Abstract: This paper analyzes the reasons for the partial clearance of the butterfly valve in the operation of Hongmen Hydropower Plant, introduces the judgment and treatment of the partial clearance of the butterfly valve, and proposes measures to prevent partial clearance of the butterfly valve.
Key words: butterfly valve; partial flushing; analysis measures Butterfly valve is one of the most common unit valves in hydropower plants. It consists of valve body, butterfly plate and control mechanism. It is installed at the water inlet of turbine volute to control The main function of the unit water flow is: (1) When a system fails and the unit is over-speed, the butterfly valve can be closed to protect the unit; (2) the butterfly valve can be closed for maintenance during maintenance; (3) The unit is adjusted for a long time. Phase operation or long-term shutdown for standby, the butterfly valve can be closed to reduce the leakage of the guide vane when the system allows.
The butterfly valve is fully open or fully closed during normal operation, and the phenomenon that the butterfly valve in operation is automatically closed when the unit is under load is called flushing. If the butterfly plate slowly deviates from the fully open state during operation, rotate 30~70° to make the butterfly valve partially closed, which is called partial flushing.
The influence and damage of the butterfly valve part on the hydro-generator unit is mainly caused by: causing mechanical vibration of the turbine; the high-speed water flow will generate cavitation erosion behind the disc, causing the disc to be cavitation-damaged; generating mechanical squeezing and making the relay cylinder Vibration, severely break the connecting screw; reduce the output of the unit.
Therefore, discussing and solving this problem has great practical significance for the safe operation of hydropower plants.
The reason and analysis of the partial clearance of the butterfly valve is more complicated. The reasons for the partial flushing phenomenon are complicated. After eliminating the mistaken operation of the handle, the accidental touch of the butterfly valve relay, and the fact that the locker is not thrown after the butterfly valve is opened, the analysis determines the partial punch. The reason for the shutdown is as follows.
(l) The butterfly valve relay and the four-way valve piston wear, so that the piston cavity packing is not tightly sealed, and the pressure oil is lost from the closing chamber, so that the piston moves to the off side under the unbalanced pressure, thereby driving the disc to turn to the closed position. When turned off to a certain position, the remaining pressure oil acts to prevent the disc from continuing to turn to the fully closed position.
(2) The butterfly valve rotation bearing fails to fall into position, causing the valve shaft to deviate from the installation center line, causing the closing torque on the butterfly plate, or the bearing to wear and slip, resulting in a decrease in the friction torque of the butterfly valve bearing, resulting in a certain reason (such as relay) during operation. When the pressure of the four-way valve is lost, or the vibration, the disc is deflected toward the off side.
(3) Accidental water flow imbalance produces an unbalanced moment on the valve body, causing the disc to turn to the off side.
(4) The butterfly valve overhaul failed to reach the quality standard, mainly because the rotating shaft failed to fall into place or the central axis was offset, so that the butterfly valve could not maintain the steady state as required.
(5) Improper daily maintenance, leaving hidden dangers.
(6) Failure to open the disc to the fully open position, leaving a travel space and burying some hidden dangers.
2 Butterfly valve partial clearance judgment and treatment 2.1 Butterfly valve partial clearance judgment According to experience, if the following phenomenon occurs during operation, it can be judged that the butterfly valve has partially flushed.
(l) The monitoring system and the protection system are working properly, and the signal and audible alarm system does not operate, but the active power meter indication at the generator outlet is slowly decreasing.
(2) The turbine governor works normally, there is no obvious change, the opening of the water guide vane does not change, but in the butterfly valve chamber, the butterfly valve opening pointer can be seen to move slowly in the direction of the positive closing direction.
(3) When the partial flushing phenomenon is serious, the butterfly valve room has obvious sound, and sometimes the air valve can be seen running in the butterfly valve room.
(4) When the butterfly plate is in the range of 30~70° and the butterfly valve is flushed by water too fast, a large water hammer pressure will be generated in the hydraulic pipe, which will generate strong vibration.
2.2 When the part of the butterfly valve is flushed, the normal processing method is to follow the procedure of the butterfly valve. Generally, the butterfly valve can be re-opened to the fully open position, and the unit re-enters the normal working state. However, if this method of operation fails, or a more serious shutdown failure occurs, it can be handled as follows.
(l) Check the butterfly valve relay and the four-way valve. If oil leakage is found, it is caused by unbalanced pressure oil. At this time, try to lift the oil source valve to fill the oil receiver.
(2) When the part of the butterfly valve is rushed to cause a serious reaction, the opening of the water guide blade should be quickly pressed to no load, and then the active and reactive load of the unit should be adjusted to 0. After the operation, stop the operation according to the shutdown process.
(3) If the butterfly plate fails to open in place, it can check whether the butterfly valve controls the oil pump to start. If it is not started, the butterfly valve is not opened. In this case, the oil pump can be started, and the butterfly valve can be opened continuously. The oil pump should be shut down afterwards.
(4) If the butterfly valve controls the oil pump to start during operation, it indicates that the butterfly valve automatic device malfunctions, or the butterfly valve operation handle is mistakenly touched to the closing side. At this time, the butterfly valve relay should be reset, the oil pump should be stopped, and the butterfly valve operation procedure should be pressed. Re-open the butterfly valve.
3 Measures to prevent the partial clearance of the butterfly valve 3.1 Technical measures (l) Install the signal device of the position of the butterfly valve. When the butterfly valve in operation deviates from the fully open position, a signal is issued, and the light plate of the central control room is illuminated, and the operating personnel can judge whether it is an accidental closing butterfly valve or a partial flushing according to the signal.
(2) After the general treatment measures for the partial flushing, the oil source valve can be lifted until the butterfly valve full open signal appears, and then the oil source valve is dropped.
(3) Improve the quality of butterfly valve inspection. Due to the large size and firm positioning of the butterfly valve, it is necessary to solve the problem of the rotating shaft in place. It is necessary to disassemble and hoist the butterfly valve, and the amount of engineering is large, and the space of the butterfly valve chamber is limited. It is also difficult to do because of the long use time and wear of the butterfly valve. It is also difficult to guarantee quality after disintegration. At present, it is common to use a gasket to adjust the center position, which can solve the problem of the butterfly valve body to a certain extent. Improve the maintenance process to ensure that the butterfly valve is parallel to the water flow after the butterfly valve is fully opened.
(4) Improve the sealing performance of the servomotor, replace the better sealing material, and periodically fill the cavity of the servomotor piston to replenish the oil.
(5) Install a water monitor at the inlet of the butterfly valve to monitor the fluctuation of the water flow, and add a periodic work content in the operating rules of the butterfly valve, that is, start the oil valve every week and fill the oil passage of the relay.
3.2 Organizational measures (l) Strengthen technical training for employees, master some judgments and technical processing skills, and master the rules of butterfly valve operation.
(2) Establish and improve relevant systems, such as defect registration, processing, and assessment reward systems.
(3) Strengthen the daily inspection and maintenance of the butterfly valve. The abnormal "butterfly valve closing" signal should be recorded and analyzed for reasons; the inspection of the butterfly valve and the bypass valve should be strengthened during the normal inspection; the operating mechanism is required to be in the correct position, each electromagnetic operating valve, relay, The monitoring system and oil pump should meet the requirements of the regulations; increase the inspection content, especially pay attention to check the oil relay, the four-way valve, and the oil drain circuit for oil leakage.
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Key words: butterfly valve; partial flushing; analysis measures Butterfly valve is one of the most common unit valves in hydropower plants. It consists of valve body, butterfly plate and control mechanism. It is installed at the water inlet of turbine volute to control The main function of the unit water flow is: (1) When a system fails and the unit is over-speed, the butterfly valve can be closed to protect the unit; (2) the butterfly valve can be closed for maintenance during maintenance; (3) The unit is adjusted for a long time. Phase operation or long-term shutdown for standby, the butterfly valve can be closed to reduce the leakage of the guide vane when the system allows.
The butterfly valve is fully open or fully closed during normal operation, and the phenomenon that the butterfly valve in operation is automatically closed when the unit is under load is called flushing. If the butterfly plate slowly deviates from the fully open state during operation, rotate 30~70° to make the butterfly valve partially closed, which is called partial flushing.
The influence and damage of the butterfly valve part on the hydro-generator unit is mainly caused by: causing mechanical vibration of the turbine; the high-speed water flow will generate cavitation erosion behind the disc, causing the disc to be cavitation-damaged; generating mechanical squeezing and making the relay cylinder Vibration, severely break the connecting screw; reduce the output of the unit.
Therefore, discussing and solving this problem has great practical significance for the safe operation of hydropower plants.
The reason and analysis of the partial clearance of the butterfly valve is more complicated. The reasons for the partial flushing phenomenon are complicated. After eliminating the mistaken operation of the handle, the accidental touch of the butterfly valve relay, and the fact that the locker is not thrown after the butterfly valve is opened, the analysis determines the partial punch. The reason for the shutdown is as follows.
(l) The butterfly valve relay and the four-way valve piston wear, so that the piston cavity packing is not tightly sealed, and the pressure oil is lost from the closing chamber, so that the piston moves to the off side under the unbalanced pressure, thereby driving the disc to turn to the closed position. When turned off to a certain position, the remaining pressure oil acts to prevent the disc from continuing to turn to the fully closed position.
(2) The butterfly valve rotation bearing fails to fall into position, causing the valve shaft to deviate from the installation center line, causing the closing torque on the butterfly plate, or the bearing to wear and slip, resulting in a decrease in the friction torque of the butterfly valve bearing, resulting in a certain reason (such as relay) during operation. When the pressure of the four-way valve is lost, or the vibration, the disc is deflected toward the off side.
(3) Accidental water flow imbalance produces an unbalanced moment on the valve body, causing the disc to turn to the off side.
(4) The butterfly valve overhaul failed to reach the quality standard, mainly because the rotating shaft failed to fall into place or the central axis was offset, so that the butterfly valve could not maintain the steady state as required.
(5) Improper daily maintenance, leaving hidden dangers.
(6) Failure to open the disc to the fully open position, leaving a travel space and burying some hidden dangers.
2 Butterfly valve partial clearance judgment and treatment 2.1 Butterfly valve partial clearance judgment According to experience, if the following phenomenon occurs during operation, it can be judged that the butterfly valve has partially flushed.
(l) The monitoring system and the protection system are working properly, and the signal and audible alarm system does not operate, but the active power meter indication at the generator outlet is slowly decreasing.
(2) The turbine governor works normally, there is no obvious change, the opening of the water guide vane does not change, but in the butterfly valve chamber, the butterfly valve opening pointer can be seen to move slowly in the direction of the positive closing direction.
(3) When the partial flushing phenomenon is serious, the butterfly valve room has obvious sound, and sometimes the air valve can be seen running in the butterfly valve room.
(4) When the butterfly plate is in the range of 30~70° and the butterfly valve is flushed by water too fast, a large water hammer pressure will be generated in the hydraulic pipe, which will generate strong vibration.
2.2 When the part of the butterfly valve is flushed, the normal processing method is to follow the procedure of the butterfly valve. Generally, the butterfly valve can be re-opened to the fully open position, and the unit re-enters the normal working state. However, if this method of operation fails, or a more serious shutdown failure occurs, it can be handled as follows.
(l) Check the butterfly valve relay and the four-way valve. If oil leakage is found, it is caused by unbalanced pressure oil. At this time, try to lift the oil source valve to fill the oil receiver.
(2) When the part of the butterfly valve is rushed to cause a serious reaction, the opening of the water guide blade should be quickly pressed to no load, and then the active and reactive load of the unit should be adjusted to 0. After the operation, stop the operation according to the shutdown process.
(3) If the butterfly plate fails to open in place, it can check whether the butterfly valve controls the oil pump to start. If it is not started, the butterfly valve is not opened. In this case, the oil pump can be started, and the butterfly valve can be opened continuously. The oil pump should be shut down afterwards.
(4) If the butterfly valve controls the oil pump to start during operation, it indicates that the butterfly valve automatic device malfunctions, or the butterfly valve operation handle is mistakenly touched to the closing side. At this time, the butterfly valve relay should be reset, the oil pump should be stopped, and the butterfly valve operation procedure should be pressed. Re-open the butterfly valve.
3 Measures to prevent the partial clearance of the butterfly valve 3.1 Technical measures (l) Install the signal device of the position of the butterfly valve. When the butterfly valve in operation deviates from the fully open position, a signal is issued, and the light plate of the central control room is illuminated, and the operating personnel can judge whether it is an accidental closing butterfly valve or a partial flushing according to the signal.
(2) After the general treatment measures for the partial flushing, the oil source valve can be lifted until the butterfly valve full open signal appears, and then the oil source valve is dropped.
(3) Improve the quality of butterfly valve inspection. Due to the large size and firm positioning of the butterfly valve, it is necessary to solve the problem of the rotating shaft in place. It is necessary to disassemble and hoist the butterfly valve, and the amount of engineering is large, and the space of the butterfly valve chamber is limited. It is also difficult to do because of the long use time and wear of the butterfly valve. It is also difficult to guarantee quality after disintegration. At present, it is common to use a gasket to adjust the center position, which can solve the problem of the butterfly valve body to a certain extent. Improve the maintenance process to ensure that the butterfly valve is parallel to the water flow after the butterfly valve is fully opened.
(4) Improve the sealing performance of the servomotor, replace the better sealing material, and periodically fill the cavity of the servomotor piston to replenish the oil.
(5) Install a water monitor at the inlet of the butterfly valve to monitor the fluctuation of the water flow, and add a periodic work content in the operating rules of the butterfly valve, that is, start the oil valve every week and fill the oil passage of the relay.
3.2 Organizational measures (l) Strengthen technical training for employees, master some judgments and technical processing skills, and master the rules of butterfly valve operation.
(2) Establish and improve relevant systems, such as defect registration, processing, and assessment reward systems.
(3) Strengthen the daily inspection and maintenance of the butterfly valve. The abnormal "butterfly valve closing" signal should be recorded and analyzed for reasons; the inspection of the butterfly valve and the bypass valve should be strengthened during the normal inspection; the operating mechanism is required to be in the correct position, each electromagnetic operating valve, relay, The monitoring system and oil pump should meet the requirements of the regulations; increase the inspection content, especially pay attention to check the oil relay, the four-way valve, and the oil drain circuit for oil leakage.
For more information, please click: http://
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