marine airbags: Innovative and Versatile Marine Tool
Marine airbags are widely used in China for ship launching ,caisson conveying and marine salvage nowadays. It is estimated that more than 80 percent new built ship whose DWT below 60,000 and about 50 percent caisson fabricated for gravity quay are launched by marine airbags.Not only in China but also other Asian countries marine airbags are acknowledged as the powerful and versatile tool for marine works.
The history of marine air bag dates back to 1990s. A Chinese ship repair and building shipyard launched a 60 DWT tank barge with marine airbags on January 20, 1981 and it is known as the first use of marine airbags. The invention of marine airbags was expected to develop a flexible, less limited ship launching method.
Over the past twenty years, marine airbags have made great advancements in the manufacture and application. The first generation marine airbags employ rubber dipped canvases as reinforcement material and two cone-shaped ends are stuck to the chamber trunk. Now the top marine airbags are seamless and their performances are about 15 times of the first generation with the same specifications. Regarding the launching/landing technology, marine airbags have also achieved a significant leap. In the beginning, only small and flat bottom ships located on a fabricated slope could be launched with marine airbags. Now this technology is more flexible and less limited by the ship and landform. The DWT of launched ship reached 55,000 and launching ramp can be aclinic. Not only for ship launching marine airbags are widely used for heavy conveying also. Marine airbags contributed much to the success of famous Nanhai No.1 ancient ship salvage project. The 4,800 tons cassion which hold the invaluable ancient ship landed from the semi-submersible barge and transported to the museum named Crystal Palace riding on 16 pieces marine airbags.
The advantages of marine airbags
Less landform limited
Marine airbags only need the enough bearing power ground.
Most less fixture needed
For most works ,marine airbags need no more than air compressors,winches and forklifts.
Environment Protective
Marine airbags do no harm to the environment.No chemical needed.
Multi-functional
Marine airbags can be used for ship launching /landing,heavy conveying, buoyancy lifting even the temporary ship fenders.
Cost-effective
For ship launching,marine airbags can save the investment of traditional slipway or drydock. For caisson conveying projects,marine airbags can save 50 percentage cost compare to the traditional way of employing crane ship and semi-submersible ship .Caisson can be launched by marine airbags and suspended in the sea with the help of attached airbags’ buoyancy then one or two tugboat can complete the sea transportation.When caisson arrive the appointed spot,airbags can be deflated to let the caisson sink.
How to select marine airbags
There are two industrial standards for marine airbags in China.: one is product standrad named “Air bag for ship up to or down to launching way “(CB/T 3795-1996 / CB/T 3795-2009) ;another is technology standard named “Technological Requirements for ship Upgrading or Launching Relying on Air-bags”(CB/T 3837-1998).The latter offer the basic calculation of marine airbags employed in a marine project.
According to Chinese industrial standards people will know the approximate quantity and specifications of marine airbags needed for their projects then consult the manufacturer to confirm the design. There maybe optional specifications to be selected for a specific marine project and a good manufacturer should know the best choice. Suggestions from Qingdao Evergreen Maritime Company :for ship launching, the airbag’s diameter and length should not execeed 2.0 meter and 18 meter respectively;for caisson conveying, the 1.0 meter diameter is suitable for most projects.
The data of marine airbags’ blasting pressure will reveal the product’s quality level. For top quality marine airbags,such as one 1.5 m diameter and 7 m length Evergreen marine airbag, the blasting pressure is 0.67 Mpa which indicates the safe coefficient is more than 5 considering its 0.12Mpa working pressure.
Full technical service is the qualification of a good company. Although general calculation formula or performance data of marine airbags can be got from most factories but detailed calculations based on mathematic model and experience is more important to the success of marine projects.
In a word
Marine airbag is a simple but powerful marine tool which should get more attention from people involved in marine fields. It is less limited by equipments and landform and can save most investment and time to complete a marine project. And the flexibility of marine airbags not only mean airbags can give more protection to being launched objects but also it can be used creatively.
