The Mark V membrane system is a cryogenic liner directly supported by the ship’s inner hull. This liner is composed of both metallic membranes (primary and secondary) combined with both insulation prefabricated panels.
The new system includes an innovative 36% nickel-iron alloy corrugated secondary membrane and offers significant improvement of the warranted daily boil-off rate (down to as low as 0,07% V/day).
This cargo containment system is adapted to all sizes of LNG carriers.
PRIMARY STAINLESS STEEL MEMBRANE
The primary membrane is identical to the Mark III primary membrane and made of corrugated stainless steel 304 L, 1.2mm thick. It contains the LNG cargo and is directly supported by and fixed to the insulation system.
SECONDARY INVAR MEMBRANE
The secondary membrane is made of corrugated 36% Ni-Fe, 0.7mm thick. It ensures a total liquid and gas tightness in case of damage of the primary membrane. It is positioned on the secondary insulation panels with corrugations oriented to the hull.
The insulation consists of both load-bearing systems (primary and secondary insulation panels) made of prefabricated panels in reinforced polyurethane foam. The secondary panels are fixed to the inner hull by means of resin ropes which serve a double purpose: anchoring the insulation and spreading evenly the loads. The primary panels are linked to the secondary panels with mechanical anchoring systems.
GTT has signed cooperation agreements with Samsung Heavy Industries and Hyundai Heavy Industries shipyards for the development and qualification of industrialization processes, such as welding robots and adaptation of specific tools. The shipyards have also built mock-ups dedicated to final developments and related tests.
ZERO STRESS CONCEPT
The orthogonal corrugation pattern enables both membranes (primary and secondary membranes) to accommodate any thermal or hull deflection stresses and to work under the fatigue limit, therefore providing outstanding lifetime.
NEGLIGEABLE EDGE LOADS
Because of low stress on both membranes, prefabricated foam corner panels can be used to anchor both membranes to the hull, therefore minimizing thermal flux.
Reinforced polyurethane foam gives high mechanical properties to the panels. The high density of the foam and the plywood covering both sides of the panels - for an even load distribution - allow the insulation to withstand high impact pressures and absorb the energy resulting from liquid motion.
This modular system calls for standard prefabricated components that can accommodate any shape and capacity of tanks and are designed for mass production techniques and easy assembly.
The two independent insulation spaces are continuously flushed with nitrogen gas. The integrity of both membranes is permanently monitored by detection of hydrocarbon in the nitrogen.
LOW BOIL-OFF RATE
Boil-off rate is reduced by increasing the insulation thickness (up to 480mm) of Mark V and using efficient R-PUF compared with current membrane systems (down to 0,07% V/day).
All materials used in Mark V are sea-proven in GTT’s technologies. Mark V has been granted General Approval by major classification societies.