LR finds cargo stowing answers for box giants

AUGUST 28, 2015 — Classification society Lloyd’s Register (LR), which is classing the world’s largest-ever containerships, has produced a series of proposals and guidelines on the safest, most cost-effective methods of stowing and lashing container cargoes.

Among the giant box ships that LR classing are six ultra-large ships (ULCS) of more than 20,000 TEU.

Four ULCS vessels of 20,150 TEU will be built for Mitsui O.S.K. Lines (MOL) at Samsung Heavy Industries’ (SHI) shipyard at Geoje Island, South Korea, while two 20,050 TEU ships are being built for Shoei Kisen Kaisha on long charter to MOL at Shoei’s affiliate company Imabari Shipbuilding at Saijo shipyard.

These giants of the sea are due to be delivered in 2017 and have been earmarked to operate on the Asia-to-Europe service.

Lloyd’s Register technical teams have investigated the rising heights and weights of the container stacks that today’s ULCSs can carry and produced new guidelines to help designers, owners and masters handle these ever-growing cargoes.

One key finding is based on vessel speed. LR says its research demonstrates that the speed at which a ship is sailing has a significant and predictable effect on the rolling motions; this is a crucial factor in cargo-carrying. Instead of designing container stows as if a ship is sailing at full speed in the harshest seas of the Atlantic or Pacific, LR produced a methodology based on a combination of ship speed and stability and the height and direction of the prevailing waves.

Another factor is the development of lashing twistlocks. Operators who use the latest fully automatic twistlocks (FATs) will have the advantage of securing their cargoes safely and effectively with minimum intervention from the stevedores. Combined with the introduction of high lashing bridges, they will be able to safely carry stacks of 10 or more tiers of containers on deck.