Komatsu PC600LC-7 Manual page 119

STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
SAFETY VALVE
Outline
• The safety valve portion consists of check valves
(2) and (3), shuttle valves (4) and (5), and relief
valve (1).
Function
• When the swing is stopped, the outlet port circuit
of the motor is closed by the control valve, but
the motor continues to be turned by the inertia of
the swing. As a result, the pressure at the outlet
port of the motor becomes abnormally high and
there is danger that the motor will be damaged.
• The safety valve is installed to prevent this prob-
lem. It acts to release the abnormally high pres-
sure oil from the outlet port (high-pressure side)
of the motor and send it to the back pressure
valve and prevent damage to the motor.
Operation
1. When starting swing
• If the swing control lever is operated to swing to
the right, the pressurized oil from the pump pass-
es through the control valve and is supplied to
port MA.
• When this happens, the pressure at port MA ris-
es and starting force is generated in the motor,
so the motor starts to turn. The oil from the outlet
port of the motor flows from port MB through the
control valve and returns to the tank.
PC600, 600LC-7
SWING MOTOR
10-87