Moisture in Gas Systems — Preventing Condensation, Corrosion, and Instrument Damage
Water in any form — liquid, aerosol, or vapour — is the most common contaminant in compressed air and process gas systems. Left unmanaged, it corrodes pipework, damages instruments, and ruins products.
Recognise the Symptoms
- Visible water droplets at point-of-use outlets or drain valves
- Internal corrosion of pipework, valves, or pneumatic equipment
- Erratic behaviour of pneumatic actuators or control valves
- Moisture-related product quality issues (packaging, coating, plastics)
- Instrument drift or failure due to condensation on sensors
- Freezing of air lines or regulators in cold environments
Root Causes
Inadequate drying capacity
the compressed air dryer is undersized, bypassed, or malfunctioning, allowing moisture to pass through
Pressure dew point too high
the dryer achieves a dew point that is above the minimum temperature the air will encounter in the distribution system, causing condensation
No point-of-use filtration
even with a central dryer, temperature drops in long pipework runs or exposed outdoor sections can cause localised condensation
Aftercooler not draining
the aftercooler condenses bulk water from hot compressor discharge air, but if drain traps fail, liquid water enters the system
Process gas moisture content
natural gas, biogas, and other process gases contain water vapour that must be removed before instrumentation or catalytic processes
Diagnostic Checklist
- 1What is the pressure dew point at the dryer outlet? Measure, do not assume.
- 2What is the lowest ambient temperature the pipework is exposed to?
- 3Are drain traps on aftercoolers, receivers, and filter housings functioning?
- 4Is there point-of-use filtration at critical applications?
- 5For instrument gas: does the application require ISO 8573-1 Class 1–3 moisture levels?
- 6Has the dryer capacity been verified against actual air demand?
Further Reading
Related Problems
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