If you use compressed air, there may be times when you noticed droplets of water in your air distribution system. Any sign of moisture is never a good sign. Moisture always leads to corrosion.
And corrosion means damage to parts of your machine or complete breakdown of the machine itself.
To prolong the lifespan of your equipment and save on repair and maintenance, you need a method of removing the moisture from compressed air. A compressed air dryer accomplishes this task.
Here are some useful information about compressed air dryers.
Water Everywhere
The formation of moisture is unavoidable. This is because water is present in all natural air. We see this every morning as dew on leaves and grass.
The creation of moisture becomes even easier when the air is compressed. Imagine the air as a piece of lemon. If you squeeze the lemon, the juice will drip out.
This analogy is admittedly simple but it demonstrates how compressing air produces moisture. In more technical terms, if the air is under increased pressure, the dew point will rise. The dew point is the temperature at which the air is saturated with water molecules.
Any temperature drop below the dew point will cause the water molecules to condense.
How “Drying” the Air Works
Most of the methods to dry compressed air involve manipulating the dew point. We want the dew point to be really low to make it hard for water vapor to condense. This is how most types of compressed air dryers work.
There are ways you can limit the moisture in your air distribution system before using air dryers. First, you need to drain the moisture from the tank regularly as part of your maintenance.
The next step is using an aftercooler. This works like a car radiator, cooling the air to condense the moisture. The moisture is then collected by a water trap. Most modern air compressors will have an aftercooler.
Other ways include using pressure regulators and coalescing filters.
Types of Compressed Air Dryers
There are many types of compressed air dryers. The most common ones are refrigerated dryers and desiccant dryers. Different types of dryers can achieve different dew point levels.
Refrigerated Dryer
The refrigerated dryer offers an affordable and effective method of drying compressed air. They come in two variants: non-cycling and cycling. Non-cycling refrigerated dryers are always on, regardless of the incoming air load. Cycling dryers allow the unit to turn on or off depending on the amount of incoming compressed air.
Refrigerated dryers work similarly to the aftercooler. They cool down the air to condense the water which is then trapped and removed. While the aftercooler can be either water-cooled or air-cooled, refrigerated dryers use refrigerants (Freon, Joule-Thompson) to achieve lower temperatures.
Refrigerated dryers can lower the dew point of the compressed air to 37-41 ºF (3-5 ºC) which is enough for most applications.
Desiccant Dryer
You know those desiccant packets you see inside a bag of chips or inside a medicine container? The desiccant dryer works just like those packets. They remove moisture by attracting the water to themselves.
Compressed air passes through a vessel filled with a desiccant material such as alumina or silica gel. The moisture is then adsorbed by the desiccant.
Desiccant dryers can achieve very low dew points (-40 ºF or -40 ºC). You’d want this dew point level for pneumatic equipment such as spray painters and print jobs.
Over time, the desiccant will become saturated with water and will need to be replaced. The usual lifetime of desiccants is one year.
The Compressed Air Dryer Is a Vital Cog
A compressed air dryer has an important role in keeping your equipment safe from the effects of moisture. The efficiency and overall performance of the manufacturing process can be improved by installing an air dryer.
For more information about air compressors, please visit our blog.