What is Compressed Air?

What is compressed air? Why is pressure important? And what is air quality? Find the answers to your questions here.

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Estimated time to read: 7 minutes

March 14, 2023

You may compress air – or used compressed air – far more regularly than you realise. Ever blown up a balloon? Pumped up a bike tyre? Yep. Both involve compressed air. You might be wondering exactly what qualifies as compressed air. And what the best way to produce it is in an industrial or manufacturing situation. Strap yourself in. It’s time to take a deep dive into the world of compressed air.

Three important elements

We typically talk about compressed air as having three very important parameters:

1.    Pressure

2.    Volume

3.    Air quality

There’s a reason we talk about them. They’re the parameters you’ll need to know to decide which compressed-air technology you need for the job you’re doing. 

Compressed air: Pressure

Pressure is the force that acts on a specific area. We know how science-y this general definition sounds. Want to simplify things? You could look at pressure as being how hard your compressed air is pushing to escape the container, pipe or balloon it’s inside. In the case of atmospheric air, it’s how hard the air is pushing against the surface of the Earth. In other words? Pressure is just how hard compressed air is pushing against something.

The higher the pressure, the harder the air is pushing against the container, pipe, balloon or Earth. We usually measure pressure  in kilopascals (kPa) or megapascals (MPa):

  • 1 kPa = 1,000 Pa
  • 1 MPa = 1,000,000 Pa or 1,000 kPa

Compressed air: Quantity

For a system that uses compressed air to operate smoothly, it always needs to have access to a certain amount of compressed air. You’ll usually find this is given as a minimum flow rate. For example:

  • 25 m³/h
  • 250 l/s

The flow rate tells you how long a specific volume of air takes to flow past a set point. The volume is usually given in cubic metres (m³) or litres (l). The period of time is given in hours (h) or seconds (s).

Compressed air: Quality

Does air have quality? Yep. Compressed air too. When you talk about the quality of compressed air, you’re usually concerned about particles that are present in the air, such as dust, moisture or water vapour, and oil or oil vapour. They’re likely to be present in very low amounts – what we call trace amounts – but they can still be an issue. Why? It depends on what you’re using your compressed air for. The food, pharmaceutical and medical industries have very strict rules about the quality of compressed air. Even barely registerable amounts of moisture and oil vapour can be incredibly problematic. Of course, regulations are a lot more relaxed if you’re using compressed air to pump up a car tyre or for your leaf blower.

The regulation in question is international standard ISO 8573-1. It categorises compressed air into quality classes based on what the air is going to be used for. This lets you know which compressed-air treatment equipment will give you the right quality of compressed air for your project. 

At ALUP, you’ll find a complete range of compressors for every class of compressed-air quality, as well as different systems for reaching different pressures and different flow rates or quantities. What if you have a question or want to double-check you’ve made the right choice? Get in touch with us at ALUP. We are always happy to help.

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