Diagnosing Slow Swing and Travel Issues on the Hitachi EX-120-2 Excavator

[MikePhua]

Overview of Slow Swing and Travel Symptoms
The Hitachi EX-120-2 excavator is known for its reliability and robust performance. However, operators sometimes encounter issues where the machine exhibits slow swing or travel functions. These symptoms significantly reduce productivity and may indicate hydraulic or mechanical problems requiring prompt attention.
Common Causes of Slow Swing and Travel
Several factors can lead to sluggish swing and travel:

• Hydraulic System Problems: Low hydraulic fluid levels, contaminated fluid, or worn hydraulic pumps can reduce flow and pressure, limiting actuator performance.
  
• Valve Blockages or Malfunctions: Spool valves or control valves may stick or leak internally, restricting hydraulic flow.
  
• Worn or Damaged Motors: Hydraulic motors driving the swing or travel mechanisms may suffer wear or internal damage.
  
• Hydraulic Filter Clogging: Dirty filters reduce fluid flow and strain the hydraulic system.
  
• Mechanical Wear: Components like swing bearings, travel motors, or final drives may degrade, causing resistance.
  

Diagnostic Procedures
A systematic diagnostic approach includes:

• Checking hydraulic fluid levels and condition.
  
• Inspecting and replacing clogged filters.
  
• Measuring hydraulic pressures at pumps and motors to detect flow issues.
  
• Examining control valves for proper operation and leaks.
  
• Inspecting mechanical components for wear or damage.
  

Using pressure gauges and flow meters helps pinpoint hydraulic inefficiencies.
Repair and Maintenance Solutions
Effective remedies may involve:

• Flushing and replacing hydraulic fluid with manufacturer-approved oil.
  
• Servicing or replacing hydraulic pumps, motors, or valves.
  
• Cleaning or replacing hydraulic filters regularly.
  
• Repairing or replacing worn mechanical parts like bearings and drive components.
  

Routine maintenance is essential to prevent recurrence.
Field Experiences and Practical Insights
One operator recalled that slow swing speed was resolved after replacing a worn swing motor that had lost internal efficiency. This repair restored normal operation and prevented further damage.
Another technician shared a case where slow travel was due to clogged hydraulic filters and contaminated fluid. After fluid changes and filter replacement, travel speed improved markedly.
Industry Context and Technological Advances
Modern excavators are equipped with enhanced filtration systems and more durable hydraulic components to minimize slowdowns. Some models include electronic monitoring to detect hydraulic inefficiencies early, allowing preventive maintenance.
Conclusion
Slow swing and travel on the Hitachi EX-120-2 excavator often point to hydraulic or mechanical issues. Careful diagnosis combined with thorough maintenance and targeted repairs restores performance and prolongs machine life. Real-world cases demonstrate that addressing hydraulic fluid quality and component wear are key to maintaining smooth, efficient operation in demanding work environments.