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Equipment

Prevent Moisture Damage with Desiccators


Grainger Editorial Staff

Desiccators help maintain a low–humidity environment that protects products or substances from moisture damage. Sometimes referred to as dehumidifiers or dehydrators, desiccators are often used in labs and industrial settings to remove moisture from a product or substance without heating it.

Desiccators are airtight enclosures usually made of glass, though desiccators made from other materials including Teflon® coating and acrylic are available. Teflon and acrylic options offer the transparency of glass without the risk of breakage.

If moisture is present in a desiccator enclosure, probable causes are:

  • It is trapped in the desiccator enclosure when it was sealed or there were water molecules on or inside the contents in the enclosure
  • Moisture leakage, i.e. moisture (humidity) entered the desiccator due to a leaky seal, porous enclosure material or the enclosure was not properly sealed
  • If the enclosure is equipped with a breather valve, moisture/humidity can enter the desiccator enclosure when the valve opens

Desiccators employ one of four basic types of technologies: standard desiccant, automatic desiccant regeneration, gas purge or vacuum.

Standard Desiccant:

Moisture in the air is absorbed by a desiccant, which is an adsorbent substance that attracts water vapor molecules. The molecules are collected and held on the desiccant's surface. Common types include silica gel, activated alumina, clay (Montmorillonite) and molecular sieves. Once the desiccant is saturated with water vapor molecules, the desiccant must be regenerated via heating or replaced. This kind of desiccator offers the flexibility to use any type of desiccant, and is usually the most economical choice.

Automatic Desiccant Regeneration:

To provide a low–humidity environment and prevent desiccant saturation, this type of desiccator employs heaters or electric fans that continually regenerate the desiccant. Automatic regeneration desiccant models require minimal monitoring, offer more precise humidity control vs. standard desiccators and can be equipped with silica gel desiccant beads that last for thousands of regeneration cycles.

Gas Purge Desiccators:

In gas purge desiccators, a continual flow of inert gas displaces the moisture–rich atmosphere inside the desiccator. These desiccators commonly use dry nitrogen as the purge gas. They can reach the desired humidity level much quicker than standard or automatic desiccant regeneration desiccators and provide a dust–free environment. Gas purge desiccators are suitable for many applications, including cleanrooms. Many models offer stopcocks that allow the option of disconnecting the purge gas stream and using standard desiccants.

Vacuum Desiccators:

These desiccators use a vacuum pump to remove air that contains moisture. They are regarded as superior to other types if total dry storage is required. Vacuum desiccators are common in cleanroom applications and provide a dust–free environment. Many models offer a stopcock so that the vacuum pump can be disconnected to use regular desiccants.

Selecting a Desiccator

Design factors to consider when purchasing a desiccator include, but may not be limited to:

  • Type of desiccator
  • How much interior volume is required in the desiccator
  • Available space in your lab
  • Required level of moisture control and protection
  • Required/desired length of time between recharge, if using a desiccator with rechargeable desiccant
  • Whether or not a breather valve or humidity indicator is required
  • Required dusting protection
  • Tolerable desiccator leakage rate

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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