FOOD HYGIENE LEGISLATION AND THE USE OF COMPRESSED AIR

Phil Black - PII Editor 18/03/2011

256 6 minutes read

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Mark White, Market Development Manager, Industrial Purification, at Parker Hannifin’s domnick hunter Industrial division, looks at the cause of contaminants in the compressed air stream and explores the practical solutions that can be introduced to ensure high levels of purity in food grade applications.

Compressed air is a vital utility in food and beverage processing and packaging, with approximately 90% of all companies in the sector using it in some aspect of their business. As a utility, compressed air is widely used in the food industry and for a diverse range of operations, from powering pneumatics, process and automation equipment, to moving, mixing and blending ingredients. Additionally, compressed air is also used as a source gas for the generation of nitrogen, commonly required for Modified Atmosphere Packaging and associated applications.

However, its use, especially in areas where it can come into direct or indirect contact with production equipment, ingredients, finished products or packaging, should be carefully controlled, to prevent the risk of contamination. Indeed, compressed air is far from clean; even in plants where filtration and drying equipment is installed it can still contain dangerously high levels of contaminants in the form of dirt, water oil and micro-organisms.

Accordingly, most countries worldwide have strict standards and laws governing hygiene in food production, which must be adhered to at all stages of the manufacturing and supply chain, to avoid criminal charges and subsequent prosecution. In particular, under European food hygiene regulation 852/2004, food manufacturers have a duty of care to protect consumers from harmful or dangerous contaminants. Article 5 of this legislation requires companies to implement written safety management procedures, based on the principles of HACCP (Hazard Analysis Critical Control Points). As a matter of course, compressed air systems should be included in the HACCP risk analysis, but unfortunately, the risks associated with compressed air are not always known and therefore compressed air is omitted from the analysis.

Compressed air contamination and its sources

Understanding the sources of compressed air contamination and the types of contaminants which must be reduced or eliminated is fundamental when planning an efficient compressed air system. In a typical system, there are ten major contaminants that have to be removed or reduced to protect the consumer and provide a safe and cost effective production facility. These contaminants originate from four different sources.

Source one: atmospheric air
Compressors draw in significant volumes of atmospheric air, which continuously fill the system with invisible contaminants including: water vapour, atmospheric particulate, oil vapour and micro-organisms.

Source two: the air compressor
In addition to the contaminants drawn in from the atmosphere, oil lubricated compressors will contribute small amounts of oil from the compression process. The oil will be in the form of either liquid oil, oil aerosols or oil vapour (this is in addition to oil vapour drawn in from the atmospheric air). After the compression stage, the after-cooler will then cool the air, condensing water vapour and introducing it into the compressed air as liquid water or water aerosols.

Sources three and four: compressed air storage devices and distribution piping
The compressed air storage device, otherwise known as the air receiver and the system distribution piping also add contamination in the form of rust and pipescale. Furthermore, the storage and distribution system will also store large volumes of contaminated air as well as providing an ideal environment for the continued growth of micro-organisms.

PHDH041 - OIL-X EVOLUTION compressed air filters

Food hygiene and HACCP

As the risks associated with compressed air contamination are not always known, it is not uncommon to find that the compressed air system and its usage points are overlooked when the HACCP hazard or risk analysis is carried out.

In reality, every point in a food and beverage manufacturing plant where compressed air is used should be classified as a CCP (Critical Control Point), due to the contamination present in the compressed air system. Once classified as a CCP, measures must be taken to remove the contaminants or reduce them to acceptable levels.

Many applications within the food and beverage manufacturing process either require complete sterility or at the very least a level of control over the presence of micro-organisms. If contaminated compressed air is allowed directly or indirectly to come into contact with production equipment, ingredients, packaging materials, partially completed or finished products, then sterility is compromised and control is lost.

Loss of sterility can cause enormous financial damage for a company as micro-organisms can diminish product quality, render a product entirely unfit for use, and potentially harm the consumer, which can, at best, lead to product recalls or, at worst, cause legal action against the manufacturer.

In addition to the problems associated with the direct contamination of the product or the manufacturing process, allowing contaminants such as water, particulate, oil and micro-organisms to exhaust from pneumatic valves, cylinders, air motors and production equipment, can lead to an unhealthy working environment with the potential for personal injury, staff absences and financial compensation claims.

Compressed air contaminants and their removal

For many compressed air users, the realisation that there are ten major contaminants in a compressed air system can come as something of a surprise. It is often thought that only three contaminants are present – dirt, water and oil – however, upon closer examination, these three contaminants can be broken down further as:

Dirt
• Micro-organisms
• Atmospheric Dirt and Solid Particulate
• Rust
• Pipescale

Water
• Water vapour
• Condensed Liquid Water
• Water Aerosols

Oil
• Oil Vapour
• Liquid Oil
• Oil Aerosols

It is important to look at each contaminant in detail, as due to the diversity of the contamination present, a number of purification technologies must be employed for to ensue that all potential contaminants are removed.

BRC / BCAS Food Grade Compressed Air Code of Practice

To help companies in the United Kingdom meet the requirements of the relevant legislation, the British Retail Consortium (BRC) and the British Compressed Air Society (BCAS) have jointly published a code of practice covering the use of compressed air in the food industry, setting minimum compressed air quality standards regardless of whether it comes into direct contact with food or not, in all food and beverage manufacturing facilities, including bottling plants.

It is also worth noting that the code of practice is not just concerned with the levels of oil in compressed air, as the greatest volume of contamination and most problems experienced are associated with water and micro-organisms. Therefore in addition to oil, the code of practice also defines minimum acceptable contamination levels for water and solid particulate, with all specifications being in line with quality levels specified in the international standard for air quality, ISO8573-1:2001.

For food processors and packers, there are many different compressed air filtration and drying systems available. Of these, coalescing filters, such as Parker domnick hunter’s OIL-X EVOLUTION Grades AO & AA, are very important pieces of purification equipment, as they remove solid contaminants (rust, pipescale, atmospheric dirt & micro-organisms) down to very low levels (0.01µ in size) as well as oil and water aerosols down to 0.01mg/m³.

These coalescing filters are typically installed in pairs, with the first unit acting as a general purpose filter to protect the second, high efficiency filter from bulk contamination. This configuration offers a long operating life, while ensuring a continuous supply of high quality compressed air with low operational costs and minimal maintenance requirements.

Despite the outstanding levels of performance and efficiency that can be achieved with today’s modern coalescing filters, they are still unable to remove water vapour, as it occurs in a gaseous form. To safely remove all contaminants down to acceptable levels, and to comply with the relevant legislation and standards, it is therefore necessary to introduce a dryer into the compressed air system.

The latest generation of environmentally friendly compressed air dryers, namely adsorption or desiccant dryers can achieve the highest quality compressed air while also providing considerable energy and operating cost savings. For example, the PNEUDRI systems from Parker domnick hunter have been developed to offer a Pressure Dew Point (PDP) better than -26°C; because at this level, the growth of micro-organisms is inhibited, which makes the technology ideal for applications where the air flow comes into either direct or indirect contact with production equipment foodstuffs or food contact packaging materials. Models also exist that can achieve a PDP of -70°C for ultra critical applications that require the driest air possible.

Conclusion

It is widely accepted that contamination removal is vital in the compressed air that is used across the whole spectrum of food and beverage processing and packaging operations. With the introduction of the latest filtration and air drying technologies, companies can now achieve a level of contamination removal that has never before been possible. Not only does this eliminate the risk of product degradation consumer safety, but it also improves performance, while helping to maintain efficient and cost effective production processes, which can deliver considerable bottom line benefits.

Parker Hannifin – Domnick Hunter
Gateshead, Tyne & Wear

Can be contacted on

Tel: +44 (0)191 4029000
Fax: 0191 482 6296
E-mail: dhindsales@parker.com
Web: www.dominichunter.com