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| Illustration 1 | g00297163 |
Components of the Secondary Steering Valve (1) Inlet from primary steering pump. (2) Oil pressure switch for the primary steering system. (3) Oil pressure switch for the secondary steering system. (4) Outlet to the steering control valve. (5) Secondary steering check valve. (6) Primary steering check valve. (7) Secondary steering pump and motor. | |
The secondary steering valve is located on the lower left inside frame. The secondary steering valve is also located above secondary steering pump and electric motor (7) .
The secondary valve contains two check valves. The check valves act as a selector valve. Check valve (6) monitors the primary steering oil pressure. Check valve (5) monitors the secondary steering oil pressure.
During normal operating conditions, oil pressure from the primary steering pump keeps check valve (6) unseated. At the same time, secondary steering check valve (5) is seated.
This allows pressure oil to flow from the primary steering pump, through the secondary steering valve, and to the steering control valve through outlet (4). With secondary steering check valve (5) against the seat, no pressure oil flows to secondary steering pump (7) .
If the primary steering pump fails, the flow of pressure oil from the primary steering pump stops. After a brief pause, the electric motor that is attached to secondary steering pump (7) starts. This causes secondary steering pump (7) to pump oil.
The pressure oil from secondary steering pump and electric motor (7) flows to the secondary steering valve. The pressure oil causes secondary steering check valve (5) to unseat. With no oil pressure from the primary steering pump, the pressure oil from secondary steering pump and electric motor (7) causes primary steering check valve (6) to seat.
The oil then flows to the steering control valve through outlet (4). With primary steering check valve (6) against the seat, no oil is allowed to flow to the primary steering pump.
The secondary steering valve also contains two pressure switches. Oil pressure switch (2) senses the pressure in the primary steering circuit. If pressure switch (2) detects a loss of oil pressure from the primary steering pump, pressure switch (2) sends a signal to the monitoring system. Pressure switch (2) also illuminates the primary steering indicator in order to alert the operator that there is a loss of primary steering pressure.
Oil pressure switch (3) senses the pressure in the secondary steering circuit. When pressure switch (3) detects oil pressure from the secondary steering pump, pressure switch (3) sends a signal to the monitoring system. The switch also illuminates the secondary steering indicator in order to alert the operator that the secondary steering system is in operation.
Note: When the loss of primary steering pressure occurs the monitoring system indicates a Warning Category 3 alarm.
Note: When the secondary steering pump and electric motor activates, a Warning Category 3 occurs. This causes the secondary steering indicator and the master action light to flash. This also causes the action alarm to sound.
Reference: For additional information, refer to Service Manual, SENR1394, "Caterpillar Monitoring System".