In a dairy or cheese plant, air demand comes mainly from the filling machine, the cheese presses and the pneumatic valves of the CIP system. A small dairy with one pot line usually needs around 800 to 1,100 L/min including a margin: a 7.5 or 11 kW 4-in-1 screw compressor covers it. The tricky part is not the flow, it is water: between washdowns and cold rooms, the air has to stay dry all the way to the point of use.
For the general rules on compressed air in food production, see our page on compressors for the food industry. Here we follow a dairy and its cheese room.
Where the air goes in a dairy
- CIP valves. Every butterfly or seat valve has a pneumatic actuator. There are many of them, but each one uses little air.
- Pneumatic cheese presses. Their cylinders build up pressure, then hold it during pressing.
- Mould turning and demoulding, by cylinders or by blow-off.
- The filling machine: forming or denesting pots, dosing, sealing, cutting. This is often the largest consumer.
- Blow guns for cleaning and maintenance.
Calculating the valves, step by step
A valve uses the volume of its actuator, filled at working pressure, every time it switches. As for a cylinder, count in absolute pressure.
- Actuator volume: on the valve data sheet. Example: 0.4 litre.
- Air per switch: 0.4 × (6 + 1) = 2.8 litres.
- Switches per minute, at the busiest point of the CIP cycle: for example, 30 switches across the whole installation.
- Consumption: 2.8 × 30 = 84 L/min.
Eighty valves therefore do not need a large compressor. Above all they need a leak-free network: with so many fittings, leaks soon weigh more than the valves themselves. Our article on compressed air leaks explains how to find them.
The calculation for the site
Indicative values, to be replaced with those on your data sheets:
| Station | Average consumption |
|---|---|
| Pot filling machine | 400 L/min |
| CIP valves | 85 L/min |
| Cheese presses | 60 L/min |
| Mould turning | 120 L/min |
| Two blow guns, intermittent | 150 L/min |
| Total | 815 L/min |
With a 25 % margin: 815 × 1.25 = about 1,020 L/min, at 8 bar.
Which compressor for which site?
- A cheese room with presses and a few valves, no filling machine: the K 75. 1.1 m³/min at 8 bar, with a 420 L receiver, refrigerated dryer and filtration.
- The dairy in the example: the K 110. 1.7 m³/min at 8 bar. The K 75 would do on paper, but with no headroom for a second filling machine.
- A two-shift site with several lines: the S 150, 2.2 m³/min at 8 bar, with receiver, dryer and filters sized to the flow.
Pitfalls of cold and humidity
A line running through a cold room or ripening room. A refrigerated dryer gives a dew point a few degrees above zero. If the pipework passes through a colder room, the remaining water condenses there and reaches the valves or nozzles. Route the line elsewhere, or fit a desiccant dryer on that branch.
Washdown. A dairy is washed with plenty of water, often with chlorinated or acid products. The compressor goes in a dry room away from washdown areas: our article on the compressor room sets out the rules.
Air in contact with the product. Blow-off demoulding, or air that touches the curd or the inside of the pots, calls for thorough treatment. Our compressors are lubricated: the ISO 8573-1 class for these stations is defined with our technicians, with fine filters as close as possible to the point of use. Our guide to ISO 8573-1 air quality explains how to read these classes.
Condensate. It contains oil. Do not send it into the washdown drains: collect it and have it treated.
Send us the list of your machines and valves with a quote request: we will size the compressor and the air treatment with you.
For your trade: Compressor for the food industry.