5000 CBM LPG Carrier Launch with marine airbags

On September 28, 2011,Evergreen Maritime engineering company, successfully launched a 5000 CBM LPG Carrier with 26 pieces ship launching airbags for Sinopacific Shipbuilding Company in Jiangsu province.

The Sinopacific Shipbuilding Group is a fast-paced, joint venture in China’s shipbuilding industry. They contracted with Jaccar Holdings for six LPG carriers building. That vessel is SINOPACIFIC’s first LPG Carrier which measures 92.5 meters by length and 17.4 meters by width.

The LPG Carrier was built on a concrete ramp with two slopes 1.3/100 and 2.5/100. The elevation of ramp end is 3.635 meters. Due to vessel’s narrow shape and deficiency of launching water the launching calculation result showed “Abrupt Drop” would happen during the launch. It is estimated the vessel would drop 2 or more meters when its gravity center passed by end of slipway. That is not acceptable because the LPG carrier will be only launched with open deck.

Evergreen technical team tried hard to destroy the launch safety trouble by adjusting launch plans. At the same time Eversafe discussed with shipyards to find solutions of launch ramp alteration. Then the launch was postponed for one month.

The light vessel has 3.87 m draft at stern and only 0.7 m at bow. To ensure launch safety people have to wait enough water since slipway alteration is not allowed by time. According to tide table at Sep. 28 there will be the high enough water. So launch date was set on Sep 28.

Evergreen team arrived at shipyard at Sep 26. By two days hard working the LPG carrier was lifted and moved forward 30 meters by ship launching balloons. The water depth was measured every 30 minutes in two days high tide time by Eversafe engineers. At Sep 28 all preparation work was finished and all people were waiting for water coming up. At 12 o’clock the launch ceremony started: when a bottle of champagne was smashed at bow people began to cut off the pulling steel wires. When the vessel was free it started to move slowly then accelerated moved into water smoothly until total floated.
To verify the launch calculation people set up an instrument to measure the inclination angle of vessel during the launch. The result comes out to be same with calculation: the vessel’s maximum inclination during launch is 3.2 degree.

People can learn from this launch project that airbags’ ship launching is not always applicable. If there was not enough launch water the launch would be dangerous at least for the vessel structure safety. To avoid the limitation of launch water people should design the good slipway with reasonable elevation. It says if the slipway can be elongated then people can launch ship in lower water level.

Airbag ship launching technology is coming up to be popular around the world. But the calculation has not been treated as deserved importance. Airbag ship launching has much more tolerance than traditional sledge launching but it still has limitations. That is natural.