Hydraulics is the transmission of signals, forces, and energy, or for lubrication purposes. The hydraulic block of today’s technology looks almost painfully full of holes; while it might remind the viewer of Swiss cheese, however, the technology behind it is complex and incredibly versatile.

Hydraulics is one method of transmission – an alternative to mechanical gears or electrical or pneumatic transmissions. The power transmission is provided by a hydraulic fluid; this is usually a particular type of mineral oil, but it can also be a more environmentally-friendly option such as water or special ester or glycol fluids. The transmitted forces are a result of the pressure and the amount of fluid streaming through. A distinction can be made here between:

hydrodynamic systems with a pump and a turbine, in which changes in revolution speed and torque is produced by kinetic energy from the fluid; and
hydrostatic systems, which, first and foremost, transform mechanical power from a machine (electric motor, diesel engine, etc.) to hydraulic power via a pump. The hydraulic power is then attached to a load (generator engine) and transformed back into mechanical power (continuously variable). In hydraulic cylinders, this translates to linear motions; in hydro-motors, to rotational movement.

machined parts out of ductile iron and ADI are used in drivetrain technology, materials handling technology and powertrain technology as mechanical high-loaded structural component
Core intensive castings made of spheroidal cast iron for hydraulic applications ( including steering function ) are moulded in high numbers in iron foundries

The flow of pressurized fluid into the cylinder forces the piston and piston rod within the cylinder to move; this movement is then used for a given work process and to power machines. Rotating drives, such as the hydraulic motor, can also be implemented using pressurized fluid.

Due to their specific advantages, hydraulic drives are frequently used in mobile machinery such as construction or agriculture machinery, and in particular to lift and shift heavy loads (forklifts, excavators/diggers, elevators, cranes, etc.).

Additional typical uses include:

  • personal and commercial vehicles: clutch and braking systems, automatic transmissions, power steering, adaptive chassis control, convertible covers, lift/tilt systems, loading tailgates, hydrostatic traction drives
  • combustion engines: camshaft adjustment, valve control, fuel injection
  • commercial airplanes: operation of wing flaps, landing gear
  • rail technology: rail brakes in the shunting station/switchyard
  • platform lifts
  • vehicles with rotating hydraulic transmissions or fluid transformers
  • hydraulic torques for pre-tensioning screws
  • construction vehicles: hydraulic propulsion of all machines, including slewing and forward movement
  • (mobile) cranes: hydraulic control of telescoping masts, hoisting unit, winding unit, slewing gearing, counterbalance, steering, and (in part) forward propulsion
  • industrial material handling: all movement (including steering and forward propulsion)
  • agriculture and forestry: hydrostatic drives for movement and machine function, lifter for machine tool(s); hydraulic (power) steering
  • lifts/loading platforms with short travel distances and high loads

The list could be extended indefinitely; in terms of part variety and designation, there are more options than holes in a piece of Swiss cheese. From hydraulic blocks to transmission covers and bell housings, a huge variety of components fall under the mantle of hydraulics. The primary material used here is SG cast iron; however, for higher pressure levels, ADI can also be used. No need here for high-temperature materials – it has been reported to us that the hydraulic fluids already have “massive difficulties” at 300° C (575°F)…