GRID
High Voltage Switchgear
PS 0004EN
03 G. BERNARD
1998-08-12
J. VIAT
2011-03-21
1 / 3
Sheet N° Revision Written by Date Signature Approved by
Date Signature Page
SAFETY SHEET
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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