For a bagging or packaging machine, start from the consumption per cycle given by the manufacturer, in NL per cycle, multiplied by the machine speed. Then add what runs continuously: vacuum generators and blow-off nozzles. In the example below, a bagger at 40 bags per minute and its case sealer need about 630 L/min including margin, which means a 7.5 kW screw compressor.
For a whole packaging site, see our page on the compressor for printing and packaging.
What uses air on a bagging line
- Cylinders for the sealing jaws, the knife, the bag clamps and the dosing gates.
- Venturi vacuum generators, which hold bags or cases on suction cups. They use compressed air for as long as they are sucking.
- Blow-off to open the bag and for cleaning.
- At the end of the line: case sealer, pneumatic strapping and wrapping tools, palletiser.
Vacuum generators and nozzles are often the largest consumers, well ahead of the cylinders.
The calculation, step by step
Step 1, the machine. The data sheet often gives a consumption in NL per cycle: litres of air at normal conditions, equivalent to the free air drawn in by the compressor. Multiply by the machine speed.
Step 2, continuous consumers. The vacuum generator manufacturer states its air consumption at the supply pressure. A nozzle left open uses around 150 L/min, as an indication.
Step 3, downstream cylinders. They are calculated per cycle, as explained in our article on pneumatic cylinder air consumption: a 50 mm cylinder with a 300 mm stroke, at 6 bar and 8 cycles per minute, uses about 61 L/min.
Indicative example, values marked "assumption" to be replaced with those on your sheets:
| Item | Calculation | Consumption |
|---|---|---|
| Vertical bagger (assumption 1.5 NL per cycle) | 1.5 × 40 cycles/min | 60 L/min |
| 2 vacuum generators (assumption 50 L/min each) | 2 × 50 | 100 L/min |
| Opening and cleaning nozzle | 1 × 150 | 150 L/min |
| Case sealer, 2 cylinders 50 mm | 2 × 61 | 122 L/min |
| Blow gun, counted at 50% | 150 × 0.5 | 75 L/min |
| Total | 507 L/min |
With a 25% margin: 507 × 1.25 = about 630 L/min. The S 55, at 0.6 m³/min, would be too tight. You need to move up to 7.5 kW.
If your sheets give m³/h, our flow and pressure converter turns them into L/min.
Which compressor for which line?
- One line, no dryer in place: the K 75. 1.1 m³/min at 8 bar, 420 L receiver, built-in refrigerated dryer and filtration.
- One line, receiver and dryer already installed: the S 75. The same flow, as a standalone compressor.
- Two or three lines with strapping and wrapping: the K 150. 2.2 m³/min at 8 bar.
Traps with packaging machines
- Venturis sucking for nothing. A vacuum generator fed permanently uses air even when no suction cup is working. Have the machine control it, so it only runs while picking the bag or case.
- Pressure set too high. Vacuum generators and nozzles have an optimum supply pressure, given by their manufacturer. Above it, they use more air without working better. A regulator at each station solves this.
- Speed peaks. Several cylinders moving together create peaks. A receiver near the line absorbs them: our air receiver size calculator gives an order of magnitude.
- Water and oil. Water wears cylinder seals and makes solenoid valves stick. Our compressors are lubricated: where air touches food packaging, add fine filters and define the air quality class with our technicians, as on our page on the compressor for the food industry.
- Leaks. A packaging line has dozens of fittings. Check them with the line stopped: see detecting and repairing leaks.
Send us your machines' data sheets with a quote request, or enter your equipment in the configurator.
For your trade: Compressor for printing and packaging.