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BHS Integral Gear Units

The BHS integral gear unit is the central component in turbo gear unit compressors. These compressors generate up to 250 bar of pressure and can reach volumetric flow rates of up to 600 000 m³/h. Voith's series of single-shaft and multi-shaft gear units covers a power range of 500 kW to
55 000 kW. Gear ratios from 1:1 to 1:25 are possible.

We customize our integral gear units to fit your application and meet your needs. This ensures that your system's drive design and the number of compressor stages are taken into consideration. The typical lifetime of a BHS integral gear unit is sev­eral decades and, with regular maintenance, it will outlast your system.

BHS multi-shaft integral gear units commonly achieve efficiencies of up to 98.5%, and up to 99.2% for single-shaft gear units. Our customers have trusted BHS in­tegral gear units for more than 40 years. More than 2 000 gear units of this type are operating reliably around the world, in many cases under very harsh conditions.

Beside this Voith offers also other types of turbo gear units.




Voith GmbH & Co. KGaA
Hans-Böckler-Straße 7
87527 Sonthofen, Germany

Tel. +49 8321 802-825

Service Sales
Tel. + 49 8321 802-826

24/7 Emergency Contact
Tel. +49 8321 802-555

Technical data

Power transmission 0.5 – 55 MW
Speeds up to 55 000 rpm
Rated output torque values up to 150 000 Nm
Efficiency up to 98.5% (99.2%)
Gear ratios 1:1 – 1:25
Compressor stages 1 – 8
Housing design cast, welded
  • single-helical with thrust collar (standard)
  • single-helical with separate axial bearing
Design versions For drives with

  • electric motor
  • steam turbine
  • steam turbine + electric motor
  • expansion turbine
  • gas turbine

Advantages and Benefits

BHS integral gear units from Voith

  • are customized to the operator's needs. These gear units deliver a very good price-performance ratio and optimize the compressor string. The result is an improved ROI for your equipment.
  • are reliable. They operate for long periods with no unscheduled downtime and increase the productivity of your equipment.
  • feature truss-braced housings, which are low in weight and yet still extremely stiff. This allows the gear set to transmit power ideally and reliably. The result is reduced stress on the gear unit, thus increasing the availability of your equipment.
  • safely deliver up to 98.5% efficiency — even at high axial thrust — thanks to Voith's optimized thrust collar technology. This saves you energy. Operating costs are reduced and fewer CO2 emissions help protect the environment.
  • allow you to design your drive system with a high degree of flexibility. Use the power sources you already have — you can even combine them. That means you operate your equipment with the drive system solution that works best for you.
  • are often the best technical solution for gas compression. With us as your partner, your job as equipment manufacturer of converting from in-line compressors to integral gear unit compressor technology will be that much easier. It will also be much simpler to expand your portfolio of services. Last but not least, working with us will increase your success in the market as a compressor manufacturer.

Typical applications

Driving machine:

  • Steam turbine
  • Electric motor, either alone or in combination
  • Gas turbine
  • Expansion turbine


  • Power generation (power plants)
  • Oil & gas (upstream, midstream, downstream)
  • Petrochemicals
  • Chemicals
  • Steel
  • Test beds

Technical information

Design and function

A BHS integral gear unit consists of a gear set and a housing that is extremely rigid and resistant to flex. The gear set consists of a central bull gear, up to four pinion shafts, and in some cases an intermediate gear. The pinion shafts typically utilize thrust collars which transmit axial forces to the housing via the bull gear and its axial bearing. All pinion shafts generally run above the first or second critical speed.

The equipment manufacturer installs his compressor scrolls on the gear unit housing. The center of each compressor scroll contains a rotating compressor wheel that is connected to one end of a gear pinion shaft. Labyrinth or gas seals prevent the compression process gas from penetrating into the gear unit housing.

BHS integral gear units increase or reduce the input speed. Speed-increasing gear units are typically used between electric motors and compressors, for example, whereas speed-reduction gear units are used between expansion turbines and generators. BHS integral gear units can be designed in accordance with a wide variety of standards: ISO 6336, AGMA 6011, API 613, API 617, API 672 or the corresponding Voith Standard that exceeds the quality requirements of these standards.