What are the properties of SF6 gas?

What are the properties of SF6 gas?  
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1 Answer

Answer :

Physical properties

1. Colourless

2. Odorless

3. Non-toxic. Pure SF6 gas is not harmful to the health.

4. Non-inflammable.

5. Density- more gas density, 5 times that of air at 20°C and at atmospheric pressure. The gas starts liquefying at certain low temperature. The temperature of liquefaction depends on pressure. At 15 kg f / cm2 the gas starts liquefying at 10°C. Hence this gas is not suitable for high pressures >15 kg f / cm2

6. The heat transferability of SF6 gas is 2 to 2.5 times that of air at same pressure. Hence for equal conductor size the current carrying capacity is relatively more.

Chemical properties

1. Stable upto 500°C.

2. Inert gas due to the chemical inertness. The life of the metallic parts, contacts is longer in SF6 gas. The components do not get oxidised or deteriorated. Hence the maintenance requirement is reduced. However moisture is very harmful to the properties of the gas. In the presence of the moisture, hydrogen fluoride is formed during arcing which can attract the metallic and insulating parts in the circuit breaker.

3. Electro negative gas – Ability of an atom to attract means carrying a negative electric charge.

These advantages offer increased safety, reduction in size, weight, noiseless operation, easy installation, handling and maintenance. 
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