Analysis and Prevention of Water Erosion on Final Stage Blade in Low-pressure Cylinder of 630 MW Units

Abstract

Shrouded blades that are widely used in the final stage of low-pressure cylinder of large steam turbines can significantly improve the performance of the units. After long low-load operation， they are susceptible to water erosion which damages or results in falling off of the tips， and thus threatens the safe operation of the units. In view of the water corrosion failure of the low-pressure last stage blade and guide ring of a 630 MW unit in a power plant， the reasons were analyzed， and measures such as ultrasonic thermal spray of the final stage rotor blade， replacing hollow stator blade， lowering the drain holes of low-pressure heaters 8A and 8B and improving the strength of the low-pressure exhaust guide ring were taken, which greatly improved the water erosion resistance ability of low-pressure cylinder. The preliminary results show that the reliability of low-pressure cylinder of large steam turbine unit can be improved by monitoring the water corrosion of low-pressure cylinder and timely taking comprehensive preventive measures.

Keywords

• shrouded blade
• water erosion
• spray
• hollow stator blade
• drainage