Taylor-Wharton LS Series User Manual
Operating Instructions
SAFETY
Before using any cryogenic refrigerator, read
the Handle with Care booklet provided with the
unit. It details safety precautions that must be
understood before using the equipment. If a
replacement booklet is needed, order publication TW-10 Handle with Care from your sup-
plier.
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
refrigerant is extremely cold: -196°C (-320°F).
Exposure to skin or eyes to liquid, cold gas or
frosted parts could result in a severe frostbitelike injury. Because of the extremely low
temperature, a face shield and gloves must be
worn when transferring liquid nitrogen and
material into or out of these containers.
These values are approximate and are based
on a standard condition with no stored material
in the container. With store material, the liquid
volume will be slightly less than the value of
the chart.
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INSERTING OR REMOVING RACKS
To prevent unnecessary loss of liquid nitrogen
and accumulation of ice, the necktube core
(the stopper) should remain in the container
when the stored material is not being accessed. When accessing stored material, the
necktube should be removed as briefly as
possible.
When removing material from the racks,
withdraw the rack just far enough to remove
contents. Completely withdrawing the rack will
unnecessarily
expose the stored
material to warm
room temperature
conditions.
TW-348
Laboratory
Systems
Use only the necktube covers 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
container may cause splashing and will generate a significant volume of nitrogen gas as cold
liquid contacts warm refrigerator 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 refrigeration depends on the pressure of
liquid nitrogen. 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 rack positioning fixture on 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 the liquid in the container.
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.
The liquid level chart shows volume of liquid
nitrogen vs. depth for LS Series refrigerators.
WARNING
Some boxes have
liquid drain openings,
some do not. If racks
are completely
removed from the
container, liquid
nitrogen may remain
in the either rack and
boxes, or simply drain
from the bottom. When
removing racks, stop
briefly at the necktube
to allow liquid to drain
completely, then
handle the rack carefully to prevent personal injury.
Avoid direct rack contact with bare skin. The use of
proper personal protective gear is strongly urged
cryogenic gloves, face shield and gown to protect
against splashing.
When room temperature is added, slowly lower
the rack into the refrigerator 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 and colors on the
rack handles are a convenient aid to inventory
control.
SECURING CONTENTS
The contents of all models may be secured
with a seal or lock through tabs on the edge of
the lid opposite the hinge.
ROUTINE CARE AND MAINTENANCE
If ice accumulates inside the necktube, a
general cleaning of the refrigerator should be
scheduled as soon as the stored material can
LS SERIES
AUTO FILL OPERATION
WARNING: In order to prevent the
relief device on nitrogen
refrigerator(s) from opening when
the system is in operation,
liquid nitrogen supply system must
be protected by a pressure relief
device that will open when the
pressure at the inlet to the
refrigerator(s) is approximately 22
psig (1.5 bar/152 kPa). Never install
the supply system pressure relief
device into a liquid service line.
Filling the Refrigerator (Initial Fill)
The LS6000-AT uses the AutoTend controller that comes
preset from the factory to operate.
The liquid nitrogen supply pressure at the inlet to the unit
should be in the range of 10 psig (0.7 bar/69 kPa) to 20
psig (1.4 bar/138 kPa) for optimum performance. Higher
operating pressures will increase transfer losses and
create excessive turbulence of the liquid in the unit which
can generate false signals to the liquid level controller
causing the unit to underfill. In liquid phase storage
applications, excessive turbulence can cause splashing
which could result in personal injury and/or damage to the
unit.
If the liquid nitrogen supply pressure at the inlet to the unit
rises above the opening pressure of the relief valve on the
unit, liquid nitrogen will be discharged into surrounding
area which can cause rapid and very dangerous depletion
of oxygen in the atmosphere. Once this pressure relief
device has opened and cooled to liquid nitrogen temperature, it will not reset until it has warmed to near ambient
temperature. THIS COULD PERMIT THE ENTIRE CONTENTS OF THE LIQUID NITROGEN SUPPLY SYSTEM
TO BE DISCHARGED INTO THE IMMEDIATE AREA OF
THE REFRIGERATOR(S).
the
Operating Parameters
When materials are immersed in liquid nitrogen, they will
assume the temperature of the liquid -320° F (-196° C).
When material is stored in the vapor phase of the liquid, the
liquid nitrogen is still a very cold refrigerant, but the units
interior temperature increases somewhat as product is
stored higher above the liquid. This temperature differential is
not significant in many biological storage applications, and is
affected by the amount of product stored in the unit, the type
and size of inventory control system, and the liquid level in
the unit.
The liquid level in the unit is determined by the position of the
sensor probes in the tube located next to the fill tube. These
probes are set at installation to maintain a specific liquid
level. (See Figure 4) The cycle repeats when the liquid level
drops to the low level sensor over time. Sensor probes may
be moved to define new high and low levels, and these levels
may be set independently to vary the liquid level differential
between fills. For adjusting the temperature probes see
Changing Liquid Level section in this manual.
Vapor Phase Storage
Vapor phase storage is normally utilized when stored product
is unable to withstand liquid nitrogen temperatures, or when
the storage medium (vials, ampules, etc.) is not designed for
liquid phase storage.
In a typical vapor phase storage system, the liquid level
sensors are positioned to maintain the liquid level at or below
the top of the spider. This positioning allows stored product to
be kept at cryogenic temperatures without being exposed to
liquid nitrogen, reducing the possibility of leakage or crosscontamination. Care must be taken in the positioning of the
level of refrigerant in the event of power outages, which may
disable the controller for an extended period of time. Consideration must also be given to liquid nitrogen availability and
delivery schedules.
WARNING: Maintain adequate ventilation to
prevent asphyxiation hazard. (See Safety Precautions)
Power Supply Connection
Connect the 24 Volt AC power supply to the rear of the
cryostorage system; then plug the power supply into a 110/
120 VAC outlet. (See Figure 5 for the Electrical Supply
Connections.) Turn on the AutoTend by turning the key on
the front panel (see Figure 5) to the on position. The
audible alarm may sound during setup; silence the alarm
by pressing the button labeled MUTE.
WARNING: If the fill fails to stop for
any reason, quickly close the liquid
supply valve to prevent overfilling
until the cause of the problem can
be determined.
The unit is now under automatic fill control. Liquid will be
added by the controller as long as the liquid supply and
electrical power are maintained.
Liquid Phase Storage
Liquid phase storage is normally utilized when liquid nitrogen
temperatures are required to maintain stored product viability
and the storage mediums are adequate for storage in liquid
nitrogen.
In a typical liquid phase storage system, the liquid level
sensors are positioned to maintain the liquid level at or below
the top level of the inventory control system. During operation, the upper levels of the inventory control system will at
times become exposed as the liquid level fluctuates.
Care must be taken to ensure that the liquid level remains
below the bottom of the lid. Operating the refrigerator with
high liquid levels characteristic of liquid phase storage may
result in turbulence during fill cycles. Caution must be
exercised if the unit lid is opened during a fill, and appropriated safety equipment should always be worn.
Sensor Positioning for the AutoTend Controller
The longer sensor probe (orange/yellow wires) contains the
Low Level sensor in a pod. The shorter probe (red/black
wires) contains the High Level sensor. The factory sensor
positions will maintain a liquid level between 2.0 in. to 4.0 in.
The dimensions used for the factory sensor installation are
shown in Figure 2.
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