In any industry that makes use of compressed air, there are four types of compressed air to consider. These are: process air, which is compressed air that comes into direct contact with the product; non-contact air, which is compressed air that is not meant to come into contact with the product; instrument air, which is compressed air that is meant for process instruments and control; plant air, which is compressed air that is used to clean machinery and operate tools.
When it comes to analyzing air contamination in the food industry, process air is the main focus. This process air finds its way into packaging operations, but also the mixing, cutting and drying of ingredients, as well as the transportation and propulsion of food in certain systems.
All these operations that bring compressed air into contact with the product either directly or indirectly, are considered key sources of air contamination.
Sources of contamination
Contaminants are bound to creep in and develop in any compressed air system. Air contamination can come in from or develop in:
The Atmosphere: Apart from gaseous contaminants, the atmosphere that is pulled in by the compressor will also contain particulate matter, water vapour, oil vapour, and micro-organisms.
Air Compressor: The compressor adds its own range of contaminants, notably oil vapour, oil aerosols, and liquid oil.
Air Receiver and Piping: The accumulated contaminants from the earlier stages inevitably end up in the receiver as well as the distribution piping. This leads to the growth of micro-organisms; the resulting chemical reactions give rise to pipe scale and rust.
Earlier posts have described the filters and dryers in place to screen out contaminants. There are the coalescing filters that screen out the oil aerosols and the wet particulate; dust removal filters remove dry particulate; adsorption dryers remove water vapour; and adsorption filters remove oil vapour. But these systems alone are not sufficient. As described above, there are many areas in the compressor system that encourage microbial growth.
The main step to limit microbial growth is to put in place sterile air filtration at specific points of contact. These trap the microbes and prevent them from coming in contact with the food product.
Point-of-use filters in general are installed right before any specific piece of equipment or application; they are generally much more effective than after filters. Other filters such as activated carbon (removes particles too small to be removed by the coalescing filters) and dust filters may also be installed at points of use.
Given the abundance of food safety standards and guidelines on maintaining clean air, regularly monitoring (with dew meters for instance) and testing the purity of compressed air is the best way to limit air contamination. That’s because the composition of contaminants in the air varies from moment to moment as does the build-up of contamination within the compressed air systems.
In addition to this, leading safety guidelines concur on the need to remove moisture wherever possible and maintaining a dew point of at least -26° C/-15°F (to limit microbial growth). They also advise setting up of filtration (with a DOP efficiency of at least 99.999%) at any point where the compressed air is likely to come into contact with the product.
It must be noted that these point-of-use filters must be maintained regularly; elements must be changed at least once or twice a year in the first two stages; the replacement frequency needs to be doubled for filter elements in stage three. Dryers, air lines, and drain taps too must be regularly maintained.
If you are looking to set up your food operations or to step up you existing operations in a manner that is both economical and compliant to high standards of hygiene, safety, and purity, explore Pneumatech’s range of products. Or get in touch with us right away.