Due to the distance in which the oil and gas fields are, in the Pre-Salt, there is a lot of talk about the use of FLNGs, ships with natural gas liquefaction plants. In this case, there are technical issues to be resolved, especially regarding the processing and transfer equipment that must be installed in the FLNG, to ensure safe and reliable operation, even in the harsh conditions of the offshore environment.
The potential of FLNG ships is enormous, but limited to the maximum size supported by shipyard dry docks. This restriction will imply frequent transfers to transport ships, with the need for an available and reliable system in whatever ocean conditions. A failure in the transfer implies the interruption of the liquefaction process. A challenging, complex and expensive exercise.
FMC Technologies has over 50 years of excellence in LNG transfer, with 360 LNG loading arms worldwide, the first being installed at Camel in Algeria in 1963. Installed the first Boom to Tanker (MTB) system of the world at Shell in Brunei, Malaysia, responsible for unloading LNG at the bow of the ship for 23 years without a single incident. It has developed the latest LNG facilities for offshore offloading with the patented “target system”, including the Statoil Hydro installation in Norway, as well as nine other projects in fabrication. It also participated in two JIP projects for the tandem system, fully certified by BTT for North Sea conditions, up to 5.5 mHs. Inspired by these successful deliveries, FMC launched the new Chicksan Atol system for transferring LNG from the bow of the vessel.
The Atol system is based on an articulated cryogenic assembly, supported by a metallic structure and maneuvered by means of cables and a hydraulic system.
The Atol system is capable of operating with an average separation between 63 and 83 meters and waves of 5.5 m Hs, ensuring an LNG transfer rate between 10 thousand and 16 thousand m3 with limited loss of vapor and liquid, similar to the arms of conventional marine loading on land. Using a state-of-the-art position monitoring system (PMS), the Atol system comes equipped with an emergency release system consisting of hydraulic couplers, double ball valves and automatic emergency sequencing for ESD1 and ESD2.
The Atol system is designed for use in Hawser brigs or DP systems, allowing a maximum lateral displacement of up to 45 meters and can operate at pressures between 19 and 30 bar, and can be vacuum insulated to allow for heat loss or vaporization during transfer operations.
The connections are 100% redundant, as are all critical components, in order to guarantee offshore requirements in terms of maximum availability with minimum maintenance. All major components can be repaired on site, without the need for special tools or large cranes.
The Atol system consists of proven components and is designed for a 25 to 30 year life expectancy, offering levels of safety equivalent to those found in conventional onshore terminals. The system is designed to be “fire safe”, meeting the same requirements that apply to terrestrial terminals.
When in storage position, the Atoll is retracted in order to prevent any possibility of collision with the cargo ships during the approach and anchorage phases. Recent tests have demonstrated the connection capability, operational envelope and performance of the Atol system in severe marine conditions. It can be easily installed on existing ships, allowing for a compact and well-protected solution.