Thursday, June 30, 2011
On May 18 2011 ,Eversafe Marine engineering company successfully launched a 37500DWT cargo ship with 50 pieces marine airbags (pneumatic rollers) in Zhejiang Taizhou shipyard. The vessel named “Dongchengyuan “ measured by 180 m length, 29.2 m breadth moulded and 15.2 m moulded depth. Its lightweight reaches 8000 tons.
The vessel was built on a concrete ramp with 2.3/100 slope. Beyond ramp end there is a 40 m long unpaved dirt ground. The launch channel water is so shallow that in low tide a 30 m long beach full of mud will appear.
The difficulty of this airbag launch project is the deficient launch ramp and launch area that may cause launch accidents. Eversafe engineer calculated the possible bearing pressure of the ground during launch and found the gravel reinforcement would suit for demand. Since time is tight dredging launch area is impossible. So people have to prepare the remedial solution to prevent vessel from getting stuck by mud: one tug boat was employed to help launch.
In the afternoon of May 17, the vessel was transported forward for 40 meters with airbags which can prevent the 40 m long ground from collapse during the launch. In the next day morning Eversafe launch team began to work as early as 6 am. People adjusted all airbags’ pressures to decide vessel’s trim angle according to the design plan. Ropes from tug attached to the stern pole with a 45 degree angle. After the launch ceremony at 8:30 am the launch commander shot the gun .When two pulling ropes were chopped the vessel started to move steadily to the water. Since launch area water was not deep enough to float stern, airbags were pressed more than 60% by stern’s weight. The slippage inertia keep vessel moving but vessel’s speed slowed down until tug’s pull force accelerated it again. When vessel entered into deep enough water it got float freely.
This launch project is a rigorous test of Eversafe launch team and ship launching airbags. Airbags bore about twice pressure than normal launch. Advantages of airbag ship launching are represented clearly by this project: airbag launch can remedy the deficiency of launch condition which is especially useful for some emergent projects.
But a good preparation work can mostly promise the success and safety of airbag ship launching. Only for some special condition people should do the launch with deficient preparation. Also quality of ship launching airbags is the vital factor for the success.