Selecting the right air compressor is a foundational decision for any workshop, job site, or mobile application relying on pneumatic tools or equipment. A mismatch between air demand and compressor output can lead to tool failure, premature wear, and operational delays - or worse, a total system shutdown. This guide outlines the core principles behind matching compressed air supply to your real-world needs, helping you understand pressure and flow requirements, proper system sizing, and factors like pipework and air treatment.
Pressure vs flow: Two critical metrics
When evaluating a compressor, two fundamental specifications must be understood: pressure and flow.
- Pressure is typically measured in PSI (pounds per square inch), bar, or kPa. It represents the force with which air is delivered. Each tool or device will have a minimum pressure requirement to function correctly. Similarly, each tool will have a maximum pressure that the tool is rated to, for safe use.
- Flow refers to the volume of air supplied over time, expressed in CFM (cubic feet per minute) or L/min (litres per minute). Flow ensures the air supply keeps up with tool consumption.
A common misconception is that “more pressure” equates to “more power.” In reality, the tool’s performance is usually determined by sufficient flow at its required pressure, not excess pressure. Oversupplying pressure can increase wear and reduce service life.
Calculating total air demand
To size a compressor accurately, begin by compiling a list of all air-powered tools and equipment that may run simultaneously. For each, note:
- Required working pressure (PSI or bar)
- Air consumption (CFM or L/min)
Sum the total flow requirement and note the highest pressure required.
Important Note: If one tool has an unusually high-pressure demand (e.g. 175 PSI where others operate at 100 PSI), it may be more efficient to:
- Use a separate high-pressure compressor, or
- Employ a booster/pressure amplifier to avoid oversizing the entire system unnecessarily.
Real-world example
If you operate a spray booth (requiring 15 CFM @ 90 PSI), a die grinder (8 CFM @ 90 PSI), and a small sandblaster (20 CFM @ 100 PSI), running all three together means:
- Total Flow: 43 CFM
- System Pressure: ≥100 PSI
Select a compressor that comfortably exceeds these figures, typically by 10–20% to allow a buffer for system losses, regulator drop-off, or future expansion. In this case, aim for a compressor delivering at least 50 CFM @ 100 PSI continuous.
Hose and pipework considerations
Even the best-sized compressor can underperform if the hose or piping is undersized, excessively long, or poorly laid out. Key considerations include:
- Diameter: Undersized hoses or pipes restrict flow and cause pressure drops.
- Length: Longer runs increase resistance and lower pressure at the tool.
- Fittings and bends: Every join or elbow introduces turbulence and loss.
- Material: Smooth-bore materials (like HDPE or aluminium) outperform materials that may have a rough internal surface or be prone to rust or scale.
- Straightness: Rigid pipework is easier to install, looks better, and assists in condensation management. Avoid running hoses in permanent positions as the dips and sags will fill up with water, causing downstream issues.
- Pressure rating: Ensure the material you use is rated for compressed air with consideration to temperature. For example blueline poly pipe – SDR11 – is rated normally for 1600kPa at 20C. For every degree over 20, we need to downgrade the pressure rating to suit. Proper HDPE compressed air pipe – SDR7.4 – has a 2:1 safety factor at the same pressure and temperature.
Where possible, use short, straight, large-diameter lines, especially for high-flow applications like sandblasting, rattle guns, or air-driven pumps.
Air treatment and filtration
Air quality is often overlooked during compressor selection. Clean, dry, and filtered air can significantly extend the life of your tools, machinery, and breathing systems.
- General filtration removes oil and particulates for tool longevity.
- Dryers (refrigerated or desiccant) are recommended where humidity is an issue.
- Breathing air systems must meet stringent purity standards. If air will be used for confined space entry, respiratory protection, or helmet-supplied air, ensure filtration complies with AS/NZS 1715 and relevant breathing air standards.
Discuss your application in detail with your supplier — especially if the air will contact workers, product surfaces, or critical machinery. Consider the most stringent requirements in your tooling and use these to guide purchase of air treatment equipment. In the case of specialised equipment – spray booth or delicate CNC machinery – it may be more viable to have separate air treatment at the machine rather than treating the entire workshop.
Compressor duty cycle and storage
Don’t overlook duty cycle. Many compressors are rated for intermittent use, making them unsuitable for sustained demand. For continuous operation, choose a model designed for 100% duty cycle.
Air receivers (storage tanks) act as buffers and help reduce cycling. They allow the compressor to run more efficiently and maintain pressure during peak demand. The size of your receiver should be proportionate to both your flow needs and compressor output. Don’t forget that in Australia, pressure vessels above a certain size require certification by your State or Territory’s regulating body.
When in doubt - ask the experts
No two applications are alike. Variability in air tools, workflow, future growth, and environmental conditions make generic advice risky. Sizing your system correctly is not just about buying the biggest machine you can afford - it’s about making sure the machine, tools, plumbing, and air treatment work together as a unified system.
At Bruder, we specialise in real-world compressed air solutions. Whether you’re outfitting a mobile service truck, a remote agricultural setup, or a high-duty workshop, we’re here to assist.
Ready to size your compressor?
Speak with our engineering team today for tailored guidance. We’ll help you specify the right system – not just a compressor, but the right solution.
Contact Bruder Australia to get started: 1300 088 990 or info@bruderaustralia.com.au