Compressed air in the food industry (Part 2)

The burning question being, can one get clean air ? The short answer is yes. But there is a but, first ‘clean’ must be specified and then the cost must be considered. Part 2 of this article looks at contaminants and offers some technical tips

Identify the contaminants

The main culprits are moisture, solid particles, oil aerosols & vapours. Each has its own removal method and specification level. Be sure to address all if they are unacceptable to your product.

Compressed air must be purified of contaminants before being used in hygienically sensitive areas. The contaminants are water vapour and moisture, solid particulates (including spores) and oil aerosols and vapours. Some are controlled at the compressor itself and some can only be done effectively just before the point of use.

The technical side of the task team must do some research as to where and how the contaminants can be generated in your specific layout of air supply. This will determine the best way and place to do the cleaning processes. Some contaminants are generated in the supply pipes to the different areas. (Rust and bacteria)

The presence of moisture is the primary concern for the food industry because moisture creates the ideal habitat for micro organisms and fungus. Moisture may reside in the piping system near the point-of-use where compressed air comes into contact with food products. Micro organisms and fungus can grow inside the piping system and then be blown onto food products or food containers.

Oil aerosols and vapours is a significant concern. One myth in compressed air systems is that the use of an oil-free air compressor frees the system of any compressed air treatment requirements. This is not the case. Ambient air ingested by air compressors will carry water vapour, particulates, and hydrocarbons and compressed air dryers and filters are always therefore required.

Typical specification

One of the most overlooked issues is the bad habit of ‘cleaning’ with compressed air. Compressed air cannot clean an area, it simply moves dust and other particles from one area to another. This should be prohibited and not just in sensitive areas. It is also unsafe as it can blow solids into eyes and ears, it is normally a noise creator of note and makes fine particles airborne that is bad for your lungs.

Pointers for the technical guys (if your company does not specify)

1. It is worth noting that refrigerated type compressed air dryers normally have significantly lower associated energy costs than desiccant air dryers. Desiccant air dryers will use a portion (can be 15%) of the compressed air to regenerate the desiccant bed and/or use electric heaters. Refrigerated dryers use relatively small refrigeration compressors and can be cycling or non-cycling.
2. Coalescing filters are required to remove solid particulates and total oil (aerosol + vapour) to the same specification levels as “Contact” systems. Please note that activated carbon filters will be required as well to remove oil vapours. As with the air dryers, each facility will have to determine if de-centralized filtration is required in addition to the centralized filtration.
3. The most common standard that is used is the ISO8573.1-2010 in conjunction with section 6 of The Code of Practice.
4. The U.K. Code of Practice for Food Grade Air provides a comprehensive resource on compressed air systems in the food industry.
5. Most facilities have a large dryer installed in the compressor room that will achieve the -40 °F dew point specification. Dryers should be monitored periodically for performance to specification and maintained regularly. However, most facilities do not have proper filtration installed at CCPs.
6. Humidity is measured at air line pressure.
7. It is recommended, when selecting compressed air filtration products, that care is taken to request coalescing filters tested to the ISO Standard 12500 Parts 1-3 or equivalent 

Author

Pieter de Waal