How do desiccant dry cabinets work?

Auto-recycling dry cabinets rely only on desiccant to reduce humidity levels, nitrogen is not required for their standard operation. Dry cabinets rejuvenate (recycle, refresh) their desiccant by routinely stopping desiccation of the cabinet, sealing off the desiccant material and turning on a low watt heater embedded within the desiccant in order to expel the captured moisture. The device that stores and refreshes the desiccant is typically referred to as the ‘dryer unit’. During the refreshing process the effectiveness of the desiccant dryer unit will be tested. Trace amounts of moisture will typically escape back into the cabinet, causing a short term spike in humidity levels. How much the moisture levels will increase inside the cabinet and how long it will be before the recycling is complete (allowing the desiccation of the cabinet to restart) relates again to the effectiveness of the dryer technology in question. Some manufacturers report moisture levels increasing by as much as 4% through the duration of the recycling process.

Some cabinet models utilize data collected from closed loop humidity sensors installed inside the cabinet to determine when and how long desiccant recycling times should be, based on a digitally selected user set point. Other manufacturers utilizing simpler analog control technology commonly “hard-wire” the RH set point at the factory providing a timer circuit to manage the recycling of the desiccant causing a maximum duration recycling each and every time the desiccant is refreshed. A typical desiccant dryer will require appx. 45 minutes every 6 hours to recharge fully saturated desiccant, although some dryer units require as long as 70 minutes to complete their recharging process. It’s important to note that during this time the dryer unit will not be desiccating the cabinet.

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