17
M1288-0056
LN
2
Backup Units for Innova & Premium Freezers
User’s Guide
4
4
M
M
A
A
I
I
N
N
T
T
E
E
N
N
A
A
N
N
C
C
E
E
4.1 LN
2
Supplies
We recommend that a record sheet be placed on or near the freezer, and that a routine
check of the liquid nitrogen remaining in the Dewar be allocated to a staff member.
Record the measurements on the record sheet. All gas supplies can leak away with time.
The majority of LN
2
backup system failures are not equipment failures; they are rather
due to empty Dewars, resulting from lack of routine checks.
4.2
Transfer Lines & Manifold
At least once annually, a qualified service engineer should inspect the LN
2
transfer line
from the Dewar to the injector, for damage or deterioration, using the following
procedure:
1.
Turn off the gas supply.
2.
If the LN
2
backup system is installed on a
Chest
freezer
, also disconnect the freezer
from its power source, and remove the compressor housing cover from the freezer so
it is possible to inspect the transfer line over its full length, up to and including the
solenoid.
3.
Carefully inspect the transfer line over its entire length for any cracks or damage.
4.
Replace the transfer line if it becomes damaged.
5.
Check connections to the Dewar and solenoid for corrosion, damage or leaks. (
Do
not
disconnect the hoses.)
6.
If corrosion or damage is found, contact a qualified service engineer to replace the
damaged item. If a leak is found, tighten the fitting and re-check.
7.
For
Chest freezers
, replace the compressor housing cover.
#
NOTE:
In the United Kingdom, the 1989 pressure vessel regulations require that the
above inspection be recorded. A suitable checklist is included at the end of
this manual.
See Section 7.1.
