Road construction technology

Road construction technology

Components and systems for road construction machinery


HYDAC is an old hand at servicing road construction machinery.

Servicing covers components and systems for:

  • control technology and system intelligence
  • collaboration
  • sensors, system electronics and displays
  • TTConnect cloud service
  • valve and control block technology
  • convenience systems and components
  • hydraulic supply
  • filtration, air separation and tank optimisation

In addition, solutions are provided for:

  • accessories
  • cylinder systems
  • fluid condition monitoring and fluid conditioning
  • service tools
  • technical cleanliness
  • HYDAC Kinesys electro-cylinders for mobile applications

Applications include:

  • road milling machines and soil stabilisers
  • asphalt and concrete pavers
  • earthworks compactors


Application focus: road milling machines and soil stabilisers

HYDAC’s involvement in applications for road milling machines and soil stabilisers is the focus in this summary.

Cab roof and bonnet adjustment

  • To lift/lower the cab roof and bonnet with integrated leakage-free load holding
  • Includes hand pump for emergency operation of both functions

Loading belt control

  • Lifting and lowering of loading belt
  • Right/left swivelling of loading belt
  • Folding loading belt into transport position

Levelling control block

  • For levelling of the mill during operation to ensure an even surface
  • The levelling is performed in interaction with the linear position and tilt sensors in four individual chassis cylinders

Chassis control block

  • To control the front or rear steering
  • Adjusting height of the chassis right/left
  • Bulkhead plate control (lift/lower) to prevent milled material from escaping during milling
  • Position retention with leakage-free poppet valves

Modular system for working hydraulics, chassis, and steering

The following functions can be integrated directly or on an optional basis depending on configuration level:

  • Height adjustment right/left
  • Edge protection right/left
  • Folding of the right-hand drive gear for rim or edge milling (track widening)
  • Chisel/tool change
  • Remote control of various belt conveyors
  • Proportional steering/additional steering
  • Lift/lower protective roof
  • Drum flap
  • Levelling boom

CMS combination cooler

  • Cooling circuits charge air, coolant, and hydraulic oil
  • Compact design
  • Optimum arrangement of the heat exchangers for optimum performance
  • Use of two small fans for reduced power consumption
  • cooling air exits upwards to ensure reduced noise level

Hydraulic filtration

The RKM return line suction filters are the interface between the open circuit of the working hydraulics and the closed circuit of the traction drive.

The return line flow is finely filtered and some of it is pressurised (0.5 bar) and supplied to the boost pump.

With an optional integrated thermos-cooler bypass valve, some of the return line flow can also be conveyed via the oil cooler.

DC small power pack for hydraulic supply

The DC small power pack for hydraulic supply is used to supply small consumers during maintenance or emergencies to prevent the main hydraulics from being used.

  • Enables slow turning of the milling roller for chisel change
  • For lifting /lowering the milling roller, bonnet, or cab roof
  • For emergency steering at 100% duty cycle so the mill can be driven from the road

Chassis cylinders cooling circuits: for crawler drives

The cylinder is attached to the crawler chassis of a road milling machine and is used to configure the height of the crawler chassis.

The cylinder is rotated about its longitudinal axis to steer the crawler chassis.

The piston rod can rotate in the cylinder at the stop on the cover or base (bronze welded on to rod end, bronze disc the top of the piston). The chassis cylinder is supplied with oil via the rod head.

Applications – control technology


  • Programming in CODESYS or C
  • New outdoor variant for the HY-eVision² display, with bonded display specially designed for off-road applications (machinery without a cab)


  • Programming in CODESYS or C l 30 to 96 inputs and outputs
  • Certified controls

For further information, download the relevant pdf at