Hydraulic Circuit - Hitachi ZW180 Technical Manual

COMPONENT OPERATION / Control Valve

HYDRAULIC CIRCUIT

Main Circuit
The main circuit contains a parallel circuit, which
enables combined operations.
The main circuit (between the pump and the cylinder)
is provided with the main relief valve. The main relief
valve prevents pressure inside the main circuit from
increasing over the set pressure during operation of
the spool (when the control lever is operated).
The front circuit (between the control valve and the
cylinder) of the lift arm and bucket is provided with the
overload relief valve. The overload relief valve
prevents surge pressure developed by external loads
in the front circuit from increasing over the set
pressure with the spool in neutral (when the control
lever is neutral).
T3-2-8