Choosing the wrong air compressor is one of the most common and costly mistakes in workshop setup. Buy too small and your tools starve for air mid-job. Buy too large and you waste money on capital and electricity for the next decade. This guide cuts through the confusion — covering compressor types, the key specifications that actually matter, how to size correctly for your tools, and what the relevant Australian Standards require. Whether you're equipping a tyre bay, fabrication shop, spray booth, or general maintenance workshop, the right answer starts with understanding Free Air Delivery, duty cycle, and the real difference between piston and rotary screw compressors.
1. How Air Compressors Work
All air compressors do the same thing: draw in atmospheric air, compress it to a higher pressure, and store it in a receiver tank until your tool needs it. The differences between compressor types come down to how they compress the air, how continuously they can do it, and how they handle the heat generated in the process.
The key cycle in a piston compressor is: motor drives the piston down (intake stroke), air fills the cylinder, piston drives up (compression stroke), compressed air pushes through a check valve into the receiver tank. When the tank reaches the cut-out pressure (typically 800–1,000 kPa / 116–145 PSI), the pressure switch stops the motor. As you use air and tank pressure drops to the cut-in pressure, the motor restarts. This on/off cycling defines why piston compressors have a duty cycle — they need rest time to cool between compression cycles.
Rotary screw compressors work differently: two interlocking helical rotors compress air continuously as it moves axially through the rotor housing. There are no pistons, no valves, and no on/off cycling — they run at continuous load, which gives them a 100% duty cycle and much lower noise levels than reciprocating piston units.
2. Types of Air Compressor
Piston (Reciprocating) Compressors
The most common type in Australian workshops. A crankshaft drives one or more pistons back and forth in cylinders to compress air. Simple, durable, and cost-effective for intermittent-to-moderate duty applications. The two sub-types are:
- Single-stage: Air is compressed once, from atmospheric pressure to tank pressure (~800 kPa). Suited to light workshop use, nail guns, tyre inflation, and general air tools with moderate FAD requirements up to around 12–15 L/s.
- Two-stage: Air is compressed twice — first to an intermediate pressure (~350 kPa), then passed through an intercooler before a second compression stage brings it to final tank pressure (~1,200–1,400 kPa). Two-stage units deliver more air more efficiently and run cooler, making them better suited to sustained duty, spray painting, and heavier pneumatic tools.
Rotary Screw Compressors
The standard choice for production environments and any application requiring continuous air supply. Key advantages over piston units at equivalent output: 100% duty cycle (can run 24/7), significantly quieter (62–78 dB(A) vs 75–95 dB(A) for piston), lower maintenance cost over a 10-year lifecycle, and more consistent pressure delivery. Higher capital cost, but cost-effective at FAD requirements above approximately 15 L/s continuous demand. Available in belt-drive and direct-drive configurations; oil-injected or oil-free.
Belt Drive vs Direct Drive
This applies mainly to piston compressors. Both designs are widely available in Australia.
| Feature | Belt Drive | Direct Drive |
|---|---|---|
| Motor–pump connection | V-belt and pulley | Direct-coupled shaft |
| Pump speed | Lower (750–900 RPM typical) | Higher (1,450–3,000 RPM) |
| Noise | Quieter | Louder |
| Duty cycle | Better (lower heat at lower RPM) | Lower (runs hotter at high RPM) |
| Service | Belt replacement, but pump/motor separately replaceable | Fewer components, but motor/pump failure often means replacing together |
| Portability | Generally heavier/larger | More compact |
| Longevity | Longer service life | Shorter (higher wear rate at speed) |
| Best for | Fixed workshop installation | Portable/site use where weight matters |
Oil-Lubricated vs Oil-Free
Oil-lubricated compressors use oil in the compression chamber to lubricate the pistons or rotors, improve sealing, and remove heat. Oil-free compressors use pre-lubricated or PTFE-coated components and do not introduce oil into the air stream.
| Factor | Oil-Lubricated | Oil-Free |
|---|---|---|
| Air purity | Oil aerosol in air stream (needs separator/filter) | No oil contamination |
| Maintenance | Oil changes required; filter maintenance | Lower maintenance |
| Noise | Quieter (oil cushions moving parts) | Louder |
| Longevity | Longer service life | Shorter (higher wear on unlubricated components) |
| Cost | Lower purchase price | Higher purchase price |
| Best for | General workshop, automotive, fabrication | Food & beverage, pharma, spray finishing where oil contamination is unacceptable |
Electric vs Petrol Air Compressors
Electric compressors are the standard choice for any fixed or semi-fixed installation where mains power is available. They are cleaner, quieter, lower maintenance, and cheaper to run. Petrol compressors exist for site use where there is no power — remote construction sites, mining, civil work, and field maintenance. If you have mains power at your work location, electric is always the better choice.
3. Key Specifications Explained
Free Air Delivery (FAD) — The Only Spec That Matters for Sizing
FAD is the volume of air a compressor delivers at atmospheric pressure conditions, measured in litres per minute (L/min) or litres per second (L/s). In Australia, FAD is rated under AS 4637:2006 — this is the standard manufacturers are required to use when stating compressor output. When comparing compressors, always compare FAD figures, not horsepower or tank size.
CFM — Converting to Australian Units
Many tool specifications and overseas guides use CFM (cubic feet per minute). To convert: 1 CFM = 28.3 L/min. So a tool requiring 5 CFM needs 141.5 L/min FAD from your compressor. When sizing, work in L/min throughout and convert any CFM tool specs before you start.
Pressure: PSI, bar, and kPa
Australian compressors are increasingly rated in kPa or bar, though PSI remains widely understood in trade contexts. The conversions you'll use most:
| Unit | PSI equivalent | kPa equivalent | bar equivalent |
|---|---|---|---|
| Typical tool operating pressure | 90 PSI | 620 kPa | 6.2 bar |
| Typical single-stage cut-out | 116 PSI | 800 kPa | 8 bar |
| Typical two-stage cut-out | 175 PSI | 1,200 kPa | 12 bar |
| High-pressure applications (tyre bays, sandblasting) | 145–175 PSI | 1,000–1,200 kPa | 10–12 bar |
Most pneumatic hand tools — impact wrenches, ratchets, drills, grinders, nail guns — operate at 620 kPa (90 PSI). Your compressor should have a working pressure well above the tool's requirement so the regulator can maintain stable line pressure as the tank cycles.
Tank Size
The receiver tank stores compressed air as a buffer between the compressor motor and your tool demand. A larger tank means the motor cycles less frequently for the same level of use — it doesn't increase the compressor's FAD output. For tools with high intermittent demand (nail guns, impact wrenches), a larger tank gives you longer run time before the motor cuts back in. For high-continuous-demand tools (spray guns, sandblasters), FAD is what matters — the tank just smooths out short peaks.
Duty Cycle
Duty cycle is the percentage of time a compressor can run within any given period without overheating. A piston compressor with a 50% duty cycle can run for 30 minutes per hour before needing 30 minutes of cooling time. Exceeding the duty cycle overheats the motor and pump, drastically shortening service life.
As a guide: single-stage direct drive units typically have a 25–50% duty cycle; belt drive two-stage piston units often reach 60–75%; rotary screw compressors run at 100% duty cycle continuously.
Horsepower — Why It's Misleading
HP ratings on compressors are often inflated and meaningless for comparison purposes. Two compressors with the same stated horsepower can have very different FAD outputs depending on pump efficiency, compression stages, and RPM. Always evaluate compressors on FAD (L/min at rated pressure) and duty cycle — never on horsepower alone. This is why AS 4637:2006 mandates FAD measurement as the primary performance metric in Australia.
4. How to Size an Air Compressor: The 5-Step Method
Getting compressor sizing right before purchase avoids the two most common and costly mistakes: undersizing (tools starve, motor overloads) and oversizing (wasted capital and electricity).
Step 1 — List every tool you will run from the compressor
Include every pneumatic tool in your workshop — current and planned. Don't skip tools you "rarely" use; if they run when the compressor is on, they affect sizing.
Step 2 — Find the FAD requirement for each tool
Check the tool manufacturer's specification. If stated in CFM, multiply by 28.3 to convert to L/min. Reference table:
| Air Tool | Typical FAD (L/min) | Operating Pressure (kPa) | Notes |
|---|---|---|---|
| Brad nail gun / finish nailer | 40–80 | 480–690 | Intermittent; small tank fine |
| Framing nailer | 100–160 | 550–830 | Intermittent bursts |
| Air ratchet (3/8") | 100–140 | 620 | Light fastening; intermittent |
| Impact wrench (1/2") | 140–200 | 620–690 | Moderate continuous demand |
| Impact wrench (3/4") | 200–280 | 620–690 | Heavy fastening |
| Air drill | 100–180 | 620 | Intermittent |
| Die grinder | 140–200 | 620 | Moderate continuous demand |
| Air sander (random orbital) | 200–280 | 620 | Sustained demand; check duty cycle |
| Spray gun (HVLP) | 280–450 | 280–480 | High FAD; continuous — size carefully |
| Spray gun (conventional) | 350–600 | 350–620 | High FAD; continuous — rotary screw often needed |
| Blow gun / air nozzle | 40–100 | 550–690 | Intermittent; low demand |
| Sandblaster (spot / cabinet) | 300–600 | 550–830 | Very high FAD; often requires 100% duty cycle |
| Sandblaster (open/production) | 600–2,000+ | 690–1,030 | Requires industrial rotary screw |
| Tyre inflator / blow-off | 40–100 | 690–830 | Short duration; intermittent |
| Pneumatic staple gun | 40–80 | 480–620 | Intermittent; light demand |
Step 3 — Identify your simultaneous tool requirement
Identify the maximum number of tools that could be running at the same time. Add their FAD requirements together — this is your peak demand figure. In most small workshops, this is one or two tools running simultaneously.
Step 4 — Add a 25–30% safety margin
Multiply your peak demand figure by 1.25 to 1.30. This accounts for: air leaks in hoses and fittings (every system loses some), tool wear over time (worn tools use more air), and future tool additions. A compressor running constantly at 100% of its rated FAD will wear faster and be more prone to thermal shutdown.
Step 5 — Match FAD to compressor output and check duty cycle
Find a compressor whose rated FAD (per AS 4637:2006) meets your calculated requirement. Then check duty cycle against your expected use pattern: if your tools will run more than 50% of the time, step up to a higher-duty-cycle piston unit or a rotary screw.
5. Sizing by Application: Workshop Scenarios
| Workshop Type | Recommended Min. FAD | Suggested Tank | Compressor Type |
|---|---|---|---|
| Home workshop (nail guns, blow off, tyre inflation) | 150–200 L/min | 24–50 L | Single-stage piston, direct or belt drive |
| General trade workshop (impact wrench, ratchet, grinder) | 250–350 L/min | 50–100 L | Single or two-stage belt drive piston |
| Automotive / tyre bay | 400–600 L/min | 100–200 L | Two-stage belt drive piston or small rotary screw |
| Spray booth (HVLP, sustained) | 450–700 L/min | 100–200 L | Two-stage piston or rotary screw; oil-free recommended |
| Fabrication shop (multiple tools) | 500–900 L/min | 200–500 L | Two-stage piston or rotary screw |
| Sandblasting (sustained production) | 600–2,000+ L/min | 200–500+ L | Rotary screw (100% duty cycle required) |
| Light production / continuous air use | 900+ L/min | 500+ L | Rotary screw |
6. Piston vs Rotary Screw: Which Is Right for You?
The most important sizing decision in workshop compressor selection. Both types are widely used in Australian industry — the right choice depends on your duty cycle, budget, and application.
| Factor | Piston Compressor | Rotary Screw Compressor |
|---|---|---|
| Duty cycle | 25–75% (intermittent) | 100% (continuous) |
| Noise | 75–95 dB(A) | 62–78 dB(A) |
| Capital cost | Lower | Higher |
| 10-yr maintenance cost | $10,000–$20,000 | $8,000–$14,000 |
| Crossover point | Best below ~15 L/s continuous demand | Cost-effective above ~15 L/s continuous demand |
| Best application | Intermittent workshop use, automotive, light fabrication | Production, spray booths, sustained multi-tool operation |
| Complexity | Simple — easy in-house servicing | More complex — specialist service often required |
7. Power Supply: 10A, 15A, and 3-Phase
Most domestic and light commercial properties have 10A single-phase power at standard GPO outlets. This limits motor size to approximately 2.2 kW (3 HP) — sufficient for light workshop compressors up to around 200–250 L/min FAD.
Compressors from approximately 3 kW (4 HP) upward typically require a 15A dedicated circuit, which needs installation by a licensed electrician. Workshop-grade compressors at 5–7.5 kW generally require 15A single-phase supply.
For compressors above 7.5 kW, three-phase power (415V) is more efficient and should be used wherever it is available. Three-phase motors start more smoothly (no capacitor start required), run more efficiently at load, and have a lower star-delta starting current spike — which matters when you're running other equipment on the same supply.
8. Noise Levels and Workshop Placement
Noise is one of the most commonly cited complaints about workshop compressors — and one of the most important safety considerations. Under AS/NZS 1269.1, workplaces must control noise exposure: continuous exposure at or above 85 dB(A) requires mandatory hearing protection and a hearing conservation programme. Most piston compressors produce 75–95 dB(A) at one metre — well into the range requiring PPE during extended use.
| Compressor Type | Typical Noise Level | AS/NZS 1269.1 Status |
|---|---|---|
| Single-stage direct drive piston | 85–95 dB(A) | Hearing protection required during operation |
| Belt drive piston (two-stage) | 75–87 dB(A) | At or above threshold — hearing protection recommended |
| Rotary screw (standard canopy) | 62–78 dB(A) | Below threshold during operation at normal distance |
| Rotary screw (sound-attenuated canopy) | <70 dB(A) | Suitable for near-workstation installation |
Placement tips: locate the compressor in a dedicated plant room or corner with adequate ventilation (compressors generate substantial heat and need clear airflow around the motor and cooling fins). Avoid enclosed rooms without ventilation — overheating from restricted airflow is a leading cause of premature failure. Anti-vibration mounts reduce noise transmission through concrete floors.
9. Australian Standards and Compliance
Three standards are relevant to workshop air compressor selection and operation in Australia:
AS 4637:2006 — Reciprocating Air Compressors: FAD Test Method. This standard defines how piston compressor output must be measured and stated in Australia. When a manufacturer states a FAD figure, it should be tested per AS 4637:2006 — this is the benchmark for comparing compressor outputs from different brands. Be cautious of non-AS-rated FAD figures, which may overstate actual output.
AS 3788 — Pressure Equipment: In-Service Inspection. Compressed air receivers are classified as pressure vessels under Australian law. AS 3788 governs inspection intervals. For commercial and industrial use, pressure vessels are typically required to undergo periodic inspection and may need registration with your state's WorkSafe or Technical Regulator, depending on design pressure and volume. Requirements vary by state:
- NSW (SafeWork NSW): Pressure vessels with a hazard level of A–D must be registered. Small workshop receivers (e.g. 50–100L at 800–1,000 kPa) typically fall below registration thresholds, but commercial and multi-outlet industrial receivers may not. Check SafeWork NSW for your specific tank specification.
- QLD, WA, VIC, SA: Similar threshold-based registration requirements. State technical regulators (WHSQ QLD, WorkSafe WA, Energy Safe VIC, Consumer and Business Services SA) hold current thresholds.
AS/NZS 1269.1 — Occupational Noise Management. As noted above, this standard covers noise exposure assessment in workplaces. It applies when compressors are installed in environments where workers are present — which is most workshop settings. At 85 dB(A) and above, hearing protection must be provided and used.
10. Air Compressor Maintenance
A well-maintained air compressor should give 10–20 years of service life. Most premature failures trace back to three neglected maintenance items: oil level/condition, condensate drain, and air filter condition.
Routine Maintenance Schedule
| Task | Frequency | Notes |
|---|---|---|
| Check oil level | Before each use (oil-lubricated units) | Low oil is the single most common cause of pump damage |
| Drain condensate from tank | After every use; at minimum weekly | Condensate accelerates internal corrosion and tank failure |
| Inspect/clean air filter | Monthly or as per manufacturer | Blocked filter increases thermal load and reduces output |
| Change compressor oil | Every 500–1,000 hours or annually | Use manufacturer-specified compressor oil only — see below |
| Check/tension drive belt | Every 3 months (belt drive units) | Loose belts slip and cause poor FAD output; over-tight belts damage bearings |
| Test safety relief valve | Every 6 months | Pull the ring briefly to confirm valve opens and reseats correctly |
| Full service (valves, rings, seals) | Every 12 months or per manufacturer schedule | Catches worn valves before they cause hard starts, pressure loss, or overheating |
| Pressure vessel inspection (AS 3788) | As required by state regulator | Commercial/industrial installations — check state requirements |
What Compressor Oil to Use
Always use oil specifically formulated for air compressors — do not substitute with engine oil or hydraulic fluid. Compressor oils are formulated to resist oxidation, thermal degradation, and moisture contamination at the temperatures inside a compression cylinder. Using the wrong oil leads to varnish deposits on valves and cylinder walls, dramatically shortening service life. Most piston compressors use a non-detergent mineral compressor oil (ISO VG 100 grade is common); rotary screw compressors typically use a synthetic compressor fluid specified by the manufacturer. For a reference chart of all ISO VG grades across oil applications, see the ISO VG viscosity chart.
AIMS stocks compressor oil formulated for both piston and rotary screw applications. Browse compressor oil →
11. Compressor Troubleshooting
Most common air compressor faults have straightforward causes. The table below covers the issues most frequently reported in Australian workshops.
| Symptom | Likely Causes | First Steps |
|---|---|---|
| Pressure loss / won't reach cut-out pressure | Air leak in tank or fittings; worn pump valves; blocked intake filter | Soapy water test on all joints; inspect filter; check valve condition |
| Compressor overheating / thermal cutout tripping | Insufficient ventilation; blocked cooling fins; low oil; exceeding duty cycle; ambient temperature too high | Ensure 500mm+ clearance around unit; clean cooling fins; check oil level; reduce run time |
| Excessive moisture / water in airlines | Condensate not drained; no refrigerant dryer in humid environment; undersized tank cycling too fast | Drain tank daily; install inline filter/water separator; consider refrigerant air dryer |
| Oil in air lines | Worn piston rings; overfilled oil; wrong oil type | Check oil level (drain to correct mark); inspect rings; install coalescing filter downstream |
| Compressor runs continuously, won't reach cut-out | Demand exceeds FAD output; leak in system; worn pump; undersized unit for the task | Check for leaks; reduce simultaneous tool use; evaluate if compressor is undersized |
| Hard starting / motor won't start | Unloader valve not releasing residual pressure; low voltage (extension lead); capacitor failure; seized pump | Check unloader valve; remove extension lead; check capacitor; assess pump freedom of rotation |
| Unusual knocking or rattling | Loose belt; worn bearings; loose pulley; broken valve plate | Check belt tension and pulleys; inspect for worn bearing play; do not run — send for service |
12. Air Compressor Accessories: Setting Up Your Workshop Airline
A compressor alone is only part of a functional workshop compressed air system. The accessories between the compressor outlet and your tools determine air quality, working pressure, and how usable the system is day to day.
For a complete guide to airline layout, thread standards, coupler types, and FRL unit selection, see the AIMS Pneumatic Fittings & Air Line Guide.
Essential Accessories
FRL Unit (Filter–Regulator–Lubricator): Installed at the point of use, an FRL unit filters particulates and moisture from the air supply, regulates line pressure to the tool's requirement, and adds a fine oil mist to lubricate pneumatic tool internals. Most workshop air tools require a lubricator in the supply line — check your tool manual. Browse compressed air lubricators →
Air Hose and Hose Reel: For workshop use, a retractable hose reel is far more practical than a coiled hose on the floor. For the full hose reel decision matrix — spring rewind vs manual, wall vs ceiling vs pedestal mount, 4:1 burst pressure safety factor, swivel joint maintenance, and the AU Retracta + Macnaught range — see the Industrial Hose Reel Guide. Retractable reels keep the hose off the ground (protecting it from damage and reducing trip hazards), extend and retract cleanly, and are lockable at any length. Match hose bore to tool demand — undersized hose creates pressure drop at the tool. For high-demand tools (spray guns, sandblasters), use at least 10mm (3/8") bore hose and keep runs as short as practical. View AIMS retractable air hose reel →
Inline Filter and Water Separator: For spray painting or other applications sensitive to moisture, install a dedicated inline coalescing filter and water separator downstream of your FRL. In humid Australian climates (coastal QLD, NSW, WA), moisture contamination in airline is a significant issue during summer months.
Pressure Regulator: Set line pressure to the tool's requirement — running tools above their rated pressure increases wear and is a safety risk. A regulator at each drop point gives you independent pressure control for different tools on the same airline.
Air Fittings and Couplers: Australian workshops predominantly use the industrial (Melbourne/Nitto) coupler pattern for general workshop tools. Ensure your compressor outlet, hose ends, and tool inlets all use compatible coupler bodies and plugs. Using mismatched coupler patterns is a common source of air leaks and unexpected tool disconnection. See the Pneumatic Fittings Guide for a full breakdown of Australian coupler standards. Browse pneumatic tools and accessories →
13. Eye Protection and PPE When Using Compressed Air
Compressed air tools generate high-speed projectiles — swarf, abrasive particles, fasteners, paint droplets, and in sandblasting applications, fine silica or abrasive media. Eye and face protection is mandatory for most compressed air tool applications.
Never direct compressed air at skin — even low pressures can inject air and contaminants into tissue, causing serious injury. Never use compressed air to clean clothing or body parts. For full guidance on selecting appropriate eye protection for grinding, abrasive, and spray applications, see the AIMS Safety Glasses Guide.
For enclosed spray booth environments, also refer to the IP Rating Guide for motor and electrical enclosure ratings relevant to spray finishing environments.
14. Choosing an Air Compressor for Specific AIMS Customers
AIMS supplies trades, maintenance teams, and industrial procurement across Australia. Here's how the guidance in this article applies to the most common customer scenarios:
Maintenance teams and facilities managers: For a general maintenance workshop running impact wrenches, ratchets, grinders, and blow guns intermittently, a belt drive two-stage piston compressor with 300–500 L/min FAD and a 100L tank is the right fit. Invest in an FRL unit at the drop points and drain the tank daily. This covers 90% of industrial maintenance applications without over-specifying.
Panel shops and automotive workshops: Spray guns demand clean, dry, high-volume air continuously. A rotary screw or a high-output two-stage piston with oil-free air supply (or a coalescing filter on an oiled unit) and a refrigerant air dryer is the right solution. Undersizing the compressor for spray work is the single most common source of finish quality problems.
Fabrication and light production: Multiple simultaneous tools — grinders, die grinders, impact wrenches — at moderate duty. A two-stage belt drive piston at 500–700 L/min FAD handles this range well. If production is continuous, step to a rotary screw to avoid cycling-induced pressure variation.
Plasma cutters require a clean, dry air supply at specific pressure and FAD — typically 90–120 PSI (620–830 kPa) and 140–300 L/min depending on the cutter's amperage rating. For amperage selection, inlet pressure and FAD requirements, and moisture filtration guidance for plasma cutting air supply, see the AIMS plasma cutter guide.
Construction and site maintenance: For sites with power, a portable electric compressor (belt drive, 50–100L) covers nail guns, impact wrenches, and blow guns. For remote sites, a petrol compressor with adequate FAD for your tool mix.
Not sure what's right for your application? Browse the AIMS pneumatic range or contact the AIMS team — we're happy to talk through your requirements.
15. Frequently Asked Questions
What size air compressor do I need for a general workshop?
For a workshop running impact wrenches, air ratchets, grinders, and blow guns on moderate duty, look for a belt drive piston compressor with at least 250–350 L/min FAD (rated per AS 4637:2006) and a 50–100L receiver tank. For sustained or multi-tool use, step up to 500+ L/min FAD or consider a rotary screw unit.
What is Free Air Delivery (FAD) and why does it matter?
FAD is the volume of air a compressor actually delivers at atmospheric pressure, measured in L/min. It is the primary performance specification for sizing — not horsepower, tank size, or working pressure. In Australia, FAD must be rated per AS 4637:2006. Always compare compressors on FAD, not on claimed horsepower.
How do I convert CFM to L/min?
Multiply CFM by 28.3 to get L/min. Example: a tool requiring 5 CFM needs 141.5 L/min FAD from your compressor. When sizing, convert all tool specs to L/min before adding them up.
What is duty cycle, and why does it limit piston compressors?
Duty cycle is the percentage of time a compressor can run within any period without overheating. A 50% duty cycle unit can run for 30 minutes per hour. Exceeding this causes thermal shutdown and accelerated wear. Rotary screw compressors run at 100% duty cycle and are the correct choice for continuous-demand applications.
Is oil-free or oil-lubricated better?
For most industrial workshop use, oil-lubricated compressors offer better longevity, quieter operation, and lower cost — provided a coalescing filter is installed for any oil-sensitive application (spray painting, food processing). Oil-free compressors are the correct choice where air purity is mandatory: pharmaceutical, food and beverage, and critical spray finishing environments.
Belt drive or direct drive — which should I buy?
For a fixed workshop installation, belt drive is the better choice in almost every case. Lower pump RPM means less heat, less wear, quieter operation, and a longer service life. The ability to replace belts and pulleys independently of the motor is a significant long-term maintenance advantage.
What PSI do most air tools need?
Most common pneumatic hand tools — impact wrenches, air ratchets, drills, grinders, die grinders, and nail guns — operate at 90 PSI (620 kPa). Your compressor's working pressure should be set above this via the regulator to maintain stable tool pressure as the tank cycles. HVLP spray guns typically run at lower pressure (40–70 PSI / 275–480 kPa) but with high FAD requirements.
Can I run a spray gun from a 50-litre compressor?
It depends on the spray gun and compressor FAD. An HVLP spray gun typically requires 280–450 L/min FAD continuously. Most 50L single-stage compressors produce only 150–200 L/min FAD — insufficient for sustained spraying. You'll find the compressor cycles constantly and pressure drops during passes, affecting finish quality. For serious spray painting, use a high-output two-stage compressor (500+ L/min FAD) or a rotary screw unit.
What size compressor do I need for sandblasting?
Cabinet sandblasting requires 300–600 L/min FAD at sustained duty; open sandblasting can need 600–2,000+ L/min. This is beyond the duty cycle capability of most piston compressors — sandblasting is one of the primary applications for rotary screw compressors. Using an undersized or insufficient-duty-cycle compressor for blasting will result in continuous running, overheating, and rapid failure.
Is a rotary screw compressor worth it for a small workshop?
If your air demand is intermittent and below approximately 15 L/s (900 L/min) continuous, a well-specified belt drive piston compressor is more cost-effective. Rotary screw compressors become cost-effective when continuous duty is required or when multiple tools run simultaneously in sustained production environments. Above ~15 L/s continuous demand, the lower 10-year maintenance cost of a screw compressor offsets the higher capital cost.
Do I need petrol or electric?
Electric is always the preferred choice when mains power is available — lower running cost, quieter, no exhaust fumes in enclosed spaces, simpler maintenance. Petrol compressors are for genuine off-grid site use where no power is available. Never run a petrol compressor in an enclosed space due to carbon monoxide risk.
What Australian Standard covers air compressor FAD ratings?
AS 4637:2006 governs FAD measurement and specification for reciprocating piston air compressors in Australia. This is the standard against which manufacturers must rate their compressor output. When comparing compressors, ensure FAD figures are stated as per AS 4637:2006 — non-standard figures may overstate actual output significantly.
How often does an air compressor need servicing?
For typical workshop use: check oil level before every use; drain condensate after every session; clean the air filter monthly; change compressor oil every 500–1,000 operating hours or annually; check belt tension quarterly; full service (valves, rings, seals) annually. High-duty or production environments require more frequent intervals — follow the manufacturer's schedule.
What causes an air compressor to keep cutting out?
The most common causes are: thermal cutout activating due to overheating (blocked cooling fins, insufficient ventilation, exceeded duty cycle), pressure switch fault, or supply voltage issues. Check that the unit has adequate ventilation clearance (500mm+ on all sides), that the cooling fins are clean, and that the air filter is not blocked. If the problem persists, the thermal overload or pressure switch may need replacement.
What accessories do I need to set up a workshop airline?
For a functional workshop compressed air system: an FRL unit (Filter–Regulator–Lubricator) at each tool drop point, appropriate hose (10mm bore minimum for most tools), retractable hose reel for practical day-to-day use, compatible industrial couplers and plugs, and a pressure regulator at each station. For spray painting or sensitive applications, add a coalescing filter and inline water separator. For humid environments, consider a refrigerant air dryer. See the Pneumatic Fittings & Air Line Guide for a complete system walkthrough.
For belt-drive RPM calculation and pulley sizing, see our Pulley Speed Ratio guide.
