CYLINDER AS 2912683 - Caterpillar

Illustration 1 g00582860
Hydraulic Schematic for the Steering System (1) Unloader spool (2) Pressure relief valve for the secondary steering system (3) Secondary steering diverter valve (4) Gear pump for the secondary steering system (5) Steering control valve (6) Check valve for the steering pump (7) Selector and pressure control valve (8) Pressure switch for the steering system "STRG OIL PRES" (9) Selector and pressure control valve (10) Hydraulic tank for the steering and brake systemsThe secondary steering system supplies oil for the primary steering system if there is a failure of the primary steering system. Also, the secondary steering system supplies oil for the primary steering system if the engine stops.Note: The machine must be moving in order for the secondary steering system to operate.Secondary steering pump (4) is a ground driven pump. The secondary steering pump operates when the machine is moving either forward or moving backward. The secondary steering pump is powered by the output transfer gears of the transmission.When the engine is running, the two primary steering pumps supply the pressure oil for the steering system. Pressure oil from the primary steering pumps also flows to selector and pressure control valves (7) and (9). The selector and pressure control valves reduce the high pressure oil to pilot pressure oil for the pilot system.During the normal operation of the machine, secondary steering pump (4) does not supply oil to the primary steering system. The secondary steering pump draws oil from hydraulic tank (10). The oil enters secondary steering diverter valve (3) through a pair of inlet check valves.As the machine moves either forward or backward, hydraulic oil flows from secondary steering pump (4) through secondary steering diverter valve (3). Pilot oil from selector and pressure control valve (9) acts on unloader spool (1) in secondary steering diverter valve (3). When the pilot oil is acting on the margin spool, the unloader spool directs the secondary oil flow to hydraulic tank (10). In this case, the oil supply for the primary steering system and the pilot system is provided from the two primary steering pumps.If the flow of pilot oil to unloader spool (1) stops, the spring in the diverter valve will shift the unloader spool. This directs the secondary steering oil flow to the primary steering system. The oil flows from the secondary steering diverter valve to steering control valve (5) .Some of the oil from the secondary steering system also flows to selector and pressure control valve (7). Selector and pressure control valve (7) reduces the pressure oil to pilot pressure oil. This supplies pilot oil to the pilot system.Check valves (6) prevent pressure oil from flowing to the primary steering pumps.Relief valve (2) limits the pressure of the secondary steering oil to approximately 20950 kPa (3040 psi). When the machine is not turning in the secondary steering mode, the secondary steering oil flows through relief valve (2). This causes the temperature of the oil to increase. Care should be taken in order to not overheat