Air compressors
Rotary screw, oil-free and piston compressors from 2.2 to 355 kW.
Overview
Three technologies cover almost every industrial requirement, and choosing between them is mostly a question of duty cycle and air quality.
Piston machines are cheap and suit intermittent use. Rotary screw machines are the default for anything running more than a couple of hours a day. Oil-free machines are for processes where oil contamination would be unacceptable at any level.
In this range
Rotary screw air compressors
The default choice for continuous industrial air, 2.2 to 250 kW.
- Free air delivery
- 0.2 – 109.0 m³/min
- Working pressure
- 2 – 35 bar g
- Motor power
- 2 – 355 kW
Oil-free air compressors
Certified Class 0 air for food, pharma, electronics and textiles.
- Free air delivery
- 0.3 – 53.3 m³/min
- Working pressure
- 4 – 10 bar g
- Motor power
- 6 – 355 kW
Piston air compressors
Reciprocating machines for intermittent and high-pressure duties.
- Free air delivery
- 0.1 – 25.0 m³/min (229 – 882 cfm)
- Working pressure
- 10 – 1,000 bar g
- Motor power
- 2 – 250 kW
Packaged and integrated air stations
Compressor, dryer, filters and receiver supplied as one item.
- Free air delivery
- 0.3 – 25.0 m³/min (9 – 64 cfm)
- Working pressure
- 7 – 30 bar g
- Motor power
- 4 – 250 kW
Key benefits
Sized on duty, not on badge
Hours, pressure and what the air touches decide the machine before anything else does.
Ten year cost shown
Electricity is around three quarters of what a compressor costs. We put that number in the quotation.
Oil free only where it is needed
Certified where the air touches product, and not sold where it would not.
Commissioned by our own team
Foundation, pipe sizing, start up and operator training included.
How to choose
Start with duty rather than with size. A machine that runs all day is a different purchase from one that runs for an hour, and the duty rating matters more than the badge on the front.
Then pressure, then flow, in that order. Ordering ten bar when eight would do costs about fifteen per cent more energy on everything for the whole life of the machine.
Oil free only where the air touches the product. Everywhere else it is money spent on a risk you do not have.
- Duty rating decided first
- Pressure chosen to what tools actually need
- Flow counted from what runs together
- Oil free only where air contacts product
- Variable speed where demand swings
- Air cooled or water cooled by plant room
- Energy cost compared over ten years
- Written sizing with the quotation
What it costs to own
Over ten years electricity is usually seventy five to eighty per cent of what a compressor costs you and the purchase price is often under fifteen.
As a rough figure, one cubic metre a minute at seven bar needs about six kilowatts running continuously. That number makes most comparisons possible without a spreadsheet.
So the question worth asking a supplier is the specific energy measured to ISO 1217 at your working pressure. Figures not measured to that standard are not comparable.
- Electricity is 75 to 80 per cent of the cost
- Purchase price often under 15 per cent
- About 6 kW per cubic metre a minute at 7 bar
- Specific energy to ISO 1217 is the comparison
- Test data supplied for the exact model
- Ten year cost shown before you commit
- Heat recovery counted where it applies
- Service cost fixed on a plan
Datasheets in this range
Two pages each: what the machine is, what it is for, and the measured table. Built from this site, so a sheet can never say something the page does not.
- PDFDirect driven screw compressors
- PDFVariable speed screw compressors
- PDFTwo stage screw compressors
- PDFPermanent magnet screw compressors
- PDFLow pressure screw compressors
- PDFMedium pressure screw compressors
- PDFHigh pressure screw compressors
- PDFSingle phase screw compressors
- PDF2.2 – 5.5 kW screw compressors
- PDF7.5 – 22 kW screw compressors
- PDF23 – 29 kW screw compressors
- PDF30 – 45 kW screw compressors
- PDF55 – 75 kW screw compressors
- PDF90 – 132 kW screw compressors
- PDF160 – 250 kW screw compressors
- PDFWater lubricated oil free compressors
- PDFOil free scroll compressors
- PDFOil-free rotary screw compressors
- PDFTwo-stage oil-free compressors 37 – 75 kW
- PDFTwo-stage oil-free compressors 200 – 355 kW
- PDFTwo-stage variable speed oil-free compressors
- PDFHeat recovery for oil-free compressors
- PDFHigh pressure piston compressors
- PDFBreathing air compressors
- PDFDiaphragm compressors
- PDFFour in one integrated compressors
- PDFLaser cutting air compressors
- PDFContainerised air compressors
- PDFSkid mounted air compressors
- PDFTruck mounted air compressors
Frequently asked questions
Piston, rotary screw or oil-free, which do I need?
Duty cycle and air quality decide it. Intermittent use, a few hours a day: piston. Anything running more than about two hours a day: rotary screw. Air that touches food, medicine, electronics or textiles: oil-free.
What does duty cycle mean and why does it matter?
It is the share of time a machine can spend compressing. A piston compressor needs to rest 30–40% of the time to shed heat. A screw compressor is rated for 100%. Running a piston machine continuously is the most common reason one dies early.
How many kW do I need for the flow I want?
At 7 bar, budget roughly 6 kW per m³/min (about 0.17 kW per cfm). So a plant needing 3 m³/min is looking at an 18–22 kW machine. Higher pressure needs proportionally more.
What is free air delivery, and why is it not the same as displacement?
Free air delivery is what actually comes out of the outlet, measured to ISO 1217. Displacement is the theoretical volume the rotors sweep. Displacement is always the bigger and more flattering number, always compare FAD, at the same pressure.
Do I need an air receiver, and what size?
Yes. A receiver steadies pressure, catches condensate and stops a fixed-speed machine short-cycling. A useful rule is 6–10 litres per cfm, so a 100 cfm machine wants a 600–1,000 litre receiver.
Is variable speed worth the extra money?
Only if your demand varies. Log the machine for a week: if it is unloaded for more than about a third of its running hours, variable speed pays back in 14–24 months. On a constantly loaded duty it may never pay, and we will tell you so.
Will a compressor work in 50 °C ambient?
Our standard build is rated to 46 °C, and a high-ambient package takes it to 52 °C. Above the rating the machine does not explode: it derates and then trips on discharge temperature, usually on the hottest afternoon of the year.
How noisy is a compressor?
A canopied screw machine is typically 66–72 dB(A) at one metre, which is quiet enough to stand beside and talk. An open piston machine is often above 85 dB(A) and needs hearing protection or a separate room.
What electrical supply does it need?
Three phase for anything above about 3 kW. Star-delta starting is standard. Variable speed machines start soft. We supply the full-load current, starting current and recommended cable and fuse sizes with every quotation.
What is included when you supply a compressor?
Delivery, positioning, connection to your existing pipework, commissioning, a performance check against the quoted figures, and operator handover. Foundation and electrical supply to the machine are normally the customer's scope, we specify both in writing.
Related products
Air receivers and tanks
Storage, separation and the vessel that stops your compressor short cycling.
- Working pressure
- 1 – 13 bar g
- Weight
- 99 – 1,240 kg
Gas compressors
Nitrogen, oxygen, biogas, LPG, natural gas, ammonia, argon and boil off gas.
- Free air delivery
- 10 – 3,500 Nm³/h
- Working pressure
- 1 – 210 bar g
- Motor power
- 4 – 250 kW
Oxygen and hydrogen generation
Making the gas on site instead of paying for cylinders and deliveries.
- Working pressure
- 4 – 5 bar g
Air blowers
High-volume, low-pressure air for aeration and conveying.
- Free air delivery
- 12.6 – 418.0 m³/min
- Working pressure
- 1 – 1,100 bar g
- Motor power
- 22 – 450 kW
Not sure which model you need?
Send us your air demand, working pressure and running hours. Our engineers will size the machine and send a written recommendation, no cost, no obligation.