Development has taken place over several years using computational fluid dynamics, CAD techniques and tank testing to optimise the shape of the below-water parts and mechanical design. Swirl energy in the slipstream from the pulling propeller is partly recovered as a propulsive force by the special shape of the leg and skeg. The pulling CP propeller itself works in clear water, factors which increase the total efficiency. The units will receive their first application in the offshore sector later this year with operator Havila retrofitting their supplyvessel ‘Havila Tampen’ with twoUlstein Aquamaster thrustersfor main propulsion, replacingconventional azimuth thrusters.

These units will be the largestbuilt to date, type AZP 120 isdesigned for inputs of up to3,000kW and will be transmitting2,500 kW in this application.Havila Tampen is a UT-Designtype UT745E and was deliveredby Kleven Werft only lastSeptember. The vessel usesdiesel-electric propulsion and the two Azipull units under the stern will be powered by electric motors in the hull. Conventionalthrusters from Rolls-Royce wereinstalled to get Havila Tampeninto service but the owner hasdecided in principle to change toAzipull units as soon as thesewere released for offshore service.

The changeover is designedto be quite simple. The existingpropulsion motors and the inputgear units in the hull can remainin place, with only the outboard parts of the main thrusters needing to be changed.Havila Tampen will havethe first two units for offshoreservice. Four more havebeen ordered to propel two UT-Design platform supplyvessels under construction forIsland Offshore and scheduledfor delivery towards the end ofthis year.

MJ Information No: 18350