1.2.1 In general, for a ship to be assigned an unrestricted service notation, a
minimum of two azimuth thruster units is to be provided where these form the sole means
of propulsion. For ships where a single azimuth thruster installation is proposed as the
sole means of propulsion or steering, a detailed engineering and safety justification is
to be evaluated by LR. This evaluation process will include a risk assessment analysis
using a recognised technique to verify that sufficient levels of redundancy and
monitoring are incorporated in the azimuth thruster’s essential support systems and
operating equipment. The risk assessment is to take into account the proposed restricted
area notation.
1.2.2 The
failure of one azimuth thruster unit or its control system is not
to render any other thruster inoperative.