Adsorbers for use on hydraulic units
Adsorbers for use on hydraulic units
Adsorbers for use on hydraulic units
GIEBEL offers a wide range of adsorbers specially designed for hydraulic power packs. They are available with and without valves, with FKM or EPDM seals, according to ATEX 2014, for indoor, outdoor and offshore use, and as disposable or refillable versions. They are divided into adsorbers for air drying and adsorbers for separation of pollutants.
Adsorbers for drying supply air Tank- / shuttle volume
0 - 50 ltr. (up to 10 l/min - max. 30 l/min)
50 - 100 ltr. (up to 20 l/min - max. 100 l/min)
100 - 400 ltr. (up to 40 l/min - max. 260 l/min)
400 - 800 ltr. (up to 80 l/min - max. 490 l/min)
800 - 1800 ltr. (up to 110 l/min - max. 610 l/min)
1800 - 3600 ltr. (up to 160 l/min - max. 930 l/min)
3600 - 5400 ltr. (up to 210 l/min - max. 1250 l/min)
Adsorbers the separation of pollutants Tank- / shuttle volume
0 - 50 ltr. (up to 10 l/min - max. 30 l/min)
50 - 100 ltr. (up to 20 l/min - max. 100 l/min)
100 - 400 ltr. (up to 40 l/min - max. 260 l/min)
400 - 800 ltr. (up to 80 l/min - max. 490 l/min)
800 - 1800 ltr. (up to 110 l/min - max. 610 l/min)
How adsorbers work on hydraulic power packs
1. The adsorber is mounted on the hydraulic power unit. The ambient air is enriched with moisture.
2. Hydraulic oil is removed from the tank, the oil level drops and pressure is equalized by incoming air. The adsorber separates moisture up to 2% rH (10% rH on average).
3. When the hydraulic oil is pumped back into the tank, the oil level rises and the pressure is equalized by escaping dry air.
4. Because the air inside the system always remains dry, no condensation takes place in the hydraulic unit even if the ambient air drops below the dew point.
Silica gel
Silica gel (also called drying beads) is the most commonly used drying agent in aeration drying. It consists of 99% silicon dioxide (SiO2). Due to its high porosity, narrow-pored silica gel has a large internal surface area of up to 850 m²/g. The funnel-shaped openings with a diameter of approx. 2 to 12.5 nm allow water molecules to be loaded in several layers (capillary condensation). This also explains the very high water absorption capacity of this adsorbent. Due to its extreme hydrophilicity (attraction of polar substances, such as water) and easy regeneration by raising the temperature to
approx. 120°C, it is preferably used as a drying agent. Especially at a relative humidity of approx. 70 % rH , silica gel shows an excellent absorption capacity and adsorbs large amounts of water from the air. Silica gel orange-green has a strong color indicator. The color change from orange to green occurs at a water loading of 15 to 20%. Silica gel orange-colorless has a weaker color indicator, which takes place only at a higher loading. It changes color at a water loading of approx. 20-25%. Silica gel white has no color indicator.
Activated Carbon
Activated carbon is a carbonaceous product with a porous structure (pore volume > 0.2 cm³/g) and a large internal surface area (> 400 m²/g) with pore diameters between 0.3 nm and several thousand nanometers, to whose surface molecules can attach. The surface of activated carbon is essentially nonpolar and thus hydrophobic and organophilic, which is why the less water-soluble a substance is, the better it is adsorbed from aqueous phase. The activated carbon surface has an affinity for organic adsorptives such as fatty acids, alcohols and esters. Due to the hydrophobic nature of the surface, adsorption of water vapor is very low at low concentrations. Only at higher concentrations (higher humidity) does the water loading increase steeply. For this reason, activated carbon is suitable for the treatment of humid gases or air. They are used, among other things, in aeration dryers
for hydraulics, in fume hoods or even in respiratory masks.
Molecular Sieve
Molecular sieves are drying agents with very specific properties. They are synthetically produced aluminosilicates. They are differentiated on the basis of their crystal lattice structure, as this results in pores of different sizes. Zeolites of type A contain sodium in their crystal lattice, thus the pore diameter is approx. 0.4 nm (pores 4A). Zeolites of structure X have a pore diameter of 0.9nm (9A). The constant structure of the crystal lattices allows a very high internal surface area of up to 1000 m²/g. Together with high electrostatic adsorption forces, these molecular sieves are therefore ideally suited for air drying. Even at low relative humidity, molecular sieves achieve a higher absorption capacity. Thus, they are able to dry the supply air very strongly. This makes their use sensible wherever the degree of drying is a decisive selection criterion. The maximum water absorption in a fully saturated
environment is approx. 23% (molecular sieve 4A) up to 27% (molecular sieve 13X). There is no colour indicator to show the loading status. The regeneration temperature of the molecular sieve is 300°C.