Manager Business Development LNG Marine
Burckhardt Compression AG
17:00 - 17:30
Tuesday, 17 September 2019
T1.2 RESERVE: Piston compressor developments for gas fuelled LNG and Ethane carriers
Reciprocating piston compressors are economically employed to compress gases to very high pressures (for example 300 bar) when the application of centrifugal compressors is less efficient and more expensive. The piston compressor does, however, have distinct advantages for lower pressure requirements in the range of 10 to 20 bar, particularly where operational flexibility is necessary. This paper reviews the latest compression machinery developments for the supply of natural boil-off gas (nBOG) to dual fuel, 2-stroke engines that is currently dominating today's market for LNG and ethane ship propulsion.
MAN Energy's high pressure dual fuel ME-GI engine has accumulated more than 3 years of successful service in the propulsion of large LNG carriers. The engine requires a fuel gas supply pressure in excess of 300 bar. Multi-stage piston compressors of the type Laby®-GI are employed to deliver boil-off gas for injection into the engine cylinders. They supply high pressure fuel gas not only to the main engines, but also to the dual fuel generators, re-liquefaction system and gas combustion unit. It forms the key component of the ship boil-off gas handling and management system. With more than 30 LNG ships running under ME-GI propulsion and 40 compressors in service, the Laby®-GI has now collected in excess of 300'000 operating hours. As with the introduction of any new marine technology, it has not been all plain sailing. Lessons have been learned and design updates introduced. This paper reviews the operating experience, maintenance intervals and the design changes that have been made to systems, controls and machinery to ensure today’s successful operation. Also discussed is an innovative piston and rod sealing design, allowing the final compression stages to operate, as with the initial low pressure stages, in completely oil-free execution. This will allow considerable simplification of gas filtration systems, reduce maintenance and optimise equipment cost.
WinGD's X-DF low pressure (13-16 bar), fuel gas (FG) supply system has, to date, been equipped with either centrifugal or screw type compressors. An alternative piston compressor design, based on contactless labyrinth sealing technology, has been developed for FG supply to the X-DF engine. The design draws directly on the well-known Laby® compressor, used extensively in the LPG shipping and refrigeration industry. Different materials are applied for LNG and ethane BOG duty to provide seamless operation over the wider, lower temperature range and capacity. Best energy efficiency, simple control, flexible operation, robust design and easy maintenance by ship crew are key features of this compressor. Many units following this design are already operating on small LNG carriers (5-45k). This paper describes the new design for X-DF application for large LNG carriers. A first Laby® reference for X-DF propulsion will also be announced and described in detail.