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.
/6
0RGHO
/6/6/6
/LTXLG/HYHO(TXLYDOHQWV
LQ OL WHUVFP O L WHUV
LQ O LWHUVFP O L WHUV
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.
Start Fill
Stop Fill
2.0 inches
CONTROLLER OPERATION
Introduction
The AUTO-TEND Control System is designed to provide
simple, reliable liquid level control in your LN
operates on 24 Volts AC and uses a two-sensor system to
freezer. It
2
open and close a solenoid valve. The liquid level, the sensor
condition, the valve condition, and the LN2 supply condition
are indicated by lights on the front panel.
Installation:
The AUTO-TEND Control System is designed to mount
onto your Taylor-Wharton Cryogenic refrigerator. The
components plug into the back of the control panel as
follows: The Solenoid Valve has a 2-pin connector. The
sensor assembly has a 4-pin connector. These plug into the
mates on the back of the control panel.
The sensor assembly should be installed with the yellow
and orange wires at the High Level and the black and red
wires at the Low Level. These are labeled for easy reference.
The Auto-Tend controller should not require additional
attention to maintain liquid level if an adequate supply of
liquid nitrogen is maintained. If your protocol calls for you to
top off the cryostorage system at the end of a work day or
work week, press the Start button. The unit will fill to the
upper allowable liquid level and stop automatically. You may
choose to manually stop the fill by pressing the STOP
button at anytime during the fill.
.25 inches
Figure 2. Sensor Positioning for the AutoTend
Normal Fill Cycle
When the unit is filled and the controller is operating, the low
level sensor is immersed in liquid nitrogen (see Figure 4.)
Its resistance value is interpreted by the controller as in
liquid. At the same time, the high level sensor is above the
liquid pool sending the controller an in-gas signal. In this
condition, the control panel will read Normal. As liquid
nitrogen evaporates, the liquid level in the refrigerator drops
slowly until the low level sensor is above the liquid and
sends a different signal to the controller. The controller
interprets this condition as low liquid and opens
the fill solenoid valve admitting more refrigerant.
The unit fills slowly, the control panel will read
LOW when the liquid level is above the low
level sensor. It will continue to display the green
filling light until the high level sensor is immersed
in liquid. Once the level of the liquid reaches the
point of the high level sensor, the Solenoid Valve
will close. Figure 4 illustrates this cycle in graph
form where liquid level is plotted against time,
and display graphics are shown as they appear
at key points in the cycle.
Figure 4. Normal Fill/Evaporation Cycle Chart
Controller Features Level LN2 Controllers
The controller is designed to maintain the LN2 level in the
unit within a user-defined range. The LN2 level will be
maintained between the low level sensor and the high level
sensor. When the liquid level reaches the low level sensor,
LN2 will be added to the refrigerator until it reaches the high
level sensor.
Basic Operation
1.) Automatic Fill: The control will open the solenoid
valve automatically when the liquid level falls below the
Low Level Sensor. It will continue filling until the High
Level Sensor is covered by liquid.
Manual Fill: The Start Fill button can be pressed at
any time and the solenoid valve will open. If the liquid
level is between High Level Sensor and the Low Level
Sensor, the solenoid will stay open until the Stop Fill
button is pressed or until the liquid level covers the
High Level Sensor. If the liquid level is above the High
Level Sensor, the solenoid valve will stay open while
the user presses the Start Fill Button but will close
when the user releases the button.
Please Note: The maximum time that the
valve will stay open when the liquid level is
above the High Level sensor is one
minute. The user can open the valve again
by simply releasing and then pressing the
Start Fill button again.
Remote Alarm Jack: The remote alarm relay has a
set of dry contacts capable of carrying 5 amperes
current at 30 volts D.C. The relay is normal during
any alarm condition. The remote alarm is triggered 30
minutes after an error condition occurs. The remote
alarm will be reset when the error condition is corrected. Pins 1 and 2 are closed in normal operating
condition while pins 2 and 3 are open in a remote
alarm condition. See Figure 8.
DESCRIPTION OF FRONT PANEL
Key Lock: This turns the control On/Off. Turning the Key to
the 3 oclock position provides power to the control while
rotating the key 12 oclock position turns the control off.
Start Fill: This button opens the solenoid valve and allows
LN2 to flow into the freezer.
Stop Fill & Mute: This button closes the solenoid valve and
stops the flow of LN2 into the freezer. This button also
silences the audible alarm.
Filling LED: Lights green to indicate that the solenoid valve
is open.
LN2 Level LED: Lights red to indicate that the liquid level is
above the high level sensor. Lights green to indicate that
the liquid level is between the low level sensor and the high
level sensor. Lights yellow to indicate that the liquid level is
below the low level sensor.
Alarm Conditions: An alarm condition occurs when
a sensor problem develops or the supply tank runs
low on LN2. When an alarm condition does occur, the
appropriate light on the front panel flashes and an
audible alarm is activated.
Testing the front panel lights: To test all the lights on
the control except the Filling LED, press the Stop Fill &
Mute button and hold for 8 seconds.
Testing the Remote Alarm: To test the remote alarm,
press the Stop Fill & Mute button and hold for 13
seconds (5 additional seconds after testing the lights,
or unplug the power supply from the wall.)
Sensor Assembly
Please note: The LED will not light if the high level
sensor is submerged in LN2 while the low level
sensor is located in gas. The only time that this can
occur is if the sensors are installed backwards.
Sensor Fault LED: Lights red to indicate that a sensor fault
has occurred. A sensor fault can be either an open circuit or
a short circuit in the sensor assembly.
Low LN2 Supply LED: Lights red to indicate that the LN
supply is low. This is triggered when the liquid level does
2
not reach the high level sensor within 1 hour of opening the
solenoid valve.
Remote Alarm24VAC Solenoid Valve
24VAC Power
Electrical Supply Connections For LS6000
Changing Liquid Level
The liquid level in the unit is determined by the position of
the sensor probes in the sensor tube next to the fill tube.
These probes have been set at installation to maintain a
specific liquid level. The controller operates a fill cycle that
adds liquid at low level, fills to a predetermined high level,
then stops the fill. The cycle repeats when liquid drops to
the low level over time.
Sensor probe positions may be changed to define new high
and low liquid levels, and these levels may be set independently to vary the liquid level differential between fills. If a
higher liquid level is desired, withdraw the sensor tube; for a
low level, the sensors must be moved further into (down)
the sensor tube.
CAUTION: Ice or frost in the sensor
tube may restrict movement of
sensor probes in the tube. Do not
pull excessively on sensor wiring
while attempting to change sensor
position. It may be necessary to
remove the sensor from the container and allow it to thaw before the
sensor can be repositioned.
Increasing the distance between low and high sensor
probes allows greater liquid level fluctuation, less frequent
filling and reduced fill loses; decreasing the distance has
the opposite effect.
To set the liquid level to a different point, or to change the
level differential, the sensors must be repositioned. Their
position within the sensor tube is held in place by the
sensor tube plug, which is split to allow the sensor leads to
pass through. The sensor tube plug holds the sensors at
the position necessary to maintain a specific liquid levels.
Two different sensor heights are specified by their position
within the sensor tube. The low and high sensor pods are
separately positioned to set the liquid levels at which the
controller will start or terminate each fill cycle. Insert the
sensor leads into the perforated sensor tube to the desired
height. Mark the sensor leads at the top of the sensor tube.
Pull the leads out just enough to install the sensor tube plug
around the marks on the sensor leads. Insert sensor plug
securely into the mouth of the tube. Perform this operation
carefully, so the sensor leads are not damaged.
Remote Alarm Connection on Taylor-Wharton Freezers
Back panelson most Taylor-Wharton freezers are equipped
with a 3 point electrical socket. The socket connects to a
control board mounted, SPDT (single pole double throw)
relay, rated at 10 amps, 125 VAC.
1
1
3
2
2
3
1
(NC)
3 (NO)
A Switchcraft plug (#05GM3M) connects to the above
socket. It is available with leads as Taylor-Wharton part
#R06K-8C20. Approximately 9 of wire extend from the
plug. The gray wire connects to Pin #1, orange wire to Pin
#2 and the purple wire to Pin #3.
3
1
2
To connect an AC load, such as an alarm light or buzzer,
connect as shown below:
AC Line
AC Line
~
~
orange
Alarm
gray
For automatic dialers and other alarm systems that are
alarmed on either a contact make or break, connect as
shown below:
orange
purple
Alarm on break
2
3
orange
gray
Alarm on make
2
1
MAINTENANCE
LS Series CryoStorage Maintenance
Defrosting your K Series CryoStorage System
NOTE: The high level sensors must be at least
1.75 in. (5.1 cm) above the low level
sensor pod.
After repositioning sensors, check to be sure the sensor
tube is secured to the fill tube and the sensor wires are
dressed and clear of rack operation, and turn the controller
on. The controller should fill the refrigerator to the new
liquid level. After sensors are repositioned, the controller
should maintain the liquid pool at the new operating level.
Remote Alarm Connection
Relay connections are provided on an external for user
installation of a remote alarm circuit (see Figure 8.) Wiring
external power supply and alarm devices must be supplied
by the user. During an alarm condition, contacts 1 & 2 are
closed and contacts 2 & 3 are open.
All liquid nitrogen storage systems are subject to ice and
frost buildup over time. Regular preventive maintenance
programs should be instituted to remove ice and frost from
the sensor and fill tubes and from the refrigerator lid.
Ice and frost build up in the sensor tube may result in false
readings being relayed to the controller from the sensors.
Ice can form a thermal barrier around a level sensor,
rendering it insensitive to the temperature differences
between vapor and liquid. Sensors and thermocouple
should be removed regularly and inspected for ice and frost
build up.
NOTE: Ice or frost in the sensor tube may restrict
the movement of sensor probes in the
tube. Do not pull excessively on the sensor
wiring while attempting to change sensor
position. It may be necessary to remove
the fill tube and tube from the container
and allow it to thaw before the sensors can
be repositioned.
Loading...