SILIPORITE® for Air Brake Systems
Air must be kept as dry as possible to avoid any freezing in the circuit but also any corrosion of the metallic parts. SILIPORITE® Molecular Sieve for this application has been designed to ensure absolute air drying and to resist to the severe mechanical solicitation to which the system is submitted.
Since 1994, CECA has developed the know-how to combine in a single Molecular Sieve:
Additional services are provided by CECA to get the most reliable performances.
CECA, in an effort to support its customers, offers specific technical services for this application:
SILIPORITE® for Air-Conditioning/Refrigeration
New refrigerant fluids need high performance Molecular Sieves in order to dry. SILIPORITE® Molecular Sieves have been used for decades in filter dryer cartridges and CECA has been a part of this since the beginning.
Since the Montreal protocol, the refrigerants chemistry has changed. In response to this, CECA has adapted its range of products by developing SILIPORITE® H3R I, a new generation of Molecular Sieve made to work well with these new refrigerants.
The water present in a refrigeration or air conditioning system has to be removed for two main reasons:
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Corrosion: The accumulation of free water in the evaporator is a source of corrosion. Water can react with the refrigerant and produce strong mineral acids leading to corrosion.
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Freeze up: The accumulation of free water in the evaporator can damage or even plug up the expansion valve and metallic tubes of the circuit.
Molecular Sieve properties
In this particular application, Molecular Sieves are placed in a cartridge which is integrated in a multi-component system where a refrigerant fluid, mixed with a small amount of oil, is continuously recycled.
For this reason Molecular Sieves used in this application must have certain properties:
water adsorption capacity : In a refrigeration/air conditioning system, the drying cartridge is placed, either between the condenser and the expansion valve (position 1), or between the expansion valve and the evaporator (position 2) .
Position 1 : (the dryer works in liquid phase)
Advantage : This avoids the freezing of the expansion valve and provides a low pressure drop across the dryer.
Disadvantage : The high temperature affects the adsorption capacity of the Molecular Sieve. Molecular Sieves are less efficient in the liquid phase than in the gas phase.
Position 2 : (the dryer is in a liquid/gas phase)
Advantage: The dryer is at low temperature
Disadvantage : there is no protection of one of the most sensitive components : the expansion valve.
For the above reasons, any chosen desiccant must have good water adsorption properties:
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at high temperatures (50 to 60°C),
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in refrigerant fluid liquid phase,
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at very low water content,
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in presence of oil traces.
Attrition resistance : in a refrigeration system, the drying cartridge is continuously in contact with the refrigerant. Under these conditions the Molecular Sieve beads rub against one another and can generate dust. These abrasive small particles can cause damage to refrigerant circuit, especially to the compressor.
For this reason, special technical procedures must be used and the SILIPORITE® Molecular Sieve must be agglomerated with a clay that generates a minimal amount of dust.
Resistance to mineral and organic acids : In a refrigeration/air conditioning system, there are always some acid traces due to the partial decomposition of the refrigerant fluid and oil.
CECA has developed tests to check that the Molecular Sieves keep all their properties in the presence of mineral and organic acids.
Density: The bulk density of Molecular Sieves must be high enough to ensure that the volume of the dryer will hold the maximum mass of adsorbent.
Particle size: The particle size distribution of the beads must be as regular as possible to ensure a predictable pressure drop and to allow the easy filling of the cartridge.
Crushing Strength: During the filling of the dryer cartridges, Molecular Sieves are subject to mechanical stress. To avoid breakage, the beads must have a good resistance to crushing.
Kinetics of water adsorption: It is critical to insure the quick removal of water contained in their drying cartridge systems (especially air conditioning systems) when the system is started. CECA has developed laboratory tests which show the performance of Molecular Sieves in terms of water adsorption kinetics.
Compatibility between Molecular Sieves, refrigerant fluid and lubrication oil: This is one of the most important concerns for refrigeration/air conditioning systems manufacturers. The binder and the zeolite must be compatible with the refrigerant and the lubricant oil.
What is a good definition of compatibility in this application ?
Molecular Sieves must keep all their original properties during the life of the cartridge (no breakdown of any characteristic due to long contact with the refrigerant fluids and the oil that can occur). Molecular Sieves cannot cause the degradation of the fluid/oil by chemical reaction.
Molecular Sieves
