Sulfur hexafluoride (SF6) is a colorless, odorless, non-toxic, and non flammable synthetic gas. It is an important gas material in modern industry, especially in the fields of power and microelectronics, known as the “golden gas” in the power industry. However, it is also one of the strongest greenhouse gases, so its use and management are strictly restricted.
Its core characteristics and typical applications can be summarized as follows:
Key characteristics
A: Excellent insulation and arc extinguishing performance
-The insulation strength is about 2.5 times that of air and nitrogen, and the arc extinguishing ability can reach 100 times that of air. It is currently the best known high-voltage insulation and arc extinguishing medium. When the circuit is disconnected and an arc occurs, SF6 molecules can quickly decompose and recombine, absorb the energy of the arc, and quickly restore the dielectric strength after the current crosses zero, making the arc quickly and reliably extinguished.
B: Stable physical and chemical properties
-Colorless, odorless, non-toxic, and non flammable at room temperature; Strong chemical inertness, non corrosive to equipment metals; Good thermal stability and high decomposition temperature. We usually fill and ship it in gas cylinders.
C: High density and easy to accumulate
-The density is about 5 times that of air, and it is easy to deposit in low-lying areas after leakage, which may cause local oxygen deficient environment. We should pay attention to ventilation in the workplace to prevent oxygen deficiency.
D: Strong greenhouse effect
The Global Warming Potential (GWP) is extremely high: SF6 has a GWP which is more than 23500 times that of carbon dioxide (CO2) (according to IPCC assessments), and is listed as a controlled object under the Kyoto Protocol. The lifespan of SF6 in the atmosphere can reach about 3200 years.
E: The products of arc decomposition are toxic
-Toxic and corrosive gases such as SO2F2, SOF2, and HF can be generated under electric arc or high temperature conditions. It is necessary to use adsorbents and monitoring devices to pay attention to protection and treatment.
Main application areas
A: Power transmission and distribution (core use)
-High voltage/extra high voltage circuit breakers, GIS (fully enclosed composite electrical equipment), pipeline transmission, gas insulated transformers, etc., used as insulation and arc extinguishing media.
Advantages :
- Small footprint: More than 70% smaller than traditional open type substations, especially suitable for places with limited space such as cities and underground substations.
- High reliability: unaffected by environmental factors such as pollution, humidity, salt spray, and high altitude, ensuring safe and reliable operation.
- Long maintenance free cycle.
- Circuit breakers (especially high voltage and ultra-high voltage circuit breakers): Utilizing the excellent arc extinguishing performance of SF6, manufacture circuit breakers with extremely strong breaking capacity for use in power transmission and distribution systems.
- High voltage transmission line (GIL): As an insulation medium for large capacity, long-distance underground or tunnel transmission lines.
- Transformers, mutual inductors, capacitors, etc.: used as insulation and cooling media.
B: Microelectronics and Semiconductor Manufacturing
Semiconductor etching: SF6 is used as an etching gas for silicon and silicon nitride in plasma processes.
Flat panel display manufacturing: used as a cleaning gas in the manufacturing process of liquid crystal displays (LCD) and plasma displays (PDP)
C: Medical and Ophthalmology
Previously used as a filling gas for ophthalmic surgery (retinal repositioning), its application has greatly decreased.
D: Processing of non-ferrous metals and materials
-Degassing and purification of aluminum and its alloy melts; Doping of fiber preform; High voltage insulation for accelerators, coaxial cables, and radar waveguides.
E: Traceability and scientific research
Due to its chemical inertness and ease of detection, it can be used for environmental monitoring, ventilation system detection, and gas leak location.
In summary, SF6 has become a “key gas” in industries such as high-voltage power and semiconductor etching due to its excellent insulation arc extinguishing ability and chemical stability. In summary, SF6 is an extremely high-performance industrial gas that has made significant contributions to the miniaturization and high reliability of modern power systems. However, its strong greenhouse effect and potential toxicity also require strict environmental and safety measures to be taken in the use, recycling, and monitoring processes.