Combined Sea & Gas Trials of a 175,000 m³ LNG Carrier

YS Marine attended the full sea and gas trial programme of a newbuild GTT Mark III Flex LNG carrier, documenting the vessel across hull, machinery, cargo gas, and safety systems ahead of delivery.

Over a two-week attendance, our team witnessed the combined sea and gas trials — from yard departure and river transit through to the gas trial. The engagement produced a baseline condition record to support the owner’s review and the classification society’s acceptance process.

Hull and superstructure overview during sea trials.

01Scope of attendance

Working alongside the owner’s site team and Bureau Veritas, we assessed the vessel through visual inspection, operational checks, and witnessing of the class-required test sequences:

Hull, structure & deck outfitting — shell plating and coatings, bow and stern, forecastle and poop deck, anchoring and mooring equipment, pipe trunk / duct keel.
Accommodation, HVAC & engine casing — superstructure, cabins and public spaces, sanitary and HVAC, galley and provision plant.
Bridge, navigation & communication — radars, ECDIS, AIS, gyro and autopilot, GMDSS, internal communication.
Machinery & propulsion — ME-GA main engines and EGR, DFDE generators and SCR, boilers, shafting, steering gear, pumps, switchboards and automation.
Fire, safety & life-saving — CO₂, foam and water-spray systems, emergency generator and fire pump, lifeboats and life rafts.
MARPOL equipment — oily-water separator, incinerator, sewage treatment, ballast water treatment.

Main engine room — ME-GA propulsion machinery.

02Machinery & propulsion

The dual-fuel ME-GA main engines, generators, boilers, and supporting machinery were reviewed through operation and the witnessed trial sequences, confirming performance across the relevant operating modes.

Trunk deck — cargo manifold, gas piping and cargo machinery.

03Cargo & gas management

On the gas side we witnessed gassing-up, initial cooldown, partial LNG loading at Yangshan Terminal, and a 100% gas-mode endurance test, with inspection of the trunk deck, domes, cargo machinery, and FGSS equipment.

Wheelhouse — navigation and bridge systems.

04Outcome

The attendance delivered an independent, decision-ready baseline of the vessel’s condition and trial performance — supporting the owner’s acceptance review and the handover to operations.

While this vessel was an ME-GA unit, YS Marine attends every type of LNG carrier regardless of propulsion — ME-GA, ME-GI, X-DF, DFDE/TFDE, Ultra Steam Turbine and conventional steam.