The Air around us
Moisture, dust, and even small droplets of oil are constantly present in the air. They can be found in greater quantities at certain times of the year or even at certain times of the day, like during a humid summer or a misty morning.
You might wonder why it’s important to have good quality air for your air compressor if there’s always moisture and oil in the air. The reason is that the more of these airborne particles in the air, the faster various parts of your system will deteriorate. Additionally, they can potentially impact the quality of the product you’re producing.
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How clean does your compressed air need to be?
The cleanliness or the quality of your compressed air depends on several factors.
1. What you will be using the compressed air for.
2. Whether the product you produce will come into direct contact with the compressed air.
3. The environment in which the compressed air will be used.
There are also other highly scientific factors that you may not have heard of or understand. Fortunately, experts have developed the International Standard ISO 85731: Compressed air for general use. This standard specifies the cleanliness requirements for compressed air based on its intended use.
Quality class | Solid particle content | Water content | Oil content | ||
Max. size mu | Max. amount mg/m³ | Dew point °C | Amount g/m³ | Max. amount mg/m³ | |
1 | 0.1 | 0.1 | -70 | 0.003 | 0.01 |
2 | 1 | 1 | -40 | 0.11 | 0.1 |
3 | 5 | 5 | -20 | 0.88 | 1.0 |
4 | 40 | 10 | +3 | 6.0 | 5 |
5 | – | – | +7 | 7.8 | 25 |
6 | – | – | +10 | 9.4 | – |
Compressed Air: Filters
According to ISO 8573-1, it’s essential to ensure that your compressed air contains only contaminants below a certain size. Thankfully, many experts in white lab coats with clipboards have developed various filters to remove contaminants of different sizes from compressed air. Let’s quickly review how these filters function.
Firstly, no single filter can efficiently remove all particles of every size and type. It’s advisable to use a series of different filters, each designed to eliminate contaminants of varying sizes. Inlet filters are used to catch various sized particles before they enter the compressor’s inner mechanisms. Air dryers are employed to eliminate water vapor and condensation generated during the compression process. A specialized filter, known as a coalescing filter, prevents oil and water vapor from proceeding further into your system. This filter works by allowing small droplets to merge into larger ones, which gravity then directs to a separate area of your system. While this may seem simple, factors such as particle size, air velocity, and the distribution of fibers of varying diameters play a role in removing different contaminants. Hence, multiple filters are necessary.
Why not opt for a single filter that captures the smallest particles and, by default, the larger ones? Such a filter would become clogged quickly, leading to more frequent replacements than actual usage.
It’s crucial to understand that compressed air experiences a drop in pressure with each filter it passes through. The finer the filter’s mesh, the tighter its structure, and the quicker it will clog, necessitating replacement and causing a significant pressure drop. This is the reason why some systems compress air multiple times. Contaminants are removed at various stages, with the air being recompressed repeatedly, ensuring that it exits your system clean and at the desired pressure.
Compressed air: Oil filters
In an oil-injected air compressor, there is typically an oil separator to remove most of the oil from the compressed air. However, to capture extremely small traces of oil, there is an additional filter containing activated carbon, which helps to remove any remaining oil.
Compressed air: Air dryers and adsorption dryers
Please keep the following information in mind:
To remove water vapor, it is recommended to use an air dryer in almost all circumstances. This is because water vapor, condensation, and moisture will inevitably lead to:
Extra maintenance, leading to additional downtime
Corrosion and rust in your boiler and pipes
Moisture contaminating and washing out the oils and lubricants in your pneumatic tools and cylinders
Clumping of blasting materials such as sand, making them less effective
A foggy result when spraying surfaces with compressed air.
A refrigeration air dryer will effectively remove moisture and deliver air quality of Class 4 or higher, with a dew point of 3°C or warmer. If you need compressed air that is Class 3 or lower, an adsorption dryer will be required. This utilizes a different approach, using material to adsorb moisture and achieve the desired results.
To enhance reliability and reduce the environmental impact of this technology, consider using our Combination. This dryer offers variable speed settings, which help reduce costs and improve sustainability, among other benefits.
The right air compressor system
Are you wondering if you need to spend a lot of money on a system to remove trace amounts of oil? The answer depends on whether your product comes into direct contact with compressed air or whether oil vapor will contaminate your working environment. You may need a systematic method to determine your ideal equipment choice.
Using Class 0 compressed air is best to eliminate air contamination in critical processes. Your filters will need to be sized to handle the air flow properly and have a larger capacity to prevent excessive pressure drop when blockages occur. However, if you don’t need Class 0 compressed air, it’s easier to use a less complex system. You may still need different types of filters or additions to your system to achieve the air quality you need, but this should be possible with less stress and at a lower cost.
Ready to start your journey into the world of filters? Instead of getting lost on the internet and in the world of cutting-edge research, consider reaching out to us at Compressed Air Systems UK. We have extensive knowledge on everything from filters to air compressor choices. We would be more than happy to provide targeted advice, insights, and recommendations. Get in touch today.
Food industry: Where clean air is critical
Are you within the food industry sector and need avice?
Please see the attached document which is written by the British Compressed Air Society, and is specific to food industry, and the air quality requirements. The attached is a guideline only, but it makes recommendations for the correct air quality classification to be applied for the type of manufacturing taking place, and in turn what equipment would need to be installed to pass said classification.
BPG 102-1 Food Beverage grade compressed air LR (1)
In effect there are three levels of contact between compressed air & product / packaging, these are:-
Direct contact
In-Direct Contact (as in packaging)
Non-contact
You would need to undertake a risk assessment to understand what parts of their process fall into the above categories. If you kindly pay attention to page number 4-13 of the attached, it will confirm the reasons for either the adsorption dryer or the refrigerated air dryers, and in what contact category we can apply each drying technology.
Once you have carried out a risk assesment, we will be able to confirm the correct air dryers for your equipment.
Our Mikropor range is not only a dryer, but an air treatment package that delivers an air quality of class 1.4.1 as per ISO 8573:2010 due to integrated filtration as standard.
Our Omega Adsorption Range dryer rating according to ISO8573-1.
Questions to keep in mind when you are sizing the dryer for your needs:
What is the desired dew point (how dry compressed air needs to be – this will determine whether it is a refrigerated or desiccant style dryer)?
• How much CFM will your compressor be sending through the dryer, and at what pressure?
• What are the ambient conditions of the dryer (ambient temperature, elevation, etc.)?
• What is the inlet temperature of the air going into the dryer?
Answering these few questions will give you a good start on selecting the right dryer technology and the appropriate size for your compressor. Remember, a desiccant dryer consumes 2% -20% of your CFM as purge air during the regeneration cycle of the vessels. With that in mind, you will need to make sure you make the necessary arrangements. If it is a new install, the compressor will need to be sized appropriately to compensate for the CFM loss during the purge cycle. If it is an existing install, you may have to upgrade the compressor. Ambient conditions and correction factors also come into play.
Why is it important to know the size of my dryer needs?
When sizing an air dryer that keeps up with your application needs; it is important to get the right fit. A dryer that is too large will cause harmful wear and tear long before normal, opposed to having an undersized dryer can lead to poor air quality downstream.
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