Air Lubrication System Now a Proof Positive Fuel Saver

By George Backwell at July 14, 2012 04:50
Filed Under: General

Air-lubrication of a ship’s hull really does pay off with significant fuel savings. Just a few days ago NYK Line announced that trials of the Mitsubishi Air Lubrication System (MALS)  in not one, but two of its module carriers in a variety of normal operating conditions over a two-year period had been completed and confirmed an average 6% reduction in fuel consumption.

Long Term Operational Trial

An air-lubrication system was installed in each of twin-designed NYK-Hinode Line ocean-going vessels, the 19,800 dwt diesel-engined heavy equipment carriers ‘Yamatai’ and ‘Yamato’; the first in March 2010, and the other in the following November.

MV Yamatai: Photo credit NYK Line

These two ships are special heavy load carriers with roll-on, roll-off rampways for the transport of large prefabricated structures. Their propulsion system is by twin shaft CPP propellors, powered by a pair of Daihatsu 6DKM36 diesel engines, maximum rating 3.218 KW at 600/196 rmp.

The experiments with the air-lubrication system (supported by classification society ClassNK and the Japan government) were designed to verify fuel reduction; to examine the behaviour of the air bubbles supplied to the vessel bottom under various operational and sea conditions; to examine the relationship between the amount of air supplied and its effect, and to validate CO2 reduction.

Earlier tank tests and sea trials had suggested a 10% reduction in CO2 emissions was to be expected, but these trials in all sorts of vessel conditions, in a variety of sea and weather conditions confirmed somewhat less – 6% – nevertheless a meaningful energy saving.

Air-lubrication System by MHI

MALS is a proprietary technology by MHI that reduces hull friction by blowing out a constant layer of small air bubbles along the bottom of a ship’s hull; imaginatively likened to ‘a magic carpet’ the ship rides on.

Air discharged from blowers is temporarily stored in a head tank and air supply branch pipes connected to the head tank are piped to the air supply portion mounted on the bottom of the hull. One air supply branch pipe is each connected to one air chamber. All of these chambers are recessed.

MALS Simplified Diagram: Image courtesy of MHI (Technical Review Paper)

With a growing awareness in the industry that this new technology delivers on its fuel-saving promise, last month Germany’s AIDA Cruises ordered MALS to be installed in its two new 125,000 gt cruise ships now under construction at MHI's Nagasaki Shipyard & Machinery Works. MHI say that the system is expected to reduce fuel consumption by 7% and will be the world’s first such installation in a large cruise ship. Deliveries are scheduled for the spring of 2015 and 2016.






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