Leica EM FC7, Operating Manual

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Page 8 Operating Manual Leica EM FC7 01/10
Only use metal Dewars specifically designated for storage of LN
2
, since only
containers of this kind exclude risks during storage. For routine cryopreparation
metal troughs (1 cm styrofoam insulation), styrofoam containers or plastic troughs
are eminently suitable and ensure low risk cryopreparation.
Check the evaporation rate of your metal Dewar regularly every three months and
compare these rates with the rate given by the manufacturer. The evaporation rate
of an undamaged metal Dewar should be well below 1 litre of LN
2
per day.
Defective Dewar vessels with higher evaporation rates are a safety risk, and should
be taken out of work or repaired.
Do not leave LN
2
standing in open vessels where it can exchange with the room
atmosphere. The boiling point of LN
2
(-196 °C) is lower than liquid oxygen’s boiling
point (-183 °C). When the exchange surfaces are extensive enough, oxygen from
the air will be taken up in exchange for nitrogen. LN
2
with high liquid oxygen content
has a faintly bluish colour. Concentrated liquid oxygen promotes vigorous burning!
Make sure that your Dewar vessel is filled only with LN
2
. Apply a note in the central
distribution place stating clearly
ONLY LIQUID NITROGEN
or similar if different liquefied gases are delivered from there. Check the colour of
cryogen: Bluish colour indicates the presence of a high percentage of liquid oxygen.
The concentration of liquid oxygen increases during long periods of storage as its
boiling point (-183 °C) is higher than the boiling point (-196 °C) of LN
2
.
Main supply must be assured: 100 – 240 VAC, 50 – 60 Hz
The instruments are equipped with protected ground. Before connecting it to the
local electrical supply make sure that the mains has the required ground and that
the instrument is connected to it according to the local regulations.
Unplug the instrument before installing or changing fuses.