Single-phase
Farms and small shops. Limited kW. Often a piston or a small screw with a soft-start. If you are at the edge of the supply, say so before anyone quotes a 7.5 kW screw.
How to work out CFM and pressure
Add the air each tool actually uses, not the peak on the carton. Most shops run at 7–8 bar (about 100–116 psi) at the tool. If the pipework is undersized, you will chase pressure that a bigger compressor will not fix.
- List tools that run at the same time. Sum their free air (CFM or L/s).
- Add 25–30% for leaks and future tools unless you have just done a leak survey.
- Set working pressure at the furthest tool, then allow for drop in the pipe.
- Duty cycle: a piston unit that runs all shift is the wrong machine.
Three-phase
Workshop and plant. Rotary screw for continuous load. Reciprocating for burst demand (tyre bays, intermittent tools).
Types
Rotary screw
All-shift engineering and fab. Oil-injected as standard. Service intervals in running hours.
Reciprocating (piston)
Burst demand, smaller shops, home workshop. Cheaper to buy, harder on duty cycle.
Portable diesel
Pits, civil, shutdowns, sites with no three-phase. High hours, dust.
Oil-free
When air can touch product or paint. Still needs dryers and filtration. Ask the ISO 8573-1 class.
Typical new-machine bands
Australian list prices, GST extra on some quotes, GST included here as a band. Exact CFM is at ~7–8 bar. Oversizing still costs money.
| Class | kW | CFM | Receiver | Phase | Typical new |
|---|---|---|---|---|---|
| Small piston | 2–4 | 8–18 | 50–150 L | 1 | $1,800–$4,500 |
| Workshop piston | 4–7.5 | 18–35 | 150–270 L | 1 or 3 | $3,500–$8,000 |
| Small screw | 5.5–15 | 25–80 | 270–500 L | 3 | $5,000–$15,000 |
| Plant screw | 18–37 | 80–200 | 500–1,000 L | 3 | $15,000–$35,000 |
Brands we commonly quote and service: Atlas Copco, Kaeser, Ingersoll Rand, CompAir, Sullair, Ceccato, BOGE, Champion, Peerless, Pilot Air, ABAC, Chicago Pneumatic. Portable diesel is usually Atlas Copco, Sullair or equivalent. We service machines we did not sell.