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BHS Parallel Shaft Gear Units

BHS parallel shaft gear units convert torque in turbo drive trains. Three gear unit series cover a power range from 500 kW to 85 000 kW. Gear ratios are available from 1:1 to 20:1.

We adapt our parallel shaft gear units to meet your needs. The BHS parallel shaft gear unit is optimally designed to meet your requirements with respect to gear toothing, housing dimensions, materials, and bearing technology. This ideal fine-tuning and the robust design result in a long lifetime of several decades, typically more than 200 000 operational hours.

BHS parallel shaft gear unit efficiency can reach levels of up to 99.3 percent. The result is high system productivity, especially at gear ratios less than 6:1.

Our customers have been placing their trust in BHS parallel shaft gear units since 1950. More than
7 000 gear units of this type are in use reliably around the world, mostly under very harsh conditions. This happens very often in combination with a BHS rotor turning gear unit and one, two or more BHS diaphragm couplings.

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 Technical Emergency Helpline
Tel. +49 8321 802-555

Technical data

Power transmission 0.5 – 85 MW
Speeds 500 – 60 000 rpm
Efficiency up to 99.3%
Center distance
  • standard 250 – 1 150 mm
  • special > 1 150 mm
Gear ratio
  • 1:1 – 11:1 (single-stage)
  • 9:1 – 20:1 (two-stage)
Housing design
  • cast, welded
  • horizontal or vertical shaft offset
  • double-helical
  • single-helical with thrust collar
  • single-helical with axial bearing
Bearing technology hydrodynamic film bearings, BHS UltraCool design as needed
Noise emissions between 75 and 88 dB(A) at full load and rated speed
Design variants
  • built-in pumps
  • built-in starter drive
  • built-in rotor turning gear unit
  • integrated system for jacking oil
  • with couplings (at high and low speed side)
  • with oil supply system

Advantages and Benefits

BHS helical gear units from Voith

  • are customized to the operator's needs. These gear units deliver a very good price-performance ratio.
  • consist of a few very robust components that are finely and optimally tuned to each other as a complete system. This makes BHS parallel shaft gear units extremely reliable and allows them to run for very long periods without un­scheduled downtime, boosting the productivity of your system.
  • possess an excellent level of mechanical efficiency of up to 99.3%. Plant operators save energy, which reduces operating costs and CO2 emissions.
  • feature bearing technology adapted to the respective requirements. This means the ratio between bearing stiffness and damping is perfect, enabling excellent rotor dynamic behavior. This increases the operational safety of your system.
  • run very quietly, usually under 80 dB(A). This is made possible by the high quality of the gear toothing, special gear tooth profiles, and the special shape of the housing, often rendering investments in special noise abatement equipment unnecessary.

Typical applications

Driving machine:

  • Steam turbine
  • Gas turbine
  • Electric motor

Driven machine:

  • Generator
  • Compressor (axial, radial)
  • Pumps (centrifugal)
  • Fans / blowers


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

Technical information

Design and function

BHS turbo parallel gear units consist of a housing and a bull gear and pinion shaft that are supported in hydrodynamic film bearings Options include both speed in­creasing and speed reducing gear units. Applicable standards are, e.g., DIN 3990, ISO 6336, ISO 13691, AGMA 6011, API 613 or the corresponding Voith Standard that insome areas exceeds the quality requirements of these standards.
As opposed to most integral gear units, the pinion shaft of a BHS parallel shaft gear unit typically runs below the first critical speed. Special bearings (BHS UltraCool bearings) make it possible to achieve low oil operating temperatures. This in­creases the lifetime and operational safety of your system.