Valves for Compressed Air Service
Compressed air is the most widely used utility in industrial plants — powering pneumatic actuators, instruments, tools, conveying systems, and process air injection. Though non-toxic and non-flammable, compressed air requires careful valve selection for moisture content, oil contamination, and pressure class.
Pressure Range
5–10 bar (instrument/plant air); up to 40 bar (high-pressure air)
Temperature
Ambient to 60°C (post-cooler discharge)
Industries
All industrial plants (utility), Pneumatic instrument systems, Pharmaceutical cleanrooms
Key Properties — Compressed Air
- Operating pressure: 5–10 bar for instrument air; up to 40 bar for high-pressure air
- Always contains some moisture — risk of corrosion and hydrate formation below dew point
- Instrument air: oil-free, dry (dew point ≤−40°C); plant air: may contain condensate
- Non-flammable at ambient oxygen concentration
- High flow velocity in small lines — velocity noise and erosion risk
Material Compatibility — Compressed Air
Ratings are indicative. Actual compatibility depends on concentration, temperature, velocity, and presence of contaminants. Always consult corrosion tables or a materials engineer.
| Material | Rating | Notes |
|---|---|---|
| Carbon Steel (WCB/A105) | Good | Suitable for dry compressed air. Corrodes in wet air — use coated internals for humid service. |
| SS 316 | Excellent | Ideal for instrument air and pharmaceutical compressed air. |
| Ductile Iron / Cast Iron | Good | Standard for general plant air at PN 10/16. |
| Brass / Bronze | Excellent | Traditional material for compressed air fittings and small-bore valves. |
| Aluminium | Good | Used in lightweight instrument air fittings; avoid in wet air with chlorides. |
Recommended Valves
Ball Valve (full-bore, SS or brass body)
Low pressure drop, fast operation, suitable for all air pressures and instrument air.
Butterfly Valve (wafer, DI or aluminium)
Large-bore plant air distribution headers — low cost, compact.
Needle Valve (SS 316)
Instrument air isolation on control valve positioners and pressure transmitters.
Solenoid Valve (3/2 or 5/2 way)
Directional control for pneumatic actuator supply and exhaust.
Valves to Avoid
Cast iron valves in instrument air service (risk of internal corrosion contaminating air supply)
Large-bore butterfly valves in pulsating or compressor discharge service without surge analysis
Plastic-bodied valves above 10 bar or in environments where UV degradation is a risk
Special Considerations
Applicable Standards
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