Water Lubricated Guide Bearing with Self-aligning Segments

Abstract

Abstract Water lubricated guide bearing was newly leased and has been applied to actual hydro turbines with vertical shaft. reAs a result, they can have not only high bearing performance but environmental advantages in meeting the demand for reducing river pollution by oil leakage from oil lubricated guide bearing. The PTFE composite guide bearing was tested by experimental equipment operated under conditions similar to those of actual hydro turbines. Circumferential and axial tilting bearing segments help to improve the bearing performance and efficiency due to low friction loss in the bearing system. Furthermore, bearing cooling systems could be eliminated and maintenance periods could be extended, thus the initial investment and operating costs of the hydroelectric power plant are reduced. Keywords : Water lubricated guide bearing, PTFE, Tilting segment, Vertical shaft hydro turbine, Hydrodynamic lubrication 1. Introduction Hydroelectric power generation, which provides electricity from clean and renewable energy without CO2 emissions, has the highest conversion efficiency and the fastest response in providing a stable power supply at low operating cost. In Japan there is not much room left for development of large capacity hydropower plants. In order to fulfill market demand for clean and renewable energy supply, small and medium capacity hydropower plants have been recently developed. The service intervals for hydropower plants have been extended and in other words, their long maintenance intervals strongly request that the radial and thrust bearings must have extremely high stability and reliability for supporting the rotating parts such as runner, turbine shaft, generator shaft and rotor. The oil lubricated radial bearings (hereinafter to be called guide bearings instead of radial bearing) have been usually applied to the hydro turbines and generators, but on the other hand the water lubricated guide bearings have recently had a strong background in construction of the hydro plants in order to prevent oil pollution in river water. The turbine guide bearing for multi-nozzle vertical Pelton turbine must have high stability throughout all kinds of operation enough to withstand high bearing pressure during operation driven with only one active nozzle. In case that shaft alignment is out of tolerance, there are possibilities of shaft vibration or partial contact between the bearing segment and the rotating shaft and, therefore, the turbine guide bearing must have preventive measures against abnormal wear and significant damage on the bearing sliding surfaces.