A feed water pump seal water automatic switching system and its working method

Abstract

An automatic switching system for the sealing water of a feed water pump and its working method disclosed by the present invention belong to the technical field of the safe operation of feed water pumps in power plants. It includes a first regulating valve, a second regulating valve, a discharge pneumatic valve, a water injection pneumatic valve, an air exhaust pneumatic valve, an electric valve, a pressure transmitter, a liquid level detector, a sealing water inlet header pipe and a sealing water return header pipe. The structure of the present invention is simple, reasonably designed and has a high degree of automation. It can monitor the working condition of the sealing water during the start-up, operation and shutdown stages of the feed water pump, and automatically adjust the sealing water discharge method, which not only ensures the safe and reliable operation of the feed water pump, but also avoids the occurrence of vacuum leakage, water in oil and oil in water in the unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of the safe operation of feed pumps in power plants, and particularly relates to a feed pump seal water automatic switching system and its working method. Background Art

[0002] The feed pump is one of the main auxiliary machines in a power plant, and its working reliability is an important factor in ensuring the safe and stable operation of the unit. At present, most of the high-parameter and large-capacity feed pump sets used in 1000MW and 600MW units are labyrinth seals. Its main working principle is to use the method of controlling leakage through gaps to achieve the sealing function. This sealing form is provided with externally supplied seal water. After entering the seal body, it is divided into two paths. One path is the pressurized return water, which flows into the inlet of the booster pump after converging with the high-temperature leaked feed water in the pump. The other path is the non-pressurized return water, which flows out of the pump and enters the condenser after being recovered through a multi-stage water seal.

[0003] After long-term operation practice of this system, the following problems are found: When the unit load changes or the vacuum fluctuates, it is easy to cause vacuum leakage in the multi-stage water seal, forming a high negative pressure in the labyrinth seal chamber, sucking the lubricating oil in the adjacent bearing chamber, causing oil to enter the condenser and polluting the water quality; during the start-up and shutdown processes of the feed pump, a large amount of feed water and seal water flow to the non-pressurized return water, which is likely to cause poor return water in the multi-stage water seal, water gushing out from the shaft end of the feed pump, and even water in the oil in the bearing chamber. Summary of the Invention

[0004] In order to solve the above-mentioned existing problems, the purpose of the present invention is to provide a feed pump seal water automatic switching system and its working method, which has a simple structure, reasonable design, and high degree of automation. It can monitor the working condition of the seal water during the start-up, operation, and shutdown stages of the feed pump, and automatically adjust the seal water discharge method, ensuring both the safe and reliable operation of the feed pump and avoiding the occurrence of vacuum leakage, water in oil, and oil in water in the unit.

[0005] The present invention is realized through the following technical solutions:

[0006] A feed pump seal water automatic switching system disclosed by the present invention includes a first regulating valve, a second regulating valve, a discharge pneumatic valve, a water injection pneumatic valve, an air exhaust pneumatic valve, an electric valve, a pressure transmitter, a liquid level detector, a seal water inlet header pipe, and a seal water return header pipe;

[0007] The sealed water inlet header pipe is connected with three branch pipes. The first branch pipe is successively connected with a first regulating valve and a labyrinth seal at the driving end and then accesses the sealed water return header pipe. The second branch pipe is successively connected with a second regulating valve and a labyrinth seal at the non-driving end and then accesses the sealed water return header pipe. The third branch pipe is connected to the water injection port of the multi-stage water seal through a water injection pneumatic valve. The sealed water return header pipe is connected to the inlet of the multi-stage water seal, and a pressure transmitter is arranged on the sealed water return header pipe. An exhaust pipe is arranged on the sealed water return header pipe, and the exhaust pipe is connected to the condenser trench, and a discharge pneumatic valve is arranged on the exhaust pipe. The outlet of the multi-stage water seal is connected to the condenser through an electric valve. The drain port of the multi-stage water seal is connected to the condenser trench through a drain pipe, and an exhaust pneumatic valve and a liquid level detector are arranged on the drain pipe.

[0008] Preferably, a filtering device is arranged at the inlet end of the sealed water inlet header pipe.

[0009] Preferably, a first check valve is arranged between the first regulating valve and the labyrinth seal at the driving end on the first branch pipe.

[0010] Preferably, a first stop valve is arranged between the labyrinth seal at the driving end and the sealed water return header pipe on the first branch pipe.

[0011] Preferably, a second check valve is arranged between the second regulating valve and the labyrinth seal at the non-driving end on the second branch pipe.

[0012] Preferably, a second stop valve is arranged between the labyrinth seal at the non-driving end and the sealed water return header pipe on the second branch pipe.

[0013] The working method of the above-mentioned automatic switching system for the sealed water of the feed water pump disclosed by the present invention includes

[0014] When the feed water pump is normally started, stopped and operated, the condensate water is respectively throttled by the first regulating valve on the first branch pipe and enters the labyrinth seal at the driving end, and throttled by the second regulating valve on the second branch pipe and enters the labyrinth seal at the non-driving end for sealing. The return water is collected into the sealed water return header pipe, and after passing through the multi-stage water seal, it is discharged into the condenser through an electric valve.

[0015] Set the threshold value of the sealed water return pressure, and monitor the sealed water return pressure in real time through a pressure transmitter. When the sealed water return pressure is greater than the threshold value of the sealed water return pressure, it is switched to the high sealed water return pressure mode. In this mode, the discharge pneumatic valve is automatically opened, and the sealed water return is shunted to the condenser trench. When the sealed water return pressure is less than the threshold value of the sealed water return pressure, it is switched to the low sealed water return pressure mode. This mode includes the following steps:

[0016] S1: Open the discharge pneumatic valve and close the electric valve to switch the sealed water return to the condenser trench without affecting the normal operation of the generator set.

[0017] S2: Open the water injection pneumatic valve and the air exhaust pneumatic valve to re-inject water into the multi-stage water seal.

[0018] S3: After detecting that the liquid level detector is triggered, close the water injection pneumatic valve and the air exhaust pneumatic valve, and the water injection of the multi-stage water seal is completed.

[0019] S4: Open the electric valve and close the discharge pneumatic valve to put the multi-stage water seal back into operation.

[0020] Preferably, the threshold value of the return water pressure of the sealing water is determined by the following method:

[0021] Collect the return water pressure of the sealing water during the full cycle of the start-up, operation and stop of the feed water pump, and calculate the average pressure P0; set a dead zone N1, and let P min = P0 - N1, set a dead zone N2, and let P max = P0 + N2; when the return water pressure P of the sealing water is greater than P max , trigger the high mode of the return water pressure of the sealing water; when the return water pressure P of the sealing water is less than P min , trigger the low mode of the return water pressure of the sealing water.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] An automatic switching system for the sealing water of a feed water pump disclosed by the present invention can monitor the working condition of the sealing water during the start-up, operation and shutdown stages of the feed water pump by setting a pressure transmitter on the return water main pipe of the sealing water; through a liquid level detector, it can measure whether there is water inside the drain pipe, so as to determine whether the multi-stage water seal has been filled with water; through various valves, the system can automatically adjust the discharge mode of the sealing water, which not only ensures the safe and reliable operation of the feed water pump, but also avoids the occurrence of vacuum leakage, water in oil and oil in water in the unit. The structure of the present invention is simple and has strong applicability. It can be used for both new units and the transformation of existing units. It can monitor the working condition of the return water of the sealing water during the full cycle operation stage of the feed water pump, and the automatic return water method can achieve the purpose of ensuring the safe operation of the feed water pump and avoiding the pollution of the water system of the unit.

[0024] Furthermore, a filtering device is provided at the inlet end of the inlet main pipe of the sealing water, which can filter the sealing water to prevent impurities from entering the system.

[0025] Furthermore, a first check valve is provided between the first regulating valve and the driving end labyrinth seal on the first branch, and a second check valve is provided between the second regulating valve and the non-driving end labyrinth seal on the second branch, which can prevent backflow.

[0026] Further, a first stop valve is provided between the driving end labyrinth seal on the first branch and the seal water return main pipe, and a second stop valve is provided between the non-driving end labyrinth seal on the second branch and the seal water return main pipe, which can isolate the labyrinth seal and the multi-stage water seal during maintenance.

[0027] The working method of the automatic switching system for the seal water of the feed water pump disclosed in the present invention uses the return water pressure as the core parameter to characterize the working state of the seal water return system; the triggering conditions for the system to work are clarified, and automatic switching can be performed when there is a vacuum leak in the multi-stage water seal and poor drainage, ensuring the normal operation of the feed water pump. The present invention has a high degree of automation, does not require manual adjustment during the working process, and has simple operation and strong reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0029] In the figure: 1 is the feed water pump, 2 is the driving end labyrinth seal, 3 is the non-driving end labyrinth seal, 4 is the filtering device, 5 is the first regulating valve, 6 is the first check valve, 7 is the first stop valve, 8 is the second regulating valve, 9 is the second check valve, 10 is the second stop valve, 11 is the discharge pneumatic valve, 12 is the injection pneumatic valve, 13 is the air exhaust pneumatic valve, 14 is the electric valve, 15 is the multi-stage water seal, 16 is the pressure transmitter, 17 is the liquid level detector, 18 is the seal water inlet main pipe, and 19 is the seal water return main pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following further describes the present invention in detail with reference to the drawings and specific embodiments, and its content is an explanation rather than a limitation of the present invention:

[0031] As Figure 1 , the feed water pump 1 is respectively provided with a driving end labyrinth seal 2 and a non-driving end labyrinth seal 3. An automatic switching system for the seal water of a feed water pump of the present invention includes a first regulating valve 5, a second regulating valve 8, a discharge pneumatic valve 11, an injection pneumatic valve 12, an air exhaust pneumatic valve 13, an electric valve 14, a pressure transmitter 16, a liquid level detector 17, a seal water inlet main pipe 18, and a seal water return main pipe 19.

[0032] The sealing water inlet header 18 is connected with three branches. The first branch is successively connected with the first regulating valve 5 and the driving end labyrinth seal 2 and then accesses the sealing water return header 19. The second branch is successively connected with the second regulating valve 8 and the non-driving end labyrinth seal 3 and then accesses the sealing water return header 19. The third branch is connected to the water injection port of the multi-stage water seal 15 through the water injection pneumatic valve 12. The sealing water return header 19 is connected to the inlet of the multi-stage water seal 15, and a pressure transmitter 16 is provided on the sealing water return header 19. An exhaust pipeline is provided on the sealing water return header 19. The exhaust pipeline is connected to the condenser trench, and an exhaust pneumatic valve 11 is provided on the exhaust pipeline. The outlet of the multi-stage water seal 15 is connected to the condenser through the electric valve 14. The drain port of the multi-stage water seal 15 is connected to the condenser trench through a drain pipeline, and an exhaust pneumatic valve 13 and a liquid level detector 17 are provided on the drain pipeline.

[0033] In a preferred embodiment of the present invention, a filtering device 4 is provided at the inlet end of the sealing water inlet header 18.

[0034] In a preferred embodiment of the present invention, a first check valve 6 is provided between the first regulating valve 5 and the driving end labyrinth seal 2 on the first branch.

[0035] In a preferred embodiment of the present invention, a first stop valve 7 is provided between the driving end labyrinth seal 2 and the sealing water return header 19 on the first branch.

[0036] In a preferred embodiment of the present invention, a second check valve 9 is provided between the second regulating valve 8 and the non-driving end labyrinth seal 3 on the second branch.

[0037] In a preferred embodiment of the present invention, a second stop valve 10 is provided between the non-driving end labyrinth seal 3 and the sealing water return header 19 on the second branch.

[0038] The following further explains the present invention with a specific embodiment:

[0039] In this embodiment, a filtering device 4 is provided on the sealing water inlet header 18. The filtering device 4 adopts a Y-type filter and is used to filter the sealing water. The pipeline after the filtering device 4 is divided into three paths. The first path is successively connected with the first regulating valve 5, the first check valve 6, the driving end labyrinth seal 2, and the first stop valve 7, and finally accesses the sealing water return header 19. The second path is successively connected with the second regulating valve 8, the second check valve 9, the non-driving end labyrinth seal 3, and the second stop valve 10, and finally accesses the sealing water return header 19. The third path is connected to the water injection port of the multi-stage water seal 15, and a water injection pneumatic valve 12 is provided.

[0040] The sealed water return main pipe 19 is connected to the inlet of the multi-stage water seal 15, and the outlet of the multi-stage water seal 15 is connected to the condenser through the electric valve 14. The drain port of the multi-stage water seal 15 is connected to the condenser trench through a pipeline, and an exhaust pneumatic valve 13 is provided.

[0041] A tee is provided on the sealed water return main pipe 19, which is connected to the condenser trench through a pipeline, and a discharge pneumatic valve 11 is provided. A pressure transmitter 16 is provided on the sealed water return main pipe 19 for measuring the pressure of the sealed water return; a liquid level detector 17 is provided on the pipeline behind the exhaust pneumatic valve 13 for measuring whether there is water inside the pipeline.

[0042] During normal start-stop and operation, the condensate water is throttled by the first regulating valve 5 and the second regulating valve 8 respectively from the sealed water inlet main pipe 18 and enters the driving end labyrinth seal 2 and the non-driving end labyrinth seal 3 for sealing. The return water is collected into the sealed water return main pipe 19, and after passing through the multi-stage water seal 15, it is discharged into the condenser through the electric valve 14.

[0043] The automatic switching method for the labyrinth seal water of the feed water pump in this embodiment includes the following steps:

[0044] 1) Define the control objective. Taking the sealed water return pressure as the main control objective, by collecting the sealed water return pressure during the full cycle of the start-up, operation and stop of the feed water pump 1, calculate the average pressure P0.

[0045] 2) Confirm the trigger condition. Set the dead zone N1, make P min = P0 - N1, set the dead zone N2, make P max = P0 + N2. When the sealed water return pressure P is greater than P max , trigger the high sealed water return pressure mode. When the sealed water return pressure P is less than P min , trigger the low sealed water return pressure mode.

[0046] 3) Execute the switching work.

[0047] a The sealed water return pressure is high. In this mode, the system automatically opens the discharge pneumatic valve 11 to divert the sealed water return to the condenser trench.

[0048] b The sealed water return pressure is low. In this mode, the system completes the sealed water switching through the following steps:

[0049] First, open the discharge pneumatic valve 11 and close the electric valve 14 to switch the sealed water return to the condenser trench without affecting the normal operation of the unit.

[0050] Second, open the injection pneumatic valve 12 and open the exhaust pneumatic valve 13 to re-inject water into the multi-stage water seal.

[0051] III. After the liquid level detector 17 is triggered, close the water injection pneumatic valve 12 and the air exhaust pneumatic valve 13, indicating that the multi-stage water seal 15 is filled with water;

[0052] IV. Open the electric valve 14 and close the discharge pneumatic valve 11 to reactivate the multi-stage water seal 15.

[0053] The above are only embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention, or equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present invention, or direct or indirect applications in other related technical fields shall all be covered within the protection scope of the present invention.

Claims

1. A working method of a seal water automatic switching system for a feed water pump, characterized in that, The feed water pump seal water automatic switching system includes a first regulating valve (5), a second regulating valve (8), a discharge pneumatic valve (11), a water injection pneumatic valve (12), an air exhaust pneumatic valve (13), an electric valve (14), a pressure transmitter (16), a liquid level detector (17), a seal water inlet header pipe (18) and a seal water return header pipe (19); The seal water inlet header pipe (18) is connected with three branches. The first branch is sequentially connected with the first regulating valve (5) and the drive end labyrinth seal (2) and then accesses the seal water return header pipe (19). The second branch is sequentially connected with the second regulating valve (8) and the non-drive end labyrinth seal (3) and then accesses the seal water return header pipe (19). The third branch is connected to the water injection port of the multi-stage water seal (15) through the water injection pneumatic valve (12). The seal water return header pipe (19) is connected to the inlet of the multi-stage water seal (15), and a pressure transmitter (16) is arranged on the seal water return header pipe (19). An exhaust pipeline is arranged on the seal water return header pipe (19), the exhaust pipeline is connected to the condenser trench, and a discharge pneumatic valve (11) is arranged on the exhaust pipeline. The outlet of the multi-stage water seal (15) is connected to the condenser through the electric valve (14). The drain port of the multi-stage water seal (15) is connected to the condenser trench through a drain pipeline, and the air exhaust pneumatic valve (13) and the liquid level detector (17) are arranged on the drain pipeline; The working method of the feed water pump seal water automatic switching system includes: When the feed water pump (1) is normally started, stopped and operating, the condensate water is respectively throttled by the first regulating valve (5) on the first branch from the seal water inlet header pipe (18) and enters the drive end labyrinth seal (2), and throttled by the second regulating valve (8) on the second branch and enters the non-drive end labyrinth seal (3) for sealing. The return water is collected into the seal water return header pipe (19), and after passing through the multi-stage water seal (15), it is discharged into the condenser through the electric valve (14); Set the seal water return pressure threshold value, and the pressure transmitter (16) is used to monitor the seal water return pressure in real time. When the seal water return pressure is greater than the seal water return pressure threshold value, it is switched to the high seal water return pressure mode. In this mode, the discharge pneumatic valve (11) is automatically opened to divert the seal water return to the condenser trench. When the seal water return pressure is less than the seal water return pressure threshold value, it is switched to the low seal water return pressure mode. This mode includes the following steps: S1: Open the discharge pneumatic valve (11) and close the electric valve (14) to switch the seal water return to the condenser trench without affecting the normal operation of the generating unit; S2: Open the water injection pneumatic valve (12) and the air exhaust pneumatic valve (13) to re-inject water into the multi-stage water seal (15); S3: After detecting that the liquid level detector (17) is triggered, close the water injection pneumatic valve (12) and the air exhaust pneumatic valve (13), and the water injection of the multi-stage water seal (15) is completed; S4: Open the electric valve (14) and close the discharge pneumatic valve (11) to re-put the multi-stage water seal (15) into operation. The seal water return pressure threshold value is determined by the following method: Collect the return water pressure of the sealing water during the full cycle of starting, running and stopping the feed water pump (1), and calculate the average pressure P0; set the dead zone N1, and let P min = P0 - N1, set the dead zone N2, and let P max = P0 + N2; when the return water pressure P of the sealing water is greater than P max , trigger the high return water pressure mode of the sealing water; when the return water pressure P of the sealing water is less than P min , trigger the low return water pressure mode of the sealing water.

2. The working method of the feed water pump seal water automatic switching system according to claim 1, characterized in that, A filtering device (4) is arranged at the inlet end of the seal water inlet header pipe (18).

3. The working method of the feed water pump seal water automatic switching system according to claim 1, characterized in that, A first check valve (6) is provided between the first regulating valve (5) and the drive end labyrinth seal (2) on the first branch.

4. The working method of the feed water pump seal water automatic switching system according to claim 1, characterized in that A first stop valve (7) is provided between the drive end labyrinth seal (2) and the seal water return main pipe (19) on the first branch.

5. The working method of the feed water pump sealing water automatic switching system according to claim 1, characterized in that, A second check valve (9) is provided between the second regulating valve (8) and the non-drive end labyrinth seal (3) on the second branch.

6. The working method of the feed water pump seal water automatic switching system according to claim 1, characterized in that, A second stop valve (10) is provided between the non-drive end labyrinth seal (3) and the seal water return main pipe (19) on the second branch.

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