VLECs designs evolve


Designers of large gas carriers specifically engineered for the long haul ethane trades will need to give particular consideration to the ships’ containment and propulsion systems to maximise their trading efficiency, a new report says.

‘Seaborne ethane’, published today by classification society Lloyds’s Register (LR), said containment technology is one of the “critical factors” in very large ethane carriers (VLECs) as traders look for the most efficient shipping options for this emerging trade.

LR Global Gas Technology Manager Leonidas Karistios said the company has spent over a year studying what a safe and efficient 80,000-cbm ethane carrier would look like for over a year.

LR’s study evaluates all the available tank technology options and concludes that either prismatic Type B tanks or membrane systems would provide the best technical fit based on a ship with three to four tanks.

It concludes that Type C tanks, which to date have been used in the ethane-ethylene carrier newbuildings designed for the trade from the US to Europe, are only really viable for vessels of up to around 40,000-cbm. However, Karistios says it is important to keep reviewing this technology as it develops.

To date only six VLECs have been contracted for Reliance Industries at Samsung Heavy Industries. These will be fitted with Mark III membrane systems designed by GTT and specially adapted for ethane use.

Future fuel

LR also flagged up the advantage of using ethane as a fuel. LR has issued approval in principle (AiP) for an M-type, electronically controlled gas-injection (ME-GI) engine designed by Man Diesel that can burn ethane. But changes will need to be made to accommodate the higher pressure required for ethane.

The class society says surplus ethane production in the US could rise to six million tonnes (mt) per year in 2015 and possibly 12 mt in 2020 but domestic demand still clouds the picture.

LR estimates annual shipments of 1 million tons of ethane could provide employment for 0.18 million cubic metres (cbm) of shipping capacity, assuming it is shipped to North Europe, 0.32 million cbm if shipped to south Asia and a similar amount to China if the Panama Canal is used.

It added: “Further ethane-capable newbuilding orders would need to be backed by long-term trade agreements.”


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