Taylor-Wharton LD Series - Manual

LD
SERIES
Liquid
Nitrogen
Dewars
TW-349
Operating Instructions
SAFETY
Before using any cryogenic dewar, read the
Handle with Care booklet provided with the unit. It
details safety precautions that must be under-
stood before using the equipment. If a replace-
ment booklet is needed, order publication TW-10
Handle with Care from your supplier.
Following are a few of the safety precautions
described in the Handle with Care booklet.
Please be sure to read the entire booklet.
Store and use these containers only in well
ventilated areas. In a confined area, nitrogen
gas from these units may cause suffocation by
displacing air needed for breathing. Install a
suitable oxygen monitor.
Do not touch liquid or cold metal surfaces
with your bare skin. The liquid nitrogen refriger-
ant in these containers is extremely cold: -196°
C (-320°F). 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 face shield and gloves must be
worn when transferring liquid nitrogen and
material into of out of these containers.
Use only the necktube core supplied with this
unit or a listed replacement part. A tight fitting
plug or stopper will cause a pressure increase in
the container that may damage the container
and/or cause personal injury.
OPERATION
Filling: Adding liquid nitrogen to a warm con-
tainer may cause splashing and will generate a
significant volume of nitrogen gas as cold 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 produced. It
is extremely cold and could cause personal injury.
WARNING
DO NOT OVERFILL. Over-filling may result in personal
injury due to liquid spillage.
DETERMINING LIQUID LEVEL: Liquid level
must be checked at regular intervals. The liquid
level in the container can be determined with a
dipstick. Insert the dipstick straight into the
container so that it rests on the bottom of the
units. 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 container.
WARNING
Never use a hollow rod or tube as a measuring rod.
When a warm tube is inserted into liquid nitrogen, liquid
will spout from the top of the tube and may cause
personal injury.
The liquid level chart shows volume of liquid
nitrogen vs. depth for LD series dewars. These
values are approximate and are based on a
standard conditions.
ROUTINE CARE AND MAINTENANCE
If ice-build up interferes with normal operation
of the dewar, the unit should be emptied and
thawed. To thaw the unit, pour out the liquid,
disposing 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 room
temperature to evaporate any collected mois-
ture. When the dewar is ice-free and dry, rinse
the inner vessel with household bleach. Wash
the inner vessel with a 40 to 1 ratio of water to
laundry detergent solution. Rinse and dry inside
and out thoroughly before placing the container
back into service. Do not use sharp instru-
ments to chip ice; permanent damage to the
dewar could result. DO NOT attempt to fasten
any device to the dewar. Welding, brazing, or
piercing of the dewar in any manner will cause
permanent damage.
Check liquid levels regularly. If high evapora-
tion rates are apparent under normal operating
conditions, the dewar may be losing its
vacuum. Sweating and the formation of frost on
the outer casing are indications that the dewar
may be losing its vacuum. Sweating or freezing
of the outside casing are definite indications
that the insulation integrity is not normal. If
these conditions persist, contact you supplier or
Taylor-Wharton’s Technical Response Depart-
ment at 1-800-TW-TANKS (898-2657) or email
us at [email protected] for infor-
mation on how to conduct a normal evaporation
rate (NER) test in the field.
TRANSPORTATION
Although these dewars are rugged, they can
be damaged if abuse or otherwise mis-
handled. When moving or transporting a
dewar, take every precaution to prevent tipping,
bumping, or dropping the unit. All dewars
must be kept upright. 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.
DEWAR CONSTRUCTION
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.
* Due to the sperical shape of the Classic-25, the linear
calculations above will not apply.
Model Liters/inch Liters/cm
LD4 0.4 0.16
5LD 0.43 0.17
LD10 0.76 0.3
LD25 1.41 0.56
LD35, LD50 2.67 1.05
Liquid Level Chart*