2.12. Cryogenic liquid mixtures have additional properties not experienced by single component liquids. While
density stratification in pure liquids is mainly temperature dependent, stratification in a multi-component liquid is
both temperature and composition dependent. In isobaric storage, this presents the problem of rollover between two
stratified layers with different densities and hence different temperatures and composition. If the density difference
is greater than about 1%, the heat influx to the lower layer becomes trapped within the lower layer, the temperature
rises and the density decreases with time. Eventually the two densities approach the same value, when an
extraordinary self- mixing process commences. All the excess heat trapped in the lower layer, together with the heat
of mixing, is released as a vapour spike, 10 to 100 times greater than the normal boil-off rate. This rollover is a
problem for the LNG industry to avoid (Scurlock, 2014).