Protection of Nano Coating to the Through-Flow Parts of Hydraulic Turbine

Abstract

One characteristic of Chinese rivers is their high silt contents. The Yellow River is unique for its excessive suspended sediment of the world river. Its annual sediment discharge is 116 million tons and its average sediment concentration is about 37.5 kg/m. Hydropower stations on the Yellow River are all facing the erosion problems on hydraulic turbines. The main harms of hydraulic turbine erosion are as follows: shorten repair cycle time and increase repair workload, less efficient plant operation, high maintenance costs and high potential safety risks. For example, Sanmenxia Hydropower Station, which is in the midstream of the Yellow River, has multi-year average sediment concentration 37.5kg/m, the maximum sediment 91lkg/m. Its hydraulic turbine is Kaplan turbine. Because of high sediment content, its turbine erosion is very serious. After running 3630 hours, the most of the 3mm stainless steel plate welded in the back of blades has come off in 4# turbine. The gap size between the blades and the middle ring already was extended from 7～8mm to 20mm and the weight loss of the blades was 780kg. After running 7595 hours, the base material of the blade back was alveolate and the gap size was extended to 40～50mm. After 31000 hours, the triangle of the blade head has been rubbed off and the gap size was extended to 120mm. The turbine was almost scrapped. To reduce or eliminate the silt erosion, an effective way is to use surface coating to the through-flow parts of the hydraulic turbine.