Hydraulic System of the Komatsu PC390 Excavator

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Machine Overview
The Komatsu PC390 series excavators are robust heavy-duty machines powering demanding earthmoving and construction applications. The PC390LC-10 and newer models feature powerful engines delivering around 257 horsepower (192 kW) combined with advanced hydraulic systems for efficient and precise machine operation.
Hydraulic System Design

• The PC390 utilizes a HydrauMind hydraulic system, which is a closed-center, load-sensing system with pressure-compensated valves and electronic control. This innovative design allows for smooth, energy-efficient operation by directing hydraulic flow precisely where and when needed.
  
• The system includes variable displacement axial piston pumps serving multiple circuits: boom, arm, bucket, swing, and travel.
  
• The maximum hydraulic flow capacity is approximately 535 liters per minute (141 gallons per minute), supporting high-demand functions simultaneously without performance degradation.
  

Hydraulic Components and Performance

• Cylinders: Typical configurations utilize large bore and stroke hydraulic cylinders:
  • Boom cylinders: 140 mm bore x 1480 mm stroke
    
  • Arm cylinder: 160 mm bore x 1825 mm stroke
    
  • Bucket cylinder varies with arm length: standard 140-150 mm bore with stroke lengths ~1285 mm
    
• Hydraulic Motors: Axial piston type motors power travel (two motors with parking brakes) and swing (one motor with swing holding brake).
  
• Pressure Settings:
  • Implement circuits: 37.3 MPa (5,400 psi)
    
  • Travel circuits: 37.3 MPa (5,400 psi)
    
  • Swing circuits: 27.9 MPa (4,050 psi)
    
  • Pilot control circuit: 3.2 MPa (470 psi)
    
• Swing System: Hydrostatic drive with planetary reduction gears, swing speed ~9.5 rpm, and swing torque around 82,000 ft-lbs (11,386 kg- m).
  
• Steering and Travel: Dual lever with pedal controls combined with hydraulic drive motors ensure precise control and high traction capability, enabling up to 70% gradeability (35° slope capability).
  

Additional Information

• The excavator uses a mechanical fan driven cooling system, and electronic all-speed control governs engine RPM for fuel efficiency.
  
• Service and parking brakes are hydraulic lock type and mechanical disc respectively, ensuring safe and reliable stops.
  
• Hydraulic fluid and tank capacities optimize system operation while supporting long maintenance intervals.
  

Terminology

• Closed-Center System: Hydraulic system where flow is directed only upon demand, improving efficiency.
  
• Load Sensing: System detects required hydraulic load and adjusts pump output accordingly.
  
• Variable Displacement Pump: Pump that can dynamically change flow output based on system needs.
  
• Axial Piston Pump: A type of hydraulic pump providing high efficiency and pressure capabilities.
  
• HydrauMind: Komatsu’s proprietary hydraulic system integrating mechanical and electronic intelligence.
  

Operational Impact
This hydraulic setup provides operators with responsive and reliable control over heavy lifting, digging, and machine mobility tasks, ensuring productivity on challenging job sites. The load sensing and variable pump technology reduce fuel consumption and minimize wear.
Summary
The Komatsu PC390 excavator features a state-of-the-art HydrauMind hydraulic system delivering up to 535 liters per minute of flow under high pressures suitable for boom, arm, bucket, swing, and travel operations. Large bore hydraulic cylinders, efficient axial piston motors, and electronic control enable precise, powerful functions. This combination ensures the PC390 maintains superior performance, fuel efficiency, and operational flexibility for demanding applications.