What Are the Small Hydraulic Lines on a Mini Excavator For?

[MikePhua]

In this discussion, the original poster noticed several small hydraulic lines on the boom of their mini excavator that were thinner than the main hydraulic hoses and wasn’t sure about their purpose. They asked experienced users on the forum for explanations.
✅ Main Functions
Experienced users explained clearly:
These small hydraulic lines are mostly hydraulic return lines or pilot control lines.
They mainly serve two purposes:
1️⃣ Controlling Auxiliary Attachments

• These lines supply hydraulic oil to attachments like hydraulic breakers, hydraulic shears, rotary grapples, hydraulic log clamps, etc.
  2️⃣ Pilot Pressure for Valve and Movement Control
  
• The main hydraulic pump provides high-pressure oil for working functions, but the pilot circuit uses low-pressure oil to precisely control the opening and closing of valve spools, enabling smooth and accurate movements.
  

✅ Common Locations

• These smaller lines usually run along the outside of the boom or arm, secured by metal clamps or brackets.
  
• Many mini excavator models reserve multiple auxiliary lines to facilitate future attachment installations.
  
• If the owner is not currently using attachments, these lines may be capped or left unused.
  

✅ Practical Tips from Users

• If you plan to install attachments, check if the machine has quick couplers and control switches on the pedals or joystick, as many manufacturers pre-install these features.
  
• Some older models require retrofitting additional hydraulic lines; the thinner lines are usually pilot or return lines, while the main pressure lines are thicker.
  
• Regularly inspect these small hydraulic lines for wear and leaks since they are thinner and more prone to damage than main hoses.
  

✅ Summary
Small hydraulic lines on mini excavators mostly serve as pilot control circuits or auxiliary hydraulic return lines for powering attachments.
They are essential for operational precision and expanding the machine’s functional capabilities.
If you intend to add hydraulic attachments, be sure to confirm whether these lines and control valves are pre-installed or reserved.