Integrally geared compressor

Integrally geared compressors – proven, reliable and highly efficient

From its invention in 1948, Siemens Energy has perfected the design and manufacture of integrally geared compressors. Today, more than 2,200 units have been installed globally proving their worth with a wide reference base in a wide range of industries and process applications.

Integrally geared compressors

Integrally geared compressors are multi-shaft machines. Several pinion shafts with one or two impellers each are arranged around a central bull gear. For each pinion shaft a perfect combination of shaft speed and impeller size can be realized. All impellers are of overhung design and can be fitted with adjustable inlet guide vanes in front of each impeller. Inter-stage cooling of the gas stream can be done after each impeller discharge. The combination of these features allows for high volume flows, outstanding energy efficiency even under part load, all in a compact design.

For small- to medium-size compressor sizes, Siemens Energy offers a package design. The package can include the compressor, driver, process gas coolers, lube oil console, process piping, and all tubing and wiring. The package design leads to significantly reduced on-site installation time. For large-size units all main train components are delivered separately to site to be installed on a concrete foundation.

Customized compressors

Our customized line of integrally geared machines can accommodate up to four pinion shafts with up to eight impellers total resulting in impressive pressure ratios which can be achieved in a compact design. Compressors can be designed according to API 617 or API 672 and customer specifications. Driver options depend on process and energy resources and can be electric motor, steam turbine or gas turbine and are suitable for direct turbine-drive or even integrated expansion turbine design.

Customized compressors with integrated radial expansion turbine

A variant of the customized integrally geared compressor allows the integration of a single- or two-stage radial expansion turbine as a direct drive option for the compressor. This allows the direct recovery and conversion of energy from pressurized high temperature process gas streams into kinetic energy driving the compressor. Depending on the amount of available energy, this drive option can serve as sole drive, or as drive in combination with other drive options such as electric motor or steam turbine. 


  • Outstanding impeller technology for high capacity and high efficiency
  • Capability for combination of multiple processes
  • Design options for any kind of gas
  • Designed according to API 617, API 672 and customer specifications
  • Up to eight impellers / stages
  • Inter-cooling between stages
  • All gear components designed and manufactured within our own supply chain
  • Comprehensive driver options
  • Gear options for cost optimized motor driver speed

Technical data

  • Volume flow rates up to 1,000,000 m³/h / 590,000 cfm
  • Discharge pressure up to 200 bar / 2,900 psi 
  • Gear box ratings up to 85,000 kW / 87,000 hp


Standardized compressors

Our standardized designs come with up to two pinion shafts with one or two impellers each. Standardized integrally geared machines come in two groups of frame sizes for 10,000-100,000 and 120,000-400,000m3/h capacity. These product lines are standardized versions of the customized integrally geared compressor series, the trusty workhorse of the air separation and process industry. The high degree of standardization results in lower capital costs and shorter delivery times as compared with fully customized compressors.

The first group is available in nine frames (sizes 10-100) for volume flow rates between 10,000 and 100,000m3/h and can be packaged as compact single-lift units. 

The second group extends the available range of volume flow rates to between 120,000–400,000m3/h capacities with additional five frame sizes (165-400). Eighty percent of the machine is pre-engineered for consistency and repeatability. 20 percent of the machine can be customized for specific customer process needs.

Frame sizes 10 - 100


  • Compact, single-lift unit
  • Maximum performance due to predesigned gears, highest efficiency impellers, tailored aerodynamics, and predefined auxiliaries
  • Up to four impellers

Technical data

  • Flow rates from 3,600 to 120,000 m³/h (2,120 to 70,680 cfm)
  • Pressure ratio up to 20
  • Electric motor drive (fixed speed)


  • Air separation
  • Plant air
  • Nitrogen (up to GC 50)

Frame sizes 165 - 400


  • Efficiencies are comparable with customized series by use of same well proven flow components
  • High flexibility derived from large number of fixed options

Technical data

  • Flow rates from 120,000 to 400,000 m³/h (70,680 to 235,600 cfm)
  • Pressure ratio up to 6.5
  • Electric motor drive (fixed speed)


  • Air separation (main air compressor)

Single stage centrifugal compressors

Our single stage centrifugal compressor is the perfect fit for atmospheric air compression at low pressure ratios. It covers a large flow range from small to very high volumes of up to 1.000.000 m3/h. This compressor uses well proven components from our integral geared compressor line and is designed in accordance with API 617. State-of-the-art aerodynamic parts allow a compact, single stage design. If necessary, an external gear box is used to match the driver speed. This modular design offers the advantage of an unchanged compressor design irrespective whether the machine is driven by a steam turbine, gas turbine or electric motor.

Integrally geared compressor


Our single stage overhung compressor boasts a simple and robust design with well referenced components, smaller dimensions and less weight at the highest efficiency level, and low maintenance requirements.

In case of higher pressure ratio requirements, the configuration comprises two single stage overhung machines driven by a double-ended steam turbine drive between the compressors.


  • Large flow range
  • Simple, robust design in accordance with API 617
  • High efficiency
  • Highest reliability due to well referenced components
  • Low service intensity
  • Easy maintenance
  • Small dimensions
  • Low weights
  • Low spare part costs

Technical data

  • Volume flow rates up to 1,000,000 m³/h / 590,000 cfm
  • Pressure ratio up to ~3 (up to ~6.5 in case of 2 units)
  • Suitable for electric motor, steam turbine or gas turbine drive 


  • Regeneration air applications in PDH (Propane DeHydrogenation) plants
  • Blast furnace blowers (2 units)
  • Fluid Catalytic Cracking (2 units)
  • Main Air Compressor for Air Separation units (2 units)

Integrally geared compressors for CO2 compression in CCUS applications - a whitepaper

In this paper, we compare various CO2 compression technologies and highlight the advantages integrally geared compressors (IGCs) provide in terms of efficiency, costs, flexibility, reliability, and footprint.


Complete the form below to download our whitepaper.

Integrally geared compressor

Mechanical Vapor Recompression (MVR) cycles open a new pathway for decarbonization

Looking for an efficient and cost-effective way to recover waste heat in your industrial processes? For waste heat temperature levels from approximately 70°C (i.e. mid-temperature levels), MVR cycles provide an alternative to closed loop heat pumps for recovering waste heat, to produce low, medium, or high-pressure steam.

MVR cycles use advanced compression technology to extract heat from industrial processes and convert it into usable energy. This technology is particularly useful for the downstream oil and gas, chemicals, pulp and paper, food and beverage, and aluminum industries, where waste heat is a byproduct of many processes.

With MVR cycles, thermal energy from a mid-temperature waste stream is used to directly evaporate feedwater. The steam is then compressed to the required temperature and pressure level of the process. The entire latent heat for evaporation is provided by the free-of-charge waste heat. Only the sensible heat, which is significantly lower than the latent/evaporation heat, is provided in the form of compression. The steam can then be used for industrial purposes, either as a feedstock or as a heating medium, e.g. in the chemical industry or in pulp and paper.

For application cases in which waste steam is present at lower than desired pressure levels, the steam can simply be compressed up to higher pressure and temperature levels, with the use of our multi-stage integrally geared steam compressors.


  • The MVR cycle can be applied for waste heat sources at temperatures as low as ~70°C and does not require the use of a refrigerant, which is often either fluorinated, flammable, or toxic.
  • Compared to a closed loop heat pump, the MVR system can be designed in a very lean and compact way – oftentimes eliminating the need for an expansion valve, the flash tank, the refrigerant condenser, and some ancillary piping.
  • COPs (Coefficients of Performance) of more than 7.0 are possible. This means only one seventh of the final heat output needs to be given in the form of electricity for the compressor drive; the remaining six sevenths are provided in the form of waste heat.
  • With the use of our proven Integrally Geared Compressor (IGC) technology, CAPEX, OPEX and footprint can be optimized.
  • Our IGCs can handle large volumetric flows up to 2.4 million m3/hr in one machine, enabling applications with 100+ MWth final heat output with only one machine. 
  • Final steam pressures up to 60 bar and temperatures up to 330°C are possible. Higher temperatures are possible as well with the use of a small downstream superheater.
  • We have extensive steam know-how and experience inhouse via 10,000+ steam turbine references.

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