6-2
Published 3/26/2018, Control # 596-05
SWING SYSTEM GRT8100 SERVICE MANUAL
THEORY OF OPERATION
Swing Drive
The hydraulic power for the swing drive Figure 6-1 is
supplied by the engine driven hydraulic pump. Oil flows from
the pump to the hydraulic swivel. Flow from the swivel is
routed to the Swing Directional Control Valve.
When the hydraulic remote control is positioned to select
right or left swing, the flow through the control valve is
directed to the Swing Motor. If the Swing Enable Switch is in
the ON position, the superstructure will rotate in the desired
direction. Shifting the control to neutral and depressing the
brake pedal will stop the swing.
Swing Brake
The (static) swing brake is spring-applied, hydraulic released
while the service (dynamic) brake is pressure applied. A two
position solenoid valve controls the pressure to release the
swing brake. A pressure reducing valve maintains a pressure
of 260 to 300 psi to the inlet of both the brake release and
brake apply valves. The circuit is designed such that when
the engine is running and the swing enable switch is
activated pressure is supplied to the swing brake release to
release the brake while at the same time pressure is ramped
up on the swing service brake proportionally to the max
pressure. When the swing control joystick is actuated to
swing left or right, the proportional valve is de-energized
there by releasing the pressure from the swing service brake
and allowing motion. When the swing joystick is returned to
the center (neutral) position, the control system gradually re-
energizes the proportional valve (apply valve), thereby
slowly increasing oil pressure to apply the brake. Actuating
the swing brake foot pedal results in the same action.
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