Since 3# generating unit of Suo Jinshan hydropower plant was officially put into operation, the bucket broken off many times, there were many through cracks appeared on the bucket and the water retaining plate of nozzle was broken off repeatedly (cancelled after upgrade), the abnormal large water consumption and output shortage problem existed in long term, seriously affected the plant safety and economic operation. The original nozzle adopts oil control water operation mode, which has a large number of servo valves, cams, connecting rods and feedback mechanism. This system has a low sensitivity and high maintenance requirements, which affect the plant production management. In addition, the close cavity of 4# nozzle got pressure loss once the pressure valve is close to the full load, caused hydraulic imbalance when the nozzle fully opened, affecting the turbine output along with vibration increasing.
The renovation was applied with direct current nozzle featured by hydraulic balance structure, dish shape spring (stainless steel) with 4.0MPa conventional oil pressure operation. The nozzle needle has a hydraulic self closing trend in the condition of small opening, at this time if the needle control pressure dismissed or in other dangerous situations, the needle will automatically shut down without excessive water hammer pressure to keep the safety of water supply system, especially in the fully closed position, the needle does not automatically open even if the operating oil pressure lost, the generating units will be in a relatively safe condition. In the condition of big opening, the needle has a hydraulic self opening trend, at this time if the needle control pressure lost, the needle will automatically open, it will not cause excessive water hammer pressure either to keep the water supply system safety.
The upgraded runner model CJA475C-L-130/4x10 is processed by high precision CNC machine to provide better machining accuracy and ensure geometric dimensions, bucket consistency and passage surface reflectance, so as to effectively reduce the cavitations may caused by machining error in potential, prolong the service life.