Gas - ABB SF6 LTB 245E1 BLG 1002A Product Manual

Dismantling the circuit-breaker

4.2 Gas

4.2.1 Emptying the gas:
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Work on the circuit-breaker's insulators or other live components as well as
transport and dismantling of complete circuit-breaker poles from the frame, may not
be done until the gas has been evacuated to a pressure of max 0.125 MPa (abs).
Gas shall be emptied fully to atmospheric pressure, when a normal pressurised
space, e.g. a breaking unit, shall be opened.
When nitrogen gas is used for cleaning inside the circuit-breaker, the gas
may be emptied into the atmosphere via a dust and absorption filter. The
emptying operation must be done outdoors and at ground level.
Unused SF gas is non-toxic, odourless and colourless. It is heavier than
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air and can therefore easily collect in low-lying places, e.g. cable trenches,
tanks, etc., if released in large volumes.
When large quantities of SF
asphyxiation may occur due to lack of oxygen.
The SF gas is evacuated and the circuit-breaker should be vacuum pumped using
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the gas handling equipment. This cleans and compresses the gas so that it can be
reused or destructed.
After vacuum pumping, the circuit-breaker is filled with dry nitrogen gas until
atmospheric pressure is reached and is then vacuum pumped again. In this way any
free-floating dust inside the circuit-breaker will be extracted.
Finally the circuit-breaker is filled again with dry nitrogen gas until atmospheric
pressure is reached. The circuit-breaker is now ready to be dismantled.
WARNING
WARNING
gas collect in such places, a risk of
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Overhaul Instructions
1HSB435409-201 enrev1