Hidroteknik Calculators
Pneumatic Cylinder Air Consumption Calculation
A pneumatic cylinder's air consumption depends on the piston volume, the working pressure (compression ratio) and the cycle rate. The result is given in normal (free) litres.
⚙ Open the Hydraulic Calculator →Formula
Compression ratio
P: working pressure (bar, gauge)
Flow (extend + retract)
A: piston area, s: stroke, n: cycles/min → free air (Nl/min)
Units
| Quantity | Symbol | Unit |
|---|---|---|
| Bore | D | mm |
| Stroke | s | mm |
| Pressure | P | bar (gauge) |
| Cycles | n | 1/min |
| Flow | Q | Nl/min |
Worked Example
Given: Bore D = 50 mm, stroke s = 200 mm, pressure P = 6 bar, cycles n = 30 /min.
1) Piston area: A = π × 50² / 4 = 1963 mm² = 19.63 cm²
2) Compression ratio: r = (6 + 1.013) / 1.013 = 6.92
3) Free air per stroke: 19.63 × 20 × 6.92 / 1000 = 2.72 Nl
4) Flow (extend+retract × cycles): 2 × 2.72 × 30 = ≈ 163 Nl/min
Frequently Asked Questions
What does free air (Nl) mean?
Normal litres; the volume of air at atmospheric pressure (1.013 bar). Compressor capacity is compared in the same unit.
What is the compression ratio?
How many times the air at working pressure is compressed relative to atmosphere: r = (P+1.013)/1.013. For 6 bar it is ≈ 6.9.
Is the rod volume ignored?
In practical calculations it is usually ignored; for precise work the rod cross-section is subtracted on the retract stroke.