Grid Solutions
SF6
Use and Handling
CAUSE OR ORIGIN OF HAZARD.
Sulphur hexafluoride (SF
6
) is a gas which in its basic state is colourless, odourless and tasteless. It is not toxic,
but it cannot sustain life. It is a heavy gas that is dispersed slowly into the atmosphere.
In its natural state, SF
6
is delivered and stored in pressurized tanks (bottles or spheres) at a pressure of
approximately 20 bar at 20°C (in its liquid form) and complies with IEC standard 376.
However, under the effect of the electric arc, the SF
6
molecules break up and the elements mostly recombine
during cooling either due to extinction of the arc or by regeneration caused by the presence of active
absorbent charges within the circuit breaker.
Various chemical reactions, associated with the volatilization of the materials in contact with the electric arc,
create either fluoridized or sulphurous secondary gas products or solid products in the form of metallic fluoride
powder ; or again, in the presence of traces of water or moisture, hydrofluoric acid or sulphur dioxide.
In the life-cycle of the equipment, SF
6
can be observed not only in its pure state, but also in its contaminated
state :
- the use of new SF
6
for filling or adding,
- leaks under normal operating conditions,
- maintenance involving the opening of circuit breakers containing old SF
6
(decomposition products),
- abnormal conditions (internal arc fault causing the shielding to break),
- circuit breaker recycling on end of life-cycle.
WORK REQUIREMENTS.
Follow the instructions for the transport of pressurized containers.
The storage of these containers is governed by the same storage regulations as compressed gas bottles :
- keep away from any source of heat and in a cool, dry and well-ventilated area,
- always fit a pressure reducing valve.
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