"Tang Shan Chang sheng 2" ship launching by Evergreen marine airbags
Evergreen successfully launched a 20,000DWT ship on a no fixture ramp with Evergreen Marine Airbags by Ever-Safe launching team. This cargo ship is 170 meter long and 27 meter width with 7800 tons light weight.
For some untold reasons, this ship was built upon a 200 meter long concrete ramp on which there is no fixture or anchor block. The connection of concrete ramp and river water is unsettled silty riverside. The only available machine on spot is an excavator grab. Then questions come out: how to start the movement of ship launching and the most important thing is how to avoid the slip of the ship when it is lifted from the wooden blocks. Fortunately we have a powerful tool "evergreen marine airbags" and experienced team.
In low tide period, the mud of riverside was cleaned by excavator grab and some sand bags were placed to fulfill pits on the riverbed. Marine airbags were placed between wooden blocks according to the calculation. Those airbags at the stern were fully inflated to lift stern as high as possible and then airbags at the bow began to inflate slowly, the inflation was stopped as soon as stern leave the wooden block. After the ship was totally lifted, wooden blocks were removed and airbags were inflated or deflated again to make the ship to be slightly retroverted.
Photo 1: Clean the mud Photo 2: Lift the ship with Evergreen Marine Airbags
In high tide period, when water reached the stern marine airbags were adjusted carefully to low down the stern to get bigger buoyancy.As the water level went higher, people began to inflate airbags at the bow to make the ship tilt forward but not exceed the angle of 0.008 radian which is the boundary of ship slipping. When the water reached the scheduled level,the excavator grab whose shovel were wrapped with tyres began to push the bulbous bow. Because the flexibility of marine airbags, the tilt angle of ship will easily exceed the 0.008 radian when ship get a obliquely upward push force. Then ship started to slowly moved and went into the water smoothly.
Photo 3: Wait for high tide Photo 4: Push the bulbous bow to start the launch
Photo 5: Enter into water riding Evergreen Marine Airbags Photo 6: Free floating
If people have to launch a ship without pull force there must be some conditions to be satisfied: deep enough water, reasonable ramp, good calculation and experienced engineer. Deep enough water means the water level at the end of ramp should exceed the ship's aft draft plus 2.5 meter. The ramp design depends on the launching water area and ship which include gravity distribution, size,etc.
The flexibility of marine airbags can remedy the practical limitations in the marine projects. By adjusting the inner air pressure to change the work heights Evergreen marine airbags can easily change the ship’s tilt angle according to the need. For example if launch a ship on a flat ramp we may lower the stern and lift the bow by giving different inner pressure to airbags. If the angle of ramp is fairly big,we may do the reverse to slow down the slipping. People can also use marine airbags with different diameters and lengths to get a wider adjustable scope. If the water level is not deep enough, people may move the ship by airbags to near the water and minish the ship tilt angle to launch it safely. The convenience and flexibility make marine airbags become the powerful tool of marine projects such as ship launching/landing, marine salvage, heavy conveying.
Photo 7: Caisson conveying by Evergreen Marine Airbags Photo 8: Old submarine landed by Evergreen Marine Airbags
