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Compressed air is the 4th largest energy source used in the food industry. It is used for different purposes: automating a process, providing energy, packaging products, etc. Its main advantage is that it can be produced on site by the user. However, this production generates inevitable contamination that must be treated to comply with food hygiene standards. What are these different contaminants? What are the different technical means to purify compressed air and ensure the manufacture of healthy products?

What are the three main contaminants treated?

If not treated beforehand, compressed air may contain contaminants that pose a risk. There are about ten contaminants, which can be grouped into three main families:

These contaminants are produced by several sources. First, the atmospheric air absorbed by the compressors contains by default a large number of impurities, water, oil and microorganisms. The operation of the air compressor itself generates minute amounts of oil during compression, and then water when the air is refrigerated at the end of the process. Finally, the air manifold and distribution system are likely to pollute the compressed air with rust or scaling.

Why do these contaminants need to be controlled?

It is important to eliminate or reduce the contaminant content of compressed air as much as possible. Compressed air contamination affects production processes and reduces their efficiency, increasing manufacturing costs and the risk of having damaged or unsuitable products for sale. Indeed, the lack of treatment can lead to problems in the compressed air production system.

As a result, contaminants from the water cause corrosion of the storage and distribution system. They can damage production tools, but also products and packaging in contact with the air. They increase the risk of microbiological contamination.
Contaminants from the oil can permeate products and packaging, creating unpleasant odours. The viscosity generated in the working environment increases the risk of accidents at work (slippery surfaces). Oil in liquid or aerosol form also deteriorates the production equipment by the action of condensate.
Finally, impurities are the most harmful. Rust and scaling can clog pipes or even cause lasting damage. In addition, particles in the atmospheric air and microorganisms can alter the quality of products and make them unfit for consumption. If the products harm the health of consumers, this can have serious financial and legal consequences for the company.

That's why a reliable compressed air supply keeps production efficient and cost-effective, while complying with health standards.

Why is water found in compressed air?

Compressors use atmospheric air to make compressed air. However, the latter necessarily contains more or less high levels of water, oil and residues, varying according to weather and pollution conditions.

The production of compressed air necessarily induces a saturation of humidity in the air. Indeed, the compression of the air causes an increase in temperature. To be injected into the network, the air must therefore be cooled beforehand in order to have a temperature close to the ambient air. These temperature variations lead to the production of moisture (condensation). The temperature at which the compressed gas releases water in liquid form is called the dew point. The more humid the air, the higher the dew point.

The air compressor and distribution system are usually lubricated with oil. During the compression process, small amounts of oil and oily vapours also contaminate the compressed air.

Good to know: What to do with the water removed from the compressed air? It is also contaminated with oil and microparticles and should therefore not be thrown away anywhere. It is considered an emulsion of oil and water and therefore must be collected and treated as such.

Why avoid contamination of humid compressed air?

Water and oil are the main contaminants in the compressed air used by the food industry. It is important to limit the liquid content for several reasons.

Humidity promotes the development of bacteria. Microorganisms can alter the quality of products or even make them unfit for consumption.
Oil and water can degrade the condition of pneumatic lines and valves by causing corrosion. The latter can then generate contaminants in the form of microparticles itself. Eventually, pipes, filters and tanks are susceptible to damage or clogging.
Liquid water in compressed air can cause outdoor lines and valves to freeze.
Finally, it can create undesirable effects depending on the product manufactured, for example the aggregate of powders (sugar, spice, sand, etc.), cause bubbles to appear or create adhesion problems.

What are the most sensitive stages of the manufacturing chain?

In food and beverage plants, compressed air is used at different stages in the manufacturing chain. Some are more susceptible than others to contamination.

The installation control is for the pneumatic drive of clamps, valves or levers. At these stations, the compressed air does not come into direct contact with the food products. However, it must be treated to avoid contamination of the foodstuffs in the event of a leak, for example.
The filling and packaging of products is the most sensitive point in the chain. At this point, the compressed air can be in direct contact with the food (e.g. for packaging thermoforming or finishing). The compressed air must be perfectly decontaminated, free of oil, water and impurities, including microorganisms.
The transport of products is also a sensitive step, as the compressed air is also in direct contact with the foodstuffs, as is manufacturing and storage. In some industries, compressed air is used to clean fruits and vegetables or in the fermentation process of food.

What is ISO 8573-1?

There are no standards setting acceptable compressed air quality thresholds in the food industry. In contrast, industry professionals in the UK have developed a Code of Practice that sets out minimum compressed air quality requirements and permitted levels of impurities, water and oil.

This code is based on the international compressed air quality standard ISO 8573-1. The latter is classified according to three criteria:

The standard thus makes it possible to know the concentration of pollutants in compressed air networks.

An air class 3/2/1 means that:

Within the production system, each device will be able to meet different requirements for compressed air quality.

In addition, manufacturers must comply with HACCP analysis to comply with health regulations in terms of food products. Logically, compressed air must be integrated into the HACCP risk analysis.

To adapt this standard to the food industry, the Code of Practice has divided air into three categories:

How do you remove or reduce contaminants from compressed air?

Today, there is a real awareness among manufacturers about air quality and factories are equipping themselves with more and more equipment to limit the contamination of the compressed air they use.

Different means are implemented and each one meets specific needs.

Filters can remove oil in all its forms, but they have a limited lifespan and can quickly become saturated. Ideally, oil-free machines should be used.
Coolers reduce the temperature of the compressed air, which fluctuates between 70 and 200°C. They also limit the water content and are systematically included in compressors. An aftercooler is also placed after the compressor.
The water separator complements the action of the chiller to remove condensation water from the compressed air.
The oil and water separator allows these two elements to be recovered and disposed of cleanly, like used oil. It is usually a membrane filter that drains the oil on one side and the water on the other.
The adsorption dryer aims to filter the air through activated carbon and a catalyst, and then through a particulate filter. This makes the air produced very pure and can even be used for medical applications.

The technical means to achieve the desired air quality

To meet the requirements for compressed air production in the food industry, manufacturers are making sure to design rigorous treatment equipment. Ideally, the air should be treated before it enters the production system, and then purification operations should be integrated throughout the distribution chain and up to the point of use.

There are several devices that can be used to achieve the desired compressed air quality. Each offers a suitable solution for one or more contaminants.

Means placed at the level of the air compressor

Water separators remove liquid oil and condensed water. Generally placed before the coalescing filters, they protect them against massive contamination. On the other hand, they are not effective against oil or water vapours.
Coalescing filters are intended to remove oily and aqueous aerosols, as well as atmospheric air impurities, rust and scaling. They are normally installed in pairs, with the first protecting the other so that it is more efficient. The coalescing filters are placed between the air manifold and the dryer.
The adsorption dryer is used to remove water vapour from the compressed air. Its effectiveness is measured by the pressure dew point (PRP). The principle is to pass air through a desiccant material. The refrigeration dryer is another type of device that cools the air to dry it out, but this equipment is generally not suitable for the food industry.
Adsorption or activated carbon filters remove oil vapours. They are placed after the dryers and before the distribution circuit.

Means placed at the points of use of compressed air

Optimisation of compressed air production in industry

The efficient production and use of compressed air is essential for many industrial processes. To optimise this valuable resource, it is important to consider several key aspects:

Choosing the right compressor

Choosing the right type of compressor is crucial for efficient compressed air production. Screw compressors are often preferred in industry for their energy efficiency and ability to deliver a consistent flow. For applications requiring oil-free air, oil-free compressors are an excellent option, especially in the food and beverage industry where air purity is paramount.

Compressed Air Treatment

Proper treatment of compressed air is essential to ensure its quality and protect downstream equipment. This process typically involves:

Energy consumption management

Compressed air is often considered the fourth largest energy carrier in industry, after electricity, natural gas and water. To reduce the energy cost associated with its production, several strategies can be put in place:

Preventive maintenance

Regular maintenance of compressed air systems is crucial to maintain their efficiency and prevent leaks. This includes:

By implementing these practices, industries can significantly improve the efficiency of their compressed air production, reducing their energy costs and carbon footprint.

The strict standards surrounding the food and beverage industries require companies to implement reliable compressed air treatment systems. Thus, the production complies with sanitary standards while optimising manufacturing.

Compressed Air in the Food and Beverage Industry: How to Control It

The importance of treating compressed air in the food industry