By Richard Juskowiak, Donaldson Process Filtration
Food and beverage processors use compressed air at multiple points in their facilities. Compressed air systems, however, can produce oil and debris, or harbor microorganisms.
Keeping air dry and oil-free is central to keeping it sterile. Liquids, chiefly water and oil are the most prevalent contaminants in compressed air systems.
Bacteria feed on water and oil, and can propagate in the crevices crannies of compressed air lines. In addition, oil and water biofilm can seep downstream and clog or permanently degrade process piping.
A series of filters after air is generated and cooled will help minimize the risk of water, oil, and bacteria migrating downstream into your product.
Here are key considerations to prevent the introduction of moisture risks:
Sequence of Filtration and Drying Steps
All compressed air systems will have a water problem starting in the compressor room. Only the volume of humidity varies with ambient air conditions and seasonal weather or climate.
Refrigerated dryers chill the air and remove bulk moisture produced during condensation, but significant liquid content can remain. A sequence of treatments is recommended to remove progressively smaller liquid particles. These filters are: 1) a cyclone separator to remove bulk water in high volumes; 2) a coalescing filter to extract more difficult aerosol liquid; and 3) an air dryer to eliminate remaining water vapor. Each component should be carefully selected and sized for your source air humidity and processing requirements.
First is a cyclone separator to spin out the bulk of remaining moisture. Next is a coalescing filter to capture and drains away the tiniest droplets. The final step is an air dryer to remove vapor. As important as it is to capture contamination, it’s just as important to dry the air so bacteria cannot thrive in it downstream. A high-quality adsorption dryer (such as the Ultrapac™ Smart dryer from Donaldson) performs this step.
The adsorption dryer also provides clues to the performance of earlier steps. If you detect a higher-pressure dew point than expected, for example, the cyclone separator or coalescing filter might not be adequately removing water.
Design for Prevention
While it’s ideal to design and install all components at once during new plant construction or remodel, improvements also can be made retroactively on existing lines.
As you develop a plan, place the coalescing filter and dryer as close to your production line as possible. Then, wherever process air contacts your product, use a fine-micron filter at each point. Fine fiber filters here address surviving micro-organisms and contaminants, such as metal flaking or corrosion, introduced by your system.
Your facility’s layout also matters. For example, if your facility routes cooled air from your compressor room through outdoor piping and different air temperatures, condensation may occur that needs to be removed once again.
Finally, account for fluctuating weather conditions where your facility is located. In regions with high humidity or significant shifts in temperature and humidity, design your equipment to the worst-case scenario to handle peak demands.
Working with an experienced compressed air filtration provider like Donaldson can help you determine the best moisture-control system for your process.
