Pressure drop in a compressed air distribution system is one of the most common and most costly inefficiencies we find in Perth and WA industrial facilities. Every 1 bar of excess compressor outlet pressure required to compensate for distribution losses adds approximately 7% to your electricity bill — a permanent, ongoing cost that correct pipe sizing and layout eliminates with no recurring expense. Get the piping right once, and the savings are there for the life of the system.
What is pressure drop in a compressed air system?
Pressure drop is the difference between the pressure at the compressor outlet and the pressure delivered at the point of use. In a well-designed system, this difference is minimal. In a poorly designed system, it forces one of two outcomes: the compressor runs at a higher pressure than the application actually requires — adding 7% in energy cost for every bar of excess — or the end-use tool receives less pressure than it needs and underperforms, reducing throughput or product quality.
The accepted benchmark is no more than 0.1 bar of pressure drop per individual section of pipework, with total system pressure drop kept under 0.5 bar from compressor outlet to point of use. Systems exceeding this threshold are wasting energy at every operating hour.
What causes pressure drop?
Pressure drop has six primary causes in industrial compressed air systems:
- Undersized pipe diameter. The most common cause. Too small a bore creates high air velocity, which increases frictional resistance. Most systems that suffer chronic pressure problems were either under-specified at installation or have grown beyond their original design capacity.
- Excessive run length. Frictional resistance accumulates over distance. Long radial runs to remote end-use points are a frequent source of end-point pressure deficiency.
- Too many elbows and fittings. Each fitting adds equivalent pipe length to the system resistance calculation. A 90° elbow on a DN50 line can add the friction equivalent of several metres of straight pipe. High fitting counts on long runs compound quickly.
- Corroded or scaled internal bore. Galvanised and black steel pipe accumulates internal corrosion and scale over time, progressively reducing effective bore diameter and increasing surface roughness. A 20-year-old galvanised system can carry significantly higher resistance than its original design assumed.
- Air velocity outside the recommended range. General distribution pipework should keep air velocity below 6 m/s. Pipework serving refrigerant or desiccant dryers should remain below 3 m/s. Velocity above these limits causes turbulent flow and disproportionate pressure loss.
- Partially closed isolation valves. A valve left partially closed after maintenance can create a restriction equivalent to a significant reduction in pipe bore. These are easy to overlook and frequently missed in routine walkthroughs.
How do you size compressed air pipework?
Pipe sizing requires four inputs: flow rate (in m³/min or CFM), total pipe length including fitting equivalents, operating pressure, and allowable pressure drop per section (0.1 bar is the standard target). For guidance on calculating your compressed air demand in CFM and pressure, refer to our dedicated flow rate guide.
The sizing calculation produces a minimum pipe bore that keeps velocity within limits and pressure drop within spec. In practice, it is almost always worth selecting the next size up from the calculated minimum — pipe is a fixed capital cost, and undersized distribution creates ongoing energy cost for the system’s lifetime.
Worked example:
A Kwinana manufacturing facility needs to run a 50-metre distribution leg at 700 kPa (approximately 100 psi), carrying a peak flow of 100 CFM (2.8 m³/min).
- At DN32 (nominal 32mm bore), air velocity would exceed 8 m/s — outside the recommended limit — and calculated pressure drop over 50 metres would be approximately 0.12–0.15 bar. Marginal to failing.
- At DN50 (nominal 50mm bore), air velocity drops to approximately 4 m/s and pressure drop over the same 50-metre run falls to approximately 0.03–0.04 bar — well within the 0.1 bar per section target.
DN50 aluminium is adequate for this application. DN32 would be marginal at best and non-compliant with best practice in any scenario where the flow rate could peak higher.
Ring main vs radial distribution: which is better?
The two standard distribution layouts for industrial compressed air systems each have clear applications.
A ring main (loop main) feeds compressed air from both directions simultaneously. The supply enters the loop from the compressor room and travels in both directions around the ring to reach any offtake point. This bidirectional feeding means that peak-flow demand at any single offtake only draws from half the ring length at most, significantly reducing the effective pressure drop. Ring mains produce excellent pressure uniformity across multi-drop industrial plants and are the preferred layout for any facility with three or more end-use points spread across a large area.
A radial (branched) layout runs dedicated branch lines from a central header to each end-use point. It is simpler and less expensive to install, and entirely appropriate for small systems with one or two end-use points close to the compressor room. The limitation is predictable: on long radial runs, end-point pressure can be problematic at peak flow, and there is no second feed path to compensate.
| Factor | Ring Main | Radial (Branched) |
|---|---|---|
| Pressure uniformity | Excellent — bidirectional feed reduces peak-flow drop | Variable — end points on long runs are vulnerable |
| Installation cost | Higher — more pipe, more fittings | Lower — simpler layout |
| System complexity | Higher — requires balancing and isolation valves | Lower — straightforward branch design |
| Best for | Multi-drop industrial plants, high peak flow variability | Small systems, one or two end-use points near compressor room |
| Resilience | High — section isolation without full shutdown | Lower — a main branch fault affects all downstream users |
For most industrial facilities in Perth operating with multiple machines, the ring main delivers a measurable improvement in system stability that more than justifies the additional installation cost.
What pipe material should you use?
Material selection affects bore quality, corrosion resistance, installation speed, and long-term maintenance cost.
| Material | Corrosion Resistance | Internal Bore Quality | Install Speed | Typical Application |
|---|---|---|---|---|
| Galvanised steel | Moderate — internal corrosion risk over time | Degrades with age; scale can shed into the system | Standard | Legacy systems; not recommended for new installs |
| Black steel | Poor — must be painted externally; internal corrosion risk | Rough; corrodes readily if moisture enters | Standard | Rarely specified for new compressed air work |
| Aluminium | Excellent — no internal corrosion | Smooth bore, consistent for system life | Fast — push-fit systems available | Preferred for all new industrial installs |
| Stainless steel | Excellent | Excellent, smooth | Slower, higher skill requirement | Food, pharmaceutical, high-purity applications |
| Composite/polymer (Transair, Maxline) | Excellent | Very smooth, clean bore | Very fast — modular push-fit | Clean-room, food, fast-deployment industrial |
One specific note for facilities on Perth’s coastal industrial strip — Fremantle, Henderson, Kwinana — and in WA’s high-humidity mining environments: galvanised steel is not recommended for new compressed air pipework. Internal corrosion rates in high-humidity conditions significantly shorten the effective service life, and shed scale from corroded bore surfaces is a real contamination risk for air tools, instrumentation, and process equipment.
Aluminium push-fit systems are our standard recommendation for new compressed air distribution across WA and Victorian industrial facilities. The installation is faster, the bore remains clean over the system’s life, and there is no maintenance burden from corrosion.
Worked example: calculating pressure drop on a WA industrial site
Scenario: A medium manufacturing plant in Kewdale (Perth’s central industrial corridor) operates three rotary screw compressors feeding a shared ring main. Peak system demand is 150 CFM (4.25 m³/min). The ring main runs 60 metres of DN65 aluminium pipework at 700 kPa operating pressure.
Key variables:
- Flow: 150 CFM / 4.25 m³/min — shared across the ring, so maximum demand at any single arc of the ring is approximately 75 CFM / 2.1 m³/min
- Pipe bore: DN65 aluminium — smooth bore, low friction factor
- Effective run length: 30 metres (half ring at peak demand) plus fitting allowance
Outcome: At 75 CFM over 30 metres of DN65 aluminium at 700 kPa, calculated pressure drop is approximately 0.025–0.03 bar at peak flow. Well within the 0.5 bar total system target, and below 0.1 bar per section. Air velocity remains below 3 m/s — compliant with dryer inlet requirements too.
For comparison: If the same plant used a 40-metre radial run in DN50 carrying the full 150 CFM, pressure drop would be approximately 0.07–0.08 bar — still within specification, but leaving far less margin for fitting losses, filter pressure drop, and future demand growth. Any increase in peak demand would push the system into non-compliance.
The ring main in DN65 gives this facility headroom. The radial run in DN50 does not.
Where compressed air leaks add to distribution losses, even a well-sized system can drift outside its design envelope — which is why distribution design and leak management need to be considered together, not independently. A compressed air energy audit is the most reliable way to quantify both.
Frequently Asked Questions
What is an acceptable level of pressure drop in a compressed air system? The standard benchmark is a maximum of 0.1 bar pressure drop per individual section of pipework, with a total system pressure drop — from compressor outlet to the furthest point of use — of no more than 0.5 bar. Systems operating with total pressure drop above 0.5 bar are wasting energy and should be assessed.
How do I know if my piping is undersized? The most common signs are: end-use tools underperforming at rated specifications, compressor outlet pressure being set higher than the application requires, pressure gauges at the point of use reading significantly lower than at the compressor, or compressors running at higher duty cycles than expected for the installed demand. A pressure survey — measuring pressure at multiple points in the system simultaneously — will confirm whether the distribution is the constraint.
Can I add to existing pipework without redesigning the whole system? In many cases, yes — particularly if the existing pipework is in good condition and adequately sized for the base load. Additions need to be sized to match or exceed the existing distribution capacity and must not introduce high-resistance fittings or undersized branches that create new pressure drop points. Any significant expansion in flow demand or distribution footprint should be reviewed against the original system design to confirm the main headers remain adequate.
How long does a compressed air system design or piping assessment take? For a site assessment with pressure profiling and a written pipe sizing recommendation, we typically require one site visit and 3–5 working days for the report. For new system design — compressor selection, distribution layout, pipe sizing, material specification, and equipment schedule — the timeline depends on site complexity, but most medium industrial systems can be fully specified within 2–3 weeks of receiving site plans and demand data.
Design your distribution system properly — once
Pressure drop is not a maintenance problem. It is a design problem, and the cost of an undersized or poorly laid-out distribution system accumulates in your electricity bill every single operating hour.
Our team designs compressed air distribution systems for industrial facilities across Perth, WA and Victoria — from pipe sizing and material selection through to full ring main layout, compressor room design, and system commissioning. We work to the same standards we apply to our own service contracts.
Compressor Systems Australia is an industrial compressed air specialist with operations across Western Australia and Victoria. Our technical team has over 100 years of collective industry experience servicing mining, manufacturing, food processing, and automotive customers.