the return water main pipe, a gate valve is installed on the water seal return water pipe, a gate valve is installed at the front end of the condensate pump on the inlet water main pipe, gate valves are installed at both the front and rear ends of the filter, gate valves are installed at both the front and rear ends of the first sealed inlet water pipe and the second sealed inlet water pipe and the second differential pressure control valve.

[0009] Furthermore, the filter and the gate valves at the front and rear ends of the filter are connected in parallel with a bypass, and a gate valve is provided on the bypass.

[0010] Furthermore, the gates at the front and rear ends of the first differential pressure control valve...

[0011] The valves are connected in parallel to a first backup pipeline, and a gate valve is also installed on the first backup pipeline.

[0012] Furthermore, the gates at the front and rear ends of the second differential pressure control valve...

[0013] The valves are connected in parallel with a second backup pipeline, which is also equipped with a gate valve.

[0014] Furthermore, the first return water pipeline is divided into four first return water branch pipelines, which are respectively connected to the hydraulic seal outlet of the drive side of the steam-driven water pump.

[0015] Furthermore, the second return water pipeline is divided into three second return water branch pipelines, which are respectively connected to the non-drive side hydraulic seal outlet of the steam-driven feed water pump.

[0016] Furthermore, a drainage pipe is provided on the return water main pipe, and a gate valve is provided on the drainage pipe.

[0017] Furthermore, a water injection pipeline is provided on the return water main pipeline, and a gate valve is provided on the water injection pipeline.

[0018] Furthermore, a water seal return water discharge pipe is provided on the water seal return water pipe, and a gate valve is provided on the water seal return water discharge pipe.

[0019] The beneficial effects of the present invention.

[0020] This invention features a novel steam-driven feedwater pump return system that controls the sealing water intake via differential pressure and temperature control. When the condensate pump pressure is not adjusted promptly, causing a sudden increase in sealing water temperature, the system can effectively and promptly interlock to trip and shut down the steam-driven feedwater pump, preventing unnecessary unit outages and demonstrating good stability and anti-interference capabilities. It can also adjust the condensate pump speed via frequency conversion interlock, reducing condensate pump energy consumption. Furthermore, the system can completely and effectively recover the sealing return water, preventing uncontrolled direct discharge and ensuring a clean and environmentally friendly production environment. Interlock control of the pre-pump outlet pressure prevents sudden increases or decreases in pressure, ensuring the safe operation and long lifespan of the main feedwater pump. Attached Figure Description

[0021] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be 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 merely illustrative of the invention and are not intended to limit the invention.

[0022] Figure 1This is a schematic diagram of the overall structure of the present invention.

[0023] In the diagram, the markings are as follows: 1 is the steam-driven feedwater pump, 2 is the first return water pipeline, 3 is the second return water pipeline, 4 is the return water main pipeline, 5 is the cleaning port, 6 is the multi-stage water seal, 7 is the water seal return water pipeline, 8 is the condenser, 9 is the inlet water main pipeline, 10 is the condensate pump, 11 is the deaerator, 12 is the filter, 13 is the first sealed inlet water pipeline, 14 is the second sealed inlet water pipeline, 15 is the first differential pressure control valve, 16 is the second differential pressure control valve, 17 is the first shut-off valve, 18 is the first air inlet, 19 is the second shut-off valve, and 20 is the second air inlet. 21 is the first sealing flush differential pressure measuring pipeline, 22 is the second sealing flush differential pressure measuring pipeline, 23 is the first differential pressure transmitter, 24 is the second differential pressure transmitter, 25 is the pre-pump, 26 is the pressure transmitter, 27 is the first temperature sensor, 28 is the second temperature sensor, 29 is the gate valve, 30 is the bypass, 31 is the first backup pipeline, 32 is the second backup pipeline, 33 is the first return water branch pipeline, 34 is the second return water branch pipeline, 35 is the drainage pipeline, 36 is the water injection pipeline, and 37 is the water seal device return water discharge pipeline. Detailed Implementation

[0024] As shown in the accompanying drawings, this embodiment provides a hydraulic spiral seal control system for a power plant feedwater pump, including a steam-driven feedwater pump 1. A first return water pipeline 2 is connected to the hydraulic seal outlet on the drive side of the steam-driven feedwater pump 1. The first return water pipeline 2 is divided into four first return water branch pipelines 33, which are respectively connected to the hydraulic seal outlet on the drive side of the steam-driven feedwater pump 1.

[0025] A second return water pipeline 3 is connected to the non-drive side hydraulic seal outlet of the steam-driven feedwater pump 1. The second return water pipeline 3 is divided into three second return water branch pipelines 34, which are respectively connected to the non-drive side hydraulic seal outlet of the steam-driven feedwater pump 1.

[0026] The first return water pipe 2 and the second return water pipe 3 converge into the return water main pipe 4. One end of the return water main pipe 4 is the cleaning port 5, and the other end is connected to the input end of the multi-stage water seal device 6.

[0027] A gate valve 29 is installed on the return water main pipe 4 to control the opening and closing of the entire return water main pipe 4.

[0028] A drainage pipe 35 is installed on the return water main pipe 4, and a gate valve 29 is installed on the drainage pipe 35. In order to facilitate the isolation and discharge of maintenance drainage in case of an accident of the multi-stage water seal device 6, the drainage pipe 35 is directly connected to the pit.

[0029] A water injection pipe 36 is installed on the return water main pipe 4, and a gate valve 29 is installed on the water injection pipe 36. Before the multi-stage water seal 6 is started for the first time, the water injection pipe 36 needs to be opened through the gate valve 29 to fill the multi-stage water seal 6 with water. The injection of desuperheating water is to prevent the return water from vaporizing on the one hand, and to start the water injection water seal on the other hand, to ensure that the unit vacuum is established.

[0030] Multistage water sealers 6 are commonly used in sealing control systems. The multistage water sealer 6 is positioned below the shaft end sealing water drain of the steam-driven feedwater pump 1, and is generally located on the 0m floor of the turbine hall. The elevation of the output port of the multistage water sealer 6 should be above the highest water level of the hot well of the condenser 8.

[0031] A water seal return water pipeline 7 is led out from the output end of the multi-stage water seal 6 to the input end of the condenser 8. A gate valve 29 is installed on the water seal return water pipeline 7. A water seal return water discharge pipeline 37 is installed on the water seal return water pipeline 7. A gate valve 29 is installed on the water seal return water discharge pipeline 37.

[0032] A main water inlet pipe 9 is led out from the output end of the condenser 8. After passing through the condensate pump 10, the deaerator 11 and the filter 12 in sequence, the main water inlet pipe 9 branches into a first sealed water inlet pipe 13 and a second sealed water inlet pipe 14.

[0033] A gate valve 29 is installed at the front end of the condensate pump 10 in the inlet main pipe 9. Gate valves 29 are installed at both the front and rear ends of the filter 12. A bypass 30 is connected in parallel with the gate valves 29 at the front and rear ends of the filter 12. A gate valve 29 is installed on the bypass 30.

[0034] The first sealed water inlet pipe 13 is connected to the hydraulic sealed water inlet on the drive side of the steam-driven feedwater pump 1. A first differential pressure control valve 15 is installed on the first sealed water inlet pipe 13. The first differential pressure control valve 15 is connected to the first shut-off valve 17 through a pipe and then to the first air inlet 18. Gate valves 29 are installed at both ends of the first differential pressure control valve 15 on the first sealed water inlet pipe 13. The first differential pressure control valve 15 and the gate valves 29 at both ends of the first differential pressure control valve 15 are connected in parallel to a first backup pipe 31. The first backup pipe 31 is used to prevent the first differential pressure control valve 15 from opening in case of failure. A gate valve 29 is also installed on the first backup pipe 31.

[0035] The second sealed water inlet pipe 14 is connected to the non-drive side hydraulic seal water inlet of the steam-driven feedwater pump 1. A second differential pressure control valve 16 is installed on the second sealed water inlet pipe 14. The second differential pressure control valve 16 is connected to the second shut-off valve 19 through a pipe and then to the second air inlet 20. Gate valves 29 are installed at both ends of the second differential pressure control valve 16 on the second sealed water inlet pipe 14. The second differential pressure control valve 16 and the gate valves 29 at both ends of the second differential pressure control valve 16 are connected in parallel to a second backup pipe 32. The second backup pipe 32 is used to prevent the second differential pressure control valve 16 from opening in case of failure. A gate valve 29 is also installed on the second backup pipe 32.

[0036] A first sealing flushing differential pressure measuring pipeline 21 branches off from the first sealing water inlet pipeline 13, which can unload excess sealing flushing water. The first sealing flushing differential pressure measuring pipeline 21 is connected to the pump inlet of the pre-pump 25, and a first differential pressure transmitter 23 is installed on the first sealing flushing differential pressure measuring pipeline 21.

[0037] A second sealing flushing differential pressure measuring pipeline 22 branches off from the second sealing water inlet pipeline 14, which can unload excess sealing flushing water. The second sealing flushing differential pressure measuring pipeline 22 is also connected to the pump inlet of the pre-pump 25, and a second differential pressure transmitter 24 is installed on the second sealing flushing differential pressure measuring pipeline 22.

[0038] The pump outlet of the pre-pump 25 is equipped with a pressure transmitter 26, which can convert the pressure into an electric signal for control and remote transmission.

[0039] A first temperature sensor 27 is installed on the first return water pipe 2, and a second temperature sensor 28 is installed on the second return water pipe 3, for detecting the temperature signal of the sealing water supplied.

[0040] The first differential pressure transmitter 23, the second differential pressure transmitter 24, the pressure transmitter 26, the first temperature sensor 27, and the second temperature sensor 28 are all connected to the central control room, and the signals are centrally processed through the central control room.

[0041] The following describes the logic control principle of this invention:

[0042] The first temperature sensor 27 and the second temperature sensor 28 detect and provide sealing water temperature signals, which are transmitted to the central control room. The central control room processes the received temperature data and then sends activation signals to the first differential pressure control valve 15 on the first sealing water inlet pipe 13 and the second differential pressure control valve 16 on the second sealing water inlet pipe 14. At the same time, it sends activation signals to the first differential pressure transmitter 23 and the second differential pressure transmitter 24. Based on the change signal of the differential pressure value of the first differential pressure transmitter 23 and the second differential pressure transmitter 24, the flow rate of the condensate pump 10 is controlled by frequency conversion, and the valve opening of the pneumatic first differential pressure control valve 15 and the second differential pressure control valve 16 is controlled. This is to regulate the flow rate and pressure of the sealing water entering the hydraulic seal of the steam-driven feedwater pump 1, so as to ensure that the return water temperature on the drive side and the non-drive side of the steam-driven feedwater pump 1 reaches the preset value.

[0043] When the return water temperature signals transmitted by the first temperature sensor 27 and the second temperature sensor 24 are both <65℃, the differential pressure values ​​of the first differential pressure transmitter 23 and the second differential pressure transmitter 24 are increased, the valve openings of the first differential pressure control valve 15 and the second differential pressure control valve 16 are adjusted, the speed of the variable frequency condensate pump 10 is increased, and the flow rate of the sealed inlet water is increased. When the return water temperature signals transmitted by the first temperature sensor 27 and the second temperature sensor 24 are both ≥65℃, the differential pressure values ​​of the first differential pressure transmitter 23 and the second differential pressure transmitter 24 are decreased, the valve openings of the first differential pressure control valve 15 and the second differential pressure control valve 16 are adjusted, the speed of the variable frequency condensate pump 10 is decreased, and the flow rate of the sealed inlet water is reduced. When the return water temperature signals transmitted by the first temperature sensor 27 and the second temperature sensor 24 are both ≥80℃, the system alarms.

[0044] Furthermore, the sealing water temperature is used as the trip protection setting for the steam-driven feedwater pump 1. The protection setting is as follows: when the return water temperature signal transmitted by the first temperature sensor 27 is ≥65℃, the steam-driven feedwater pump 1 is controlled to alarm; when the return water temperature signal transmitted by the first temperature sensor 27 is ≥80℃, the steam-driven feedwater pump 1 is controlled to trip.

[0045] The sealing water for the steam-driven feedwater pump 1 is drawn from the condensate in the condenser 8. After being filtered through the filter screen of filter 12, the inlet water flow is controlled by the first differential pressure control valve 15 and the second differential pressure control valve 16 and supplied to the hydraulic shaft seal. The sealing condensate is returned to the inlet of the booster pump 25. The pressure transmitter 26 installed at the inlet of the booster pump 25 can transmit the return water pressure value to the central control room.

[0046] During normal operation, a certain pressure and flow rate of sealing water is required to be injected between the hydraulic seal shaft sleeve and bushing inside the steam-driven feedwater pump 1. Part of the flow flows into the steam-driven feedwater pump 1, and part of the unpressurized seal unloading return water leaks out and is collected through the first return water branch pipe 33 and the second return water branch pipe 34. After flowing through the return water main pipe 4, it enters the multi-stage water seal 6 and then enters the condenser 8. Another part flows into the inlet of the booster pump 25 after being controlled by the first differential pressure transmitter 23 and the second differential pressure transmitter 24.

[0047] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.

Claims

1. A hydraulic spiral seal control system for a power plant feedwater pump, characterized in that, The system includes a steam-driven feedwater pump (1), with a first return water pipeline (2) connected to the hydraulically sealed outlet on the drive side of the steam-driven feedwater pump (1) and a second return water pipeline (3) connected to the hydraulically sealed outlet on the non-drive side of the steam-driven feedwater pump (1). The first return water pipeline (2) and the second return water pipeline (3) converge into a return water header pipeline (4). One end of the return water header pipeline (4) is a cleaning port (5), and the other end is connected to the input end of a multi-stage water seal device (6). A water seal device return water pipeline (7) is led out from the output end of the multi-stage water seal device (6) to the input end of the condenser (8), and an inlet water header pipeline (9) is led out from the output end of the condenser (8). The main inlet pipe (9) passes through the condensate pump (10), deaerator (11), and filter (12) in sequence, and then branches into a first sealed inlet pipe (13) and a second sealed inlet pipe (14). The first sealed inlet pipe (13) is connected to the hydraulically sealed inlet on the drive side of the steam-driven feedwater pump (1), and the second sealed inlet pipe (14) is connected to the hydraulically sealed inlet on the non-drive side of the steam-driven feedwater pump (1). A first differential pressure control valve (15) and a second differential pressure control valve (16) are respectively installed on the first sealed inlet pipe (13) and the second sealed inlet pipe (14). The first differential pressure control valve (15) The first shut-off valve (17) is connected to the first air inlet (18) via a pipeline. The second differential pressure control valve (16) is connected to the second shut-off valve (19) via a pipeline and then to the second air inlet (20). A first sealing flush differential pressure measuring pipeline (21) branches off from the first sealing water inlet pipeline (13) and is connected to the pump inlet of the pre-pump (25). A second sealing flush differential pressure measuring pipeline (22) branches off from the second sealing water inlet pipeline (14) and is also connected to the pump inlet of the pre-pump (25). A first differential pressure transmitter (23) is installed on the sealing flush differential pressure measuring pipeline (21), a second differential pressure transmitter (24) is installed on the second sealing flush differential pressure measuring pipeline (22), a pressure transmitter (26) is installed at the pump outlet of the pre-pump (25), a first temperature sensor (27) is installed on the first return water pipeline (2), a second temperature sensor (28) is installed on the second return water pipeline (3), and the first differential pressure transmitter (23), the second differential pressure transmitter (24), the pressure transmitter (26), the first temperature sensor (27) and the second temperature sensor (28) are all connected to the central control room. A gate valve (29) is installed on the return water main pipe (4), a gate valve (29) is installed on the water seal return water pipe (7), a gate valve (29) is installed at the front end of the condensate pump (10) on the inlet water main pipe (9), gate valves (29) are installed at both the front and rear ends of the filter (12), a gate valve (29) is installed at both the front and rear ends of the first sealed water inlet pipe (13), and a gate valve (29) is installed at both the front and rear ends of the first differential pressure control valve (15) on the second sealed water inlet pipe (14). The first return water pipeline (2) is divided into four first return water branch pipelines (33), which are respectively connected to the hydraulic seal outlet of the drive side of the steam-driven water pump (1); The second return water pipeline (3) is divided into three second return water branch pipelines (34), which are respectively connected to the non-drive side hydraulic seal outlet of the steam-driven water pump (1).

2. The hydraulic spiral seal control system for a power plant feedwater pump according to claim 1, characterized in that, The filter (12) and the gate valves (29) at the front and rear ends of the filter (12) are connected in parallel with a bypass (30), and the bypass (30) is equipped with a gate valve (29).

3. The hydraulic spiral seal control system for a power plant feedwater pump according to claim 1, characterized in that, The first differential pressure control valve (15) and the gate valves (29) at the front and rear ends of the first differential pressure control valve (15) are connected in parallel to a first backup pipeline (31), and a gate valve (29) is also provided on the first backup pipeline (31).

4. The hydraulic spiral seal control system for a power plant feedwater pump according to claim 1, characterized in that, The second differential pressure control valve (16) and the gate valves (29) at the front and rear ends of the second differential pressure control valve (16) are connected in parallel to a second backup pipeline (32), and a gate valve (29) is also provided on the second backup pipeline (32).

5. A hydraulic spiral seal control system for a power plant feedwater pump according to claim 1, characterized in that, A drainage pipe (35) is installed on the return water main pipe (4), and a gate valve (29) is installed on the drainage pipe (35).

6. A hydraulic spiral seal control system for a power plant feedwater pump according to claim 1, characterized in that, A water injection pipeline (36) is provided on the return water main pipeline (4), and a gate valve (29) is provided on the water injection pipeline (36).

7. A hydraulic spiral seal control system for a power plant feedwater pump according to claim 1, characterized in that, The water seal return water pipeline (7) is provided with a water seal return water discharge pipeline (37), and a gate valve (29) is provided on the water seal return water discharge pipeline (37).

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