Two different concepts have been developed for offshore bunkering. A pressurised system has been designed for LNG supply up to 300 m³. For supply in larger quantities, a pump system has been designed.
Pressurised bunker system
The pressurised offshore bunker system concept follows the idea of minimising maintenance on key units such as rotating equipment. LNG is transferred to the customer by increasing the pressure in the IMO C-Type tank. Pressure build-up units (PBU) ensure the necessary pressure level. The required energy comes from the waste heat of the ship’s engines. The process unit as well as the instrumentation and automation are installed in the “coldbox” and receive constant ventilation. This concept has been deployed in the LNG bunker vessel SeaGas.
Bunker ship with pump system
Supply of larger quantities of LNG to clients requires a higher flow rate during bunkering. The LNG is stored in horizontal or vertical C-Type tanks that are either vacuum insulated or externally insulated, depending on the holding time of the bunker ship. The storage capacity is designed for tanks of up to 1,000 m³. Submerged pumps, installed in C-Type tanks, transfer the LNG to the customer.
Boil-off gas is generated during loading of the C-Type tanks or during the holding time. MAN Cryo can adjust the boil-off gas handling system to the customer’s needs. Typically, the boil-off gas is consumed by the ship’s engine. Boil-off gas compressors provide the required pressure level.