On May 29, 2020, China National Power Construction Corporation announced that the electromechanical installation branch of the Seventh Hydropower Bureau undertook to install the last welding weld of the volute of the No. 5 volute on the left bank of the Baihetan Hydropower Station. Draw a full stop.

Baihetan Hydropower Station is located in Ningnan County, Sichuan Province and Qiaojia County, Yunnan Province. It is the second cascade power station developed in the cascade of the main stream of the lower reaches of the Jinsha River. And develop comprehensive benefits such as navigation in the reservoir area. The normal storage level of the reservoir is 825 meters, and the corresponding storage capacity is 20.6 billion cubic meters. The underground plant is equipped with 16 units. The initial planned installation capacity is 16 million kilowatts, and the average annual power generation is 60.24 billion kilowatt hours. The power plant plans to generate electricity from the first units in 2021, and the project will be completed in 2022. After the completion of the power station, it will become China's second largest hydropower station after the Three Gorges Hydropower Station.

The seat ring and the volute are the two major components of the embedded part of the Francis turbine. They are both the basic part of the unit and the component of the flow-through component of the unit. And the force transmitted from the top cover. The seat ring is generally a welded structure composed of upper and lower ring plates and fixed guide vanes. The spiral case is welded with steel plate, and its wrap angle is generally within the range of 345-360. The volute is welded to the disc edge or transition plate on the outer edge of the upper and lower ring plates of the seat ring to form a whole. The welds need to be strictly inspected for flaw detection, and if necessary, a hydraulic test.

The volute is the water diversion component of the turbine. It is connected to the diversion pressure steel pipe and the draft tube. It is located on the outermost layer of the turbine. , Guide the water guiding mechanism evenly and symmetrically, and then enter the runner after forming a circulation to ensure that the runner is always immersed in water when working.

Eight turbine generator units with a single machine capacity of 1 million kilowatts are arranged on the left and right sides of the Baihetan Hydropower Station. For the first time, all the domestically produced million-kilowatt turbine generator units are used. The million-kilowatt giant hydro-generator set is the "Everest Mountain" in the world hydropower industry. The Baihetan hydropower unit is the world's first million-kilowatt hydro-generator set.

It is understood that the carbon content of 800 MPa high-strength steel is quite large, the welding crack sensitivity coefficient is high, the low-temperature impact performance requirements are high, and the welding is difficult. After the close cooperation of all parties involved in the construction, the left and right volutes are installed according to the planned nodes, and the various indicators of the welding quality of the volutes are in line with the quality requirements.

Baihetan Hydropower Station started the installation of the volute of the left bank unit on December 12, 2018, which took 534 days to complete; on December 31, 2018, it started the installation of the volute of the right bank unit, which took 479 days to complete. With the end of the volute installation, Baihetan Hydropower Station will usher in the peak of unit installation.

China Power Construction has excellent welding skills, don't you want to see it? Editor/Peng Xue