Taylor-Wharton LABS Series - Manual (Page 15)

13
LABS
MAINTENANCE
Strainer Cleaning Instructions
The container will not fill properly if the strainer is clogged with ice or dirt. To clean the
strainer, first close the supply valve to the refrigerator. Vent the fill line of all pressure.
Remove and warm the strainer to ambient temperature. Purge the strainer from both
directions with dry nitrogen gas or dry oil-free air. Rinse the strainer with alcohol and
purge it again with dry nitrogen gas or dry oil-free air to clear contaminants. If the
cleaning process doesn’t clear the blockage, replace with a new filter (P/N 7631-1080).
Defrosting Your LABS Cryostorage System
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 buildup 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. If
the fill line becomes blocked, it must be warmed until the ice blockage is cleared.
Ice and frost buildup in the fill tube may block the flow of liquid nitrogen into the
refrigerator during fill. This blockage can result in the liquid level dropping to
dangerously low levels, and may result in the Low Alarm sensor being activated. In
addition, a fill line blockage may cause the Low LN
2
Supply Alarm to be activated.
If it is determined that defrosting is necessary the following procedure must be
followed. Cryogenic freezers of these types must be carefully warmed to ambient
temperatures to avoid the ingress of water. As long as liquid nitrogen is present in
the unit, the evaporation of the liquid nitrogen provides slightly positive gas pressure
in the unit, preventing the entrance of moisture laden air. When all of the liquid
nitrogen has evaporated but the unit temperature is still below the dew point of the
surrounding atmosphere, condensation will start to collect in the unit. When frost
and condensation collect in the unit, staining of the carousel or damage to the level
sensors will occur. If one of these units is to be taken out of service for any reason
the following steps must be performed to avoid damaging the unit.
1. Disconnect power and liquid nitrogen source.
2. Remove all stored product and inventory control system components.
3. Remove Sensors.
4. A source of nitrogen gas must be found and used to purge the unit as the
temperature rises to ambient. The purge gas can be installed on the sensor
tube or fill tube or into the liquid via the trap door in the bottom of the carousel
after the appropriate components have been removed. The purge gas may also
simply be delivered to the unit through a bent metal tube under the lid. A flow
rate of 5 to 10 SCFM is sufficient to prevent water from collecting inside the
unit. This flow of purge gas will also speed the warming of the unit to ambient
temperature.
Cleaning Your Taylor-Wharton Cryostorage System
The cryogenic vessel of all LABS Cryostorage Systems may need to be cleaned, and
sterilized if the type of stored product is changed or the unit is taken out of service.
The vessel must be defrosted, cleaned, and sterilized regardless of the type
of stored product, prior to return to Taylor-Wharton for repair or maintenance.
Prior to cleaning, the unit must be warmed and defrosted as described in the
previous section.
WARNING:
Never use chlorine-
based disinfectants
to clean a LABS
Cryostorage System.
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