Prelude’s Remarkable Turbomachinery - The Story From Selection To First Drop Of LNG

Abstract This is the story of the remarkable turbomachinery of the Prelude floating liquefied natural gas (FLNG) facility that was selected, designed, manufactured and extensively tested to achieve the highest levels of technical assurance, to serve what was the FLNG facility ever sanctioned in the world, a pioneering project destined to be an exemplary success. The Prelude FLNG project is unique for its size and numerous innovations. Its large onboard turbomachinery is usually applied at this size only to onshore liquefied natural gas (LNG) plants. The technical requirements of the Prelude FLNG facility went far beyond the limits of offshore experience, with consequences on the selection and design of the onboard turbomachinery. The management of this new technical solution was successfully achieved using detailed modelling and engineering analysis, an extensive test campaign using purpose-built test beds, and the development of dedicated start-up and operating procedures. This paper focuses on the pumping heart of this largest offshore facility ever constructed: the main refrigerant compressors and steam turbine generators, in addition to the seawater lift pumps that are used to extract seawater from a water depth of 150 meters, sustaining the main cooling capacity for the FLNG facility. The paper also mentions other sophisticated machines such as the combined boil-off gas (BOG)/end-flash gas (EFG) compressor, amongst others. Extraordinary work has been performed to ensure that each step in the realization of the turbomachinery for Prelude FLNG was an incremental success. Proper preservations, precise and careful installations of turbomachinery in steel modules, as well as preparations for start-up during the pre-commissioning and commissioning phases are explained.