Troubleshooting the Lincoln Dual-Line Greasing System on the RH120E Mining Excavator

[MikePhua]

The RH120E and Its Role in Ultra-Class Mining
The O&K RH120E hydraulic mining excavator, later branded under Terex and Bucyrus before becoming part of Caterpillar’s mining division, is a 250-ton class machine designed for high-volume overburden removal and ore loading. With a bucket capacity exceeding 22 cubic meters and an operating weight over 250 metric tons, the RH120E is a staple in surface mining operations worldwide. Its hydraulic systems, swing gear, and boom pivots endure extreme loads, making automated lubrication essential.
To manage this, the RH120E is equipped with a Lincoln dual-line automatic greasing system—a centralized lubrication network designed to deliver precise amounts of grease to dozens of critical points across the machine. When functioning properly, it reduces wear, extends component life, and minimizes manual maintenance. But when it fails, downtime escalates quickly.
Understanding the Dual-Line Greasing Architecture
Lincoln’s dual-line system operates on a pressurized two-line configuration:

• One line delivers grease under pressure
  
• The second line acts as a vent or return
  
• Grease injectors meter the flow at each lubrication point
  
• A hydraulic or electric pump drives the system
  
• A controller sequences the grease cycles
  

Unlike progressive systems, dual-line setups are ideal for large machines with long hose runs and high grease demand. Each injector operates independently, allowing consistent delivery even if one line is blocked or a fitting fails.
On the RH120E, the system typically includes:

• Hydraulic-driven pump mounted near the engine bay
  
• Grease manifold blocks feeding swing bearings, boom pins, and bucket linkage
  
• Electrical control panel with cycle timer and fault indicators
  
• Grease reservoir with level sensor and refill port
  

Common Failure Modes and Diagnostic Challenges
Operators have reported persistent downtime due to greasing system faults. The most frequent issues include:

• Blocked grease lines due to hardened lubricant or contamination
  
• Faulty injectors failing to cycle or leaking
  
• Electrical faults in the control panel or wiring harness
  
• Hydraulic pump stalling or losing prime
  
• Pressure relief valve malfunction
  

One technician noted that the pump itself is rarely the root cause. Instead, failures often stem from poor maintenance, incorrect grease type, or wiring degradation. Machines operating in high-dust environments or extreme cold are especially vulnerable to injector clogging and seal failure.
Wiring Diagrams and Electrical Troubleshooting
Accessing accurate wiring diagrams for the Lincoln system on the RH120E can be difficult, especially given the machine’s branding transitions and regional variations. However, most systems follow a standard logic:

• Power supply from the machine’s 24V circuit
  
• Relay-controlled pump activation
  
• Timer module to regulate grease cycles
  
• Feedback loop from pressure switch or cycle sensor
  

Technicians should inspect:

• Voltage at the pump terminals during operation
  
• Relay function and fuse integrity
  
• Ground continuity and corrosion at connectors
  
• Sensor feedback from injectors or pressure switches
  

In one documented case, a faulty relay caused intermittent pump activation, leading to dry pins and accelerated wear on the boom pivot. Replacing the relay and cleaning the terminals restored full function.
Grease Type and Compatibility Considerations
Using the wrong grease can cripple the system. Lincoln systems on mining excavators typically require:

• NLGI Grade 2 lithium complex grease
  
• Base oil viscosity of 220–460 cSt at 40°C
  
• Dropping point above 260°C
  
• EP additives for high-load applications
  

Grease must be compatible with the injectors and pump seals. Mixing incompatible greases can cause separation, hardening, or injector blockage. Always purge the system when switching grease brands or formulations.
Preventive Maintenance and System Optimization
To keep the Lincoln greasing system running reliably:

• Inspect injectors monthly for leaks or dry points
  
• Flush lines annually with compatible cleaner
  
• Replace worn hoses and cracked fittings
  
• Monitor grease consumption and refill intervals
  
• Calibrate the timer based on operating hours and ambient conditions
  

Some mines have adopted remote monitoring systems that track grease cycles and alert operators to faults in real time. These upgrades reduce downtime and improve component longevity.
Conclusion
The Lincoln dual-line greasing system on the RH120E is a vital component of machine health—but it demands attention, precision, and proactive care. When faults arise, the solution is rarely a single part—it’s a system-wide inspection of hydraulics, electronics, and lubrication behavior.
In mining, uptime is everything. And when the greasing system falters, the cost isn’t just in repairs—it’s in lost production, worn steel, and the silent grind of metal against metal.