Sulphur hexafluoride (SF6) is an excellent dielectric gas for high voltage applications. It is chemically inert, gaseous even at low temperature, non flammable, non toxic, non corrosive. Its combined chemical, thermal and electrical properties allow many advantages to be achieved.
SF6 allows simplified design of high and medium voltage switchgears because of size and weight reduction, quiet and reliable handling and maintenance. Outstanding properties are its dielectric strength and dielectric constant unchanged from a few Hz up to several GHz, and such as arc quenching properties to prevent arc from occurring while its molecular fragments rapidly recombine after the source of arc is removed. Furthermore the high molar heat capacity and low viscosity enables it to transfer heat very effectively.
SF6 is used in several non-electric and electronic applications. Processes have been developed for magnesium casting in which a protective atmosphere of SF6 based gas mixture prevent the formation of undesirable hyproducts. Other foundry applications are those employing N2/SF6 mixtures in aluminum casting as refining and degassing agents.
SF6 is also used in the semi-conductor industry, as etching gases for plasma etching or as cleaning gases to clean the chambers after the etching process.
Several minor applications are regarding leak detection, tracer gas studies, loud speakers and lasers.
Electric Grade
Application as dielectric gas
Gas insulated high voltage circuit breakers and other switchgears
Gas insulated power transmission lines and power distribution substations
High voltage transformers, linear accelerators, coaxial cables, waveguides, switches,x-ray apparatus and capacitors
Component of inert atmosphere during the primary casting of Aluminum and Magnesium. Refining agent for Aluminum foundry applications. N2 / SF6 gas mixtures (5 - 10 % by volume of SF6) are employed to refine pure Aluminum or its alloys at melt temperatures in the range 650 - 750 °C. SF6 is a source of fluorine atoms reacting in the melt and removing inclusions of H2, oxides, particles and other casting impurity
