Understanding Diverter Valve Configurations on the Komatsu PC220-6

[MikePhua]

Quick Summary
The Komatsu PC220-6 excavator may feature auxiliary diverter valves that reroute hydraulic flow between attachments like hammers and thumbs. These components are often gray market additions, especially on imported units, and require careful inspection to ensure compatibility and safe operation.
Komatsu PC220-6 Background and Auxiliary Circuit Design
The Komatsu PC220-6 was introduced in the early 1990s as a mid-size excavator optimized for general earthmoving, trenching, and demolition. With an operating weight around 22 tons and a Komatsu S6D102 engine producing approximately 150 hp, the PC220-6 became a popular choice for contractors worldwide. Its hydraulic system includes a main control valve block, pilot controls, and optional auxiliary circuits for attachments.
Auxiliary hydraulic lines are typically routed along the boom and stick, terminating in quick couplers near the bucket linkage. These lines can be configured for single-acting (hammer) or double-acting (thumb or grapple) flow, depending on the diverter valve setup.
Diverter Valve Function and Configuration
Diverter valves are used to switch hydraulic flow between different attachment modes. On the PC220-6, they may appear as:

• Pressure relief-integrated diverters
  These include a built-in relief valve to protect downstream components. One example routes flow to a case drain on the swing gear, allowing excess pressure to bleed off safely.
  
• Return-to-filter diverters
  These direct return flow through a filter before reaching the hydraulic cooler. This setup is common when switching from hammer to thumb operation, ensuring clean fluid circulation.
  
• Manual or solenoid-actuated valves
  Some diverters require manual lever operation, while others use electric solenoids triggered by cab switches.
  

Gray Market Indicators and Inspection Tips
Machines with unusual diverter valve configurations may be gray market imports—units originally sold in Japan or other regions and later brought into North America. Signs include:

• Japanese manufacturer tags on valves or components
  
• Non-standard guarding or missing decals
  
• Serial numbers that don’t match domestic Komatsu databases
  

Gray market machines often lack full service documentation, making valve identification and maintenance more challenging.
Field Anecdote
In Oklahoma, an operator inspected a PC220-6 with two diverter valves in the auxiliary circuit. One had a pressure relief port teed into the swing gear case drain, while the other routed through a filter toward the cooler. The machine had a fixed thumb installed, but the diverters suggested it had previously run a hydraulic hammer. After tracing the lines and confirming valve function, the operator determined the setup allowed switching between hammer and thumb modes—though the thumb was now fixed and inactive.
Recommendations for Owners and Buyers

• Trace all hydraulic lines before operating attachments.
  
• Verify valve function—some diverters may be stuck or misconfigured.
  
• Check for relief valves to prevent overpressure damage.
  
• Inspect filters and cooler connections for contamination risk.
  
• Confirm machine origin if components appear non-standard.
  

Solutions for Mixed Attachment Use

• Install a dual-function diverter block with labeled ports and manual selector.
  
• Use quick couplers with color-coded lines to simplify switching.
  
• Add a cab-mounted switch for solenoid control if electrical integration is feasible.
  
• Replace fixed thumbs with hydraulic units if dual-function operation is needed.
  

Conclusion
Diverter valves on the Komatsu PC220-6 play a critical role in managing auxiliary hydraulic flow. Whether switching between hammer and thumb or managing return pressure, understanding their configuration is essential for safe and efficient operation. Machines with gray market components require extra diligence, but with proper inspection and setup, they can perform reliably across a range of attachment tasks.