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Measures to prevent internal leakages of valves are as follows:

1. Flushing the pipe

During valve inspection, it is common to find scratches on the valve. During the operation of power plant units, it is often found that the valve does not leak before opening, but leaks occur during operation, which are all caused by impurities in the pipeline. For example, valves are closed during operation for water gates below the boiler, and they can only be opened after the boiler discharges water under normal circumstances. Before the boiler enters the water, it is closed under the condition of no pressure, whether it is in the state of opening the valve or in the state of closing the valve. Under the condition of no pressure, the substances existing in the pipeline cannot be removed in time, and some impurities will remain in it, which may damage the sealing surface in the process of closing the valve, and lead to internal leakages of the valve. Under normal circumstances, all valves in thermal power systems of thermal power plants should be flushed under pressure before starting, and the generated wastewater is directly discharged to the corresponding position.
 
2. The filter being in a good condition
In the thermal system of a thermal power plant, it is a very critical step to prevent impurities from entering the thermal system only by ensuring that the filter is in a good condition. The thermal system filter screen of a thermal power plant refers to the filter screen in the front water supply, main water supply and other departments. The filters in these parts should be cleaned in time during use, and the damaged filters should be replaced in time so as to effectively prevent impurities from entering them.
 
3. Calibrating the electric valve
In order to reduce the internal leakage of electric valves, some electric valves which cannot be opened automatically should be adjusted to automatic mode to ensure that no angle is reserved for the valve. For some electric valves that have been able to start automatically, no matter what state they are in, they can be opened automatically, so the tightness of the electric valve should be ensured.
 
4. Not recycling unqualified condensate
In the process of starting the unit, if the superheater of the boiler is pressurized, the welding slag impurities in the steam system inside the boiler will flow into the main steam pipe of the steam turbine. Impurities entering the high side and superheater will flow to the condenser. In this way, the quality of the condensate water will not meet the standard. In the process, the condensate water will be discharged to the corresponding position, and the water volume in the condenser will be increased in time to ensure that the water quality of the condenser can meet the corresponding standards. After the water quality in the condenser meets the standard, the water in the condenser can be recycled in time.
 
5. Maintenance of the check valve
In the process of overhauling the valve, the method of pressing red lead can be used to check the degree of integration of the valve, and checking one by one should be carried out. If it is found that the quality of the valve does not meet the standard after overhauling, the valve cannot be used and must be repaired again. The valve of the thermal system should also be measured. The purpose of this is to better understand the internal leakage of the valve during operation, and to provide corresponding help for closing the valve for maintenance. In the process of measuring the temperature of the valve, it is generally measured once a week.
 
6. Standardizing the valve operation method
In the process of opening and closing the valve, some shut-off valves can only be fully opened or fully closed under normal conditions, and cannot be left in a half-open or half-closed state to ensure that internal leakages will not occur in the valve. In some of these pipelines, water gates should be set up. In order to prevent the internal leakage of the valves, the water gate should be opened once before opening, and then it should be opened again; the water volume can be effectively adjusted by twice opening. Open the valve once and then open it again to protect the equipment.
 
7. Closing the valve well after the unit being started
After starting the unit, it is necessary not only to ensure that the moving door is closed, but also to evacuate its electric water door; manually depressurize it after closing the electric door. After 4 hours, the temperature needs to be measured, and the result is used to judge whether the valve is closed well. If it is found that the temperature of the valve has dropped in the process, but it has not dropped to the ambient temperature, it is necessary to retighten it again, so that the valve can be closed.
 
Conclusion
All in all, the energy consumption of thermal power plants can be well reduced by controlling valves, and taking preventive measures against internal leakages of valves is also the main method to reduce internal leakages. Only effective prevention can reduce the leakage of valves and improve the economic benefits of thermal power plants.