Broderson IC-400-3B, Operation And Maintenance Manual

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STEERING SYSTEM
The steering system is also shown in the hydraulic schematic. The IC-400 steering system is a
load-sensing, demand-type system that takes only as much flow as needed when steering,
and directs the excess flow to the control valve for boom and outrigger functions.
Oil from pump P2 goes into the priority valve at port P. When no steering is required, the en-
tire flow goes through the priority valve and leaves through other ports, to the outrigger control
valve or the lower control valve, based on the load-sense driven requirement for flow.
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.
Since the amount of oil required for steering is usually a small portion of the pump output, the
lower 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.
The steering system pressure was set at 2060 PSI (142 bar) at the factory, and should not
need adjustment.
The three steering modes are selected by switches on the drivetrain control panel and activate
the automatic alignment system. Electronic proximity sensors and logic controls delay the
switching of the steering mode until the wheels are centered.