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Sulfur Hexafluoride - The gas with a double-edged sword

Dec 10, 2018

Physical Appearence

Colourless in-noxious and non-flammable gas at atmospheric temperature, sulfur hexafluoride is actually one of the most stable gaseous chemicals.

Sulfur hexafluoride, or SF6 as it’s usually named, is a heavy, inert, nontoxic and incombustible gas.

Its main uses are as an insulation medium in electrical transmittance systems and electrical distributing devices, making an inert cover, or simply for displacing the gas mixtures in metals smelting.

Colourless in-noxious and non-flammable gas at atmospheric temperature, with a molecular weight of 146.06, the density of SF6 gas is 6.139 g/l (20oC) and is almost five times as much as that of air (1.29 g/l).

It is one of the most stable gaseous chemicals and the inertia is similar to that of nitrogen gas. With excellent electric insulating and arc-quenching capacity, sulfur hexafluoride gas has been widely used in the fields of electronics, laser, medical, meteorological, freezing, fire-fighting, chemical, military, space aviation, non-ferrous metallurgy and physical research.



Brief history
The industrial production of SF6 began in 1953 in the US, stimulated by the market introduction of electrical switchgears with gas insulation. Its introduction allowed for the replacement of flammable oils and the use of more compact electrical equipment, particularly in urban areas.

At around the same time, studies regarding SF6 application began in the former USSR. From this period and to date, production of SF6 is constantly growing with the rate of this growth increasing at the beginning of the 1970s - a period of broad introduction of gas-insulated high-voltage switchgears and other electrical equipments.

SF6 is used in the electrical industry as a gaseous dielectric medium for high-voltage (generally 40 KV and above) circuit breakers, switch gears and other electrical equipment, often replacing oil-filled circuit breakers (OCBs).

SF6 gas under pressure is used as an insulator in gas insulated switchgear (GIS) because it has a much higher dielectric strength than air or dry nitrogen, ensuring it is possible to significantly reduce the size of electrical gear.


SF6 finds application in the following areas, though some of these areas are now being covered by other gases:

* Production of electrical equipment (Utilities (use of electrical equipment - refilling, leakages compensation, accidents; use in accelerators for scientific and/or military purposes)

* Adiabatic properties applications, notably in tennis balls, shoe soles and in truck tyres.

* Electronics industry – SF6 is used by the semiconductor industry for plasma etching prior to Chemical Vapor Deposition (CVD).


And the downside…
Its applications aside, SF6 is a highly potent greenhouse gas. It has a global warming potential (GWP) 23,900 times greater than that of CO2 and an atmospheric life of 3,200 years.

As recently as 2002, industry released 600 metric tons of SF6 into the atmosphere – the equivalent of 3,103,896 passenger cars driven for a year, or the burning of 72,866 railcars of coal.

SF6 is also a product that presents a double-edged sword. Indispensable for the safe transmission of electrical power, yet due to its global warming potential, it represents a longer-term problem if used carelessly.

Through greater awareness and improved gas management techniques, user industries can not only reduce their emissions, but also save money in the process.


Storage & safety
SF6 is a nonflammable, compressed gas packaged in cylinders under its own vapour pressure of 310.2 PSIA at 21.1 degree Celsius.

It can cause rapid suffocation when concentrations are sufficient to reduce the oxygen level below 19.5 %, while exposure to this limit can cause dizziness and diminished mental alertness.

Exposure to atmospheres containing less than 12 % oxygen will bring unconsciousness without warning and so quickly, that the individuals can’t actually help themselves.


Referenced from gasworld.com

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