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.
Friday, October 14, 2011
Sunday, October 9, 2011
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.