National Crane 600H, Service Manual

Page: 60 / 232

ELECTRIC SYSTEM 600H
3-6
08-19-2022 Control # 092-13
Hydraulic System Description
Solenoid Valve Assembly
Flow Control Valve in Inlet Section
1. Electrically controlled priority flow control valve which
can be remotely actuated to control the amount of oil
flow from the inlet to the bypass or the regulated ports.
a. Oil supply of 5 - 18 GPM is pumped to inlet port.
b. With electrical voltage up to 2 volts on the valve coil,
0 GPM of inlet oil is directed to the solenoid valve
sections and the remaining oil goes through the
bypass port and into the manual control valve, then
back to tank.
c. As voltage increases linearly from 2 to 9 volts. there
is a resulting linear increase of oil flow to the
solenoid sections to 18 GPM maximum. Any
remaining oil is directed back to tank through the
bypass port.
Solenoid Valve Sections
2. An electrically actuated directional control valve which
receives oil from the regulated port of the flow control
valve and directs it to the various crane functions.
a. When 12 VDC power is applied to any of the electro-
magnetic coils on the valve, the resulting force
pushes a spring centered spool from its neutral
position to allow oil flow out the work port opposite
the energized coil.
b. Oil flow through the solenoid valve is then increased
and decreased at the flow control valve to get
desired crane operating speeds.
3. Pressure relief valve (part of solenoid valve) in inlet
section.
a. Protects remote control hydraulic circuit from over
pressurization. Must be set to match crane manual
system pressure.
Shuttle Valve
Biased shuttle valves are located in the turn and hoist
functions on units equipped with remote hoist operation.
Oil Cooler Fan Group
Cooling Core
Temperature
Switch
20 Amp Breaker
(Resets automatically
located in engine
compartment firewall)
Relay
Fan Motor
FIGURE 3-5
REFERENCE ONLY