CRYOSAFE CM Series User manual

Owners Manual
CM Class
SSC Class
SSC-ET Class
VS Class
LD Class
Revised 08/03

A cryogenic dewar is really two containers, one within
the other. High-technology insulation is used in a
sealed, vacuum space between the inner and outer
containers. The integrity of the vacuum is the key to
continued performance.
The Vacuum Maintenance System can intercept these
trace leaks of air molecules only up to a point. Then the
vacuum will become less efficient and more nitrogen
refrigerant will be required between refills.
The most frequent cause of vacuum failure, however, is
All dewars fail eventually. A perfect vacuum that
abuse.
The inner container is supported by the
necktube, which supports the weight of the nitrogen
refrigerants as well. A blow to the dewar may cause the
does not leak cannot be achieved.
Some minute
leakage of air molecules into the vacuum occurs from
the moment of manufacture. A “Vacuum Maintenance
necktube to deform or break.
Any unit subjected to
System”, consisting of materials that trap and hold
these molecules is built into the vacuum space to
prolong the service life of the container by many years.
physical damage may fail more rapidly than one that
has been carefully handled.
If ice accumulates inside the necktube, a general
cleaning of the dewar should be scheduled as soon as
the stored material can be conveniently transferred to
another dewar. To clean the unit, first remove stored
material, then pour out the liquid. Dispose of it out-of-
doors where the cold liquid will not damage driveways
and other surfaces. Warm the dewar by purging it with
a stream of room-temperature air. Continue purging
with air even after the dewar has warmed to evaporate
any collected moisture. When the dewar is ice-free and
dry, rinse the inner vessel with household bleach.
Wash the inner vessel with a solution (40 to 1 water to
DO NOT attempt to fasten any device to the dewar.
Welding, brazing, or piercing of the dewar in any
manner will cause it permanent damage.
Refrigeration depends on the presence of liquid
nitrogen in the dewar. Be sure to maintain correct
refrigerant levels to prevent loss of stored material.
Check liquid levels regularly. If high evaporation rates
are apparent under normal operating conditions, the
dewar may be losing its vacuum. Sweating or freezing
of the outside casing are definite indications that the
insulation integrity is not normal. All necessary steps
should be taken to preserve valuable product. Read
the Handle with Care section for more information on
the proper handling of your cryogenic dewar.
laundry detergent).
Rinse and dry inside and out
thoroughly before placing the dewar back into service.
Do not use sharp instruments to chip ice: permanent
damage to the dewar could result.
Although these dewars are rugged, they can be
damaged if abused or otherwise mishandled. When
moving or transporting a dewar, take every precaution
to prevent sliding, tipping, bumping, or dropping the
unit.
Dewars containing liquid nitrogen must never be
transported in sealed compartments. Ventilation must
be assured to prevent the displacement of air and the
related suffocation hazard.
Safety “WARNING”
Transportation “WARNING”
Routine Care & Maintenance
Dewar Construction

Before using any Cryogenic dewar, read the Handle
with Care section provided with the unit. It details
safety and unit-care precautions that must be read and
understood before using the equipment.
face shield and gloves must be worn when
transferring liquid nitrogen into or out of these
containers.
Use only the necktube core provided with this unit
Following are a few of the precautions described in
Handle with Care. Please be sure to read the entire
section.
or a listed replacement part.
A tight-fitting plug or
stopper will cause a pressure increase in the container
that may damage the dewar and/or cause personal
injury.
Do not touch liquid or cold metal surfaces with your
bare skin. The liquid nitrogen used as a cryogenic
refrigerant in these dewars is extremely cold: -320F (-
196C). Exposure of skin or eyes to liquid, cold gas, or
frosted parts could result in a severe frostbite-like injury.
Because of the extremely low temperature, a
Store and use these dewars only in well-ventilated
places. In a confined area, nitrogen gas from these
units may cause suffocation by displacing air needed
for breathing.
Operation
Filling--Adding liquid nitrogen to a warm dewar may
cause splashing and will generate a significant volume
of nitrogen gas as old liquid contacts warm dewar
surfaces. Add liquid slowly to minimize these effects.
Be sure there is adequate ventilation. Keep your head
clear of the heavy volume of vapor that may be
stored material, the necktube core should be removed
as briefly as possible.
When inserting or removing the racks, grasp the rack
handle, lift and tilt the rack toward the center of the
dewar and withdraw the rack only far enough to remove
the contents. Completely withdrawing the rack will
unnecessarily expose stored material to warm
conditions.
produced:
it is extremely cold and could cause
personal injury.
Determining Liquid Level--Liquid level must be
checked at regular intervals--refrigeration depends on
the presence of liquid nitrogen. The liquid level in the
dewar can be determined by measuring with a dipstick.
Insert the dipstick straight into the dewar so that it
always rests on the canister-positioning fixture in the
bottom of the unit. After 5 to 10 seconds, withdraw the
dipstick and wave it back and forth in the air. A frosted
section will form representing the depth of liquid in the
dewar.
WARNING
Some racks have liquid drain openings; some do
not.
If racks are completely removed from the
container, liquid nitrogen may remain in the rack or
drain from the bottom. When removing racks, stop
briefly at the necktube to allow the liquid to drain
completely, and then handle the rack carefully to
prevent personal injury.
When room temperature product is added, slowly lower
the rack into the dewar to reduce the boiling of
refrigerant and the surge of cold nitrogen gas. When
inserting the rack, tilt the bottom of the rack in the
direction of the index ring notch. The numbers on the
index ring notches are a convenient aid to inventory
control.
WARNING
Never use hollow rods or tubes as dipsticks. When
a warm tube is inserted into liquid nitrogen, liquid
will spout from the top of the tube and may cause
personal injury.
Inserting or Removing Racks--To prevent the
unnecessary loss of liquid nitrogen refrigerant, the
necktube core should remain in the container when the
stored material is not being accessed. When accessing

Handling LN2Safely
area. The gas issuing from the liquid is also extremely
How to take care of your liquid nitrogen refrigerator
or dewar while taking care of yourself.
cold. Delicate tissue, such as that of the eyes, can be
damaged by an exposure to the cold gas that would be
too brief to affect the skin of the hands or face.
Protect yourself and others. Read and understand
this section. Keep it available for reference at all
times. You can get additional copies through your
supplier.
Never allow any unprotected part of your body to
touch objects cooled by liquid nitrogen.
Such objects may stick fast to the skin and tear the
flesh when you attempt to free yourself. Use tongs to
withdraw objects immersed in the liquid, and handle the
object carefully.
Warning
Use only liquid nitrogen or liquid argon in Liquid
Nitrogen Refrigerators and Dewars. Do not use liquid
air or liquid oxygen, both of which may present a
combustion hazard with some materials used in the
construction of these units, or materials stored in them.
Wear protective clothing.
Protect your eyes with a face shield or safety goggles
(safety glasses without side shields do not give
adequate protection). Always wear gloves when
handling anything that is, or may have been, in
immediate contact with liquid nitrogen. Insulated gloves
are recommended, but heavy leather gloves may also
be used. The gloves should fit loosely, so that they can
be thrown off quickly if liquid should splash into them.
When handling liquid in open containers, it is advisable
to wear high-top shoes. Trousers (which should be cuff
less if possible) should be worn outside the shoes.
Introduction
The safe handling and use of liquid nitrogen in
cryogenic refrigerators and dewar flasks is largely a
matter of knowing the potential hazards and using
common-sense procedures based on that knowledge.
There are two important properties of liquid nitrogen
that present potential hazards:
1. It is extremely cold. At atmospheric pressure,
liquid nitrogen boils at -320 F (-196 C).
Use only containers designed for low-temperature
liquids.
2. Very small amounts of liquid vaporize into large
amounts of gas. One liter of liquid nitrogen
becomes 24.6 cu. ft. (0.7 m3) of gas.
The safety precautions in this section must be followed
to avoid potential injury or damage that could result
from these two characteristics. Do not attempt to handle
liquid nitrogen until you read and fully understand the
potential hazards, their consequences, and the related
safety precautions. Keep this handy for ready reference
and review.
Cryogenic containers are specifically designed and
made of materials that can withstand the rapid changes
and extreme temperature differences encountered in
working with liquid nitrogen. Even these special
containers should be filled SLOWLY to minimize the
internal stresses that occur when any material is
cooled. Excessive internal stresses can damage the
container.
Do not cover or plug the entrance opening of any
liquid nitrogen refrigerator or dewar. Do not use any
stopper or other device that would interfere with
venting of gas.
Note: Because argon is an inert gas whose physical
properties are very similar to those of nitrogen, the
precautions and safe practices for the handling and use
of liquid argon are the same as those for liquid nitrogen.
These cryogenic liquid containers are generally
designed to operate with little or no internal pressure.
Inadequate venting can result in excessive gas
pressure that could damage or burst the container. Use
only the loose-fitting necktube core supplied or one of
the approved accessories for closing the necktube.
Check the unit periodically to be sure that venting is not
Handling Liquid Nitrogen
Contact of liquid nitrogen or cold gas with the skin
or eyes may cause serious freezing (frostbite)
injury.
Handle liquid nitrogen carefully.
restricted
by
accumulated
ice
or
frost.
The extremely low temperature can freeze human flesh
very rapidly. When spilled on a surface the liquid tends
to cover it completely and intimately, cooling a large

Because nitrogen gas is colorless, odorless and
tasteless, it cannot be detected by the human senses
and will be breathed as if it were air. Breathing an
atmosphere that contains less than 18 percent oxygen
Use proper transfer equipment.
Use a phase separator or special filling funnel to
prevent splashing and spilling when transferring liquid
nitrogen into or from a dewar or refrigerator. The top of
the funnel should be partly covered to reduce
splashing. Use only small, easily handled dewars for
pouring liquid. For the larger, heavier containers, use a
cryogenic liquid withdrawal device to transfer liquid from
one container to another. Be sure to follow instructions
supplied with the withdrawal device. When liquid
cylinders or other large storage containers are used for
filling, follow the instructions supplied with those units
and their accessories.
can
cause
dizziness
and quickly result
in
unconsciousness and death.
Note:
The cloudy vapor that appears when liquid
nitrogen is exposed to the air is condensed moisture,
not the gas itself. The issuing gas is invisible.
Never dispose of liquid nitrogen in confined areas
or places where others may enter.
Disposal of liquid nitrogen should be done outdoors in a
safe place. Pour the liquid slowly on gravel or bare
earth where it can evaporate without causing damage.
Do not pour the liquid on the pavement.
Do not overfill containers.
Filling above the bottom of the necktube (or specified
maximum level) can result in overflow and spillage of
liquid when the necktube core or cover is placed in the
opening.
First Aid Notice
If a person seems to become dizzy or loses
consciousness while working with liquid nitrogen, move
to a well-ventilated area immediately. If breathing has
stopped, apply artificial respiration. If breathing is
difficult, give oxygen. Call a physician. Keep warm and
at rest.
Never use hollow rods or tubes as dipsticks.
When a warm tube is inserted into liquid nitrogen, liquid
will spout from the bottom of the tube due to gasification
and rapid expansion of liquid inside the tube. Wooden
or solid metal dipsticks are recommended; avoid using
plastics that may become very brittle at cryogenic
temperatures.
If exposed to liquid or cold gas, restore tissue to normal
body temperature 98.6 F (37 C) as rapidly as possible,
followed by protection of the injured tissue from further
damage and infection. Remove or loosen clothing that
may constrict blood circulation to the frozen area. Call a
physician. Rapid warming of the affected part is best
achieved by using water at 108 F (42 C). Under no
circumstances should the water be over 112 F (44 C),
nor should the frozen part be rubbed either before or
after re-warming. The patient should neither smoke, nor
Nitrogen Gas can cause suffocation
warning.
without
Store and use liquid nitrogen only in
ventilated place.
a well-
As the liquid evaporates, the resulting gas
tends to
drink
alcohol.
displace the normal air from the area. In closed areas,
excessive amounts of nitrogen gas reduce the
concentration of oxygen and can result in asphyxiation.
Handling LN2Safely (cont’d)_