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Water instead of oil  - positive energy budget thanks to new developed water-injected compressor

New water-injected compressor stages from Aerzen for the special energy-efficient production of absolute oil-free compressed-air

The challenge in terms of sustainability:

Over a ten year operating period, energy costs equate to about 90% of the total Life Cycle Costs of a compressor. With this in mind, the Delta Hybrid was developed with the focus on increasing energy efficiency and achieving a significant reduction of energy costs and greenhouse gas emissions.

The initial situation:

Regarding production of absolute oil-free compressed-air the market offers three possible solutions.

  • However, in case of oil-injected screw compressors high additional costs may arise due to the oil-free preparation and residual risks by faulty processing components.
  • Oil-free compressing units produce absolutely oil-free compressed-air, however, due to the two-stage design they require considerably
  • increased investment costs.
  • So far, the water-injected compressors have not worked with optimum efficiency, as the polymeric-ceramic materials of the rotors are not dimensionally stable and require, therefore, higher gap dimensions.

The solution:

So far, rotors of water stages have been mainly made of polymeric-ceramics. However, with pressures above 7 bar this material leads to a plastic deformation of the rotors. This reduced profile accuracy must be balanced with bigger clearances within the compressor stage, leading to a  considerable deterioration of efficiency. Based on the long-time experiences regarding production of oil-injected compressor stages with rotors made of steel, Aerzener Maschinenfabrik has selected this material also for the new VMW-water stages.
The high-alloy, non-corrosive steel works also at higher pressures up to 13 bar resistant to deformation, so that the clearances have been decreased considerably and the efficiencies could be improved essentially. Now, they are comparable directly with the values of the oil-injected screw compressors.Instead of lubricating the new water stages by injection water or selecting  maintenance-intensive grease-lubricated bearings, Aerzen has decided in favour of oil-lubricated roller bearings. This solution leads in connection with a special lubricant to a permanent lubrication during the life time cycle of the compressor stage. Consequently, no more oil changing or refilling tasks are necessary. An atmospheric gap between bearings and compression room protects reliably the oil chamber from water penetration or from oil entering the water room. Both rotors precisely operated are free from wear and will work until the end of the entire plant. They are driven via a high-precision synchronisation gearbox with high gearing quality for a particular smooth running.

The sustainable strengths:


  • Unrivalled maintenance intervals min. 2 years (16.000 hours)
  • Long lifetime
  • High C.O.P.
  • Absolute oil-free compressed-air
  • Highest-possible energy efficiency
  • Reduced investment costs

The inventors:

Aerzener Maschinenfabrik GmbH

Brief profile of the company:

Name: Aerzener Maschinenfabrik GmbH
Headquater: Aerzen
Year established: 1864
Employees: 1800 (worldwide)
Solutions:  blowers, compressors, rotary lobe compressors, gas meters, turbo blowers
Internationalität: 40 Subsidiary companies worldwide