KEVOS® MAKEOS · Pneumatics
Compressed-Air Main Sizing (Bore, Pressure Drop, Velocity, Receiver)
What is the smallest standard pipe bore for this compressed-air main within my pressure-drop and velocity limits, and how big a receiver covers the peak demand?
Sizing of a compressed-air main: velocity, Reynolds number, friction factor and pressure drop for a bore (as the compressed-air pipe drop tool), the smallest standard bore that keeps both the drop and the velocity within your limits (searched through common nominal bores), the check of the bore you chose, and the receiver volume to cover a peak demand above the compressor output over a pressure band (as the air receiver tool).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Flow (free air) | m³/min | Flow of free air the main carries at peak. |
| Line pressure | bar | Gauge pressure in the main. |
| Air temperature | °C | Air temperature in the main. |
| Equivalent length (pipe plus fittings) | m | Pipe length plus the equivalent length of bends, tees and valves. |
| Pipe roughness | mm | Absolute roughness of the pipe bore. |
| Bore chosen | mm | Inside diameter of the pipe you intend to use. |
| Largest pressure drop | % of line pressure | Largest pressure drop you allow along this main (often 1–5% of line pressure). |
| Largest air velocity | m/s | Largest air velocity you allow in the main (about 6–10 m/s for mains). |
| Receiver | ||
| Peak demand above compressor output (free air) | m³/min | How far the peak demand exceeds compressor output. |
| Duration of the peak | min | How long the peak lasts. |
| Pressure when the peak starts | bar | Receiver pressure when the peak begins. |
| Least pressure allowed | bar | Least pressure the users can accept. |
Method and formulas
- Actual flow and density from free air at line pressure and temperature; Re and Colebrook friction factor; Δp = f (L ÷ d) ρ v² ÷ 2 (as the compressed-air pipe drop tool).
- Search the common bores 15, 20, 25, 32, 40, 50, 65, 80, 100, 125, 150, 200, 250 and 300 mm for the first that meets both limits.
- Receiver V = t × deficit × p_atm ÷ (p₁ − p₂) (as the air receiver tool).
- Example: 5 m³/min in 50 mm runs at 5.4581 m/s with 0.05902 bar drop; the smallest bore that passes is 50 mm; the receiver needs 1.351 m³.
Limitations
- Equivalent length must include fittings; long branch lines need their own check.
- Steady flow; compressor control band and dryer drops are not included.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a new compressed-air ring main or header
- Check an existing line after adding machines
- Size a receiver for a peak demand
Who it is for
- Plant engineers
- Maintenance engineers
- Energy managers
What you get
- Velocity and pressure drop in the chosen bore
- Smallest standard bore that meets the limits
- Receiver volume for the peak
Interpreting the result
- A ring main halves the flow path and lets a smaller bore meet the same drop.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 3036–3041, 3024–3027. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Compressed-Air Main Sizing (Bore, Pressure Drop, Velocity, Receiver) calculator
