Mechanical face seals - Application to compressible and two-phases fluids

Mechanical seals are sealing systems used in a wide range of machines, from the simplest such as washing machine pumps, to sophisticated systems such as nuclear power plant circulation pumps or gas pipeline compressors. They are therefore required to operate under a wide range of pressures (from vacuum to 50 MPa), speeds (up to 200 m/s) and temperatures (from cryogenic conditions to several hundred degrees). Although they are mainly used to seal liquids, they are also used to seal compressible fluids such as gases, or liquids undergoing partial or complete vaporization as they pass through the seal. The latter is referred to as a two-phase fluid. Typical examples are centrifugal gas compressors and hot water circulation pumps. The physical phenomena specific to this type of flow and fluid must be taken into account to master the behavior of mechanical seals operating with compressible, two-phase fluids. This article presents a classification of the different flow regimes (low-pressure and high-pressure gas, two-phase flow) and the associated physical phenomena. The behavior and specific features of mechanical seals used in these conditions are then presented and analyzed, providing the reader with the keys to understanding the operating principles of this mechanical component.

At the end of the article, readers will find a glossary and a table of symbols used.