What is the difference between an oil-free and oil-lubricated air compressor?

  • The difference is the oil content in compressed air.
  • For the Class 0 oil-free air compressor, we use water as the lubricating medium instead of oil(Water-injected oil-free single-screw air compressor) or use no lubricating medium(Dry oil-free double twin-screw air compressor), so there will be no oil at all. Find the comparison between water-injected type and dry type oil-free screw air compressor.
  • For the Oil-lubricated screw air compressor, we use oil as the lubricating medium, so the compressed air will contain oil. But which can be reduced down to 0.003 microns by filters.

Then, Should I go with a Class 0 oil-free air compressor or the oil-lubricated air compressor?

What you need to do is to assess your facility’s requirements.

  • If your plant can’t tolerate any oil in contact with the product, choose a Class 0 oil-free air compressor is a must. Such as pharmaceutical, food & beverage, hospital, critical electronics, and other industries. To ensure that there is no chance of contamination by oil.
  • But, if there is no need for 100% oil-free, the majority of manufacturing, industrial or small workshops use oil-lubricated compressors. Although there is oil in compressed air, they use filters to reduce the oil content. Because it will be more economical.

Differences

Oil-free Screw air compressor

Oil-injected Screw Air Compressor

Lubricated medium

Water Oil

Temperature

The superior cooling capability of water
1) Removes the heat and gives more air per kW of power. Ideal isothermal compression guarantee energy efficiency
2) Reduces the stress on components ensuring long life
The high working temperature of the whole unit
1) Energy lost due to hot air discharge
2) Shorter lifetime of the components

Structure

Simple and compact, small volume and lightweight
without oil air separation unit
Complex,
need oil air separation unit

Rotor

Rotor never deformation and without the need of coating
50℃ ideal isothermal compression
Rotor easy to be deformed and coating easy to be broken off
110℃ high-temperature compression

Cooler

Only air cooler Air cooler and Oil cooler

Air Quality

100% oil-free oil concentration 3ppm traces of oil in compressed air need cleaned up further by filters

Cost-purchase

Higher Lower

Cost-maintenance maintenance

Only need to replace the Air filter element and Water filter elements Air filter+Oil filter+ Air oil separator elements, Oil, rotor, cooler

Cost-energy

Reduce your electricity bill to a minimum Extra energy consumption of oil-air separation unit and heat

Oil-free Screw Air Compressor

Oil-injected Screw Air Compressor

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