3-13
HYDRAULIC SYSTEM
The IC-35 hydraulic system consists of three subsystems, driven by a triple pump. The
34 gpm (129 L/min) piston pump powers the propulsion system. The 6 gpm (23 L/min)
gear pump supplies the hydrostatic steering function and the boom and outrigger
functions. The hoist and optional front winch are powered by the 17 gpm (64 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 17 gpm (64 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-35 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 and 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 recenter when the steering wheel is released. The
steering wheel must be turned back to center at the end of a turn.
There is a check valve in the pressure line between the priority valve and the steering
control unit. This prevents pressure in the steering cylinders from venting back into the
pressure line when the pressure is low. This eliminates steering wheel kickback when
the steering wheel is released.
The steering system pressure relief valve inside the priority valve is set at 1250 psi (86
bar) at the factory and should not need adjustment.
Courtesy of Crane.Market
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