Sunday, January 30, 2011

How to select marine airbags for your marine project

Marine airbags are widely used for ship launching, heavy transportation and marine salvage nowadays. Marine airbags are often called ship launching airbags that indicate the most popular application of these heavy duty airbags is for ship launching. It is estimated that more than 80 percent new built ships who’s DWT below 60,000 are launched by marine airbags.
Marine airbags are found to be powerful and versatile tools for many other marine projects such as disembarking ships, heavy transportation, re-floating salvage etc. But how to select suitable marine airbags for a specific project? Let us see suggestions from Eversafe Marine Engineering Company.
Marine airbag's specifications
Select the airbag's effective length not less than the maximum width of vessel or anything you want to move by airbags. But when you arrange two rows of airbags keep in mind to calculate the total length to avoid contact of airbags in two rows. The total length of airbags can be estimated to be effective length plus diameter. It says an airbag whose effective length is 16 meters and diameter is 1.5 m then its total length is 17.5 m.
Diameter of airbag is decided by the height of your vessel's support blocks. If the support block is 1 m high, then you should choose airbag's diameter not less than 1.5 m. If you get 1.5 m high blocks, the airbag with 2m diameters will suits you well.
For air lift use, airbag's diameter or length is mainly decided by the buoyancy you need from airbag. And also consider the pressure of airbag stands if you apply airbags in deep water.
For caisson transport by marine airbags, the most suitable diameter is 0.8-1 m. Marine airbag's performance is decided by its component plies. For air lift use or light vessel (launch weight below 2000 tons) launch, mid-pressure airbags are enough. For heavy duty work, the high pressure airbag should be selected. Generally speaking, airbags with 6 plies are enough for most engineering works. Only in some rigorous situation, airbags will need 7-8 plies to enhance its performance. For example, if people use airbags to lift heavy caisson but their contact area is limited, and then airbags will need higher pressure and more plies to ensure the safety.
Reference for marine airbag selection
There are two industrial standards for marine airbags in China.: one is product standard 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. 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
Good selection of marine airbags is vital for the success of marine projects. Get basic knowledge of marine airbags selection then consult with manufacturers can help people complete projects in shortest time.

Friday, January 28, 2011

Eversafe Marine Launch SINOPEC's Biggest Pipelaying Barge with Marine Airbags

On Nov. 26 ,2010 Eversafe Marine successfully launched a pipelaying barge for SINOPEC (China Petroleum and Chemical Corporation) using airbag ship launching technology in Shenli oilfield construction base. That 14,500 tons pipelaying barge named " shengli 902" measures 118 meters in total length and 30.4 meters in molded width. It is SINOPEC's biggest and most advanced pipelaying barge designed to lay maximum 1540 mm diameter pipe at 100 meters deep water .
The hull of this pipelaying barge need to be completed in six months. At that time there was only one 150 meters long concrete ramp available in the construction base. Eversafe technical team was invited by the construction company for the feasibility research of airbag ship launch for the hull. When got positive conclusion, the construction company knew they can take the job.
Eversafe Marine as the launch contractor did lots of preparation work for this launch project. Main disadvantageous conditions for the launch are the shallow water and narrow launch area. With the help from construction company's design department, based on detailed calculation Eversafe technical team designed the launch plan which employ ballast water to adjust the barge's inclination and attached ropes to the stern to turn vessel around.
At 8 AM of Nov. 26, the Sacrifice Sea ceremony was hold on in the construction base. All the people involved in this project gathered to the platform to make a bow to the mother sea. At 8:30 AM the fireworks resounded across the sky and the launch started. When the pulling ropes were released the barge started slowly with the rolling marine airbags and entered into water smoothly. Airbags jumped onto the water surface from the bottom of vessel bow like piquant fishes which aroused excited screams from watching crowd.
Total 67 pieces ship launching airbags were used to launch the barge. All airbags executed good works during the launch. Eversafe Marine ( as the subsidiary of Evergreen Maritime, is the first professional global contractor of airbag launch projects and get a very good track record. In addition Eversafe Marine makes his distribution to the airbag ship launching technology by consummating the airbag launch theory.
Marine airbags ship launching can help shipbuilding company to do a better work with less investment. Some people called marine airbags " mobile floating docks" that indicate the flexibility and convenience of this powerful marine tools.