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How to Install a Refrigeration Air Dryer

How to Install a Refrigeration Air Dryer

This is a guide of 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 thermal overload of one of the air dryers. For Example, the filters with the least pressure drop (the one with the cleanest filter element) will let more air through it. 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, this represents thermal load, than its partner and can easily get into a situation where the dryers dew point and mechanical stability is affected, in short, the dryer fails or trips out, and the compressed air gets wetter.

What is Thermal Load?

It’s the combination of:
* Air volume in m3 or in Cubic Feet per Minute
* The air pressure entering the dryer normally shown in Bar G or PSI
* The temperature of the compressed air entering the dryer
* The targeted dew point required to be achieved by the dryer

Dryers are designed to handle a defined thermal load, the heat exchanger, condenser and Freon compressor are a thermally matched set. They are designed to handle a published airflow at 7 bar gauge and 25 °C ambient air with a 35° air inlet to the dryer at a dew point of 3 °C. This is the European standard. Compressed air dryers manufactured in the East or America may have different design conditions.

The Causes of Thermal Overload

* Too much compressed air flowing through a dryer
* Ambient temperature too high, or a lack of cooling air or water on the dryers condenser coil
* The inlet air temperature too high

If Thermal Overload is ignored, the following problems will follow

* Repeated Freon high pressure trip outs and / or venting of Freon gas through 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

The Correct Installation of a Compressed Air Dryer

This schematic below is the correct way of installing the dryer.

All of these faults will lead to water downstream of the dryer, high dew point, which is not what you purchased an air dryer for!

Air Filter Installations

Like compressed air dryers, 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.

The element with the lowest pressure drop will lead to 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 dryers equipment and cause general lower system pressures!

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

Bypass Piping

ANy dryer should be installed with a bypass airline, this allows maintenance work to be carried out in normal working hours. If you are worried that an unskilled operator will open bypass, remove the handles or install a double block valve system as shown below. In this situation, the mini valve, normally a 1″ ball valve is left open (when the bypass is closed) to prove the bypass is not pressurised.

Bypass Systems are Essential, Air Dryers Should Not be Installed Without One!

Artic  Driers International (Pty) Ltd ®  © Sept 2019

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