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Making good choices

08 November 2021

Andy MacPherson offers advice on the selection of pneumatic components for use in food production applications. 

Food production poses some unique challenges for machine builders and specifiers. There is a need to ensure that pneumatic controls are correctly specified to support hygiene and safety regimes, in addition to helping to reduce downtime and keeps operational costs under control. 

Here are some key points to consider when selecting pneumatic components for food applications:

• What food zone is involved? When selecting pneumatic automation, it is important to consider the working environment of the equipment to maintain food quality, safety and the correct working life of the machinery. Correct selection depends on which zone the equipment will be working in. The European standard EN 1672-2 (Food processing machinery – Basic concepts) defines three production zones – the food zone, the splash zone and the non-food zone.  

Pneumatics for food and splash zones must be easy to clean and disinfect, corrosion-resistant, non-toxic and non-absorbent. They should also present a smooth, continuous or sealed surface to reduce contamination risk. Pneumatics for non-food zones – where machine components do not come into contact with the product – do not need to meet such rigorous toxicity and contamination requirements. However, they should still be manufactured from corrosion-resistant materials and need to be easy to clean and disinfect.

• What material specification is best? The material specification of pneumatic components is critical to meeting strict hygiene requirements in food applications. Take into consideration not only the materials used for the drive unit but also those used for interface components, such as connections and seals, and lubricants. All materials need to be compatible with the cleaning process of the plant.

High-alloy stainless steel is usually the material of choice for the food industry. However, aluminium is an affordable alternative that can be rendered resistant to cleaning agents through the application of an additional coating or anodised oxide layer. Plastics can also play a part, as long as they do not give off or absorb hazardous substances. 

• What air quality is required? It is essential to check whether any compressed air could come into contact with either the food product or the packaging. Direct and indirect contact points include bagging, mixing, drying, air knives (blow-off) and the pneumatic cylinder exhaust. 

Compressed air is a major potential source of contaminants including moisture, particulates and bacteria. It has been calculated that a 75hp compressor with a capacity of 300 scfm takes in 100,000 to 1 million bacteria each hour. To uphold hygiene and safety, it is therefore essential to make sure that the air has been filtered to the correct standard. The level of filtration required differs from wet foods to dry foods. 
• What about seals and lubricants? Using the wrong seal material can result in premature failure of a product. Intensive cleaning can also wash out the lubricating grease and impair operation of pneumatic components. 

For example, selection of the correct wiper seal on a cylinder will ensure long life performance. Using dry-running seals will ensure that washed out machine components will still function reliably. Lubricating greases and oils must comply with FDA regulations or ISO 21469. Where they may come into contact with food or its packaging, NSF-H1 greases are required.

•  What cleaning regime is in operation? Cleaning regimes and chemicals used on the production line can affect pneumatic component performance. Determine the type of cleaning process (foam, power wash, etc) and how long the components will be exposed to the cleaning agents. Then select the correct materials and hygienically designed components that will ensure food safety along with the required life of the components.

The materials used for machine parts must not react with the cleaning agents or the anti-microbial chemicals (disinfectants). They must therefore be corrosion-resistant and mechanically stable. If the cleaning regime is changed, the pneumatic components should be reassessed to ensure they will continue to perform as expected.

More advice about the use of  pneumatics in food applications can be found in a Festo whitepaper:

Andy MacPherson is product manager – Food & Beverage at Festo UK.

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