Instruction manual
20220109E
15
4
CONSTRUCTION AND PRINCIPLE OF
OPERATION
The HLD is delivered completely assembled with tank, reversible
hydraulic pump and a balanced hydraulic cylinder. The HLD is
therefore a completely closed system.
4.1
Tank
The tank is machined out of
solid aluminium and all
necessary oil ways are
drilled out.
A bypass valve is mounted
in the tank, to allow the
mechanical steering system
to be used, when the
autopilot is not in operation.
The bypass valve is a
standard ON/OFF solenoid
valve, normally open.
When the autopilot is in
STBY mode, the solenoid
valve will be in open
position.
When AUTO or NAV mode
is selected, the solenoid
valve will be in closed
position.
The solenoid valve opens
immediately when the
autopilot is switched off, and
handsteering is allowed.
Previous versions
An early version of HLD350
and HLD350S did not have
check valves. The following
serial no. codes can identify it:
H30 (HLD350) and H31 (HLD350S).
The principle of operation was similar to that of HLD2000L. The
(suction) valves, however, operated as combined suction and (non-
return) check valves controlled by internal pressure and direction of oil
flow. The resulting effect was a smoother check valve operation as
Functional diagram
1.
Electrical motor (Elektromotor)
2.
Gear pump (Tannhjulspumpe)
3.
Suction valve (Innsugingsventil)
4.
Check valve (Tilbakeslagsventil)
5.
Oil tank (Oljetank)
6.
By-pass valve (By-pass ventil)
7.
Hydraulic actuator (Hydraulisk
sylinder)
7
6
M
4
4
3
3
2
1
5
