Hydraulic Oil Tank Pressure Vent - Hitachi Zaxis 200LC Operator's Manual

Hydraulic Oil Tank Pressure Vent

The purpose of this system is to provide the operator a
method of minimizing oil leakage in the event of an oil line
rupture or part failure. The hydraulic oil tank on the
machine is fitted with a filler cap that allows a pressure of
48 kPa (0.48 bar) (7 psi) to be created inside the tank.
The purpose of this pressure is to maintain a positive
pressure on the suction side of the main pumps to prevent
pump cavitation. The downside effect of this pressure is
that hydraulic oil will continue to leak until the operator
vents this pressure.
The system incorporates a hydraulic oil tank pressure vent
solenoid (1) that bypasses the cap and provides an
electrically controlled method for venting the tank
pressure. A hydraulic oil tank pressure vent switch (2)
(momentary push-button switch) on the left console, in the
cab operates this valve. To prevent inadvertent actuation
and possible pump cavitation, the controls are electrically
interlocked with the key switch so that key switch must be
in OFF position before the system can be activated.
1—Hydraulic Oil Tank Pressure Vent Solenoid
2—Hydraulic Oil Tank Pressure Vent Switch
Operation—Operator's Station
Hydraulic Oil Tank Pressure Vent Switch—Side Entry Cab Shown
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