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# Compressed Air - Water Content

## Saturation pressure and maximum water content in compressed air.

The maximum content of water in air at saturated conditions decrease with pressure and increase with temperature as indicated in the diagrams below.

### Pressure in bar (gauge)

For full table with Pipe and Water Weight - rotate the screen!

Compressed Air - Water Content
Temperature
(oC)
Mass of Water in Air (kg H2O /m3 free saturated air)
Pressure (bar gauge)
02468101214
0 0.0045 0.0015 0.00091 0.00065 0.00051 0.00041 0.00035 0.00030
20 0.018 0.0058 0.0035 0.0025 0.0019 0.0016 0.0013 0.0012
40 0.059 0.019 0.011 0.0079 0.0062 0.0050 0.0043 0.0037
60 0.18 0.053 0.031 0.022 0.017 0.014 0.012 0.010
80 0.65 0.14 0.078 0.054 0.041 0.034 0.028 0.024
100 0.38 0.19 0.13 0.094 0.076 0.063 0.054
120 0.49 0.29 0.21 0.16 0.13 0.11
• 1 (kg/m3 ) = 0.0624 (lb/ft3 )

### Example - Water Extracted from an Air Compressor

Free air enters a compressor at atmospheric conditions 20 oC and 70% humidity ratio . The air leaves saturated at gauge pressure 8 bar and 40 oC .

Based on the diagram and table above the water content in saturated air entering the compressor can be estimated to be approximately 1.8 10-2 kg per m3 free air (0.018 kg water /m3 air ) .

The amount of water with 70% saturation can be calculated as

( 0.018 kg water /m3 air ) (70%) / (100%)

= 0.0126 (kg water /m3 air )

The water content in the 100% saturated air leaving the compressor can be estimated from above to be approximately 0.62 10-2 kg per m3 free air (0.0062 kg water /m3 air ) .

The water extracted in the compressor can be calculated as

( 0.0126 kg water /m3 air ) - ( 0.0062 kg water /m3 air )

= 0.0064 ( kg water /m3 air )

## Related Topics

• ### Air Psychrometrics

Moist and humid air calculations. Psychrometric charts and Mollier diagrams. Air-condition systems temperatures, absolute and relative humidities and moisture content in air.
• ### Gases and Compressed Air

Properties of air, LNG, LPG and other common gases. Pipeline capacities and sizing of relief valves.

## Related Documents

• ### Air - Maximum Moisture Carrying Capacity

Maximum water content in humid air vs. temperature.
• ### Moist Air - Degree of Saturation

Humidity ratio of moist air to humidity ratio of saturated moist air.
• ### Moisture Content Calculation

Calculate the moisture content in products like wood on wet and dry basis.
• ### Rating of Air Compressors and Air Equipment

Common rating terms for air flow capacity are ICFM, FAD, ANR, SCFM or nl/min.

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## Citation

• The Engineering ToolBox (2008). Compressed Air - Water Content. [online] Available at: https://www.engineeringtoolbox.com/water-content-compressed-air-d_1275.html [Accessed Day Month Year].

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8.21.8

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