Steam turbine shaft seal system

Abstract

The utility model discloses a steam turbine shaft seal system which comprises a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, an external shaft seal steam supply pipe, a steam supply pipeline and a steam exhaust pipeline, and two auxiliary steam supply branch pipes are arranged between the external shaft seal steam supply pipe and the steam supply pipeline and are respectively provided with an electric heating device and a cooling device. The external shaft seal steam supply pipe is provided with a temperature sensor and is electrically connected with the controller, and the auxiliary steam supply branch pipe is in linkage with the controller through an electric control valve. The system monitors the temperature of steam in an external shaft seal steam supply pipe in real time through a temperature sensor, when a boiler is started in a cold state to introduce low-temperature steam, a controller triggers an electric heating branch pipe to heat the steam, and deformation caused by sudden temperature drop of a steam supply pipeline and a shaft seal body is avoided; during normal operation, high-temperature steam is cooled and decompressed through the cooling branch pipe, overtemperature of a shaft seal body and bending of a large shaft are prevented, dynamic and accurate adjustment of the steam supply temperature and pressure of the shaft seal is achieved, potential safety hazards of a traditional system in the start-stop and operation stage are effectively eliminated, and the safety and economical efficiency of a unit are improved.

Description

A steam turbine shaft sealing system Technical Field

[0001] This utility model relates to the field of steam turbines, and in particular to a steam turbine shaft sealing system. Background Technology

[0002] The turbine shaft sealing system uses steam seals to prevent steam leakage from the high-pressure cylinder, which could damage the plant environment and waste steam. It also prevents water from entering the lubricating oil, affecting the safe and economical operation of the unit. Simultaneously, it prevents outside air from leaking into the low-pressure cylinder, affecting the condenser vacuum and reducing the unit's thermal efficiency. In existing technology, high-pressure valve stem leakage is connected to the shaft seal steam supply system. During boiler cold start-up and pressure rise, low-temperature steam enters the steam supply pipeline through the high-pressure valve stem leakage pipe of the main steam valve, causing a drop of approximately 200°C in the temperature of the steam supply pipeline and the shaft seal body of the intermediate and high-pressure cylinders. This leads to rapid cooling of the high-pressure and intermediate-pressure cylinder shaft seal bodies, resulting in localized deformation. Furthermore, after the shaft seal system is operational, high-temperature steam enters the steam supply pipeline through the high-pressure valve stem leakage pipe of the main steam valve, causing a rise of approximately 130°C in the temperature of the steam supply pipeline and the shaft seal body of the intermediate and high-pressure cylinders, and a 3 kPa increase in the pressure of the shaft seal steam supply pipeline. This poses a safety hazard of turbine shaft bending.

[0003] Therefore, it is necessary to propose a turbine shaft sealing system to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a turbine shaft sealing system to solve the problems of rapid cooling of the high-pressure and intermediate-pressure cylinder shaft seals caused by low-temperature steam, resulting in local deformation, and high-temperature steam causing the temperature of the steam supply pipeline and the high-pressure and intermediate-pressure cylinder shaft seals to rise, leading to the bending of the turbine shaft.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A steam turbine shaft sealing system includes a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, an external shaft seal steam supply pipe, a steam supply pipeline, and an exhaust pipeline. The steam supply pipeline is connected to both ends of the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder. The exhaust pipeline is also connected to both ends of the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder. The external shaft seal steam supply pipe is connected to the steam supply pipeline, and a high-pressure valve stem leakage pipeline is connected to the external shaft seal steam supply pipe. Two auxiliary steam supply branch pipes are provided between the external shaft seal steam supply pipe and the steam supply pipeline. Both ends of the auxiliary steam supply branch pipes are connected to the external shaft seal steam supply pipe and the steam supply pipeline, respectively. A valve is installed on the external shaft seal steam supply pipe. A temperature sensor is installed on the external shaft seal steam supply pipe, and the temperature sensor is electrically connected to a controller. Electrically controlled valves are installed on the two auxiliary steam supply branch pipes, and the electrically controlled valves are electrically connected to the controller. An electric heating device is installed on one of the auxiliary steam supply branch pipes, and a cooling device is installed on the other auxiliary steam supply branch pipe.

[0007] Preferably, a second valve is installed on the exhaust pipe, and the exhaust port of the exhaust pipe is connected to the outside.

[0008] Preferably, the temperature sensor is installed on the outer straight pipe section of the external shaft seal steam supply pipe.

[0009] Preferably, the electric heating device is an electric heating tape wrapped around the auxiliary steam supply branch pipe, and the cooling device is a water cooler.

[0010] Preferably, a pressure monitoring point is provided on the external shaft seal steam supply pipe near the pipe inlet.

[0011] Preferably, temperature and pressure monitoring points are installed on both the steam supply pipeline and the steam exhaust pipeline.

[0012] Preferably, valve three is installed at the connection between the two auxiliary steam supply branch pipes and the steam supply pipeline.

[0013] The technical effects and advantages of this utility model are as follows:

[0014] 1. When the boiler is started up in a cold state, the steam leaking from the high-pressure valve stem is low-temperature steam. After monitoring by the temperature sensor, the controller automatically triggers the electric control valve of the electric heating auxiliary branch to open. The electric heating cable heats the low-temperature steam to the target temperature, avoiding a sudden drop in temperature of the steam supply pipeline and the high-pressure cylinder shaft seal, preventing local deformation of the shaft seal due to rapid cooling, and reducing the risk of dynamic and static rubbing of the shaft seal. When the unit is running normally, the steam leaking from the high-pressure valve stem is high-temperature steam. After the temperature sensor detects overheating, the controller automatically switches to the cooling auxiliary branch, which lowers the steam temperature through the water cooler, avoiding the risk of overheating expansion of the shaft seal and bending of the main shaft.

[0015] 2. The temperature sensor monitors the data in real time and transmits it to the controller. The controller automatically switches the auxiliary branch pipe according to the preset threshold, without the need for manual operation, thus improving the efficiency and accuracy of regulation.

[0016] 3. By precisely adjusting the steam supply temperature, the energy consumption of auxiliary steam supply is reduced, while the energy of leakage steam from the high-pressure valve stem is recovered, thereby improving resource utilization. Attached Figure Description

[0017] Figure 1 is a schematic diagram of the structure of a steam turbine shaft sealing system according to the present invention.

[0018] In the diagram: 1. High-pressure cylinder; 2. Medium-pressure cylinder; 3. Low-pressure cylinder; 4. External shaft seal steam supply pipe; 5. Steam supply pipeline; 6. Exhaust steam pipeline; 7. Auxiliary steam supply branch pipe; 8. Valve 1; 9. Temperature sensor; 10. Electrically controlled valve; 11. Electric heating device; 12. Cooling device; 13. Valve 2; 14. Valve 3. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] This utility model provides a turbine shaft sealing system as shown in Figure 1, including a high-pressure cylinder 1, an intermediate-pressure cylinder 2, a low-pressure cylinder 3, an external shaft seal steam supply pipe 4, a steam supply pipeline 5, and an exhaust pipeline 6. The steam supply pipeline 5 is connected to both ends of the high-pressure cylinder 1, the intermediate-pressure cylinder 2, and the low-pressure cylinder 3. The exhaust pipeline 6 is also connected to both ends of the high-pressure cylinder 1, the intermediate-pressure cylinder 2, and the low-pressure cylinder 3. The external shaft seal steam supply pipe 4 is connected to the steam supply pipeline 5, and a high-pressure valve stem leakage pipeline is connected to the external shaft seal steam supply pipe 4. A connection is provided between the external shaft seal steam supply pipe 4 and the steam supply pipeline 5. There are two auxiliary steam supply branch pipes 7. The two ends of the auxiliary steam supply branch pipes 7 are connected to the external shaft seal steam supply pipe 4 and the steam supply pipe 5, respectively. A valve 8 is installed on the external shaft seal steam supply pipe 4. A temperature sensor 9 is installed on the external shaft seal steam supply pipe 4. The temperature sensor 9 is electrically connected to a controller. An electric control valve 10 is installed on the two auxiliary steam supply branch pipes 7. The electric control valve 10 is electrically connected to the controller. An electric heating device 11 is installed on one of the auxiliary steam supply branch pipes 7, and a cooling device 12 is installed on the other auxiliary steam supply branch pipe 7.

[0021] Steam supply pipe 5 connects the two ends of the high, medium and low pressure cylinders to provide sealing steam for the main shaft seal, maintaining the functions of preventing leakage at the high pressure end and preventing air intake at the low pressure end; exhaust pipe 6 also connects the two ends of the three cylinders to collect leakage steam and condensate from the shaft seal, and connects to the outside through the exhaust port to maintain system pressure balance.

[0022] Furthermore, valve 2 13 is installed on the exhaust pipe 6, and the exhaust port of the exhaust pipe 6 is connected to the outside.

[0023] Furthermore, the temperature sensor 9 is installed on the outer straight pipe section of the external shaft seal steam supply pipe 4;

[0024] Temperature sensor 9 is installed on the outer straight pipe section of the external shaft seal steam supply pipe 4. This position is far away from valve 8 and pipe bends, tees, and other disturbing areas to ensure a stable steam flow field and avoid temperature measurement distortion caused by steam flow turbulence. The choice of installing it on the outer straight pipe section allows the temperature sensing element of temperature sensor 9 to be inserted vertically into the central area of ​​the pipe, deep into the mainstream steam zone, to accurately capture the true temperature value of the steam. It also facilitates subsequent maintenance and calibration operations. This installation method meets the requirements of the thermal pipeline instrumentation installation specifications regarding the temperature measuring point being in a stable flow field and having sufficient insertion depth, providing reliable temperature data for the controller, ensuring accurate and effective switching control of the dual auxiliary steam supply branch pipes 7, and thus ensuring the temperature stability of the turbine shaft seal system under different operating conditions.

[0025] Furthermore, the electric heating device 11 uses an electric heating cable, which is wrapped around the auxiliary steam supply branch pipe 7, and the cooling device 12 uses a water cooler.

[0026] The electric heating device 11 uses an electric heating tape, which is evenly wrapped around the outside of the auxiliary steam supply branch pipe 7 to dynamically heat the low-temperature steam inside the pipe. The electric heating tape can automatically adjust its output power according to the preset temperature threshold and heat the steam through conduction through the pipe wall, avoiding the direct entry of low-temperature steam into the steam supply pipeline 5, which would cause the shaft seal to cool down rapidly. The cooling device 12 uses a water cooler, whose shell-and-tube structure allows steam to flow on the shell side and cooling water to flow in the opposite direction inside the tube. By forcing convection heat transfer, the steam temperature is reduced, preventing the steam supply pipeline 5 from overheating and overpressure. The two work together to achieve precise bidirectional regulation of the steam temperature and improve the operational safety of the shaft seal system.

[0027] Furthermore, a pressure monitoring point is installed on the external shaft seal steam supply pipe 4 near the pipe inlet;

[0028] Furthermore, temperature and pressure monitoring points are installed on both the steam supply pipeline 5 and the steam exhaust pipeline 6;

[0029] A pressure monitoring point is installed on the external shaft seal steam supply pipe 4 near the pipe inlet to monitor the initial pressure of the upstream steam source in real time, providing a basis for adjusting the opening of valve 8 and ensuring that the steam pressure entering the steam supply pipe 5 remains stable within the design range. Furthermore, temperature and pressure monitoring points are installed on both the steam supply pipe 5 and the exhaust pipe 6. The monitoring point on the steam supply pipe 5 provides real-time feedback on the temperature and pressure of the steam supplied to the shaft seal, directly reflecting the actual stress and heat state of the shaft seal body. The monitoring point on the exhaust pipe 6 monitors the temperature and pressure of the steam returning to the shaft seal, determining the sealing effect of the shaft seal and the operating status of the vacuum system. Data from these monitoring points are all connected to the controller, forming a linkage with the temperature sensor 9 and the electrically controlled valve 10 of the auxiliary steam supply branch pipe 7, achieving dynamic monitoring and safety redundancy protection of the entire shaft seal system process.

[0030] Furthermore, valves 314 are installed at the connection points of the two auxiliary steam supply branch pipes 7 and the steam supply pipeline 5;

[0031] In one embodiment of this utility model, when low-temperature steam is introduced into the external shaft seal steam supply pipe 4 during the boiler cold start-up and pressurization process via the high-pressure valve stem leakage pipe (not shown), the steam pressure is monitored at the pressure monitoring point of the external shaft seal steam supply pipe 4 using external monitoring equipment, and the steam temperature is monitored by temperature sensor 9. The temperature sensor 9 sends the data to the controller (not shown). The controller controls the electrically controlled valve 10 equipped with an electric heating device 11 to open, and the electrically controlled valve 10 on another auxiliary steam supply branch pipe 7 to close. The controller uses the electric heating device 11 to control the steam according to preset parameters. After heating, the steam is delivered to the steam supply pipeline 5. When the boiler has been running for a period of time, high-temperature steam is introduced into the external shaft seal steam supply pipeline 4 through the high-pressure valve stem leakage pipeline. The steam pressure is monitored at the pressure monitoring point of the external shaft seal steam supply pipeline 4 by external monitoring equipment, and the steam temperature is monitored by temperature sensor 9. The temperature sensor 9 sends the data to the controller, and the controller controls the electric valve 10 with cooling device 12 to open and the electric valve 10 on another auxiliary steam supply branch pipe 7 to close. The controller uses the cooling device 12 to cool the steam according to the preset parameters before delivering it to the steam supply pipeline 5.

[0032] Using external equipment, temperature and pressure monitoring points (not shown) are installed on both the steam supply pipeline 5 and the exhaust pipeline 6 to monitor the internal conditions of the unit's pipelines in real time. When the temperature and pressure inside the unit's pipelines are within the normal range, the amount of steam leaking from the high-pressure cylinder 1 shaft seal into the steam supply pipeline 5 meets the sealing pressure requirements of the low-pressure cylinder 3 shaft seal, and the unit is in a self-sealing state. When the temperature and pressure inside the unit's pipelines are higher than the normal level, valve 2 13 is opened, and steam is discharged to the outside through the exhaust pipeline 6 to relieve pressure. When the temperature and pressure inside the unit's pipelines are lower than the normal level, valve 3 14 is opened, and steam is introduced through the high-pressure valve stem leakage pipeline to replenish the pressure until the temperature and pressure inside the unit's pipelines return to the normal level.

[0033] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A steam turbine shaft sealing system, comprising a high-pressure cylinder (1), an intermediate-pressure cylinder (2), a low-pressure cylinder (3), an external shaft seal steam supply pipe (4), a steam supply pipeline (5), and an exhaust pipeline (6), wherein the steam supply pipeline (5) is connected to both ends of the high-pressure cylinder (1), the intermediate-pressure cylinder (2), and the low-pressure cylinder (3), the exhaust pipeline (6) is connected to both ends of the high-pressure cylinder (1), the intermediate-pressure cylinder (2), and the low-pressure cylinder (3), the external shaft seal steam supply pipe (4) is connected to the steam supply pipeline (5), and a high-pressure valve stem leakage pipeline is connected to the external shaft seal steam supply pipe (4), characterized in that: Two auxiliary steam supply branches (7) are provided between the external shaft seal steam supply pipe (4) and the steam supply pipe (5). The two ends of the auxiliary steam supply branches (7) are connected to the external shaft seal steam supply pipe (4) and the steam supply pipe (5) respectively. A valve (8) is provided on the external shaft seal steam supply pipe (4). A temperature sensor (9) is installed on the external shaft seal steam supply pipe (4). The temperature sensor (9) is electrically connected to a controller. An electric control valve (10) is installed on the two auxiliary steam supply branches (7). The electric control valve (10) is electrically connected to the controller. An electric heating device (11) is installed on one of the auxiliary steam supply branches (7), and a cooling device (12) is installed on the other auxiliary steam supply branch (7).

2. A turbine shaft sealing system according to claim 1, characterized in that: The exhaust pipe (6) is equipped with valve 2 (13), and the exhaust port of the exhaust pipe (6) is connected to the outside.

3. A turbine shaft sealing system according to claim 1, characterized in that: The temperature sensor (9) is installed on the outer straight pipe section of the external shaft seal steam supply pipe (4).

4. A turbine shaft sealing system according to claim 1, characterized in that: The electric heating device (11) uses an electric heating tape, which is wrapped around the auxiliary steam supply branch pipe (7). The cooling device (12) uses a water cooler.

5. A turbine shaft sealing system according to claim 1, characterized in that: A pressure monitoring point is installed on the external shaft seal steam supply pipe (4) near the pipe inlet.

6. A turbine shaft sealing system according to claim 1, characterized in that: Temperature and pressure monitoring points are installed on both the steam supply pipeline (5) and the steam exhaust pipeline (6).

7. A turbine shaft sealing system according to claim 1, characterized in that: Valve 3 (14) is installed at the connection between the two auxiliary steam supply branch pipes (7) and the steam supply pipe (5).

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