The liquefaction vessel is based on a standard Moss type LNG carrier of 155 – 170,000 m3 capacity and equipped with Dual Fuel Diesel Electric (DFDE) propulsion. The Moss containment system eliminates risk of damage from sloshing in slack tanks during filling. There is no documented evidence of sloshing damage to the tanks in a Moss type LNG containment system although some early designs required reinforcement of the pump tower foundations.
A standard LNG carrier with DFDE power plant will have 30 – 40 MW of installed power. This is increased by 72 MW of installed power by adding 4 x 18 MW MAN V18 DF 51/60 engines in a new mid-ship section engine room. The power required to drive a 2 MTPA liquefaction plant is approximately 70 MW, depending on gas composition and cooling water temperature. The four mid-ship engines provide primary liquefaction power while the existing ships power plant is electrically interconnected to provide sparing and redundancy.
The 30 m long mid-ship “sandwich” section is spliced in between the Nos. 2 and 3 cargo tanks and houses:
- 4 x 18 MW DFDE engine gensets
- disconnectable turret, turret trunk & auxiliaries
- switchgear including transformers, variable frequency drives & magnetic bearing controls
- seawater/freshwater heat exchangers & cooling water pumps
By inserting the sandwich piece at mid-ship, any increased hull stresses resulting from increasing the waterline length are primarily in the new section and can be accommodated in the design. The turret contains a single10 in. NB, ANSI 900 gas swivel to deliver pre-cooled gas to the liquefaction vessel from the host platform. The turret contains an additional swivel for a deep seawater intake hose to provide cold seawater for process cooling. At a depth of 1500 ft., typical seawater temperatures will be 48 – 50 F.