With any air dryer, the removal of liquid condensates before the inlet to the dryer is vital. With refrigeration dryers, liquids entering the dryer impose an extra heat load on the dryer’s refrigeration system. This wastes energy, as the freon system is designed to condense water vapour into a liquid. If we allow liquid condensates into the dryer at its inlet, the system is now working to condense water vapour into a liquid, and also cooling down actual liquid water to a temperature of 3°C.
This creates a problem in the main air-to-freon exchanger, and also in the condensate drain system. They are being forced to handle more actual liquid content than the dryer and its drain were designed for. This can lead to liquids being entrained in the air flow and pushed into the compressed air system. This automatically leads to a higher dewpoint, resulting in wet compressed air in the plant’s distribution system.
What is an aftercooler?
An air compressor’s aftercooler is the integral first stage in the air treatment system. It is essentially a radiator with hot compressed air inside the tube stack. This has a fan to push colder atmospheric air over the radiator to cool the hot compressed air in the radiator. This cooling process can condense up to 70% of the water vapour that is pulled in by the air compressor from atmosphere, and compress it to 7 bar for your factory. The aftercooler is supposed to eject this condensed liquid to waste via an attached water separator and autodrain system.
This partially dried air leaving the aftercooler can be now allowed to enter the prefilter and air dryer for further treatment. If the aftercooler is not fitted, or a water separator is missing (or not supplied by the OEM) or the drain has malfunctioned, there will be a liquid water overload in the air dryer, leading to wet compressed air.
Inline air filters are not designed for bulk liquid removal; they are installed to coalesce compressor oils and trap airborne particles and debris. Poor piping installations can also add to bulk liquid contamination. The correct layout is shown below. Inlet and outlets, valves and filters should be located at the highest points.
Compressor aftercooler and filter drains must be function checked daily. The installation of a low-cost dewpoint monitor S305 from Artic’s Suto iTEC range is a good protection against compressed air system contamination. A high dewpoint alarm tells operators that a fault on a drain valve, a failure, or a trip condition of a dryer has occurred.
The same issues of bulk water contamination, aftercooler, and piping issues can also be applied to heatless twin tower chemical air dryers.
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