Section 7
7-2
Maintenance
7.3 Internal Soda Lime/Desiccant
NOTE:
Internal soda lime/desiccant
must
be changed annually.
CAUTION!
The instrument should not be turned on for about 24 hours
after changing the internal chemicals. The time needed will depend, of
course, on how much CO
2
and/or water vapor gets into the detector housing
during the exchange of bottles. Leaving the instrument off is done so that
water vapor which may have entered the system during the time the
chemicals were exchanged will not condense in the optical path when the
Peltier coolers controlling the detector temperature are powered up.
There is a small plastic bottle inside the LI-6262 that contains a mixture of
soda lime and anhydrous Mg(ClO
4
)
2
(magnesium perchlorate). This bottle
is attached to the CO
2
/H
2
O analyzers' detector housing. Its purpose is to
keep the detectors free of CO
2
and water vapor, and their dewpoints below
-5
°
C.
If the CO
2
/H
2
O concentration in the detectors rises, the analyzer response
curves will change, and the calibration polynomials will no longer match the
response curves, and the factory-supplied calibration functions will be
invalid. If the dewpoint in the detectors rises above -5
°
C, condensation may
form, resulting in a large shift in the zero and/or span. The READY light
may also fail to light.
For these reasons, the internal soda lime/desiccant
must be changed annually.
The plastic bottle of soda lime/desiccant is located inside the nickel-plated
desiccant bottle cover, which is connected perpendicularly to the detector
housing (Figure 7-1). The bottle cover is attached with 2 Allen head screws,
which may be removed with the hex key included in the LI-6262 spare parts
kit. Be careful not to drop the screws onto the LI-6262 circuit boards, as
damage may occur.
Follow these steps to replace the soda lime/desiccant bottle:
