Classification society Bureau Veritas has granted Approval in Principle to a 4,000 cu m Bunkering Ship concept developed by France’s LNG containment manufacturer, GTT.
The concept is for a bunker tanker which could deliver LNG as ship’s fuel using tanks with a GTT Mark III Flex Cargo Containment system operating up to a pressure of 2 barg.
“This pressurised membrane tank concept from GTT means LNG bunker tankers can manage Boil Off Gas (BOG) better and increase loading and delivery flow rates. Our studies show it is both safe and practical. We look forward to seeing the concept taken forward to a new construction,” says Philippe Donche-Gay, Executive Vice President and head of BV’s Marine and Offshore Division.
Under GTT’s system the BOG management during loading and bunkering operations is made more flexible because of the wide vapour pressure operating range.
Vapour can be buffered and condensed in the tanks to help the fuelled ship or feeding facility handle the vapour. Condensation may be performed by spraying LNG into the vapour phase. The higher pressure also means that during voyage and stand-by mode, the duration before gas pressure in the bunker tanker’s tanks reaches the upper limit is longer. According to BV, this improves the holding time when BOG is not being consumed and reduces the use of reliquefaction plant, diminishing costs.
In addition, Bureau Veritas has published requirements for LNG Bunkering tankers. The requirements, set out in Rule Note NR 620 LNG Bunkering Ship, cover special arrangements for ships carrying LNG which will transfer that LNG to ships using LNG as fuel.
NR 620 covers the design and installation of the LNG transfer systems from bunkering ship to the receiving ship and the vapour transfer system from the receiving ship to bunkering ship, including LNG hoses, transfer arms and auxiliary systems for handling the LNG system.
The certification society has also published requirements for ships which are designed and fitted out for dual-fuel or LNG fuel propulsion but which are not initially intended to use gas as a fuel.
The requirements, set out in Rule Note NR 627 Gas-Prepared Ships, cover special arrangements for new ships that are designed with specific arrangements to accommodate future installation of an LNG fuel gas system.