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Oil-free rotary screw compressors

Class 0 air with no oil anywhere in the compression chamber.

Technical data

Free air delivery
0.3 – 65.5 m³/min (11 – 2,313 cfm)
Working pressure
5 – 13 bar g
Motor power
7 – 355 kW
Weight
300 – 7,600 kg
Noise level
61 – 71 dB(A)
Oil-free rotary screw compressors

Overview

There is an important difference between air that has been filtered until it is nearly oil-free and air that never touched oil. If your product is food, medicine, electronics or textiles, only the second one protects you, a filter element that fails silently does not announce itself until the batch is ruined.

Green Air oil-free screw compressors use precision-timed rotors that never touch each other or any lubricant. The result is certified ISO 8573-1 Class 0 air: not a low oil content, but no measurable oil content at all.

Key benefits

Certified Class 0

Independently tested to ISO 8573-1 Class 0 for total oil, including vapour. Certificate supplied with every machine.

No condensate to treat

Nothing oily leaves the machine, so there is no oil-water separator to buy, maintain or explain to an environmental inspector.

No filtration pressure drop

You are not pushing air through three stages of coalescing filters, which typically saves 0.4 bar and the energy that goes with it.

Lower risk, not just lower oil

Removes the single point of failure that ruins batches in food, pharma and electronics plants.

How it is built

Two rotors turn in the housing without ever touching each other and without any lubricant between them. Timing gears hold the clearance, and the clearance is held by manufacturing accuracy rather than by a film of oil.

Because nothing is sprayed into the chamber to carry heat away, the heat has to leave through the casing and the intercooler instead. That is why an oil free machine is physically larger than an oil injected one of the same output, and why the cooling design is the part that decides how long it lasts.

The rotor coating is the wearing part, not a bearing surface. Kept within its temperature limits it lasts many years, and the controller exists largely to keep it there.

  • Timed rotors that never touch
  • No lubricant anywhere in the air path
  • Certified to ISO 8573-1 Class 0
  • Intercooling between stages
  • Air cooled or water cooled
  • No oil water separator needed downstream
  • No coalescing filter pressure drop to pay for
  • Variable speed available

What the controller does

The controller watches the temperatures that matter to a coated rotor and shuts the machine down before they matter, which is a different job from the one a controller does on an oil injected machine.

Pressure, load, running hours, both stage temperatures and the service countdown are on the home screen. The stage temperature trend is the number an engineer reads, because it moves long before anything fails.

It sequences with other machines, holds a pressure band rather than a single number, and runs to a shift clock so the plant is not making Class 0 air at three in the morning for nobody.

  • Both stage temperatures monitored and trended
  • Pressure band control
  • Service countdown in hours
  • Sequencing with other machines
  • Shift clock for start and stop
  • Remote monitoring as standard
  • Fault history kept on the machine
  • Automatic restart after a power failure

Parts and service kits

Kits for an oil free machine are mostly filters, seals and bearing service rather than separators and fluid, because there is no oil in the air path to separate.

The gearbox and the bearings are the scheduled items. They are changed on hours rather than on condition, and doing that on time is what keeps a rotor coating intact.

Every kit is confirmed against the serial number. We also supply the Class 0 certificate with the machine and again after any work that could affect it, because an audit will ask for it.

  • Air filters and seal kits by interval
  • Scheduled bearing and gearbox service
  • Intercooler clean included
  • Class 0 certificate supplied and reissued after works
  • Confirmed against your serial number
  • Local stock in every country we trade in
  • Airend exchange available
  • Fixed price under a service plan

Model range

Air cooled

GAC-F 1515 kW / 20 hp
8 bar g
2.30 m³/min
Noise level
68 dB(A)
Weight
672 kg
Dimensions L x W x H
1309 × 848 × 1612 mm
GAC-F 2222 kW / 30 hp
8 bar g
3.50 m³/min
Noise level
68 dB(A)
Weight
691 kg
Dimensions L x W x H
1309 × 848 × 1612 mm
GAC-F 3737 kW / 50 hp
8 bar g
5.86 m³/min
Noise level
71 dB(A)
Weight
960 kg
Dimensions L x W x H
1686 × 886 × 1657 mm

Water cooled

GAC-F 1515 kW / 20 hp
8 bar g
2.30 m³/min
Noise level
65 dB(A)
Weight
624 kg
Dimensions L x W x H
1309 × 848 × 1612 mm
GAC-F 2222 kW / 30 hp
8 bar g
3.50 m³/min
Noise level
65 dB(A)
Weight
643 kg
Dimensions L x W x H
1309 × 848 × 1612 mm
GAC-F 3737 kW / 50 hp
8 bar g
5.86 m³/min
Noise level
61 dB(A)
Weight
860 kg
Dimensions L x W x H
1686 × 886 × 1657 mm

Variable speed

GAC-FV 15Variable speed, cooling configuration specified in quotation15 kW / 20 hp
5 – 10 bar g
0.32 – 2.34 m³/min
Noise level
67 dB(A)
Weight
687 kg
Dimensions L x W x H
1309 × 848 × 1612 mm
GAC-FV 22Variable speed, cooling configuration specified in quotation22 kW / 30 hp
5 – 10 bar g
0.68 – 3.45 m³/min
Noise level
67 dB(A)
Weight
687 kg
Dimensions L x W x H
1309 × 848 × 1612 mm
GAC-FV 37Variable speed, cooling configuration specified in quotation37 kW / 50 hp
5 – 10 bar g
1.09 – 6.87 m³/min
Noise level
71 dB(A)
Weight
995 kg
Dimensions L x W x H
1722 × 920 × 1659 mm

GAC series, fixed speed

GAC77.5 kW / 10 hp
8 bar g
1.20 m³/min (42.4 cfm)
10 bar g
1.00 m³/min (35.3 cfm)
13 bar g
0.80 m³/min (28.3 cfm)
Connection
G 1/4
Weight
≈ 300 kg
Dimensions L x W x H
1000 × 700 × 1220 mm
GAC1111 kW / 15 hp
8 bar g
2.00 m³/min (70.6 cfm)
10 bar g
1.80 m³/min (63.6 cfm)
13 bar g
1.60 m³/min (56.5 cfm)
Connection
G 1/4
Weight
≈ 350 kg
Dimensions L x W x H
1200 × 750 × 1400 mm
GAC1515 kW / 20 hp
8 bar g
2.88 m³/min (101.7 cfm)
10 bar g
2.41 m³/min (85.1 cfm)
13 bar g
2.02 m³/min (71.3 cfm)
Connection
G 1/4
Weight
≈ 600 kg
Dimensions L x W x H
1250 × 750 × 1400 mm
GAC2222 kW / 30 hp
8 bar g
3.97 m³/min (140.2 cfm)
10 bar g
3.43 m³/min (121.1 cfm)
13 bar g
3.02 m³/min (106.7 cfm)
Connection
G 1
Weight
≈ 650 kg
Dimensions L x W x H
1250 × 750 × 1400 mm
GAC3030 kW / 40 hp
8 bar g
5.20 m³/min (183.6 cfm)
10 bar g
4.72 m³/min (166.7 cfm)
13 bar g
4.29 m³/min (151.5 cfm)
Connection
G 1 1/2
Weight
≈ 850 kg
Dimensions L x W x H
1650 × 850 × 1650 mm
GAC3737 kW / 50 hp
8 bar g
6.70 m³/min (236.6 cfm)
10 bar g
6.08 m³/min (214.7 cfm)
13 bar g
4.88 m³/min (172.3 cfm)
Connection
G 1 1/2
Weight
≈ 950 kg
Dimensions L x W x H
1650 × 850 × 1650 mm
GAC4545 kW / 60 hp
8 bar g
8.24 m³/min (291.0 cfm)
10 bar g
7.40 m³/min (261.3 cfm)
13 bar g
6.20 m³/min (219.0 cfm)
Connection
G 1 1/2
Weight
≈ 1,250 kg
Dimensions L x W x H
1650 × 850 × 1650 mm
GAC5555 kW / 75 hp
8 bar g
10.52 m³/min (371.5 cfm)
10 bar g
8.90 m³/min (314.3 cfm)
13 bar g
8.00 m³/min (282.5 cfm)
Connection
G 2
Weight
≈ 1,550 kg
Dimensions L x W x H
1850 × 1050 × 1800 mm
GAC7575 kW / 100 hp
8 bar g
14.36 m³/min (507.1 cfm)
10 bar g
12.02 m³/min (424.5 cfm)
13 bar g
10.34 m³/min (365.2 cfm)
Connection
G 2
Weight
≈ 1,750 kg
Dimensions L x W x H
2050 × 1050 × 1850 mm
GAC9090 kW / 125 hp
8 bar g
16.20 m³/min (572.1 cfm)
10 bar g
14.52 m³/min (512.8 cfm)
13 bar g
12.60 m³/min (445.0 cfm)
Connection
G 2
Weight
≈ 2,050 kg
Dimensions L x W x H
2050 × 1050 × 1850 mm
GAC110110 kW / 150 hp
8 bar g
22.0 m³/min (776.9 cfm)
10 bar g
19.1 m³/min (674.5 cfm)
13 bar g
15.5 m³/min (547.4 cfm)
Weight
≈ 2,515 kg
GAC132132 kW / 175 hp
8 bar g
26.0 m³/min (918.2 cfm)
10 bar g
22.0 m³/min (776.9 cfm)
13 bar g
18.8 m³/min (663.9 cfm)
Weight
≈ 3,025 kg
GAC160160 kW / 215 hp
8 bar g
30.3 m³/min (1070.0 cfm)
10 bar g
26.6 m³/min (939.4 cfm)
13 bar g
22.5 m³/min (794.6 cfm)
Weight
≈ 3,225 kg
GAC200200 kW / 270 hp
8 bar g
38.0 m³/min (1342.0 cfm)
10 bar g
36.0 m³/min (1271.3 cfm)
13 bar g
28.1 m³/min (992.3 cfm)
Weight
≈ 4,727 kg
GAC250250 kW / 335 hp
8 bar g
45.7 m³/min (1613.9 cfm)
10 bar g
39.8 m³/min (1405.5 cfm)
13 bar g
33.0 m³/min (1165.4 cfm)
Weight
≈ 5,017 kg
GAC315315 kW / 430 hp
8 bar g
56.0 m³/min (1977.6 cfm)
10 bar g
50.8 m³/min (1794.0 cfm)
13 bar g
45.7 m³/min (1613.9 cfm)
Weight
≈ 6,625 kg
GAC355355 kW / 485 hp
8 bar g
65.5 m³/min (2313.1 cfm)
10 bar g
55.2 m³/min (1949.4 cfm)
13 bar g
49.6 m³/min (1751.6 cfm)
Weight
≈ 7,600 kg

GAC VSD series, variable speed

GAC7VSD7 kW / 10 hp
13 bar g
0.3 – 1.2 m³/min
Connection
G 3/4
Weight
≈ 450 kg
GAC11VSD11 kW / 15 hp
13 bar g
0.3 – 2.0 m³/min
Connection
G 1/4
Weight
≈ 550 kg
GAC15VSD15 kW / 20 hp
13 bar g
0.5 – 2.8 m³/min
Connection
G 1
Weight
≈ 650 kg
GAC22VSD22 kW / 30 hp
13 bar g
0.7 – 4.02 m³/min
Connection
G 1
Weight
≈ 750 kg
GAC30VSD30 kW / 40 hp
13 bar g
1.16 – 5.5 m³/min
Connection
G 1
Weight
≈ 950 kg
GAC37VSD37 kW / 50 hp
13 bar g
1.54 – 6.70 m³/min
Connection
G 1 1/2
Weight
≈ 1,250 kg
GAC45VSD45 kW / 60 hp
13 bar g
1.54 – 8.04 m³/min
Connection
G 1 1/2
Weight
≈ 1,450 kg
GAC55VSD55 kW / 75 hp
13 bar g
1.54 – 10.5 m³/min
Connection
G 2
Weight
≈ 1,650 kg
GAC75VSD75 kW / 100 hp
13 bar g
2.52 – 15.0 m³/min
Connection
G 2
Weight
≈ 1,950 kg
GAC90VSD90 kW / 125 hp
13 bar g
2.52 – 16.5 m³/min
Connection
G 2
Weight
≈ 2,350 kg
GAC110VSD110 kW / 150 hp
13 bar g
3.77 – 22.0 m³/min
Connection
G 3
Weight
≈ 2,615 kg
GAC132VSD132 kW / 175 hp
13 bar g
3.77 – 26.0 m³/min
Connection
G 3
Weight
≈ 3,125 kg
GAC160VSD160 kW / 215 hp
13 bar g
4.0 – 30.3 m³/min
Connection
G 4
Weight
≈ 3,425 kg
GAC200VSD200 kW / 270 hp
13 bar g
10.0 – 38.0 m³/min
Connection
G 4
Weight
≈ 4,827 kg
GAC250VSD250 kW / 335 hp
13 bar g
10.0 – 45.7 m³/min
Connection
G 4
Weight
≈ 5,117 kg

FAD measured to ISO 1217 Edition 4, Annex C and E at 1 bar a intake, 20°C, 0% humidity. Noise measured to ISO 2151 in free field conditions, tolerance ± 3 dB(A). Water-cooled versions of every model are available. Ask us for their sheet.

A weight shown with ≈ is our own estimate from the machine's own dimensions, not a measured figure, and is waiting on the factory. Do not plan a lift or a foundation against it — ask us and the confirmed weight comes with the quotation.

Overall dimensions are supplied for the selected configuration with the quotation and the arrangement drawing. Tell us the model and the duty and we will send them. Ask us

Frequently asked questions

How do the rotors avoid touching without oil?

They are held in mesh by precision timing gears, so they never contact each other or the housing. That is why the tolerances and the price are both higher.

What certificate comes with the machine?

An ISO 8573-1 Class 0 certificate covering total oil content including vapour, issued from independent testing.

What is the rotor coating for?

It seals the small clearances and resists corrosion in place of oil. Coating condition is what the scheduled inspection actually checks.

How long do these machines last?

Comparable to an oil-injected screw when maintained correctly. The wearing items are the bearings, seals and the coating rather than an oil circuit.

Do I lose efficiency compared with oil-injected?

At full load a single-stage oil-free machine is slightly less efficient. Two-stage recovers that and more, which is why most oil-free installations above 37 kW are two-stage.

What air quality do I actually get?

No measurable oil, plus whatever particulate and dew point your downstream treatment provides. Oil-free solves one of the three ISO classes, not all three.

Can I retrofit oil-free instead of my existing machine?

Yes, and it usually simplifies the installation: you can remove the coalescing and carbon filter stages and the oil-water separator with it.

What is the noise level?

Similar to an equivalent oil-injected machine in a canopy. Gearbox noise is the difference and it is contained within the enclosure.

Is a receiver still needed?

Yes, exactly as with any compressor: to steady pressure, catch condensate and stop short-cycling on a fixed-speed unit.

What are the running costs?

Energy dominates as always. Consumables are lower than an oil-injected machine because there is no separator element and no oil, but scheduled interventions are more specialised.

Related products

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.