Our GIEBEL aeration dryers are usually filled with GIEBEL Xdry® – a mixture of Silica gel orange-green & Molecular sieve 13X. When drying the supply air of hydraulic units, gearboxes, drums, IBCs, storage tanks & transformers, GIEBEL Xdry® shows a high drying performance with a high water absorption capacity at the same time and thus has advantages compared to a fill of pure silica gel or pure molecular sieve. For inline adsorbers in pipelines, molecular sieve may be the better desiccant due to its ability to adsorb other substances as well. The same is true for applications where a very high degree of desiccation is desired, such as in the ventilation of optical equipment.
Activated carbon is used when odors, oil mist, vapors and other pollutants are to be filtered out of the air. Activated carbon is therefore the main component of our oil mist separators.
Valves are used in aeration dryers when air rarely flows through the adsorber during its service life, i.e. the system is only occasionally in operation. In this case, valves prevent moisture from diffusing through the holes in the bottom of the adsorber and gradually loading the adsorber with moisture from the ambient air.
For systems that are in regular or continuous operation, the effect of valves is negligible. Here it is more favorable to use adsorbers without valves and to accept a minimal loading by the ambient air via the adsorber bottom.
When a new, unsaturated adsorber is installed, it achieves a residual air humidity of approx. 0% – this means that the dew point is around -40°C. At full load, i.e. at a saturation of approx. 33%, the residual air humidity is around 40%. The dew point is then about 6°C (depending on the temperature).
In general, the sooner an adsorber is replaced and fresh desiccant is used, the lower the dew point and the less water enters a system. For use on hydraulic power units, gearboxes, drums, IBC containers, storage tanks & transformers, it is sufficient to replace an adsorber when it has completely discolored – i.e. at 33% load. Up to this point, both the amount of water entering and the dew point have no significant negative effect on the system.
As a rule of thumb, 1kg of GIEBEL Xdry® adsorbs about 350ml of water from the air.
Factors such as relative humidity and temperature influence the water absorption capacity. Low humidities and high temperatures have a negative influence. Since the water molecules begin to vibrate as the temperature rises, they are less easy to adsorb. At about 80°C, the molecular movement is so strong that the silica gel contained in GIEBEL Xdry® is hardly able to absorb water molecules anymore. This is where the molecular sieve, which is capable of adsorbing moisture up to about 250°C, takes effect.
Hydrophobic membranes retain liquid water, but at the same time allow water vapor and air to pass through. They are therefore used in our water separators as well as in waterproof textiles, in microfiltration, in packaging materials or in pressure equalization elements. However, the membranes are unsuitable for ventilation drying.
Nitrogen blanketing of containers is preferable when a substance is to be protected from oxygen to prevent oxidation. However, if the main purpose is to protect the substance from moisture, an adsorber is a much better choice. It is easier to handle and cheaper to use.
The use of a tank air dryer in combination with the blanketing of an inert gas such as nitrogen is not recommended. The blanketing creates a continuous positive pressure, while an adsorber requires a negative pressure to draw in air and dry it. Thus, the two processes work in opposite directions. The expensive nitrogen would constantly escape via the adsorber.
After mounting an adsorber, moisture from the ambient air should normally not enter the system. However, if there is water in the system after a period of time, check for other air openings such as cylinder seals or damage.
Adsorbers protect hygroscopic substances stored in IBC containers from contact with atmospheric moisture and guarantee consistently high product quality. To achieve long maintenance intervals, adsorbers with valves are used. They prevent the adsorber from being loaded by the humidity of the ambient air.
If an IBC with valve adsorbers is emptied at high speed, i.e. within a few minutes, a high negative pressure is created and the plastic walls of the IBC are drawn inwards. The effect becomes visible when about 2/3 of the contents have been removed. If you want to empty an IBC at a high rate, you must use an adsorber without valves and with the largest possible cross-section to minimize the pressure build-up.
If the water is already dissolved in a hydraulic oil, it can no longer be absorbed by the adsorber. In this case, active drying is recommended. For this purpose, we have developed a so-called Tank Dryer. This is a desiccant bag that is lowered onto the bottom of a tank on a long cord and absorbs the water there.
If a plant is operated at permanently low humidity, the use of a breath dryer is not necessary. Adsorbers are used when plants contain hygroscopic liquids, air humidities from 70% rH and ambient temperatures +25°C prevail or plants are exposed to temperature fluctuations of +/- 10°C.
The adsorbers are usually mounted vertically so that the connection is at the bottom. This type of mounting ensures that the desiccant is evenly distributed and the air inlets are protected from the weather, which at the same time increases IP protection.
It is also possible to install an adsorber in horizontal position. However, we recommend this type of installation only for sizes 1 and 2. In the case of adsorbers from size 3 onwards, horizontal installation can result in an air pocket which impairs the drying performance. In addition, a greater leverage force acts on the connection here, so that damage cannot be ruled out.
If vertical installation is difficult, an adsorber can also be mounted offset by means of an angle adapter or attached at a different location by means of a wall bracket and a hose.
Yes, this is possible – but at the same time, the ingress of dirt or water through the holes in the adsorber base must then be prevented. If the adsorber is installed outdoors, we recommend using our TB-DV, TB-RV and TM-RV series, which are specially designed for this type of installation.
When mounting an adsorber without valves, the openings are closed with protective plugs. This allows the adsorber to be stored for a longer period without loading. The plugs must be removed during commissioning. For plants with slow air flow it is sufficient to remove 1-2 plugs, for plants with high air flow all 4 plugs should be removed.
The maintenance interval of an adsorber depends on both the plant to be ventilated and the ambient conditions. If the plant draws a high volume of air that must be dried by the adsorber, the maintenance interval is shortened. The same applies to high humidity, which introduces a large amount of water molecules into the adsorber. If there is already moisture in the system, it puts additional strain on the adsorber. This is quickly visible by a discoloration of the silica gel from above.
If you are unsure which adsorber is suitable for your system and the desired maintenance interval, please contact us. We will be happy to advise you.
If an adsorber does not discolor over a long period of time, it 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 amount of water absorbed.
If the adsorber discolors from above, this indicates moisture escaping from the system. This is the case when an aeration dryer is not installed from the beginning, but only after a few months (or years) of operation. Then the air in the tank and possibly the stored liquid already contain a certain amount of water. This moisture is absorbed by the adsorber and shows up in the coloration from above.
If an aeration dryer is saturated very quickly, this can have several causes. The most common cause is a high volume flow to be dried and an adsorber that has been selected that is too small. If the system already contains a high amount of moisture, the adsorber will also absorb it. It is then loaded from both sides.
When our adsorbers come into contact with atmospheric moisture, they turn green as the load increases. However, some substances, such as amines and AdBlue, can cause a purple coloration if they evaporate from the tank and enter the adsorber. If this is the case, the desiccant must be replaced – it is then no longer able to absorb water.
When using an adsorber, the silica gel contained in the desiccant mixture may change color differently depending on the ambient conditions and operating parameters. Adsorbers without valves have air inlet openings in the bottom and allow air (and thus moisture) to flow continuously to the desiccant. If the granules are loaded slowly and constantly (in a system with very weak or no air movement), the load will discolor uniformly over the entire body. This is because the desiccant wants to reach equilibrium and therefore distributes the water. The orange hue of the silica gel grains gradually changes to a dark green hue, but only when the silica gel is about 15 to 20% loaded. In the phase before this, the orange tends to become darker and therefore appears slightly brownish.
A dark brownish to black color, on the other hand, is caused by oil aerosols or other vapors. This means that when the upper activated carbon disc (black layer) can no longer absorb the escaping particles, they slowly settle on the desiccant. If oil particles escape from a system, we recommend using one of our oil mist separators from the VG-D and VG-R series.
In principle, it is possible to install an adsorber to dry the supply air on a compressor. However, this is not recommended. Due to the large amount of air that a compressor takes in, an average-sized adsorber with 3kg of desiccant would already be loaded within a very short time and would have to be serviced. This enormous maintenance effort is out of proportion to the benefit. It is more advantageous to use an adsorber in the compressed air line after the compressor.
KC Drying Beads® and Sorbead Chameleon® from BASF also belong to the silica gels and have comparable properties. A small difference is their content of approx. 3% Al2O3, which improves heat transport. For aeration dryers with less than 10 kg adsorbent, this factor does not play a role. Because of their very early color change at about 6% loading, BASF products are also rather unsuitable makes for aeration drying of hydraulic power units, gearboxes, drums, IBCs, storage tanks, … also rather unsuitable makes.
However, for adsorption plants, which adsorb and regenerate cyclically, they are ideally suited. Here, their higher half-value diffusion coefficients and the resulting higher number of regeneration cycles offer clear advantages.
Silica gels adsorb moisture from the air or in the form of mist. However, when liquid water is adsorbed, so much energy is released that the silica gel grains break. Therefore, a special silica gel – silica gel waterproof – is used for adsorption of liquid water. You can get it on our desiccant website: www.giebel-desiccants.com.
Oil significantly impairs the water absorption capacity of silica gel. This means that where oil mist or oil droplets occur and silica gel is used for drying, further measures are required to prevent the two substances from coming into contact with each other.
Color indicators are added to silica gels to indicate the state of loading with water by a color change. They are divided into ph indicators and metal salts.
pH indicators change color because their originally acidic or basic environment evolves toward pH 7 (neutral) with increasing water absorption. Methyl violet, used in our Orange-Green silica gel, is such a pH indicator.
Metal salts form complexes when they absorb water – either by the incorporation of water of crystallization or by a reaction of the metal salts with water and chloride ions. Iron(III) chloride, used in Silica Gel Orange Colorless, is one such metal salt.
Another color indicator that has become known as blue gel in connection with silica gel is the heavy metal cobalt(II) chloride. However, this substance is considered carcinogenic and mutagenic – its use is therefore expressly not recommended!
According to the EC Directive (67/548/EEC or 1999/45/EC), pure silica gel does not require labeling and is not hazardous to health or the environment. Furthermore, silica gel is non-flammable and chemically stable. If handled and used properly, no ecological problems are to be expected.
If a color indicator is added to the silica gel, the labeling requirement depends on the color indicator used and its concentration. Sustainability and products that are compatible with health and the environment are very important to us at GIEBEL, which is why we only use silica gels that do not require labeling. The manufacturers’ safety data sheets in accordance with Regulation (EC) No. 1907/2006 always provide information on the use and compatibility of chemicals – you can find them on our website www.giebel-desiccants.com.
Due to the different regeneration temperatures of the silica gel and molecular sieve contained in GIEBEL Xdry® , regeneration of the desiccant bed is not recommended. It would have to be separated into its individual components in advance. Instead, you can simply refill our refillable adsorber series with fresh GIEBEL Xdry®.
If your adsorbers are filled with pure silica gel or pure molecular sieve, the debris can be regenerated. Colorless silica gels can be regenerated at 140°C and orange silica gels at 120°C in a commercial oven. Microwave is not suitable for regeneration. Molecular sieves can be regenerated at 300°C in ovens designed for this purpose.
If oil-laden silica gel is regenerated, the oil reacts at approx. 110 °C on the silica gel surface and the color indicator is destroyed.
If the dry beads are moistened again, they absorb significantly less water. In short: Oil-laden silica gel should be replaced.
All original GIEBEL Adsorbers® are made of harmless and reusable materials. These include: Acrylic glass, aluminum, galvanized steel, polyamide (PA), polyoxymethylene (POM), NBR, FKM, EPDM, activated carbon, silica gel orange, molecular sieve.
GIEBEL adsorbers are disposed of at the end of their service life in accordance with statutory regulations. Metal and plastic parts should be disposed of separately. Desiccant loaded with water can be disposed of with household waste. Components loaded with oil, or components loaded with other pollutants must be disposed of according to the specifications of the oil / pollutant used.
GIEBEL Xdry®, silica gel (independent of the color indicator) & molecular sieve are assigned to waste code number AVV 06 08 99 and must be disposed of in accordance with this. If these desiccants are not only loaded with water, but also with oil or other pollutants, the waste code number AVV 15 02 02 applies.
Activated carbon is assigned to waste code number AVV 15 02 02.