Agriculture

Hydraulics are a central system for transmitting forces and movements in agricultural engineering. They use an incompressible fluid (typically hydraulic oil) to transfer pressure and provide mechanical energy.

Hydraulics are used wherever powerful, precise and compact actuators are required, for example for lifting, lowering, swivelling or dosing implements.

Common agricultural machines equipped with hydraulic systems include:

• Tractors (three-point hitch, steering, implements)
• Combine harvesters and harvesting machines
• Ploughs, harrows and seed drills
• Fertiliser spreaders
• Potato harvesters and corn or beet harvesters

Typical functions include driving a sweeping or harvesting roller, operating a spreading disc or actuating lifting and swivelling cylinders on implements.

Hydraulic systems offer several technical advantages:

• High power density in relatively small installation space
• Excellent controllability and fine adjustment of movements
• Flexible hose routing and easy integration into existing systems
• Long service life and low wear when correctly designed and maintained
• Hydraulic oil additionally provides cooling and lubrication

The selection of a hydraulic system depends on the specific requirements of the application. Important criteria include:

1. Operating and environmental conditions

• Maximum and minimum operating pressure
• Operating temperature range
• Chemical exposure and media compatibility of materials and seals
• Dusty or humid environments and required protective measures

2. Technical performance parameters

• Pump and line sizing for flow volume and flow rate
• Requirements for precision, speed and controllability
• Type of control (manual, proportional, electrically actuated)

3. Material and component selection

• Materials such as stainless steel or aluminium according to corrosion requirements and budget
• Standard-compliant selection of hoses regarding pressure, temperature and flexibility

In agriculture, hydraulic systems are typically operated under changing weather conditions, dust and dirt. Therefore, the focus is on robust, low-maintenance solutions.

To ensure reliability, essential components are usually made of steel or aluminium with suitable surface protection systems. Seals and valves use highly durable plastics and elastomers.

Design considerations include corrosion protection, wear resistance and leak-tightness to ensure functionality under harsh operating conditions.

Regular and proper maintenance is essential for the service life of hydraulic systems. With proper design and care, operating hours in the range of several tens of thousands of hours are achievable.

Maintenance typically includes:

• Oil changes according to manufacturer specifications
• Regular filter replacement
• Inspection of hoses, seals and fittings
• Monitoring oil quality and system pressures

Oil quality and system cleanliness are among the most important factors for reliability and wear behaviour.

For applications requiring high precision and dynamics, component selection is based on the required control type and controllability.

Systems with proportional valves are commonly used. Check valves, pressure-relief valves and other control valves are added to regulate flow, pressure and movement direction.

For manual operation, specific manual control valves are available, sometimes with features such as rapid travel mode to optimise work processes.

Various specialised hydraulic components are used in agricultural engineering, often driven via the PTO shaft. Examples include:

PTO gearboxes with hydraulic pump (gear pump)

• Gearboxes with stub or hollow shaft and fixed transmission ratios (e.g. 1:3.8)
• Mounted gear pumps with selectable displacement (e.g. 20 to 63 cm³/rev in size 3)

Manual control valves (monoblock valves)

• Flow control capability (e.g. 60 l/min or 80 l/min)
• Integrated pressure-relief valves with adjustable working pressures (e.g. 63–200 bar or 160–315 bar)

Scraper-floor drives

• Hydraulic gearboxes using a hydraulic motor as input
• Designed for torques of approx. 1900 Nm (depending on size and application)