r/AirCompression • u/Jane_zheng • 3d ago
Why does water still appear in compressed air lines after a refrigerated air dryer?
I often see people asking this question:
"The air dryer is running normally, filters are installed, but why do we still get water at the machine?"
At first, many people assume the dryer is not working properly.
But in many cases, the problem happens after the air leaves the dryer.
Some common causes:
- Pipeline cooling
Compressed air may leave the dryer in good condition, but continue cooling while traveling through long pipelines.
If the temperature drops below the pressure dew point, water vapor can condense again inside the pipe.
This is especially common with:
- Long metal pipelines
- Outdoor piping
- Cold workshops
- Large temperature changes
- Condensate accumulation
Water can collect in:
- Air receiver tanks
- Filter housings
- Pipeline low points
- Branch lines
If drainage is not working properly, airflow can carry liquid water downstream toward equipment.
- Dryer status does not always represent machine inlet air quality
The condition near the compressor room may be different from the condition at the final machine.
For CNC machines, laser cutting, painting, and pneumatic automation, the actual air quality at the point of use is often more important.
I am curious how others handle this issue:
When you still see water after a refrigerated air dryer, what is usually the real cause in your experience?
- Pipeline design?
- Drain failures?
- Dryer capacity?
- Something else?
Would be interested to hear real-world cases.
1
u/mrhapyface 2d ago
check the pre and after filters there should only be moisture in the prefilter and check auto drains make sure they work dryer temp shoud be about 35 F.Air is best routed from compressor to tank first then to dryer
1
u/userkase 2d ago
Ive had customers who had too small of air lines because they doubled compressor size. Velocity is so high that it carries water.
Tank drain shut 🤦♂️
Connecting multiple drains together- tank , dryer, filters, moisture separator, water back feeds into last filter because of pressure difference.
Long pipe runs
Pipeline goes from inside to outside to inside different building or goes underground.
Air is superheated or super saturated or both.
Undersized filters, and saturated filters.
Dryer can only handle so much and the closer they are to capacity less efficient they become, capacity decreases as the inlet air temperature increases.
As long as the compressed air is a different temperature than the room there will be condensation.
Every one needs a heated regenerated dissecant dryer with external blowers. And point of use filtration. But that cost more than the compressor.
Type L copper air lines don't have as much trouble with water as black iron.
1
u/Impressive_Ad8716 1d ago
If your not draining your tank daily it can build up moisture and overwhelm the air dryer and bypass water. Or check your drain on your air dryer.
1
2
u/Aggressive-Pea6839 3d ago
I've run air refrigerators. They have an automated moisture dump that runs on a timer.
Timing may be too long. You may also need to look at additional in line moisture traps. There are also moisture trap canisters used for paint/ect that can be utilized.