The Spiral Case Hydrostatic Test

　　At 12:05, March 27, 2021, first Unit of CHMC Laos Nam Ngum 4 Hydropower Station successfully completed the spiral case hydrostatic test.

　　The hydrostatic test, through gradually pressure increasing, pressure maintaining, and pressure decreasing and several procedures, totally lasted 3.5 hours. The maximum test pressure value was up to 6.3MPa, and the test remained in this maximum pressure for 30 minutes. The whole test process was stable and orderly, with the quality and safety control.

　　The spiral case hydrostatic test was the “Big Test” in the installation stage of the Unit embedded parts of Laos Nam Ngum 4 Hydropower Station Project. Its aim was to wholly test the design, manufacture and installation of the spiral case, at the same time to eliminate welding residual stress. The spiral case of each Unit must pass the test before embedding in the concrete to ensure that the overall quality of the spiral case could meet the long-term safe and stable operation requirements. 

　　The successful completion of the spiral case hydrostatic test marked that the installation work of the embedded parts of Unit 1 was basically finished, which laid a foundation for subsequent concrete pouring and generator stator rotor assembling.