Excavator Main Hydraulic System: Load-Sensing Control

Background

Hydraulic excavators need to drive multiple high-force actuators — boom, arm, bucket, swing and travel — often simultaneously. Traditional fixed-displacement systems waste significant energy by producing full flow regardless of demand.

Requirements Analysis

• Deliver precise, independent control of multiple actuators
• Minimize energy waste and fuel consumption
• Provide smooth operation under varying loads
• Protect the system from overload

Solution Design

We implemented a load-sensing (LS) closed-center system with a variable-displacement piston pump:

1. Variable piston pump with load-sensing compensator that only produces the flow actually demanded by the actuators
2. Proportional directional valves that meter flow to each actuator based on joystick input
3. Load-sensing lines that communicate the highest load pressure back to the pump compensator
4. Pressure compensators on each valve section for flow sharing under simultaneous operation

Implementation & Results

• Energy savings: Pump flow matches demand, reducing parasitic losses by 20–30% compared to fixed-displacement systems
• Better control: Independent, proportional speed control of each actuator
• Reduced heat: Less wasted flow means lower oil temperature and smaller coolers
• Fuel economy: Significant reduction in engine load during partial-operation duty cycles

This load-sensing architecture is now standard on modern excavators for its combination of efficiency, control and compactness.