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Vietnamese 7280 tons DSV launch story

Evergreen-Maritime successfully launched another DSV with 7280 tonnes  in Vietnam

On December 7, Eversafe marine engineering company, the subsidiary of Evergreen Maritime, successfully launched a 7280 tons DSV using airbag ship launching technology in Vung Tau Vietnam. It is the second DSV and third vessel launched by Evergreen company for the same client-Strategic Marine (Vietnam). “Caballo Maya” was launching on April.6.2010

That vessel named “CABALLO MARANGO” gets 143 meters total length; 22 meters molded width and 7280 tons launch weight. It is built on a plain ramp which consists of two parts: one is 70 meters long with a 3% angle; another part is 74 meters long with a 4.5% angle. In the ramp only five meters there is a 25 cm wide concrete stripe, the left parts are filled with uncompressed debris. The most gravity of vessel is located on the bow which upon the 3% angle part. Supporting blocks is arranged to make vessel’s bottom parallel to the 4.5% angle ramp then the height of bottom is getting higher and higher from the knuckle of ramp.

The main difficulty of this launch project is lifting up vessel to remove blocks since the heights of part vessel’s bottom are bigger than the diameters of airbags. For launch, it should not be a big problem if the ship’s gravity can be located on the 4.5% angle ramp.

By several times discussion with shipyard, Evergreen technical teams decided to build temporary platform to enable airbags to lift up vessel. After the lifting up, vessel will be moved forward 30 meters which will make the vessel’s gravity center beyond the knuckle about 10 meters. But a subsequent problem will come up that after vessel moved its stern will get float when in high tide time. Evergreen teams have to do more detailed calculation to avoid the possible premature stern float. At last ballast water is employed to antagonize the stern buoyancy.

On December 4th, Eversafe engineers supervised shipyard workers to arrange airbags and pump them to lift vessel with back pull from two 50 tons winches. Limited by the temporary platform, only 30 pieces airbags can be used for lifting. Based on accurate calculation, the lifting work went smoothly but it still took two days to take out all supporting blocks. In 6th morning, low tide time, people began to move the vessel. Because the subsidence of ramp, marine airbags rolled arduously and the friction counteracted vessel’s slip down force which lighten the burden of winches. Total 3 hours it took people to move vessel forward 30 meters and recalibrate marine airbags. After the vessel shift, ballast water was added. On
December 8, a ceremony was hold to bless the nice vessel. At pm 3, after everything is checked again, the vessel was launched. When steel ropes were chopped down, the vessel started to move swiftly by riding rolling airbags and entered into water smoothly accompanied by scream from crowded watching people. It took 62 seconds from vessel start to total floatation.

This launch project is a rigorous trial of Evergreen marine airbags and his airbag ship launching technology. Some airbags are compressed 80% and their inner pressures reach 0.25 Mpa during the lifting and launch period. Evergreen marine airbags are proved to be reliable for cruel heavy duty. Also for this launch project, airbag ship launch technology exhibited its peerless flexibility and power. To lift the vessel, airbags were arranged to make vessel bottom being parallel to 3% angle ramp; while to launch the vessel, airbags’ pressures were adjusted to make vessel bottom being parallel to 4.5% angle ramp. People can easily find that to do this launch project airbag ship launching is the most effective, the most economical method.

Evergreen Maritime, the leading manufacturer and service provider of marine airbags and fenders, always take delight in challenges to achieve bigger accomplishment.

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