Start from the result, not the cfm
The question “how many cfm do I need?” is usually asked too early. A cylinder moving a stop, an air motor driving a mixer, a vacuum gripper lifting a sheet and a nozzle drying a bottle all use compressed air very differently. Two applications with the same average consumption can need completely different pressure stability, response, air quality and standby arrangements.
A sound application brief answers five questions in order:
- What result is required: force, speed, torque, impact, vacuum, transfer rate, drying or a stable reference?
- What pressure is needed at the device inlet while it works, not at the compressor?
- What is the flow pattern: steady, cyclic, intermittent peaks or occasional large bursts?
- What air quality does the device or product need, expressed as ISO 8573-1 classes for particles, water and oil where relevant?
- What happens if the air stops: nuisance, scrap, safety risk or plant shutdown?
With those answers, compressor, dryer, receiver, piping and controls can be specified sensibly. Without them, plants either oversize everything or run at higher pressure than needed to hide a distribution problem.
Application families compared
| Family | Typical pressure at use | Flow pattern | Air quality concern | Typical supply |
|---|---|---|---|---|
| Percussive tools (breakers, rock drills, chipping) | About 6–7 bar (87–101.5 psig); some rock drills 7–10 bar (101.5–145 psig) | High, intermittent | Water and dirt; lubricated tool air | Portable diesel or plant ring main |
| Rotary tools and air motors | About 6–6.3 bar (87–91.4 psig) | Steady while running, varied use factor | Water, particles, lubrication | Plant air with FRL |
| Cylinders and valves | Often 4–6 bar (58–87 psig) | Cyclic, short peaks | Dry air protects seals and valves | Plant air, local regulation, small receivers |
| Vacuum ejectors | Usually 4–6 bar (58–87 psig) supply | Continuous while gripping | Particles and oil can foul ejectors | Plant air; consider vacuum pump for high duty |
| Blowing, drying, cooling | Often well below line pressure | Continuous or long bursts | Oil-free contact air in food and pharma | Plant air or dedicated blowers |
| Pneumatic conveying | Dilute phase below about 1 bar; dense phase a few bar | Continuous, large volume | Dry, oil-free air for most products | Blowers or dedicated compressors |
| Instrument and process air | Commonly 5.5–7 bar (79.8–101.5 psig) | Steady, critical | Dry (typical −40 °C PDP for outdoor lines), oil-free or well-filtered | Duty and standby compressors and dryers |
| PET blowing and high-pressure test | Up to about 40 bar (580.2 psig) for PET | Cyclic, high peaks | Oil-free for product contact | High-pressure compressors or boosters |
| Site projects (blasting, shotcrete, cable blowing, pigging) | 7–14 bar (101.5–203.1 psig) typical | Continuous at site | Cool, dry air for coating and cable work | Portable compressors on hire with aftercoolers |
These are typical ranges for orientation. The device maker’s documented inlet requirement always governs.
Dynamic pressure: the most common hidden problem
Most “the tool is weak” or “the machine is slow” complaints are not a shortage of compressor capacity. They are a pressure drop between the compressor and the device while it is working. Undersized hoses, quick couplings, long drop legs, blocked filters and over-tight regulators all take a share. A gauge at the compressor reading 7 bar can coexist with 5 bar at a breaker under load.
- Measure pressure at the device inlet while it is running at its heaviest duty.
- Check couplings and hose bore before raising compressor pressure; each extra bar costs roughly 7% more compressor power.
- Add local storage near large intermittent users so the peak is supplied from the receiver, not from the whole network.
- Separate critical steady users (instrument air, air bearings) from heavy intermittent users (blow guns, tools) where they share a header.
Flow: average, peak and diversity
Compressor capacity is set by real demand over time, but receivers, piping and treatment must handle the peaks. For tool-based plants, add each tool’s consumption multiplied by its realistic use factor, then allow for leaks and future growth. For automation, calculate air per cycle times cycles per minute for each actuator and add the continuous users such as ejectors and blow-offs. For conveying, the process designer’s free air and pressure at the blower or compressor govern.
Always convert to the same reference. Free air delivery from a compressor is stated at inlet conditions; tool and device ratings may be stated differently. Mixing them leads to undersized or oversized machines.
Air quality by application
Not every application needs the same air. A breaker on a construction site tolerates water that would ruin a paint finish or a packaging valve. Treat the air to the class each user needs, and treat locally where only a few users need higher purity.
- General tools and cylinders: refrigerated drying at a typical +3 °C PDP and general-purpose filtration are usually adequate indoors.
- Instrument air and outdoor lines: desiccant drying to a typical −20 °C or −40 °C PDP prevents condensation and freezing in cooler or air-conditioned areas.
- Food, pharma, electronics and product contact air: oil-free compressors or oil-injected compressors with high-grade coalescing and carbon filtration, verified by sampling.
- Painting, coating and fibre-optic cable blowing: cool, dry, oil-free or well-filtered air; aftercoolers and separators are essential on portable supply.
Directory of application pages
Each page below covers one application in depth: what the device needs, how to measure it, common faults and what to send us.
Tools and site equipment
Percussive and rotary tools draw high, intermittent flow at about 6–7 bar (87–101.5 psig) at the tool.
- Breakers, rock drills and air tools
- Pneumatic breaker air supply
- Chipping and riveting tool air supply
- Impact wrench air supply
- Drill and assembly tool supply
- Grinder and sander supply
- Tool air demand and diversity
- Air hoist supply and operating duty
- Air motor selection
- Air-operated diaphragm pump supply
Automation and motion
Cylinders, valves and grippers depend on stable dynamic pressure and fast response more than on large volumes.
- Pneumatic circuit design requirements
- Cylinder sizing and motion control
- Rotary actuator selection
- Directional valve flow and circuit response
- Proportional pressure control
- End-use air preparation and FRL selection
- Air for robotics and end effectors
- Air for packaging machines
- Tensioning and web handling
- Machine air consumption acceptance
Vacuum and handling
Ejectors convert compressed air into vacuum; they are convenient but heavy users of air.
Blowing, drying and cooling
Open blowing is the most energy-hungry use of air; nozzle choice and pressure control matter.
- Air knife drying
- Air jets and blow-off alternatives
- Compressed-air cooling
- Laser cutting air assist
- Spray painting point-of-use air
Bulk materials
Conveying and aeration often run at low pressure with large volumes, frequently from blowers.
- Pneumatic conveying requirements
- Dilute-phase conveying air supply
- Dense-phase conveying air supply
- Powder fluidisation and aeration
Process, instrument and gas generation
Clean, dry, continuous air, usually with defined ISO 8573-1 classes.
- Instrument air distribution
- Valve actuation for process plants
- Nitrogen generator feed air
- Oxygen generator feed air
- PET high-pressure forming air
- Air bearings and precision air support
- Suspension and test bench supply
- Leak testing fixtures
Site and project applications
Mostly portable diesel or electric compressors on hire, often with aftercoolers and separators.
- Abrasive blasting nozzle and air supply
- Blast pot and compressor interface
- Shotcrete and guniting air supply
- Fibre-optic cable blowing air
- Pipeline pigging air supply
- Pneumatic pressure testing planning
Indian plant and site conditions
High summer ambient temperatures of 40–45 °C, monsoon humidity and dust all affect pneumatic applications in Telangana, Andhra Pradesh and across India. Hot intake air reduces compressor capacity and raises the water load on dryers. Dust shortens filter life and wears tools and seals. Long distribution lines in large plants, such as pharma units in Genome Valley or engineering units in industrial estates around Hyderabad, often have more pressure loss than the original design expected. Site applications on construction, metro and pipeline work need portable machines that tolerate heat and dust and are serviced on a disciplined schedule.
How Reddy Compressors helps
Reddy Compressors, Tarnaka, Secunderabad, has served industry since 2002 as an independent multi-brand specialist. We sell new and used compressors, rent compressors from 50–2,000 cfm and 2–30 bar (diesel and electric), and service and supply spares for ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other makes. We are not an authorised dealer of any brand. We have tie-ups with all major and reputed brands.
- Application reviews: pressure at the point of use, flow pattern, air quality and standby need.
- Pressure-drop and air-quality audits to find why a tool or machine underperforms.
- Supply of compressors, dryers, filters, receivers and blowers matched to the application.
- Rental compressors with hoses, aftercoolers and separators for site and shutdown work.
- Service and AMC across Telangana and Andhra Pradesh by over 20 service engineers and technicians; supply across India.
What to send us
- The application and the result it must achieve.
- Device make and model, and its documented inlet pressure, flow and air-quality requirement.
- Number of users and how often they run.
- Existing compressor, dryer and piping details, with measured pressures if available.
- What happens if air is lost, and whether standby or rental cover is needed.
- Site location and duration for project work.
Frequently asked questions
How do I calculate the compressed air required for my machines?
List every user with its documented consumption at its working pressure. For tools, multiply by a realistic use factor; for cylinders, multiply air per cycle by cycles per minute; add continuous users such as ejectors and blow-offs. Add an allowance for leaks and growth, convert everything to free air at the same reference, and size receivers and piping for the peaks, not just the average.
Watch
A short explainer on this topic
Slide-by-slide engineering explainers from Reddy Compressors. More in the video library.
Why is my air tool weak even though the compressor shows full pressure?
The pressure at the tool while it runs is lower than at the compressor. Small hoses, quick couplings, long drops, blocked filters and regulators all cause drops that only appear under flow. Measure at the tool inlet under load. Fixing the restriction is cheaper than raising compressor pressure, which costs roughly 7% more power for each extra bar.
What pressure do pneumatic tools need?
Most industrial air tools are rated at about 6–6.3 bar (87–91.4 psig) at the tool inlet, and breakers at about 7 bar (101.5 psig). Some rock drills work at 7–10 bar (101.5–145 psig). Always check the maker’s rating and measure at the tool while it works, because the line pressure at the compressor does not tell you what the tool receives.
Do all pneumatic applications need oil-free air?
No. Tools, breakers and most cylinders work well on correctly filtered and dried air from oil-injected compressors. Oil-free air, or very well-filtered air verified by sampling, is needed where air touches food, medicines, electronics or paint, or where oil would harm a process such as fibre-optic cable blowing. Treat the air to the class each user actually needs.
Should I use a blower or a compressor for pneumatic conveying?
Dilute-phase conveying usually runs below about 1 bar and is normally supplied by Roots, screw or other blowers, which deliver large volumes efficiently at low pressure. Dense-phase conveying needs a few bar and is normally fed from a compressor. The conveying system designer’s pressure and free-air figures decide; we sell, rent and service both blowers and compressors.
Can I rent a compressor for a pneumatic application on a project site?
Yes. We rent diesel and electric compressors from 50–2,000 cfm and 2–30 bar, with hoses, aftercoolers, moisture separators and dryers where the work needs them. Tell us the application, the tools or equipment, the pressure and flow they need, the site location and the duration, and we will propose a suitable machine and set-up.
Related pages
Calculators and worked examples
These tools give indicative figures for screening, comparison and for preparing an enquiry. They run in your browser and send nothing. No prices or tariffs are assumed: enter your own to see costs. Efficiencies and other figures shown are example values: replace them with your own. Results are not a performance guarantee or a design certificate; final selection is confirmed by a service engineer against the machine data sheet and the site.
Compressed air demand estimate
Add up the air your tools and processes use, apply duty and simultaneity, then add leakage and growth allowances to reach a capacity to enquire about.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Unit for the air each tool uses: L/s
- Group A: number of tools: 6
- Group A: free air each (in the unit above): 4
- Group A: duty (%): 40
- Group B: number of tools: 2
- Group B: free air each (in the unit above): 15
- Group B: duty (%): 60
- Group C: number of tools: 1
- Group C: free air each (in the unit above): 40
- Group C: duty (%): 80
- Simultaneity of all tools (%): 65
- Leakage allowance (%): 15
- Growth allowance (%): 10
Result
- Connected demand: 94 L/s = 199 cfm
- Average demand (duty-weighted): 59.6 L/s = 126 cfm
- Simultaneous peak: 61.1 L/s = 129 cfm
- Design basis (higher of average and peak): 61.1 L/s = 129 cfm
- Design capacity with allowances: 77.29 L/s = 4.64 m³/min = 163.8 cfm
Method. Average demand = Σ(number × air per tool × duty). Peak = Σ(number × air per tool) × simultaneity. The peak can never be lower than the average, so the design basis is the higher of the two. Design capacity = design basis × (1 + leakage) × (1 + growth).
What to take from it. Leakage and growth allowances move the answer as much as any single tool. Where you can, replace catalogue figures with measured ones.
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.
Pneumatic cylinder air consumption
Work out the free air a cylinder uses per cycle and per minute.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Bore (mm): 63
- Stroke (mm): 200
- Working pressure (bar g): 6
- Cycles per minute: 20
- Number of cylinders: 8
- Double acting? (2 = yes, 1 = single): 2
- Rod diameter (mm; 0 to ignore): 20
Result
- Free air per cycle (each): 8.2 litres
- Total consumption: 21.9 L/s
- 1.311 m³/min = 46.3 cfm
- Theoretical force, outstroke: 1,870 N (before friction; allow 10–20% less)
- Theoretical force, return stroke: 1,682 N
Method. Air per stroke (free air) = swept area × stroke × (P + 1.013) / 1.013. The outstroke uses the full bore area π/4 × D²; the return stroke of a double-acting cylinder uses the bore area less the rod area π/4 × d². Enter rod 0 to ignore it (a small over-estimate).
What to take from it. Many small cylinders add up. Reducing stroke, pressure or cycle rate lowers consumption in direct proportion.