Clearing the air – why better air quality doesn’t mean ditching oil-based compressors
Different applications require compressed air of differing qualities. Whilst the air flow and pressure requirements for an application can be easily identified, ensuring that you are specifying the correct air quality can be a bit trickier.
Air quality is measured via a classification system. The purity classes range from the cleanest, least contaminated class 0, to the most impure, class 9. It is important to understand that class 0 air still has a level of impurity, albeit a fraction of the higher classes and at this level the acceptable purity levels must be agreed between the user and the original equipment manufacturer. In essence however Class 0 means purer air than Class 1, but it does not mean zero contamination.
Here are the top three common misconceptions around air quality that our engineers come across on a regular basis.
Myth number 1: I need an oil-free compressor to produced oil-free compressed air.
Fact: a certain level of oil droplets exists in the atmosphere around us, from car exhausts and industrial processes for example, which means that when a volume of air is taken into your compressor and compressed it will contain a certain level of oil even if it is an oil-free compressor.
The only way to produce oil free air is to fit the correct filter for your air quality requirements to your compressor – whether it is an oil-lubricated compressor or not. By using the correct filtration for your needs, your oil-lubricated compressor will achieve the air quality standards that you require.
Myth number 2: Air purity is just a measure of oil in the air
Fact: air purity isn’t only affected by oil contamination, but also particulates, water, dust and debris. Man-made particulate matter mainly comes from industry, diesel and petrol engines, friction from brakes and tyres, and dust from road surfaces. There are also natural sources of particulate matter, such as pollen, soil and sea spray. All of these, including oil, are circulating in the atmosphere and can find their way into the air taken into your compressor. The result is an increase in the concentration of airborne particles in the compressed air stream. It is important to remove these contaminants from the compressed air to the level required by each application.
Myth number 3: If I use an oil free compressor the air will always be pure.
Fact: Many oil-free compressors have a lower ‘duty cycle’ than their oil-lubricated counterparts, in other words they are not able to operate 100% of the time. Instead they need periods of rest in each cycle of use to cool down. For example, many oil-free compressors have a 25% or 50% duty cycle. Using a compressor beyond its intended duty cycle risks damage and the eventual failure of the machine. Damage to an oil-free compressor can lead to weakened seals that could lead to contamination of the compressed air stream and therefore lower air purity levels.