Plumbing a Kobelco SK120 Mark IV Excavator

[MikePhua]

The Kobelco SK120 Mark IV hydraulic excavator, a part of the renowned Mark IV series, is celebrated for its robust performance and versatility in various construction and excavation tasks. However, like all heavy machinery, it requires meticulous maintenance and occasional modifications to enhance its functionality. One such modification involves plumbing additional hydraulic circuits to accommodate attachments like thumbs or tilt buckets. This article delves into the considerations, procedures, and best practices for plumbing a Kobelco SK120 Mark IV excavator.
Understanding the Hydraulic System
The SK120 Mark IV is equipped with a sophisticated hydraulic system designed to deliver high efficiency and power. The system comprises several key components:

• Hydraulic Tank: Houses the hydraulic fluid and includes components like the breather assembly, suction valve (rated at 0.7 psi), discharge valve (rated at 9.9 psi), and a 10-micron return filter. These elements ensure proper fluid circulation and filtration, maintaining system integrity.
  
• Main Hydraulic Pump: The primary source of hydraulic power, delivering pressurized fluid to various actuators. The pump's performance is crucial for the overall efficiency of the excavator.
  
• Control Valve: Directs the flow of hydraulic fluid to different parts of the machine, enabling precise control over movements and operations.
  
• Hydraulic Cylinders: Actuators that convert hydraulic energy into mechanical force, driving movements such as boom lifting, arm extension, and bucket operation.
  

Challenges in Plumbing Additional Circuits
Adding extra hydraulic circuits to the SK120 Mark IV involves several challenges:

1. System Compatibility: The existing hydraulic system is designed for specific operations. Integrating additional circuits requires careful consideration to avoid overloading the system or causing pressure imbalances.
   
2. Space Constraints: The compact design of the excavator leaves limited space for installing additional components like valves and hoses.
   
3. Electrical Integration: Many attachments require electrical control, necessitating the integration of solenoid valves and wiring into the existing system.
   

Recommended Approach
A practical and cost-effective method to add a hydraulic circuit for an attachment such as a thumb or tilt bucket is to install two 3-way directional control valves (DCVs) with cartridge valves. These valves can be mounted on each side of the arm using a 3/4-inch orb ported steel manifold. The configuration is as follows:

• Port 2: Connects to the existing bucket cylinder hose from the end of the boom.
  
• De-energized State: The valve remains open, allowing fluid to return to the bucket cylinder.
  
• Energized State: The valve redirects fluid to the new attachment, activating its function.
  

This setup is estimated to cost around $3,000, offering a balance between functionality and affordability.
Best Practices for Installation
To ensure a successful installation:

• Use Quality Components: Opt for reputable brands like SUN Hydraulics for valves to ensure reliability and performance.
  
• Proper Sizing: Ensure that hoses and fittings are appropriately sized to handle the expected flow rates and pressures.
  
• Secure Mounting: Install valves and manifolds securely to prevent movement that could lead to wear or damage.
  
• Electrical Safety: When integrating electrical components, ensure proper insulation and protection against environmental factors.
  
• System Testing: After installation, thoroughly test the new circuit under operational conditions to verify functionality and identify any issues.
  

Maintenance Considerations
Regular maintenance is crucial to the longevity and performance of the hydraulic system:

• Fluid Checks: Regularly monitor hydraulic fluid levels and quality, replacing the fluid as recommended by the manufacturer.
  
• Filter Replacement: Replace filters at specified intervals to prevent contaminants from entering the system.
  
• Component Inspection: Periodically inspect hoses, valves, and cylinders for signs of wear or damage.
  
• System Monitoring: Utilize diagnostic tools to monitor system pressures and flows, identifying potential issues before they become critical.
  

Conclusion
Plumbing additional hydraulic circuits to a Kobelco SK120 Mark IV excavator can significantly enhance its versatility, allowing it to handle a broader range of attachments and tasks. By understanding the hydraulic system's components, addressing installation challenges, and adhering to best practices, operators can successfully integrate new circuits, thereby extending the machine's capabilities and lifespan. Regular maintenance ensures that the system remains in optimal condition, delivering reliable performance throughout its service life.