Ijmuiden-based OSD Holland BV has revealed details of its latest design, the ‘Azistern 2250e’ hybrid harbour tug featuring a podded drive system.

The world of ship-handling towage is constantly evolving, driven by requirement to attend increasingly larger vessels and the demands for enhanced safety provision at oil and LNG terminals, both onshore and offshore. At the same time there is also the continual drive to reduce costs and develop more environmentally friendly operations including greater efficiencies while at the same time ensuring the bollard pull is available when required.

Alternatives to traditional forms of producing the power are now in service including hybrid and LNG-powered tugs and OSD manging director Michiel Wijsmuller introduces the latest design: “The Azistern-e has the typical low resistance stable hull and all-round visibility that is associated with all Azistern designs. What makes this particular Azistern tug different is that it is driven by a revolutionary podded drive and that it has a flexible and green electro/diesel-electric configuration.”

The proposed tug is classed by Bureau Veritas with the notation: BV1+HULL, +MACH, AUT-UMS, TUG, Battery System, Green Passport, Unrestricted Navigation. Main dimensions include: LOA 22.25m, beam overall 11.5m and design draught (to keel mld) 4.54m. Tank capacities include: fuel oil 43m3 and fresh water 15m3.

The hybrid power is generated by two 970kW variable speed gensets supported by two 400kWh lithium battery packs. The propulsion system comprises two 2,300mm diameter azimuthing electric podded drives delivering a bollard pull ahead of 50 tonnes and speed 12 knots. Low emissions are a feature of the design and can be delivered compliant with IMO Tier 3 requirements suitable for ECA areas through an after-treatment system. It is also equipped with an innovative energy management system with uniform and optimised loading of the propulsion system ensuring low maintenance and fuel costs with transient sailing and manoeuvring performed using batteries with zero emissions.

Short reaction time is claimed for the power train with use of batteries as a booster producing maximum bollard pull in seconds with the relatively small size of the engines and shaftless configuration freeing up more space below deck and providing optimum flexibility with division of space and piping. Highest levels of comfort for the four man crew of the MLC-compliant tug is provided thanks to the podded drives and double elastic mounting of the gensets.

Deck equipment includes a two-speed towing winch forward with a pull of 25 tonnes (0-10 m/min) low speed and 8 tonnes (0-28 m/min) at high speed. A 60 tonne SWL towing hook is included.

The tug is provided with the standard array of navigation and communication equipment common to such vessels, the radio installation conforming to GMDSS Area A-1. Accommodation is provided for six persons in two single and one double cabin.

By Peter Barker