5 Troubleshooting
C
HECK AND
C
LEAN THE
D
EWAR
When handling Dewars, follow the precautions outlined in
Always handle glass Dewars with care. Any product incorporating a vacuum is a
potential safety hazard and should be treated with caution. If in doubt, contact your
safety officer.
Ice and suspended frost particles may accumulate in the bottom of the analysis port Dewar.
Particles or deposits exceeding 1/4 in. (6 mm) in depth may jam between the bottom of the sample
tube and the bottom of the Dewar.
Accumulations of fine particles impede liquid nitrogen circulation around the bottom of the sample
tube. This causes the sample temperature to be slightly higher which, in turn, can cause pore
volume measurement errors in those samples exhibiting high isotherm slope above 0.97 relative
pressure.
Accumulated ice is likely to melt and form a pool of water in the Dewar if all liquid nitrogen
evaporates. The water must be removed, otherwise it will solidify when liquid nitrogen is added
and could press on the bottom of the sample tube causing breakage.
To ensure problems do not develop due to ice accumulation, check the Dewar after each use.
Clean on a weekly basis.
1. Remove the Dewar from the analyzer.
2. Pour out liquid nitrogen into an appropriate cryogenic container. Do not re-use liquid nitro-
gen.
Do not pour liquid nitrogen directly into a sink. Doing so may cause drain pipes to
burst.
3. Rinse the Dewar with warm water to melt any remaining ice accumulation which may
remain. Dry thoroughly.
4. Replace the Dewar.
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Gemini VII Keypad Operator Manual
239-42801-01 (Rev E) — July 2021
