Thursday, December 15, 2011

Eversafe project of concrete structure shift with air bags

Tieshan Port Industrial Park is located in Guangxi Zhuang Autonomous Region, China. The Park is one of the three important industrial zones for the Beibu Gulf Development, which was approved by China’s Central Government.
The construction project consisted of two phases: the NO.1-2 berth construction have already been finished and NO.3-4 berths construction work started from August 2010.
In plan total 40 Caissons will be installed for NO.3-4 berths construction. Eversafe Marine was engaged by the Administration for the Beibu Gulf to carry out caisson transportation works, from fabrication site to submersible barge with heavy lifting marine airbags. Caisson transportation with marine air bags is a new technology which doesn’t need rails and trolleys and can transport concrete structure on compacted ground. So it enables fabricating caissons on temporary site which can be located near shipping position. Using balloons to transport caissons to submersible barge then launch it can save more than 40 percent investment comparing with trolley transportation method,not mention the time saving.
The first caisson measures 24 meters by length, 16.4 meters by width and 20.75 meters by height. Its weight reaches 3050 tons. To move caissons from construction site to shipping out position , Eversafe team made the masterly plan which consists of three steps: lifting first ,length ways move then transverse move. Total four winches were employed to control caisson movement: two winches from submersible barge to pull caisson move forward and other two winches were used to stop caisson.
Total 8 pieces heavy lifting air bags with 1 m diameter and 16 meters length were used to lift the caisson. Each air bag carry about 380 tons with 0.25 Mpa pressure. To roll caisson out 24 pieces 8 meters long air bags were arranged in two rows and kept in 40 cm height to ensure caisson movement stability. It took us about 3 hours to transport the first caisson to ship out position.
When using air bags to move caissons aboard submersible barge, the barge need not to sit on seabed. Often people use steel plates to connect bank and barge deck to roll caisson on to board. Submersible barge can rise or sink by adjusting ballast water to adopt coming caisson. And in flood tide the barge operation will be easier.

Sunday, December 11, 2011

Wuzhou Heavy industry launched DWT36000 cargo ship

On 24th November Wuzhou Heavy industry launched a DWT36000 cargo ship with Eversafe airbag launching service. This cargo ship measures 190 meters by total length and 28.3 meters by moulded breadth. It is named “ Meishan gang 57” by owner Zhejiang Hongchen Shipping Company which is a private owned transportation company.
Lianyungang Wuzhou Shipbuilding Heavy Industry Co., Ltd. was founded in May 2007, is located in Jiangsu Guanyun County town of Lianyungang which is adjacent to the Guanhe River estuary. Currently the company covers an area of 880,000 square meters, has 1.1 kilometers of coastline. Has built five berths below 20,000 tons, eight berths between 30,000-50,000 tons, one berth of 80,000 tons. The shipyard equipped with 32 gantry cranes which include 200 tons and 100 tons.
This river is in low water period so launching water is 2 meters lower than normal level. To conquer this big difficulty Eversafe marine performed detailed calculations to find good solutions of airbag launching. By discussing with shipyard Eversafe Marine decided a dredging plan to ensure the launching.
On 22th November Eversafe launching team arrived at shipyard to prepare the launch. After two days working, we finished the air bag ship lifting and blocks removal works. In 5 PM of 24th the final launching started. After pulling ropes were cut off the ship started to move slowly. With rolling airbags it entered into water smoothly and steadily until floated totally. The whole launch took 90 seconds.
One client from South American shipyard was invited for this airbag launching view. The client was interested in changing slipway launching to air bag launching in near future.
In November Eversafe successfully launched 4 new built vessels which include two cargo ships and two OSV. In the winter of shipbuilding industry around the world Chinese shipbuilding market still hold a strong increasing posture that is food for thought.

Friday, October 14, 2011

LPG Cargo Tank Air bags lifting Project-Eversafe Marine

On May 29 2011 Eversafe Marine Engineering Company successfully completed a LPG Cargo Tank lifting Project with heavy lifting airbags in COSCO shipyard. That VLGC cargo tank weighs 1600 tons with 40 m length , 30 m width and 20 m height.
During the Japanese Tsunami in March 2011 that VLGC hold space was damaged and water ingress of approximately 7m above the inner bottom caused the cargo tank to float freely. As a consequence the 64 pieces wooden liners from the lower tank supports have floated out and the tank was sitting directly on the steel plates. The cargo tank had to be lifted in order to fit back the wooden liners.
Airbag lifting would take and distribute the load evenly over the inner bottom and tank bottom. Contrary to hydraulic jacks and floating crane no additional reinforcements of the structure was necessary.
Also airbag lifting can be precisely controlled which is also one of selection reasons. The tank in hold place has very limited space from the top and sides: the space on top of tank is limited to 12 cm and in four sides only 60 cm space is available. To put back wooden liners tank need to be lifted up11 cm from the support blocks and lowered down one centimeter by one centimeter. So the lifting and descent must be totally controlled.
A pre-inspection was carried out by Eversafe Marine in order to determine the space available for the airbags. One access hole was cut in the portside of the hold space to allow smooth transport of airbags.
To settle airbags in proper positions the limited space made troubles for us. Since no heavy instruments can be installed for the airbag hauling in the hold space people have to use chain blocks as main transportation tool. The height from hold space to tank bottom is 64 cm people even can not squat when they work under the tank. It is a hard work to settle total airbags in their positions in two days.
In the morning of May 29 2011 the airbag tank lifting work started. Eversafe technicians carefully controlled the inflation process to ensure upright lifting up. In our hour the tank was lifted 11 cm up from the support blocks. In the afternoon when all wooden liners were placed in proper positions the tank was lowered down one centimeter by one centimeter until liners fit into frames. Tank lifting/lowering was completed on 29 May, 17:00 local time. All 64 pieces of wooden liners were placed back successfully.

Sunday, October 9, 2011

DWT 47,000 cargo ship launching with marine airbags

Evergreen Maritime is the professional manufacturer of ship launching airbags and dock fenders. Also his Eversafe marine engineering company is well known as the leading engineering company engaged in ship launching/landing and heavy lifting projects.
Recently Eversafe Marine successfully launched a DWT47000 cargo ship with marine airbags in Nanjin Jinda shipyard. That ship named “ tai he da” weights 9000 tons, measured by 190 m length, 32 m moulded width and 16 m depth.
The launch slipway is a concrete ramp with 1/80 slope angle. From end of slipway to the Yangtse river there is a 60 m natural ground paved with gravel. Yangtse river is one of the most busy channel so our launch is strictly limited for the launch time and launch area by local Maritime Safety Administration.
The elevation of launching ramp end is 2 m and stern draft is 1.7 m so stern will not be refloated when it is launched at 120 m distance. To remedy the practical disadvantage Eversafe team performed the detailed calculation of using ballast water to adjust the vessel trim angle during launch. At last 2000 tons ballast water was added into the bow cabin.
In the morning of May 21 our launch team begun to prepare all necessary work for the 40 m forward move and successional launch that must be completed within there hours. At 9 am the vessel transportation work started and got finished in one hour. According the plan this vessel will be launched at 12 am when the water reaches highest level in the day. Because of some emergency reason the local Maritime Safety Administration demanded the launch to be carried out at 10:30 am. So we got only 30 minutes to prepare the launch.
Water level in the launch area is 100 cm less than plan so marine airbags and ramp will bear more pressures than expected figures. People reinforced the conjunction of ramp with steel plates temporarily and adjusted pressures of airbags at stern. At 10:30 as soon as adjustment work finished pulling ropes from winches were chopped and the launch started. The vessel got total floatation at 300 m and stopped at 460 m distance.
After the launch people found there was a gap at launch ramp conjunction position. Provided without the temporary reinforcement the part of ramp may collapsed during the launch.
It is a very urgent launch project. Eversafe team depends on the scientific calculation and profound experience overcomes all practical disadvantages and did a great job. It is the fourth vessels launched by our company in this month . Airbag ship launching is proved to be successful and flexible in deficient conditions.

Thursday, June 30, 2011

Eversafe Airbag Ship Launching -37500 DWT Cargo Ship

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.

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.