Invar (36% Ni)

Invar is a 36 percent nickel iron alloy with a near-zero coefficient of thermal expansion around 1.2 microns per meter per Kelvin near room temperature, roughly a tenth that of carbon steel. That property is why GTT uses 0.7 mm Invar sheet for both the primary and secondary membranes of the NO96 LNG containment system: the membrane barely contracts when chilled to minus 163 C, so it needs no corrugations to absorb thermal movement, unlike the corrugated stainless membrane of Mark III. The 500 mm Invar strakes are welded continuously and backed by plywood boxes filled with perlite. Invar is the original Gaz Transport membrane material.