Desiccants

There are many types of desiccants. Liquids like acetone and alcohols are dehydrating agents that can pull water vapor from the air. Solid salts like NaCl can also pull water vapor from air. Desiccants like these are chemically reactive and therefore unsuitable for many applications.

We offer natural silica gel, clay and Molecular Sieve, that can be in direct contact with goods and not be harmful. Clay is the most cost efficient alternative when large amounts are needed during normal conditions. Silica Gel is the preferred alternative when smaller amounts are needed during normal conditions. Molecular Sieves is the preferred alternative when extra dry conditions must be met and when when conditions are cold or hot.

  • Clay: A natural, safe all-rounder, suitable for standard applications in all areas of industry. See link
  • Silica gel: Commonly found in small packaging used in industry, pharmaceutics, diagnostics and the food sector due to its high adsorption capacity. See link
  • Blue/Orange Silica gel: Silica gel with a color indicator to show if it’s dry or wet. Cobalt (II) chloride is deep blue when dry and pink when wet. Methyl violet can be formulated to change from orange to green, or orange to colorless. See Link
  • Molecular sieve: Suitable for pharmaceutics and diagnostics, as well as special technical applications (various types: 3Å, 4Å, 5Å, 10Å / 13X). See link

 

Desiccant Polymers

Desiccants can also be combined with polymers, so they can be moulded into shape. The adsorption speed of the desiccant is slowed down by the polymer and this is a desired characteristic for some applications, as the desiccant will not be fully saturated in short time when a container is open for inspection. The speed of adsorption is a function of the thickness and desiccants deep inside a moulded piece will therefore never adsorb any water. This limits the useful thickness for moulding. Note also that the polymer has high viscosity when moulding, and this sets a limit on its ability to fill narrow moulds. 

Example 1: Brownell Ltd. – VMAP

Example 2: Tropack Packmittel GmbH – TROPApuck 2 g

Example 3: Tropack Packmittel GmbH – Active-Film M-0026

 

Humidity Indicator Cards

The most common humidity indicator cards use cobalt (II) chloride and change color from blue (less than indicated RH level) to pink (greater than indicated RH level). These are available in many versions and are easy to read. They can be used for many years, but will degrade over time if exposed in direct sunlight (UV-light) and they will also degrade if exposed to liquid water or condensation, as cobalt (II) chloride is a salt that will wash away with water.

The humidity indicators are inexpensive, so you cannot compare their accuracy with that of expensive electronic instruments like the NEPS. The tolerance is +/– 5% relative humidity at 20°C (+/– 2°C) and deviations are approximately 2.5% relative humidity per 5°C above and below 20°C. The cobalt (II) chloride color changes later in temperatures above 20°C, and earlier in temperatures below 20°C.

Example 1: Card 10-40% RH
Example 2: Diameter 0.81 inch card for indicator window

Although the European Community (EC) has issued a directive that classifies items containing cobalt (II) chloride as toxic, it has not banned these indicator cards. There is however a desire to replace these with Cobalt free humidity indicator cards. One example is based on copper (II) chloride and its Brown when dry and Azure when wet.

Example 3: Cobalt Free card

More information about Humidity Indicator Cards. See link

 

Immersion Proof Breathers

Immersion Proof Breathers are also called protective vents or “free breathers”. They are based on a membrane that keep liquid water and water droplets out, but will let water vapor and air through for pressure equalization. The hydrophobic properties of the membrane prevent the breakthrough of liquid water, but allow permeation of water vapor. Other gases with a similar molecular size (~3.1Å or less) to water vapor also permeate through the membrane. Some membranes work equally good in both directions, but some membranes have one side that is designed to be out and one side to be in. We can help you determine what type to use and help you calculate the right dimension. More information is available in this brochure from AGM Container Controls – IPB datasheet

Pressure Valves

Pressure Valves, also known as Pressure Relief Valves, Pressure Release Valves or Breather Valves. These are spring loaded valves that protect sealed containers from excessive pressure or vacuum. The cost, weight and size of these containers can therefore be reduced. These spring loaded valves offer higher flow rates than Immersion Proof Breathers. They are also 100% sealed when the pressure difference is low, as compared to Immersion Proof Breathers.

These valves come in different sizes for different air flows, and also with different opening pressure. For Two-Way Pressure Relief Valves the opening pressure can be different for over pressure, as compared to vacuum. Some containers can withstand high overpressure, but are very sensitive to vacuum. It’s therefore important that calculations are made to determine what pressure valves to use. We can help you with these calculations or you can follow the calculation guide in this brochure from AGM Container Controls – Breather Valves

AGM manufactures a variety of Breather Valves, which include valves that keep dust, water, and blowing sand from entering containers. Some are also protected against Radio Frequency Interference (RFI) to keep radio signals inside or outside the container. Some high flow versions are magnetic valves, and they open faster to full air flow. These Breather Valves meet SAE AS27166 (replaces cancelled MIL-V-27166) and MIL-DTL-27166 which is the re-instated version of MIL-V-27166.

Demonstration – Train Tanker Implode from Vacuum