A dry compressed air system is crucial to allow an air compressor to work effectively – but the mechanics of these deceptively simple devices can sometimes seem complex!
Air drying functions vary between different compressors and different applications. They could be:
- Refrigerant dryers
- Over compression dryers
- Absorption/adsorption drying
Given the fundamental value of dry air to any compressor, we thought it would be worth clarifying why this is so essential and what a dry compressed air system does with that resource.
How Much Water is in a Dry Compressed Air System?
Air, as an asset, is abundant, and one of the reasons a compressor is often the most cost-effective method for a vast range of manufacturing techniques.
All atmospheric air contains at least a little water, although often a minimal amount of water vapour that we wouldn’t feel on our skin.
By compressing those molecules, a dry compressed air system will naturally force the water vapour from the air – which means that the system is exposed to dampness.
Therefore, wet air must be treated and dried to avoid causing problems, hence the range of drying solutions we’ve mentioned above.
How Does a Dry Compressed Air System Work?
So, the issue with compressed air is that the compression process itself impacts the concentration of water.
The technical term for the water content in compressed air is the ‘pressure dew point’, which you might know as PDP.
PDP means the temperature when the water vapour will condense, depending on the pressure it is working under. If there is a low PDP, there is a small amount of moisture in the compressed air.
The pressure forces the water from the air. This action can create an excess of fluid in a concise space of time, depending on the environment’s humidity. Water can cause no end of issues for compressors, such as:
- Water ingress in the pipes.
- Leakages to other components.
It’s therefore of utmost importance that air is dried before it is compressed.
PDPs vary between dryers, and it can be a technical challenge since you can’t simply filter the air to reduce the moisture levels since the more it is cooled, the more condensation appears.
Why Should You Dry Compressed Air Systems?
We’re no strangers to the perils of water – from flooding to damp, mould to rot, it can be a pest in many different ways.
In the world of air compression, moisture can cause similarly detrimental outcomes:
- Moisture increases rust and speeds up the wearing down of moving parts due to lubrication being washed away.
- Water can damage paint applications, affecting the colour, adhesive levels and finish when applied with an air compression spraying system.
- In process industries, many processes rely on pneumatic controls, which can rust, scale, become clogged and malfunction if vapour exists.
- Moisture can freeze in cold weather, causing faults in control lines during the winter.
- Vapour is also responsible for corrosion in instruments powered by air or gas. It can cause false readings and even shut down the plant.
As we can see, water in a dry compressed air system is no small problem and can cause disastrous outcomes in repair costs, lost productivity, and downtime.
What Happens to the Condensed Water After Drying?
Of course, once you have removed all water from your dry compressed air system, you’re going to need to dispose of that water responsibly.
Most air compressors use oil-injected functions and lubrication, so it’s crucial never to dispose of the condensate without proper management. There will be small oil particles in the water, which can’t be seen but can damage the environment.
Condensation from a dry compressed air system is produced through waste condensate drains. These usually run out of the back of your compressor and dryer.
Commercial waste disposal laws dictate that you should:
- Dispose of this contaminated water through a foul drain.
- Install an oil and water separator.
Businesses can be fined for irresponsible waste disposal, including water contaminated with oil.
What is the Right Dry Compressed Air System Dryer?
As with compressors, there are lots of choices of air dryer, so to select the optimal equipment, you’ll need to think about:
- How the compressed air is used. Moisture tolerance levels can vary substantially between applications.
- Your required PDP. That means assessing at what temperatures your equipment will work and the average ambient temperature.
- How long the air remains dry. It’s often insufficient to dry the air for one application and assume it will remain moisture-free. There is always some level of vapour present, even at microscopic levels, and so you’ll need a dryer that can keep pace with your operations.
Any dry compressed air system requires moisture removal to run at its most effective. The best-case scenario is that un-dried air will cause the functions to run slower.
The worst-case scenario is severe damage to materials, equipment and compressors.