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OSD unveils e-tug concept

Ship & Boat international: eNews October 2016OSD unveils e-tug concept

Greater space savings below deck, a short power train reaction time and reduced emissions are some of the key benefits of the 22m Azistern 2250 e tug concept.

Offshore Ship Designers (OSD) is hoping to offer tug operators a compact, low-emissions vessel concept suitable for operations in designated emission control areas (ECAs) and compliant with IMO Tier III requirements.

Designated the class name ‘Azistern 2250 e’, the e-tug concept is set to combine two 970kW gensets, a pair of 2.3m-diameter azimuthing electric podded drives and two 400kWh lithium battery packs into a diesel-electric configuration. Not only is this arrangement intended to significantly cut emissions and lower fuel costs, but the relatively small size of the engines and the shaft-free nature of the set-up should result in greater space savings below deck, says OSD. 

The concept has been approved by class society Bureau Veritas, which has awarded it BV I + HULL + MACH +AUT-UMS, TUG, Battery System, Green Passport, Unrestricted Navigation notations. The tug has also been designed to be in compliance with the terms of the Maritime Labour Convention, 2006 (MLC). For extra crew comfort, the gensets have been mounted in a ‘double elastic’ fashion. A spokesperson for OSD tells Ship & Boat International: “The diesel engine is mounted by rubber elements on a common base frame, along with the generator. The base frame as a whole is then again elastic-mounted onto the ship’s foundation – so it is ‘double elastic’-mounted to the ship’s steel structure.”

The vessel’s power arrangement will grant it a speed of 12knots and a bollard pull (bp) of 50tonnes ahead. OSD claims: “The vessel’s power train has a remarkably short reaction time. By using the batteries as a booster, maximum bp can be achieved within seconds.”

The Azistern 2250 e will feature a length of 22.25m overall, an overall breadth of 11.5m (or 10.8m moulded), a depth of 4.5m and a gross tonnage of 235tonnes. Draught is predicted to be 3.45m to baseline, or 4.54 to keel (moulded). Onboard capacities will include 43m³ of fuel oil and 15m³ of fresh water. The tug will accommodate a four-man crew, spread across one twin and two single cabins.

Deck equipment will include a 5tonnes-capacity capstan and a two-speed tow winch; in low-speed mode, this winch will pull 25tonnes at 0-10m per minute and, in high-speed mode, 8tonnes at 0-28m per minute. The winch comes with a towing hook with a SWL of 60tonnes.

The OSD spokesperson adds: “We are in discussion with various yards to work out the concept into a basic design.”

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