This module discusses the operation of the secondary steering system. The following motor graders are covered in this module:
The secondary steering system charges the primary system with hydraulic oil under two modes of operation: MANUAL and AUTOMATIC.
The secondary steering system has the following main components:
- Electric Drive Pump
- Relief Valve
- Combination Valve
- Check Valves
- Pressure Switch
- Hydraulic Tank and Filter
- Secondary Steering Control
Electric Drive Pump
The electric drive pump is an electric motor that drives a gear pump. The gear pump provides oil flow to the combination valve. Do not operate the electric drive pump past two minutes of operation.
The relief valve in the secondary steering system is a safety valve. The relief valve prevents system oil pressure from rising too high. If the pressure reaches 17225 kPa (2498 psi) the relief valve will open. The relief valve routes the pressurized oil back to the hydraulic tank.
In the event of hydraulic pressure loss in the primary steering system, the combination valve receives hydraulic oil from the secondary steering system. The combination valve then directs the hydraulic oil to the steering metering unit.
The check valves in the secondary steering system prevent oil from flowing backward through the system.
The pressure switch is installed in the combination valve. The pressure switch will close when primary steering system pressure rises. If the primary steering system pressure drops, the pressure switch will open. The opening of the pressure switch sends a signal to the secondary steering control in order to activate the electric pump drive.
Hydraulic Tank and Filter
The hydraulic tank supplies oil to the hydraulic system. The filter is located inside the hydraulic tank. The filter screens return oil from the hydraulic system.
Secondary Steering Control
The secondary steering control will perform the necessary electrical functions in order to activate the secondary steering system. The secondary steering control receives input signals from the alternator and from the pressure switch. The secondary steering control will energize the electric drive pump when the input signals indicate a primary system failure.