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 (77o F – 85o 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 0.25o to 0.50o F per minute.
- Set the temperature of the oven to 245o F, and allow the bags of desiccant to reach equilibrium temperature. WARNING: Tyvek has a melt temperature of 250o F – 260o F. (NON MIL-D-3464E, activation or reactivation of both silica gel and Bentonite clay can be achieved at temperatures of 220o 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 ZipSeal 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.
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