Frequently asked questions.

Functionality / Efficiency

Depending on the field of application, our adsorbers are provided with different fillings: Activated carbon adsorbs non-polar substances immiscible with water and is suitable for adsorption of odors, oil mists, vapors and other pollutants. Molecular sieves are excellent for selective separation of gases and for very strong drying of air in the ventilation of optical equipment. Silica gels have become the standard in aeration dryers because their absorption capacity is about 40%, the color indicator is highly visible, and easy regeneration is possible. Silica gel filters dry the air to an average of 10% RH.

Read more:

Do I use an adsorber with or without valves?
In which dew point range can an adsorber be used?
How much water can an adsorber absorb?
When is silica gel or activated carbon used in the adsorber?

Alternatives / Processes

Hydrophobic membranes can also be used for adsorption. However, it should be noted that these are not capable of separating water molecules from the air and only separate mist and water droplets. If humidity is to be separated, a desiccant is always required.
The use of nitrogen also protects containers from contact with humid air, but requires considerably more effort. Combined use is also not recommended, as the expensive nitrogen would continuously escape through the adsorber.

Read more:

Is a hydrophobic PTFE membrane suitable for water separation?
Adsorbers as an alternative to nitrogen?
Combine nitrogen blanketing with adsorber?

System Advantages

After mounting an adsorber, moisture from the ambient air should not normally enter the system. If there is nevertheless water in the system after a certain time, check whether there are other air openings, such as cylinder seals or damage.
If water is already dissolved in a hydraulic oil, it can no longer be absorbed by the adsorber. In this case, active drying is recommended.
When aerating plastic containers (e.g. IBC), an adsorber without valves should be used, contrary to the general recommendation. These containers react to negative pressure, so that adsorbers with a minimum pressure build-up are more suitable.

Read more:

Water in the tank, despite adsorber?
1000L IBC contracts under negative pressure. What are the causes?
How to remove liquid water from a tank?
Is oil in a tank dried by an adsorber?
Can an adsorber be used on a compressor?

Conditions / Usage

If a plant is operated at permanently low humidity, the use of a respiratory dryer is not necessary. Adsorbers are used when plants contain hygroscopic liquids, air humidities from 70% rH and ambient temperatures from 25°C prevail or the plants are exposed to temperature fluctuations of +/- 10°C.
In addition, air displacement volume and air flow rate play an important role in determining a suitable adsorber.

Read more:

At what temperature and humidity should an adsorber be used?
How is the correct air pendulum volume determined?
What is the correct air flow rate for an adsorber?

Installation / Assembly

Adsorbers are usually mounted vertically, with the connection at the bottom. This type of mounting ensures that the desiccant is evenly distributed and the air inlet openings are protected from the weather, which increases the IP protection.
When mounted horizontally, adsorbers, series 3 and above, can create an air pocket that affects drying efficiency. In addition, a greater leverage force acts on the connection here, and damage cannot be ruled out. From series 3 (diameter 110mm), a different type of mounting (e.g. by means of a wall bracket) is therefore recommended.
If the adsorber is mounted from top to bottom, it is important to prevent the ingress of dirt or water through the openings. If the adsorber is installed outdoors, a specially manufactured adsorber of the TB or TM series should be used.

Read more:

Can an adsorber be mounted horizontally?
Can an adsorber be mounted from top to bottom?
How many plugs have to be pulled out during assembly?

Maintenance / Handling

Adsorbers are packed and delivered in an airtight package and can be stored for several years in dark and cooled rooms. If an adsorber is unpacked for use, the protective caps must be removed. Adsorbers with valves are already better protected by their own structure. Adsorbers without valves have the number of sealing plugs removed, depending on the system, so that they can breathe freely.
The maintenance interval of an adsorber depends on the plant to be ventilated and the environmental conditions. If the plant draws in a high volume of air that must be dried by the adsorber, the maintenance interval is shortened. The same applies to high humidity levels, which introduce a high quantity of water molecules into the adsorber.
If there is already moisture in the system, it will additionally load the adsorber. This is quickly visible by a discoloration of the silica gel from above.
If an adsorber does not change color over a longer period of time, this is a good sign. The valves protect the desiccant and extend the service life. Nevertheless, it may be useful to check the function. To do this, the desiccant can be weighed. The difference to the dry mass indicates the water absorption.

Read more:

Why does the adsorber load from above?
Why can an adsorber be loaded very quickly?
Why does an adsorber turn purple?
Why does the silica gel in the adsorber turn brownish?
What is the maintenance interval of an adsorber?
How long can an adsorber be stored?
How can I check if my adsorber is working?

Desiccants / Drying Capacity

Whether desiccant, drying granules or adsorbent – silica gel has many names. KC drying beads or Sorbead Chameleon from BASF are also silica gels and have comparable properties. A slight deviation due to 3% Al2O3 improves the heat transport, but this is not relevant for aeration dryers with less than 10 kg adsorbent. In addition, the color indicator changes to colorless at a very early stage and considerably shortens the maintenance interval.
The possibility of colored loading indication by the included color indicator makes the use of silica gels simple and easy. Here it is important to note which color indicators are included. Heavy metals, as in blue gel, are a discontinued model and were replaced years ago by metal salts and pH indicators. Metal salts in particular, such as iron salt, make it possible to use Silicagel Orange safely. In addition, these silica gels do not require labeling and can be regenerated.
Molecular sieves have a stronger bond to water and achieve lower residual moisture and lower dew points than silica gels. However, a lower water absorption capacity and a lack of color indicator make the use of molecular sieves in respiratory dryers considerably more difficult.

Read more:

Can silica gel adsorb liquid water?
What is the difference between KC dry beads OC and silica gel?
What influence does oil have on silica gel?
Are there differences in the silica gels with color indicator?
How do molecular sieve and silica gel differ?
What color indicators are used with silica gel?
Are silica gels with color indicator subject to labeling?

Regeneration / Disposal

Adsorbents can be regenerated by increasing the temperature, lowering the partial pressure and flowing a dry fluid through them. After the use of air drying, heat addition, is the most commonly used desorption process.
However, the regeneration temperatures of molecular sieves and silica gels differ greatly. While molecular sieves require a temperature of 300°C to completely release water, 140° is optimal for colorless silica gels and 120°C for orange gel.
Thus, it is easily possible to dehumidify orange silica gel in a commercial oven. If the desiccant is spread flat on a sheet, it will be completely orange again within a few hours.
Regeneration in a microwave oven works only to a limited extent. The resulting hotspots explosively dissolve the water molecules and damage the silica gel grains.
Unloaded as well as loaded silica gel orange is harmless and can be disposed of without any conditions. All other components of our GIEBEL adsorbers are also harmless and can be disposed of in the residual waste. Of course, a material separation is recommended.

Read more:

What are the options for regeneration / desorption?
Can silica gel be regenerated in the oven?
Can an adsorber be regenerated by compressed air?
Can silica gel be regenerated in the microwave?
Can oil-laden silica gel be regenerated?
How to dispose of a used adsorber?