MARK III SYSTEM'S ORIGINAL DESIGN
PRIMARY STAINLESS STEEL
The primary membrane is 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. Standard size of the corrugated sheets is 3m x 1m.
This membrane is folded to create corrugations. The knot is the intersection of the corrugations (small and large corrugations).
Mark III stainless steel corrugated membrane
The secondary membrane is made of Triplex, a composite laminated material: a thin sheet of aluminum between two layers of glass cloth and resin. It is positioned inside the prefabricated insulation panels between the two insulation layers.
The insulation consists of a load-bearing system made of prefabricated panels in reinforced polyurethane foam including both primary and secondary insulation layers and the secondary membrane. The standard size of the panels is 3m x 1m. The total thickness of the insulation is 270mm. The panels are bonded to the inner hull by means of resin ropes which serve a double purpose: anchoring the insulation and spreading evenly the loads.
Mark III prefabricated panel
The corrugated membrane technology continuously improved since 1967 is approved by all the major classification societies. It benefits from more than 50 years of experience at sea.
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.
Zero stress concept
The orthogonal corrugation pattern enables the membrane to accommodate any thermal or hull deflection stresses and to work under the fatigue limit thus providing outstanding lifetime.
Negligible edge loads
Because of low stress on the primary membrane, prefabricated foam corner panels can be used to anchor the membrane to the hull thus minimizing thermal flux.
An insertion of fiberglass in the polyurethane foam gives high mechanical properties to the panels. The density of the foam (130kg/m3) 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.
The low thermal conductivity of the foam and of the corners results in a thin insulation; thus maximizing the cargo capacity for any ship external constraints.
This modular system calls for standard prefabricated components that can accommodate any capacity of tank and are designed for mass production techniques and easy assembly.