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Filling Instructions
Thermo Scientific
Operation
Section 3
Warning Liquid nitrogen is extremely cold; it boils at -196°C. Extreme
caution should be exercised when handling cryogenic liquids. Always wear
proper safety attire when transferring liquid ni-trogen into or out of
Thermo cylinders. Contact with a cryogenic liquid or cold gas may cause
frostbite to unprotected areas of the body. Protect eyes and skin when
transferring liquid. Stand clear of vent during filling. Loose fitting,
insulated gloves and long sleeves are recommended for arm protection.
Cuffless pants should be worn outside boots or overshoes to shed spilling
liquid. Goggles or face shields shouldbe worn if the possibility of splashing
liquid exists. Failure to observe this warning may lead to severe burns or
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eye injuries.
Caution Never overfill your Thermo dewar with liquid nitrogen. Filling the
tank up to or above the bottom of the necktube may cause immediate or
premature vacuum failure.
To avoid damage to your Thermo cryogenic vessel (Thermo® 5, 10, 20 and
30), which may result in premature vacuum loss, it is important that the
following procedure be used during the addition of liquid nitrogen to a
warm vessel and on subsequent additions.
1. Add only a small amount of liquid nitrogen (5-10 liters) to new or
warm vessels.
2. Allow this small amount of liquid nitrogen to sit in the covered vessel
for a minimum of 2 hours. This will limit stress caused by the sudden
temperature change associated with adding liquid nitrogen to a warm
vessel.
3. Fill your vessel to the desired level.
4. If you are filling your Thermo dewar from a pressurized source, make
sure that the source tank is at a low pressure (22 PSI or below).
5. If the transfer hose is used for extracting liquid nitrogen from a
pressurized liquid source, always use a phase separator at the end of the
hose (see Parts List for transfer hoses and phase separators).
6. Remember to always wear proper safety attire over clothing, including:
face shield, cryogenic gloves and apron.
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Cryogenic Transfer Vessels
3-1
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