How to deal with the internal leakage of coal-fired power plant valves?

The thermal loss caused by the internal valve leakage of the thermal system is an important factor that affects the thermal efficiency of the boiler. The control of the internal ball check valve leakage is an effective way for coal-fired power plants to establish a long-term mechanism for safe production, improve the level of economic operation and establish a good social image. How to deal with the internal leakage of coal-fired power plant valves? Let us find the answer from the article.

 

 

Causes of valve internal leakage

Unqualified water quality produces internal leakage

When the unit is started, because the system is out of service for a long time, there is more rust and salt accumulation in the pipeline. This requires flushing the drain valve of the fully open system during the unit startup. If the flushing is not thorough, the valve core and valve Impurities such as rust accumulate between the seats. These impurities are stuck at the bottom of the valve core and cause the stainless steel ball valve to be not closed tightly, causing internal leakage.

 

The influence of the control part

The traditional control method of electric actuated valves is through mechanical control methods such as valve limit switches and over-torque switches. Because these control elements are affected by ambient temperature, pressure, and humidity, the internal leakage of the electric valve is caused. The pressure, cleanliness of the compressed air used in the instrument, the opening of the intake valve and the positioning of the closing feedback will all cause internal leakage of the pneumatic valve.

 

Internal leakage caused by unqualified valve

The valve manufacturer does not strictly control the valve material, processing technology, assembly technology, etc. during the production process, resulting in unqualified sealing surface grinding, pitting, trachoma and other defective products are not rejected, and professionals perform quality inspections before installation There is no strict control, which leads to unqualified products entering the production site and causing internal valve leakage.

 

 

Measures to prevent valve internal leakage

1. Regular inspection

The purpose of regular inspection of thermal system valves is to monitor the development of internal leakage during valve operation. Manually isolate the drain pneumatic door with serious leakage before closing. Periodic temperature measurement of the valve should be at least once a month. Periodic temperature measurement of the valve is divided into regular temperature measurement during operation, temperature measurement at the later stage of startup, and temperature measurement after working conditions change. If the unit is too negatively separated. After the high-pressure heater is drained and repaired.

 

2. Standard operation

*When the unit starts and stops, choose the right time to switch the valve. If the valve is closed too late or opened too early, the high temperature and high pressure steam will cause serious erosion of the valve;

 

*When opening and closing the valve, in principle, the shut-off valve can only be fully closed or fully opened, and these valves cannot be half-open and half-closed to prevent the valve from being blown out and causing internal leakage of the valve;

 

*Some butterfly valves should clearly mark the switch position on site. If these valves are closed in place, they should not be closed, otherwise, over-switching will cause valve erosion;

 

*In order to prevent and reduce the internal leakage of electric valves, for electric valves and adjustment doors that are not automatically opened, manual pressure closing is set as the full-close stroke, and in principle, the valve opening cannot be reserved;