Fluid Couplings

Esco Aandrijvingen BV provides a complete range of fluid couplings

The fluid couplings of Transfluid provide a solution where a start-up must be performed in a controlled way without shock loads. Damage and premature wear and tear on the engine and machine are prevented because the torque is transferred by the fluid and the impellers.

Esco Aandrijvingen provides a complete assortment of fluid couplings for diesel engines and electric drives.

More details about fluid couplings


The fluid coupling is a Hydro Kinetic Transmission.

The impellers act like a centrifugal pump and a hydraulic turbine. With a drive on the pump side (e.g. electric motor or diesel engine) the kinetic energy is transferred to the impeller on the input side. The oil moves through the centrifugal force over the blades to the outside of the coupling. The kinetic energy of the oil is transferred on the turbine impeller and therefor transfers torque and speed. The wear is practically nil because there is no mechanical contact. The efficiency is only affected by the speed difference (slip) between pump and turbine.

The slip is essential for the operation of the coupling: there can be no torque transfer without the slip! The formula for slip, from which the loss can be deduced is as follows:

  • SLIP% = ((input speed – output speed)/input speed) x 100

In normal conditions the slip can vary between 1.5% (high power) up to 6% (low power).

Additional information?

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K-series Fluid Couplings

The K-Series fluid coupling is a “Constant Fill” type and consists of three main elements:

  • Impeller (pump) at the input shaft
  • Propelled impeller (turbine) on the outgoing shaft
  • Lid, flanged to the outgoing impeller, with a seal
  • The first two elements can operate both as pump and/or turbine
More about K-Series
  • The K series works with oil as standard, but is also available for drives that use water (on request)
  • Available in accordance with guideline 94/9/EC (ATEX)
  • Very smooth start-ups
  • The engine starts with a minimum load
  • Protection of the engine and the driven components due to avoiding blocking and overload
  • Energy savings thanks to a reduction in peak power
  • Limited start-up torque (up to 120%) in versions with dual delayed filling chamber
  • Absorption of torsional vibrations thanks to fluid transmission
  • Many start-ups possible, also with a reversal of the direction of the rotation
  • High efficiency
  • Minimum maintenance
  • Viton seals
  • Material is cast iron and steel with anti-corrosive treatment

K Serie Brochure

MPD and SPD Pump Drives

The MPD and SPD pump drive is an innovative module that fits between engine and transmission. With this module it is possible to drive several hydraulic pumps, with the required power coming directly from the engine’s flywheel. The MPD or SPD are mounted directly on the SAE housing and SAE flywheel.

More about MPD and SPD series
  • The output is a SAE dummy flywheel and housing where, for example, transmissions or PTOs can be connected
  • A self-lubricating unit
  • The following table shows the technical specifications:
    SizeSAE InputSAE OutputWeightQuantity of oil (ltr)Max. RPMMax. Torque Input (Nm)Total Power Pump outputs (kW)Power per pump output (kW)Ratio
    181 - 14"1 - 14"35018220033503001201.0 en 0.88
    221 - 14" en 0 - 18"0 - 18"53035210063004001750.95
  • The SPD is an innovative modular pump drive designed for mounting on industrial engines with SAE flywheel and housing
  • The input is a Rubber Block Drive. This elastic coupling absorbs radial and angular misalignments and dampens torsional vibrations
  • The SPD 11 has two SAE A or B pump outputs, a SAE flywheel and flywheel connection. The pumping tower can be mounted in 12 possible positions over 360 degrees
  • On the flywheel output, transmissions, pumps, compressors and PTOs can be connected
  • The SPD 7 has a single SAE A or B pump output and can be mounted in 8 possible positions over 360 degrees. On the shaft a pully for belt drive or directly to drive can be connected

Rubber Block Drives

Rubber Block Drives are flexible couplings between the engine’s flywheel and the powered unit, such as generators, pumps and compressor sets, and mobile applications such as forklifts and earthmoving machines.

RBD couplings have many advantages:

Easy assembly, low weight and short fitting. The drives are also supplied with standard SAE flanges for easy installation.

More about the RBD
  • The couplings are also available as SRBD versions, which means that RBDs are delivered complete with SAE or DIN 5480 finished hubs and selected SAE flanges. As a result you as the customer quickly select the right coupling at a competitive price
  • ATEX certification is available



Coupling can be provided:

  • With or without hub
  • With spline or shaft and keyway
  • With conical coupling
  • With housing for hydrostatic drives


Construction of the coupling:

The coupling has internal and external teeth. Between the teeth are blocks of special compound rubber. The external ring, of aluminum, has a profile that corresponds to the rubber molded compound and can be mounted directly on the output flange. This method makes it possible to capture small angle and radial alignment errors.

KPTO Variable Fluid Couplings

A KPTO is a fluid coupling which is connected to the diesel engine by means of a SAE housing. The coupling meets the demand for the technical characteristics of a conventional PTO but with the performance of a fluid coupling. The KPTO has an internal pump which is powered by the diesel engine. With a remote control on-off valve, the fluid coupling can be controlled at variable speeds.

More about the KPTO

Other Features:

  • Permanent lubrication of the bearings
  • The KPTO range is suitable for capacities up to 1000 KW
  • The motor flywheel is connected to the KPTO input by an elastic coupling. The output shaft can be connected to the powered machine by elastic coupling, cardan shaft or pulley
  • Supplied as standard: oil feed pump, oil filter with pressure and temperature gauges, On-Off electric valve, oil temperature switch level indicator
  • Optional: Water or air heat exchanger, Quick release valves, output pulleys, elastic couplings, output flange for cardan shafts and the cardan shaft itself


Benefits of the KPTO liquid coupling:

  • Works like a PTO, the powered machine can be effortlessly disconnected from the drive
  • Warming up the engine without load
  • Smooth start up, no slipping belt
  • Protection against shock and overload
  • Absorption of vibrations
  • High radial load is possible
  • Remote control by means of electric valve
  • Easy maintenance by external assembly of the main components such as oil filter, power supply pump and control valve
  • Long life span

SRBD Pump Drive

The SRBD is designed to connect a pump directly to the engine using a SAE housing and Rubber Block Drive.


Components are:

  • RBD coupling
  • QD Bus (machined)
  • SAE housing with inch threaded holes

About Transfluid

Transfluid is the market leader in the design and production of fluid couplings. The company was founded in 1957 and now produces more than 10,000 couplings per year. Pump drives, transmissions and PTOs are part of the program. Hybrid drives have also been developed recently. Contact Esco Aandrijvingen for your enquiries about fluid couplings.