Liquid nitrogen is used as a cost effective coolant for multiple industrial applications. However, even with the best possible insulation, it is impossible to prevent the absorption of ambient heat by storage and transfer systems completely. Therefore, liquid nitrogen is only available at or near saturation temperature at the prevailing system pressure, and the slightest pressure drop within the transfer system results in the formation of portions of gas inside the liquid. The same applies to other cryogenic media such as liquid oxygen and argon.
It often suffices to vent these gas fractions to atmosphere via a phase-separator. In other cases, however, it may be necessary to supply the liquid to the application under elevated pressure conditions, and to de-pressurise it subsequently without any significant formation of gas, or to allow adequate heat-absorption before the liquid reaches its boiling point.