Abstract: Tidal current turbines are designed to extract energy from bi-directional tidal current. Power take - off train of such a turbine typically consists of rotor, gearbox, mechanical brake, coupling, generator, converter and controllers. The rotor is attached to the main shaft, which transmits power to a generator through a gearbox. The main seal mounted on the main shaft has the dual purpose of retaining lubricant and preventing the ingress of seawater. The locating bearing of the main shaft (main bearing) is positioned immediately after the main seal.
Reliability assessment of tidal turbines, being a new technology, is hampered by lack of
historical data on failures. A method for estimation of failure rates by adjustment of base failure rate to conditions of tidal turbines is applied. Failure rates are assumed constant and three components are considered in details: main shaft, main seal and main bearing.
An improved reliability model of the main bearing with variable failure rate is developed,
which takes into account uncertainties associated with bearing load, lubricant viscosity, lubricant contamination. Failure rate distribution, obtained using Monte Carlo simulation, is approximated by a lognormal distribution and 90% confidence interval is established.
