3-14
HYDRAULIC SYSTEM
The IC-40 hydraulic system consists of 3 sub-systems, driven by a triple pump. The 36-
GPM (136 L/min) piston pump powers the propulsion system. The 6-GPM (23 L/min)
gear pump supplies the hydrostatic steering function, and the boom & outrigger functions.
The hoist and optional front winch are powered by the 18-GPM (68 L/min) pump.
The boom, outrigger and hoist functions are controlled by a single valve assembly with
two inlet ports. The 6-GPM (23 L/min) pump flow enters the left-hand port and supplies
the swing, boom, telescope, and outrigger sections. The 18-GPM (68 L/min) pump flow
enters the mid-inlet port to supply the hoist. Adjustment procedures for the crane
hydraulic functions are given on page 3-25.
The schematic of the hydraulic system is shown on the page 3-12. The steering system
and propulsion systems are also shown in diagrams on the following pages.
STEERING SYSTEM
The IC-40 steering system is a load-sensing, demand-type system that takes only as
much flow as is needed when steering, and directs the excess flow to the control valve
for boom & outrigger functions. The priority flow-control valve is in the line between the
6-GPM (23 L/min) pump section and control valve.
Oil from the 6-GPM (23 L/min) section of the pump goes into the priority valve at port "P."
When no steering is required, the entire flow goes through the priority valve and leaves
through port "EF" to the crane valve. The crane operating speed is not affected, since
there is no loss of volume passing through the priority valve.
When the steering wheel is turned, the load-sensing line signals the priority valve to
divert the required amount of oil to the steering control unit, to meet the steering system
requirements. The excess oil, not required for steering, flows to the crane control valve
as usual. Since the amount of oil required for steering is usually a small portion of the
pump output, the crane control valve is always operational while the unit is being steered.
Crane operation speed is reduced such a slight amount, it is usually not noticed.
The steering control unit is non-load-reactive. This means that bumps, curbs, and
obstacles cannot change the steering angle and are not felt in the steering wheel. It also
means that the wheels do not re-center when the steering wheel is released. The
steering wheel must be turned back to center at the end of a turn.
The steering system pressure relief valve inside the priority valve is set at 1400 PSI (97
bar) at the factory, and should not need adjustment. The three steering modes are
selected by a switch on the dashboard, which activates the automatic alignment system.
Electronic proximity sensors and logic controls delay the switching of the steering mode
until the wheels are centered. The proximity sensors should be cleaned periodically with
a rag to prevent dirt build-up from blocking their operation.
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