Can the Hitachi EX120-2 Run a Hydraulic Hammer

[MikePhua]

The Hitachi EX120-2 and Its Hydraulic Capabilities
The Hitachi EX120-2 excavator was introduced in the late 1990s as part of Hitachi’s second-generation compact hydraulic excavators. With an operating weight of approximately 12 metric tons and powered by a 4-cylinder Isuzu diesel engine, the EX120-2 was designed for versatility in trenching, site prep, and light demolition. Hitachi, founded in 1910, became a global leader in hydraulic excavator design by emphasizing reliability, smooth control, and modular hydraulic systems.
The EX120-2 features a robust hydraulic system with auxiliary circuits originally intended for attachments like thumbs and hoe packs. These circuits can be adapted to run hydraulic breakers, but compatibility depends on several factors including flow rate, pressure, return line configuration, and control valve setup.
Terminology Notes

• Hydraulic Breaker: A percussion tool powered by hydraulic pressure, used to break concrete, rock, or asphalt.
  
• Auxiliary Circuit: A hydraulic pathway used to power attachments beyond the standard boom, arm, and bucket functions.
  
• Return-to-Tank Line: A low-pressure hydraulic line that allows fluid to bypass the control valve and return directly to the reservoir.
  
• Pilot Valve: A low-pressure valve that controls the actuation of high-pressure hydraulic components.
  

Hydraulic Flow and Pressure Requirements
To operate a hydraulic breaker effectively, the excavator must meet the following hydraulic specifications:

• Flow rate: 30–50 gallons per minute (GPM) depending on breaker size
  
• Operating pressure: 2,000–2,500 psi
  
• Return line pressure: ideally below 100 psi to prevent backpressure damage
  

The EX120-2’s auxiliary circuit typically delivers flow through ¾-inch steel piping and #12 four-wire hoses, which are sufficient for mid-size breakers. However, if the return line routes through the main control valve, it may introduce excessive backpressure. A direct return-to-tank setup is strongly recommended.
Control Valve and Flow Management
The EX120-2 often includes a three-way pilot valve operated by a foot pedal, allowing on/off/on control of auxiliary flow. At the end of the stick, flow control boxes may be present to adjust speed and direction. These components are suitable for thumb operation but may require modification for hammer use.
Recommendations include:

• Installing a shut-off valve to isolate the thumb circuit when switching to a breaker
  
• Using high-quality quick couplers to minimize flow restriction
  
• Ensuring the breaker hoses are matched to the machine’s output and return lines
  

A contractor in Alberta retrofitted his EX120-2 with a dedicated return kit sourced from a John Deere dealer, allowing his hoe pack to operate without pressure spikes. The same principle applies to breaker installation.
Return Line Configuration and Backpressure Risks
Hydraulic breakers are sensitive to return line pressure. If the return flow passes through the excavator’s main valve block, it can create backpressure that damages seals and internal components. In some cases, this can add several hundred psi to the return path, leading to premature failure.
Solutions include:

• Installing a direct return hose from the breaker to the hydraulic tank
  
• Using a high-flow filter to prevent contamination
  
• Avoiding restrictive couplers or undersized hoses
  

A technician in Oregon reported that resealing a damaged breaker cost over $3,000 due to improper plumbing. Investing in proper setup can prevent such failures.
Breaker Selection and Setup Tips
When choosing a breaker for the EX120-2:

• Match breaker weight to machine class (typically 1,000–1,500 kg)
  
• Verify flow and pressure compatibility with the excavator’s auxiliary circuit
  
• Use a flow meter to calibrate relief settings and ensure optimal performance
  
• Avoid over-sizing the breaker, which can overload the hydraulic system
  

Some operators install flow restrictors or pressure relief valves to fine-tune performance. A fleet manager in Wisconsin uses a flow meter during setup to prevent overpressure and ensure consistent impact force.
Recommendations for Technicians and Owners

• Inspect auxiliary hoses and fittings for wear or internal collapse
  
• Document flow rates and pressure settings for each attachment
  
• Train operators on switching between thumb and breaker modes
  
• Keep spare seals, couplers, and pilot valve components in stock
  
• Monitor hydraulic temperature during extended breaker use
  

Conclusion
The Hitachi EX120-2 can run a hydraulic breaker effectively if its auxiliary plumbing is properly configured. Key factors include adequate flow and pressure, low-return backpressure, and clean control valve integration. With thoughtful setup and attention to hydraulic dynamics, this excavator can transition from trenching to demolition with confidence—extending its versatility and value on the jobsite.