Customary name for a mechanical seal for media with a temperature below 0°C. As a rule these media are liquid gases (including liquefied gases), hydrocarbons with a low freezing point, and refrigerating mixtures. Either mechanical seals with O-ring as secondary seal or metal bellows mechanical seals are used for temperatures down to -50°C at the mechanical seal; for temperatures below -50°C, only metal bellows mechanical seals are used. Media with temperatures below -50°C are often conveyed with vertical pumps, in which a gas chamber acts as a thermal buffer between the liquid pumped material and the seal casing.

A special case are pumps for mobile service, e.g. on tanker vehicles, most of which are operated with single mechanical seal without quench. The mechanical seal runs frequently in the gas phase of the medium. The resultant short life of the mechanical seal is taken into account.


Typical vertical pot pump to convey liquified ethylene gas