The importance of filtration to compressed air quality in the food industry
Food hygiene is quite correctly high on the public agenda and recent scares have only highlighted those concerns. An important part of the food preparation process includes the use of compressed air; here Andrew Macpherson of Festo takes a holistic view of air quality in the food processing sector and explains how it is vital that the purity of this air is maintained throughout the process to safeguard the food from contaminants.
There has been a good deal of discourse over recent months about the importance of maintaining compressors to ensure air quality is kept high in systems. While the approach is laudable, it is only part of the solution that is required to ensure that air quality is maintained throughout food production processes.
The compressor supplies the air that is fed throughout the system. At its point of use when it actually comes into contact with the food or packaging higher, air quality is required and this enhanced purity is achieved by utilising a cascade filter system.
The plant air will be fed around the facility by a series of pipes and valves that may have been in place for many years. To ensure that the system continues to deliver air at the required quality it is vital that rigid Total Productive Maintenance (TPM) is enforced. A vital component of this TPM system will be to ensure that the filters, which are the end of the purification chain, are correctly specified, maintained and replaced when required.
By its very nature compressed air is not clean so before it comes into contact with food it needs to be filtered. Concentrating on the compressors, which feed the entire system can only impact the air quality at the start of the process. Strict requirements are mandated for compressed air within the manufacturing process governed by ISO 8573-1. This standard sets requirements for maximum particle sizes of contaminants of solid particles, water content and total oil content for air at various stages of the production process. For example, the air that comes from the compressor to feed the system must conform to an air quality of class 7.4.4 (solid particles at class 7, water particles at class 4 and oil particles at class 4).
However, while that modest level of quality is acceptable for the airing main, significantly higher levels of purity are required when compressed air comes into contact with food. Different levels of air quality are required at different points of the process so a carefully thought out concept is required that features a combination of basic centralised compressed air preparation alongside decentralised auxiliary preparation supplied by a series of high quality filters. This is achieved by treating the air quality as close as possible to the consuming device to ensure that only the amount of air required is prepared to the higher quality, eliminating pressure drops and wasted energy.
Even within a food plant there are varying qualities of air requirements. For direct contact with non-dry foods such as beverages, meat or vegetables class 1.4.1 air is required. However when dry foods are being prepared, whether transporting or mixing, then a higher quality of class 1.2.1 is demanded.
Part of any TPM system is an effective hazard analysis and critical control point (HACCP) analysis. According to the British Compressed Air Society (BCAS) and its 'Food Grade Compressed Air Best Practice Guide' compressed air is seen as a utility and its provision is normally included in the pre-requisite programme rather than directly as part of the HACCP activity.
A hazard analysis shall include items subject to a pre-requisite programme to establish whether there is a need to include the compressed air provision at any specific critical control point. Compressed air is an essential part of many aspects of food/beverage production and processing from the farm to fork and with the ever-increasing demands to improve health and hygiene in the food chain. The HACCP activity needs to recognise both accidental and intentional contact with food, recognise the potential risk and the filter use that can mitigate this.
Sometimes it can't be avoided. For example, if you are picking and placing biscuits automatically using a tripod robot you have a vacuum cup at the end to pick a biscuit up. There will always be a risk there if the fitting was to slightly leak, say if the vacuum generator is on the head of the pick and place unit. Risk can be avoided by having the right grade of air filtered at that point. At least that way, if there is a leak, the consumer is not put at risk by having the poorly filtered air tin contact with the product.
A basic filter system will have a manual or automatic dump valve before the filtration process so that the air can be isolated. It is also good practice to have a regulator to ensure that the air pressure is neither too high nor too low. There will then follow a series of filters, perhaps a five micron filter, followed by a one micron filter, followed by a 0.01 micron filter and, even then, that possibly followed by an activated carbon filter. That combination gives you class 1.4.1.
To get 1.2.1 you have a five micron filter, followed by a one micron filter, an absorption dryer filter, then a 0.01 micron filter and again an activated carbon filter to remove odours. The difference between the two is the reduction in water particles.
Armed with an efficient compressor, thorough TPM and HACCP systems that recognise the importance of maintaining and replacing filters, food manufacturers can be assured that they are producing food to a high standard.
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