By: Paul Cockfield
How to achieve Clean & Dry Compressed air in your Concentrator or Reduction plant
Clean dry compressed air is essential to ensure the pneumatics and control instrumentation faultlessly operate 24/7/365. The choice of compressed air treatment is really driven by the air quality demands of your plant.
If ultra dry compressed air is required with very low dewpoints, i.e. in the minus ≤40°C range then the choice is really about which type of desiccant air dryer you will install. Volumes under 50 m³/min can be handled by pressure swing heatless air dryers. These may be equipped with dew point controllers to reduce c/air purge wastage
Above these volumes, heat regenerative dryers could be considered. They are more expensive than the heatless varieties, but offer operational cost savings by reducing air purge wastage. The feed air to this dryer style should be from oil free compressors
If the flow requirements for low dewpoint c/air are relatively small compared with the total air flow, a decentralized desiccant air dryer can be installed at the point of use to reduce capital cost and compressed air purge air wastage
For dew points above 3°C the obvious choice is a refrigeration air dryer. The capital cost is lower than its desiccant cousin. Reliable & cost-effective refrigeration dryers are easy to install and maintain.
But be aware if air borne contaminants are in the area, refrigerant dryers have copper and aluminum exposed to the ambient air. The internals of our dryers that are in contact with compressed air are manufactured from stainless steel.
Always remember to re-rate the dryer’s capacity for your local ambient air temperature. Failure to do this will lead to a multitude of problems caused by excessive heat loads adversely affecting the refrigeration circuit within the dryer. Lubricated compressed air may be handled by these dryers with no real issues.
Inlet pressures will also affect the sizing of a dryer, don’t forget to consult the potential supplier before you purchase the unit. If re-rate factors for ambient, inlet air temperature and air pressure are not shown in the sales brochure, we suggest you look for an alternative supply chain!
Desiccant air dryers are susceptible to compressor oil contamination. Oils are detrimental to the adsorption chemical’s ability to remove water vapor from the compressed air stream. This can lead to poor dew points. So, compressor oils need to almost be eliminated from the incoming air stream.
The use of Pad Separators helps remove bulk water and oil contamination prior to Inline Coalescing filters. Coalescing filters then have less contamination load, and the elements will last longer. After filtration, downstream of the dryer is also essential to “polish” the air prior to delivering the c/air to your system. Filtration media is can also be detrimentally affected by high inlet air temperatures and low inlet pressures. The lower inlet temperature, the better e.g. ≤40°C Study the sales literature in depth or consult the proposed supply chain to ensure reasonable service intervals.
It is possible to get oil vapor contamination down to 0.001 mg/m³ or even lower if activated carbon filters are installed.
Inline Filtration is never cheap, it is prudent to oversize the casings relative to the inlet air flow rate this will assist with reducing pressure drops across the filter bank, so to giving the elements longer service life intervals between change outs,
The drainage of condensate from air filters and refrigeration dryers is vital. Reliable auto drains are critical. Elements “drowning” in condensate in the base of the casing with not function and may well collapse. The choices are from low cost, simple timer solenoid drains to sophisticated level-controlled units that will send an alarm out if they fail to the eject condensates
Artic Driers manufactures the Sahara range of desiccant heatless dryers in Africa to survive the harshest conditions. The dryers are constructed on a heavy duty skid fitted with fork lift slots and to fit into standard 20’ or 40’containers, making it easier for ship into Africa. Container shipping is always desirable as eliminates transport damage. Inline pad separators and filtration c/w bypass piping can be pre-assembled on the heavy-duty skid. Pressure vessels can be constructed a variety or pressure codes please talk to us prior to order placement
Dewpoint controllers or alarms can be fitted to any air dryers to either extend cycle times or to act as an alarm system in the event of a c/air quality problem
While considering the choice of air filters and dryers, do not neglect the oily waste condensate treatment system to ensure that waste oils are separated from the water condensates, retained and properly disposed of when the adsorption cartridge is saturated.
The clear clean water condensate, the largest component, is allowed to run to waste, while the oils are retained for proper waste disposal. A liter of waste compressor oil can, and will contaminate a square kilometer of wetland area. As we all know, water is a precious resource in Southern Africa.
Having bought the equipment, you should take a long hard look at the where and how the equipment will be installed. This is another discussion topic in its own right, and too broad for this article. Please call us or email us to have the “Notes on Compressor House Design” sent to you, it’s a thought provoking read
Compressed Air Quality Testing, Artic is able to monitor particle, dewpoint & residual oil levels from one mobile or static auditing data logger & we are also able to monitor a variety of gases via the unit. Dewpoint monitoring provides an early warning of a dryer treatment system hiccup
It’s a better solution than relying on an operator or infecting your factories air line
Artic Driers is a family operated & controlled company with a huge range of air treatment products with a 34-year history of solving compressed air problems. Visit www.articdriers.co.za
Call Paul Cockfield now for more information on +27 (0)11 420 0274 or email info@articdriers.co.za