Hitachi EX270LC Center Joint Removal: Experiences and Best Practices

[MikePhua]

Introduction to the Center Joint and Its Importance
The center joint, also known as the swing joint or swivel joint, is a critical hydraulic component in excavators such as the Hitachi EX270LC. It allows hydraulic fluid to pass between the upper structure and undercarriage while enabling continuous rotation of the upper frame. Proper maintenance and timely replacement are essential to prevent hydraulic leaks, loss of control, and costly downtime.
Common Reasons for Center Joint Removal

• Hydraulic Leaks: Over time, seals within the center joint degrade, causing oil to leak.
  
• Wear and Tear: Mechanical wear can damage internal parts, reducing hydraulic efficiency.
  
• Contamination: Dirt and debris may infiltrate the joint, leading to premature failure.
  
• Scheduled Maintenance: Periodic replacement as part of preventive maintenance.
  

Challenges in Removing the Center Joint on Hitachi EX270LC
Removing the center joint on the EX270LC model is known to be a challenging task due to the following:

• Heavy Weight and Size: The joint is bulky and heavy, requiring lifting equipment.
  
• Tight Space: Limited clearance between upper structure and undercarriage complicates access.
  
• Corrosion and Seizure: Bolts and fittings can become rusted or seized after years of use.
  
• Alignment Issues: Proper realignment is critical when reinstalling to avoid premature wear.
  

Step-by-Step Insights from Operators and Mechanics

1. Preparation and Safety
   • Secure the machine on a flat surface with the parking brake engaged.
     
   • Disconnect battery and relieve hydraulic pressure.
     
   • Remove any attachments and clear surrounding area.
     
   • Use appropriate lifting gear such as cranes or hoists rated for the weight.
     
2. Accessing the Center Joint
   • Remove protective covers, bolts, and any obstructing components.
     
   • Drain hydraulic fluid if necessary to minimize spills.
     
   • Label hydraulic lines to ensure proper reattachment.
     
3. Unbolting and Separation
   • Apply penetrating oil to stuck bolts ahead of time.
     
   • Use impact wrenches or breaker bars for stubborn fasteners.
     
   • Support the upper structure to prevent shifting during removal.
     
   • Gently separate the center joint from the upper and lower sections.
     
4. Removal and Handling
   • Lift the center joint carefully using lifting eyes or slings.
     
   • Avoid damage to seals and mating surfaces.
     
   • Inspect the joint for wear, cracks, or contamination.
     
5. Installation Considerations
   • Clean all mating surfaces thoroughly.
     
   • Replace seals and O-rings with OEM-quality parts.
     
   • Align the joint precisely to manufacturer specifications.
     
   • Torque bolts to recommended values using calibrated tools.
     
   • Refill hydraulic fluid and bleed the system to remove air.
     

Operator Tips and Lessons Learned

• Use Manufacturer’s Service Manual: Detailed diagrams and torque specs are invaluable.
  
• Prepare for Rusted Components: Expect to replace some bolts or use heat to loosen.
  
• Document Hydraulic Line Positions: Photographs and labels prevent reassembly errors.
  
• Take Your Time: Rushing can cause damage or unsafe conditions.
  
• Engage Experienced Technicians: Complex removals may require specialist knowledge.
  

Terminology Explained

• Center Joint / Swing Joint: Hydraulic swivel component connecting upper and lower excavator structures.
  
• Hydraulic Lines: Tubes that carry pressurized fluid for machine functions.
  
• Penetrating Oil: A lubricant used to loosen rusted or seized bolts.
  
• Torque Specifications: Manufacturer-recommended tightness levels for bolts.
  
• Bleeding Hydraulic System: Removing trapped air from hydraulic lines to ensure proper operation.
  

Case Stories and Practical Examples
One Hitachi EX270LC operator recounted spending two days on center joint removal due to severely seized bolts, eventually resorting to cutting tools and replacements bolts. Another mechanic recommended pre-soaking bolts with penetrating oil for 48 hours before attempting removal, which saved considerable time. These experiences emphasize the importance of preparation and patience.
Summary of Best Practices

• Secure machine and ensure safety.
  
• Thoroughly prepare by labeling and cleaning.
  
• Use correct lifting equipment and tools.
  
• Follow manufacturer instructions precisely.
  
• Inspect and replace worn or damaged components.
  
• Perform careful reassembly and hydraulic system bleeding.
  

Conclusion
Removing and reinstalling the center joint on the Hitachi EX270LC is a demanding task that requires thorough preparation, proper tools, and technical know-how. By following experienced operators' advice and adhering to service guidelines, downtime can be minimized, ensuring the excavator remains reliable and efficient in the field. This procedure highlights the broader importance of hydraulic system maintenance in heavy equipment longevity.