It’s a box that contains heat exchangers. a Freon cooling system and often a pair externally mounted filters before and after the air dryer.

The air dryers’ function in life is to reduce the incoming warm wet air temperature to a temperature of 3 °C. At 3 °C the water and oils will turn from a gas/vapour into a condensed liquid. Liquids can be trapped and ejected into a wastewater treatment system, when water and oils are vapour from (hot) they cannot be trapped and ejected.

The water is entrained from the atmosphere at the intake of the compressor itself. Oils are carried out into the airline from the air compressor.

This liquid waste is drained out of the dryer automatically by timed or level-controlled condensate drains. An oily waste condensate is very toxic to our river systems, please get a proper waste separation system that will allow you to eject clean water in the drains legally, and retains the oil waste for proper disposal.

Thermal overload is the #1 cause of dyer failure, what are the causes?

• Too much compressed air flowing through a dryer
• Ambient temperature too high, or lack of cooling air or water on the dryers’ condenser coil
• The inlet air temperature is too high
• A very low inlet air pressure

Look carefully at your potential suppliers’ brochure, it should show a number of tables that relate to the variables above and it will show you how to de-rate a dryer for our hot African climates.

If the tables are note shown, request the tables from your dryer supplier! The chances of getting a dryer to work in Africa without de-rating the flow rates down from our cooler cousins’ catalogues in the Northern Hemisphere are next to zero on a hot summer’s day.

The hotter the workshop or compressor room is, the bigger and more expensive the dryer will be. The cooler environment, the smaller the dryer will be and the price will go down.

Failure to re-rate a dryer, especially in the hotter areas of our country will lead to hours of frustration and downtime. The dryer will trip and will not work or it will break components within the air dryer. That’s not why you wanted to buy a dryer, now was it? Dryers in RSA should be sized for 30 °C ambient and 40 °C inlet at 7 bar and 3 °C dew point as a Minimum.

The chart below shows Artic’s range of dryers flow capabilities at different site conditions.

This is just a sample, we offer much larger refrigeration air dryers with capacities much larger than the models shown.

• Repeated Freon high-pressure trip outs and/or venting of Freon gas through the safety valve, if fitted
• Freon compressor electric motor winding, failure
• Freon compressor internal thermal overloads continually cuts (activates and cuts out) the Freon compressor
• Freon compressor mechanical seizures caused by Freon compressor oil migration to other parts of the Freon circuit

There are three ways to establish air volume.

• Ask the compressor supplier for the FAD volume from your compressor at the working pressure that you plan to work at.
• Or, measure the flow with a thermal mass meter. This can be done, but you need to contact a specialist supplier for this, or perform a timed pump-up test on your air receiver! If you want to do this, call us for the formula!
• Estimate the air volume based on the kW’s fitted to the air compressor’s main motor.
• See the tables, which shows the amount of compressed air that is delivered from the two types of compressors based on the kW’s fitted. It is a general guide but will suffice for 95% of the applications.

Compressor Capacity Guide

Volumes are shown in m³/min, and are shown for guidance purposes only. Always try to confirm exact air volumes prior to installing the air dryer or filter systems.

Well on rare occasions maybe! But like most things in life, you get what you pay for. Buying lower-priced dryers may lead to problems later. It’s best to go to the established leaders in the compressed air treatment industry, they have superior knowledge and aftercare skills. Air treatment skills and aftercare knowledge, by the way, are not necessarily found in a compressor supply chain.

Strangely enough compressed air treatment companies will have more in-depth knowledge of compressor air treatment, than the guys in the compressor industry. It’s two different trades… Would you buy a smart new luxury car from your local caravan dealer?

Having upset a few friends and maybe some enemies for this somewhat humorous view of the air dryer selections, they may not wish me well.

The truth is that many companies get re-rate selections wrong, or fail to apply them and don’t understand the impact on refrigeration in the air drying process. The result of getting it wrong is huge, and when it’s wrong, it’s wrong, there is no magic trick to rectify an undersized air dryer or filter. You have to get it right the first time.

Well, actually, most people. The elements will periodically need changing, yes, it will cost money, but the improvement in compressed air quality is immense.

Filters remove the contamination generated by the compressor and rust debris released by old pipe systems. The pre-filter will remove oils and particles, draining liquids to waste and retaining particles from the incoming air from the compressor before the automatic drain inside the dryer is jammed with airborne rubbish.

A dryer with a jammed condensate drain is a water generator, not a water remover! The final filter will remove the final trace of oil and filter down to at least 0.01 micron and 0.01 mg/m³ of oil. If you have really great eyes, you can only see 40 microns at best. So this level of filtration is very fine. If necessary, for demanding applications, you can add an activated carbon filter to “remove” the final traces of oil vapours and smells. Activated carbon filters remove down to 0.003 mg/m³. Filters are also sized on airflow and pressure, again, read the sales literature and select the correct filter for your flow and pressure ratings.

Like compressed air dryers, inline compressed air filters should not be operated in parallel, if this is attempted, it leads to short element life cycles and rising maintenance expenditure.

It is impossible to direct equal airflow through two or more inline filters working in parallel.

The element with the lowest pressure drop will allow a priority airflow through it. This, in turn leads to premature element failure and anti-entertainment sock disintegration. Element failure means no filtration and polluted airlines. Sock failure leads to material being carried downstream into the air system or the dryer. There it will stop or slow the flow through dryer equipment and cause general lower system pressures!

Note, airflow is from inside the core to outside. This is a coalescing type filter.

This is a guide on how to install a refrigeration air dryer complete with its filters.

To have a common manifold feeding into two pre filters with two air dryers is not considered good practice. This will lead to a thermal overload of one of the air dryers. For Example, the filter casing with the least pressure drop (the one with the cleanest filter element) will let more air through them. Or, if the dryers are not the same brand and model, the internal air pressure drops may be different.

This means that one of the dryers will see a higher compressed air, which represents thermal load, than its partner and can easily get into a situation where the dryer’s dew point and mechanical stability are affected, in short, the dryer fails or trips out, and the compressed air gets wetter.

The Correct Way

The Wrong Way