Pilot Relief Valve - Hitachi ZW180 Technical Manual

PILOT RELIEF VALVE

1. The pilot relief valve prevents pressure in the pilot
circuit from increasing over the set pressure dur-
ing operations of the actuators like the pilot valve.
2. When the pilot circuit pressure is more than the
set pressure, pressure oil acts on the poppet in
the pilot relief valve.
3. The poppet moves toward the spring and is con-
nected to port DR.
4. Pressure oil in the pilot circuit returns to the hy-
draulic oil tank through port DR.
5. When the pilot circuit pressure is below the spring
force, the poppet moves to the left and is not
connected to port DR.
COMPONENT OPERATION / Charging Block
During Normal Operation
Poppet
(Section V-V)
During Relief Operation
Poppet
(Section V-V)
T3-7-7
From Port P
Port DR
Spring
T4GB-03-06-007
T4GB-03-06-008