Keeping vessels of all kinds stable at sea or in port is an essential part of Hoppe Marine's DNA.
We are therefore naturally delighted when our rolling damping and anti-heeling solutions also contribute to new ways of increasing efficiency or enabling more environmentally friendly operation of ships.
GTT has now received approval from the China Classification Society and DNV for their Shear-Water concept. The idea is to use a large bilge keel and a FLUME® anti-rolling tank supplied by Hoppe Marine for their LNG bunker and feeder ship design, instead of the usual method of achieving the necessary draft and associated stability by taking seawater.
The FLUME® roll damping tank is designed for maximum efficiency in the empty condition where rolling might be more severe. However, it may also be operated in design draft condition with slightly less efficiency.
Most merchant vessels worldwide use ballast water when the bunkers are empty or only partially loaded to maintain seaworthiness. Therefore, a considerable amount of ballast water is carried by ships every day. However, ballast water has to be purified of pollutants and organisms in an elaborate way due to applicable IMO regulations. But even if the ballast water is treated, there is a risk of harmful aquatic organisms and pathogens being transferred from one area to another. With the solution developed by GTT, this risk is completely eliminated. This is because the envisaged FLUME® tank is operated with fresh water, which eliminates this costly and energy-intensive cleaning of harmful organisms. In addition, a ballast-free ship also offers advantages in terms of investment and operating costs, simplification of ship operation, reduction of corrosion and extension of service life.
The seakeeping behaviour of the Shear-Water design was extensively tested at the Hamburg Ship Model Basin (HSVA), including different bilge keels and the operation of the ART in various load cases, sea-states and headings. The results were in line with the expectations and confirmed the efficiency of the installation, with generally a rate of roll reduction between 15% and 40 % for the Full condition and 44% to 64% for the Empty condition.
FLUME® is a passive free surface open channel box type roll damping tank. It has the unique ability to adapt to changes in the vessel’s loading and operating condition. The stabilizers’ natural response period can be adjusted by a liquid level variation to match the corresponding roll period of the ship. Equipped with a Liquid Level and Roll Period Indication System that constantly monitors the operating condition of the vessel and the stabilizer the system assists the crew in achieving the maximum roll stabilization. As an add-on, the system can be upgraded with a designated pump to adjust the liquid level in the tank automatically, therefore no interaction of the shipboard personal is required. The FLUME® Roll Damping tank is especially suitable for vessels with a very large variance in loading conditions. As it has no moving parts maintenance and initial installation cost are relatively low.