Centre Joint Removal on Hitachi EX60URG Excavator: A Comprehensive Guide

[MikePhua]

The Hitachi EX60URG is a reliable and durable mini-excavator, widely used in construction, demolition, and various other industries. Like all heavy machinery, the EX60URG requires regular maintenance and occasional repairs to keep it operating at peak performance. One crucial component that may require attention over time is the centre joint, which is an essential part of the machine’s hydraulic system. This article explores the process of removing and replacing the centre joint on the Hitachi EX60URG excavator, troubleshooting tips, and key considerations to ensure a successful repair.
What is the Centre Joint and Why is it Important?
The centre joint in an excavator is a pivotal component that connects the upper and lower structures of the machine, allowing for flexible movement while maintaining hydraulic fluid circulation. It is responsible for enabling the smooth movement of the excavator's boom, arm, and other parts, by allowing hydraulic fluid to pass through while the upper structure rotates.
In a machine like the Hitachi EX60URG, the centre joint serves several functions:

• Fluid Transfer: The centre joint allows hydraulic fluid to pass through to the upper part of the machine, such as the boom and arm.
  
• Rotation Flexibility: It enables the upper structure (including the cabin and boom) to rotate independently from the lower structure, offering enhanced flexibility during operation.
  

When the centre joint malfunctions or wears out, the performance of the excavator is compromised, leading to issues like leaks, reduced hydraulic pressure, or difficulty in rotating the upper structure. In these cases, removing and replacing the centre joint is necessary to restore optimal functionality.
Signs You Need to Remove the Centre Joint
Before diving into the removal process, it’s essential to recognize the symptoms of a failing or damaged centre joint. Common signs include:

1. Hydraulic Leaks: If hydraulic fluid is leaking around the centre joint, it’s a clear indication that the seals have failed, and replacement is needed.
   
2. Loss of Hydraulic Pressure: A decrease in hydraulic pressure, especially during rotation or when operating attachments, can suggest an issue with the centre joint.
   
3. Difficulty in Rotation: If the upper structure becomes difficult to rotate or experiences jerky movement, the centre joint may be blocked or damaged.
   
4. Unusual Noises: Grinding or squealing sounds during operation can indicate wear in the centre joint or related components.
   

If any of these signs are noticed, it's essential to take action promptly to avoid further damage to the hydraulic system and ensure the safety and efficiency of the machine.
Steps for Removing the Centre Joint on Hitachi EX60URG
Removing the centre joint from the Hitachi EX60URG requires specific tools and careful attention to detail. Here’s a step-by-step guide for a successful removal:

1. Prepare the Excavator for Service
   • Safety First: Before starting, make sure the excavator is turned off, the battery is disconnected, and the parking brake is engaged.
     
   • Lift the Boom: Use the hydraulic controls to raise the boom and arm to an accessible height, ensuring that there is sufficient clearance to work around the centre joint.
     
   • Secure the Excavator: Place the machine on level ground and use blocks or jacks to stabilize it during the repair.
     
2. Access the Centre Joint
   • On the Hitachi EX60URG, the centre joint is typically located between the upper and lower structures. Depending on the design of the excavator, you may need to remove certain components, such as panels or covers, to gain full access to the joint.
     
3. Disconnect Hydraulic Lines
   • Carefully disconnect the hydraulic lines that connect to the centre joint. It is crucial to relieve pressure in the hydraulic system before disconnecting any lines to avoid leaks or injury. Use appropriate tools to unscrew the fittings and cap the open lines to prevent fluid loss.
     
   • Make sure to clean the area around the hydraulic connections before disconnecting to prevent contaminants from entering the system.
     
4. Remove the Centre Joint Bolts
   • Use a wrench or impact gun to remove the bolts that secure the centre joint to the upper and lower parts of the machine. Depending on the machine’s design, there may be several large bolts holding the joint in place.
     
   • It may require multiple attempts to loosen and remove these bolts, especially if they’ve been in place for years.
     
5. Separate the Centre Joint
   • Once all the bolts have been removed, the centre joint can be carefully separated from the machine. You may need a crane or lifting equipment to remove the joint, as it can be heavy and difficult to handle manually. Take care not to damage surrounding components during the removal process.
     
6. Inspect the Centre Joint and Components
   • Once the centre joint is removed, inspect it for wear, damage, or signs of hydraulic leaks. Pay attention to the seals, bearings, and hydraulic ports for any cracks or deterioration.
     
   • Clean the surrounding area to ensure that no debris enters the system during reassembly.
     
7. Install the New Centre Joint
   • Install the new centre joint by following the reverse steps of removal. Carefully position the joint into place and secure it with the bolts that were removed earlier.
     
   • Reconnect the hydraulic lines, ensuring that they are properly tightened and free of leaks. Make sure that the hydraulic fittings are aligned correctly to prevent damage to the seals.
     
8. Test the System
   • After installation, test the system to ensure that the centre joint is functioning properly. Check for hydraulic leaks, ensure that the upper structure rotates smoothly, and verify that the machine’s hydraulic pressure is operating as expected.
     
   • Monitor the machine closely during the first few hours of operation to ensure that everything is working as intended.
     

Troubleshooting Common Issues
While removing and replacing the centre joint is typically straightforward, there are some common issues that operators may encounter. Here are a few tips for troubleshooting:

• Hydraulic Leaks After Installation: If you notice hydraulic fluid leaking around the centre joint after installation, inspect the seals and hydraulic lines for damage or improper installation. Tighten any loose fittings and ensure that the seals are correctly positioned.
  
• Difficulty in Rotation or Jerky Movement: If the upper structure is not rotating smoothly after reassembly, it may be due to improper installation or air in the hydraulic system. Bleed the system to remove any trapped air and check for proper hydraulic fluid levels.
  
• Unusual Noises: If the machine produces grinding or squealing sounds during operation, it could be a sign that the bearings in the centre joint are not correctly aligned or have been damaged. Reinspect the bearings and replace them if necessary.
  

Conclusion: Proper Maintenance for Longevity
The centre joint is a critical component of the Hitachi EX60URG excavator’s hydraulic system. Regular inspection and timely replacement of worn-out centre joints can prevent costly repairs and ensure the continued reliability of the machine. By following the steps outlined in this guide, operators and technicians can effectively remove and replace the centre joint, ensuring smooth operation and minimal downtime.
Investing in proper maintenance and addressing issues early can significantly extend the lifespan of your excavator. Whether you’re working on a construction site, mining operation, or a demolition project, a well-maintained Hitachi EX60URG will continue to deliver high performance for years to come.