Clean, dry air is essential for the food and beverage industry. How do you ensure that air used for food processing and packaging meets ISO purity requirements for particulates, moisture and oil carryover? Here’s what food manufacturers should know about choosing a compressed air solution.
Where Is Compressed Air Used in the Food Industry?
Compressed air is used for many different applications throughout the food and beverage industry. First and foremost, it is used to power conveyors, sorters, mixers, bottling lines and other production equipment, just as in other types of manufacturing facilities.
However, the use of compressed air isn’t limited to powering conveyors or equipment. Compressed air is also used in ways that bring it in more direct contact with food ingredients. Some of these include:
- Blow-off/cleaning/drying (e.g., blowing food debris off conveyors and equipment, air cleaning and drying of containers or produce).
- Food packaging and vacuum sealing.
- Carton form, fill and seal.
- Dairy processing/agitation.
- Meat processing and packaging.
Compressed Air Standards for the Food Industry
Quality is an essential consideration when using compressed air in food and beverage applications. Air used in the food industry must be clean, dry and oil-free. Exactly how pure air must be depends on how compressed air is used. Compressed air use in the food and beverage industry can be broadly classified into two categories:
- “Direct contact” applications (like cleaning/blow off of produce or containers).
- “Indirect contact” applications (like powering production machinery and conveyors).
Air purity is especially important for direct contact applications. However, even air used strictly to power machinery must be as contaminant-free as possible. Why? Small leaks in the compressed air system can result in contamination in the ambient air of the production environment - and this contamination can end up in the food products on the production line. For this reason, air purity is an important consideration for all compressed air applications in food and beverage processing.
What Kind of Contaminants Are in Compressed Air?
Compressed air may contain three different types of contaminants, all of which can be a problem for food safety.
- Particles may include pollen, dust, mold spores and diesel fumes from intake air; rust from the air distribution or storage system; or particulates generated by the compressor itself through component wear. None of these particles belong in our food supply. Mold spores can be especially dangerous in a food processing facility, as they can lead to growth of dangerous molds in the food or inside the facility.
- Water enters the compressed air system primarily through the intake air. Ambient air contains water vapor (humidity); the exact amount varies by temperature (warm air holds more water than cool air) and overall climate conditions (e.g., arid desert vs. rainforest). Water is also dangerous in a food production or packaging environment. Excess moisture enables microbial growth, including molds and food-borne pathogens. Water in the compressed air system can also lead to corrosion inside ductwork or air-powered equipment, further increasing contamination levels.
- Oil carryover refers to the concentration of oil droplets in the compressed air supply. In an oil-flooded air compressor, most of this oil comes from the compressor itself. However, oil can also make its way into compressed air through intake air. This happens when oil aerosols from production machinery or vehicles end up in the ambient air of the compressor room. If not removed, oil from ambient air will end up in compressed air. This is bad news for obvious reasons: who wants to eat motor oil?
Compressed Air Standards for Food Safety
Compressed air quality is classified using metrics created by the International Standards Organization (ISO). ISO 8573-1:2010 lays out purity classes for compressed air according to the concentrations of particles, oil and water in the final product.
ISO has specifications for each type of contaminant.
- [A] Dry Particulate
- [B] Humidity and Liquid Water
- [C] Oil Total Concentration (aerosol, liquid and vapor)
Air is rated for a purity class for each contaminant type, in an [A]:[B]:[C] format. So, if air is classified as purity class 1:2:1, that means that it meets Class 1 requirements for dry particulate and oil and Class 2 requirements for water. Class 0 compressed air is the cleanest; it must exceed Class 1 quality criteria and meet application-specific criteria (e.g., cleanrooms).
ISO 9573-1:2010 does not specify which purity classes must be used for specific applications; it is simply a method of classifying and comparing compressed air quality. The Food and Drug Administration (FDA) doesn’t specify air purity classes, either. However, under the Food Safety Modernization Act (FSMA), food processors and handlers must take steps to minimize the risk of food contamination.
The SQF Code, from the Safe Quality Food Institute, provides the following guidance for food and beverage manufacturers (from Food Safety Code for Manufacturing Edition 9):
- 184.108.40.206: Compressed air or other gasses (e.g., nitrogen, carbon dioxide) that contacts food or food contact surfaces shall be clean and present no risk to food safety.
- 220.127.116.11: Compressed air systems and systems used to store or dispense other gasses used in the manufacturing process that come into contact with food or food contact surfaces shall be maintained and regularly monitored for quality and applicable food safety hazards.
In the absence of specific regulatory guidance, the onus is on food and beverage manufacturers to select the right air purity class for their application. This will depend on questions such as:
- Does the air come in direct contact with food or food packaging? Any processes where air comes in direct contact with food or final packaging must meet the highest purity standards.
- How important is humidity control for the application? Dry processes (such as packaging crackers) will be less tolerant of moisture in compressed air than wet processes (such as mixing or packaging liquid milk).
The British Compressed Air Society has developed a guidance document for food and beverage manufacturers that lays out recommended purity classes for particulate, water and oil [A:B:C].
- For direct-contact applications, they recommend a purity class of 2:2:1 or better.
- For indirect-contact applications, they recommend a purity class of 2:4:2 or better.
These guidelines are now used by many companies globally. However, food and beverage manufacturers should do their own due diligence in choosing a purity class for their specific compressed air applications.
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Is an Oil-Free Air Compressor Required for Food & Beverage?
Many manufacturers assume that an oil-free air compressor must be used for food and beverage applications. However, this is not always the case. In most cases, adequate air quality can be achieved via high-efficiency inline filtration and air drying.
Oil-flooded rotary screw air compressors use oil to lubricate and cool the rotors and provide a seal between the rotors and the walls of the air end. An oil-free compressor, on the other hand, uses rotors with very tight mechanical tolerances and a non-stick coating (e.g., Teflon) to reduce friction. Air or water is used for cooling instead of oil.
In theory, an oil-free compressor will eliminate all oil carryover, since there is no oil in the air end. However, there are some things to keep in mind.
- The oil-free compressor will not eliminate oil that enters the system through the intake air. An oil-free compressor may thus provide a false sense of security; companies assume that inline filtration for oil is not necessary. However, if intake air is contaminated by oil mists created by production machinery or vehicles operating in the vicinity of the compressor, this oil will end up in the air supply.
- An oil-free compressor is much more expensive to purchase and operate. An oil-free compressor may be as much as twice the capital cost of an oil-flooded rotary screw with the same CFM. And even with non-stick coatings, there is more friction on the rotors compared to an oil-flooded model, which significantly reduces the service life of the machine. Repairs can be very expensive for an oil-free compressor, as well.
When you consider capital, repair and maintenance costs, along with the shorter service life of an oil-free compressor, it is almost always cheaper, in the long run, to go with an oil-flooded compressor and invest in high-efficiency filtration.
Achieving Air Purity Standards for Food and Beverage Manufacturing
An oil-flooded rotary screw compressor is a good choice for most food production applications, including powering bottling lines, conveyor systems, sorters and other pneumatic equipment. But with the right filtration, an oil-flooded compressor is also a viable choice for many direct-contact applications. High-efficiency filtration and air dryers can remove nearly all dry particulate, oil and water to meet ISO purity classes of 2 or better.
There are several steps to producing high-purity compressed air.
- Start with a good intake filter to remove large particulates and some oil mists from intake air. This will reduce wear and tear on your inline filters.
- Use an air dryer to remove water from compressed air. A refrigerated air dryer can get air down to a dew point of ~38°F, equivalent to an ISO 8573-1:2010 [B] Class 4. This may be alright for applications that are not moisture sensitive, but to achieve ISO 8573-1:2010 [B] Class 1, 2 or 3, you will need a desiccant air dryer. A desiccant dryer can achieve dew points as low as -40°F to -100°F, or ISO 8573-1:2010 [B] Classes 2 and 1.
- Use inline filtration to remove oil and dry particulate. A high-efficiency coalescing inline filter removes particulates down to 0.01 microns (ISO 8573-1:2010 [A] Class 1) with a maximum oil carryover of 0.008 PPM (ISO 8573-1:2010 [C] Class 1). Activated carbon inline filters also remove hydrocarbon mists, vapors and odors, with a maximum oil carryover of 0.002 PPM, which may meet even Class 0 requirements.
- For added safety in food applications, the compressor can be run on food-grade oil. This ensures that even the tiny amounts of oil that make it through the inline filter are food safe. It also adds an element of security in the unlikely event of a compressor failure or separator failure that results in oil downstream.
Aire Tip: Inline filtration should be used for food processing applications even when using an oil-free compressor to ensure that contaminants from intake air do not make their way into the air supply.
Talk to the Compressed Air Experts
Fluid-Aire Dynamics has extensive experience in delivering high-purity compressed air for the food and beverage, pharmaceutical and medical industries. We have installed oil-flooded rotary screw air compressors with high-efficiency inline filtration in bottling plants, meat processing facilities, pharmaceutical manufacturing facilities, and medical cleanroom environments.
Talk to us about your compressed air needs.