There is no universal ISO 8573-1 class for compressed air that touches food. It is set point of use by point of use, based on each machine manufacturer, your HACCP plan and your customers' specifications. For direct contact, the requirements are strictest on all three contaminants: particles, water and oil. Our compressors are lubricated: the class is defined with our technicians, then the dryer and filters are chosen to reach it.
For all the air needs of a food plant, see our page on compressors for the food industry. Here we only deal with air that touches the product.
Identify the direct-contact points
Air touches the food itself in more places than people think:
- blowing products on a conveyor: biscuits, dried fruit, pieces of meat to be dried;
- air-jet rejection on a sorter;
- pneumatic conveying of powders, sugar or flour;
- release by blowing from moulds, or air that pushes a product into its packaging;
- blow cleaning of surfaces that later touch the food.
List them one by one, with their flow. The other points (cylinders, valves, machine controls) do not have the same requirements: treating the whole network to the strictest level is costly for no benefit.
What an ISO 8573-1 class says
A class is written as three figures, [particles : water : oil]. The lower the figure, the cleaner the air. Each figure is dealt with by a different piece of equipment:
- particles by filters, from coarse to fine;
- water by the dryer: refrigerated for a dew point a few degrees above zero, desiccant to go well below;
- oil by fine filters that capture aerosols, then activated carbon for vapours and odours.
Our guide to ISO 8573-1 air quality gives the class tables.
The starting point, at the compressor outlet
A lubricated compressor leaves traces of oil in the air. According to their data sheets, the outlet content is 3 ppm at most on the K series and 3 to 5 ppm on the standalone S series compressors. That is not air ready for food contact: it is the base on which the treatment is built. The dryer and filtration built into the K series form the first stage; the filters at the point of use do the rest.
Sizing the treatment at the point of use
Example, a biscuit line with one blowing station in contact with the product (indicative values, to be replaced with those on your data sheets):
- Station flow: 4 nozzles at 100 L/min, or 400 L/min.
- Margin: 400 × 1.25 = 500 L/min. The station's filters are chosen for at least this flow, at network pressure. An undersized filter drops the pressure at the nozzle and saturates faster.
- Rest of the line: cylinders, bagger and valves, 500 L/min, handled by the dryer and general filtration.
- Compressor total: 400 + 500 = 900 L/min, or 1,125 L/min with the margin. The K 110 delivers 1.7 m³/min at 8 bar and leaves room for a second line.
For a larger site, the standalone S 110 fits into a network with a dryer, receiver and filters chosen for your classes.
How to define your class with us
- List the points of direct contact, then those in contact with packaging.
- Ask each machine manufacturer for the class it requires.
- Check what your HACCP plan and your customers require.
- Send us this list: our technicians define with you the class for each station and the treatment that achieves it.
- Have the air measured or checked at the point of use if your quality system requires it.
What makes you lose the class
A saturated filter. A filter element past its replacement date no longer protects. Replace it according to its manufacturer's instructions, without waiting for it to clog.
The network itself. Old steel pipework releases rust downstream of the dryer. Point-of-use filters therefore go as close to the nozzle as possible, after the network.
The intake air. The compressor draws in the air of its room. A clean, dry room away from flour and washdown keeps filters effective for longer: our article on the compressor room covers the installation.
Condensate. It contains oil: collect it and have it treated.
For a brewery, the approach is the same and we have detailed it in our article on compressed air in breweries. For your site, send us the list of your points of use with a quote request.
For your trade: Compressor for the food industry.