Mil-spec desiccant regeneration – Juniper Systems Allegro Desiccant Kit User Manual
Page 5
MIL-SPEC DESICCANT REGENERATION
Regeneration of Tyvek desiccant bags or brown paper bags can be accomplished
by the following method:
•
Arrange the bags on a wire tray in a single layer to allow for adequate
airflow around the bags during the drying process. The oven’s inside
temperature should be room or ambient (77
o
F – 85
o
F.) A CONVECTION,
CIRCULATING, FORCED AIR TYPE OVEN IS RECOMMENDED FOR THIS
REGENERATION PROCESS. SEAL FAILURES MAY OCCUR IF ANY OTHER
TYPE OF HEATING UNIT OR APPLICANCE IS USED.
•
When placed in a forced air, circulating air, or convection oven, allow a
minimum of 1.5 to 2.0 inches of air space between the top of the bags and
the next metal tray above the bags. If placed in a radiating exposed infrared
element type oven, shield the bags from direct exposure to the heating
element, giving the closes bags a minimum of 16 inches clearance from the
heat shield. Excessive surface film temperature due to infrared radiation
will cause the Tyvek material to melt and/or the seals to fail.
•
Seal failure may also occur if the temperature is allowed to increase
rapidly. This is due to the fact that the water vapor is not given sufficient
time to diffuse through the Tyvek material, thus creating internal pressure
within the bag, resulting in a seal rupture. Temperature should not increase
faster than 0.25
o
to 0.50
o
F per minute.
•
Set the temperature of the oven to 245
o
F, and allow the bags of desiccant
to reach equilibrium temperature. WARNING: Tyvek has a melt temperature
of 250
o
F – 260
o
F. (NON MIL-D-3464E, activation or reactivation of both
silica gel and Bentonite clay can be achieved at temperatures of 220
o
F).
•
Desiccant bags should be allowed to remain in the oven at the assigned
temperature for up to 24 hours. At the end of the time period, the bags
should be immediately removed and placed in a desiccator jar or dry (0%
relative humidity) airtight container for cooling. (
LPTG01 foil ziplock bags
are ideal
) If this procedure is not followed precisely, any water vapor driven
off during reactivation may be re-absorbed during cooling and/or handling.
•
After the bags of desiccant have been allowed to cool in an airtight
desiccator, they may be removed and placed in either an appropriate type
polyliner tightly sealed to prevent moisture absorption, or a container that
prevents moisture from coming into contact with the regenerated
desiccant.