ROD 2107512 - Caterpillar

Illustration 1 g01189609
Secondary Steering System Schematic
(1) Left steering cylinder assembly. (2) Right steering cylinder assembly. (3) Steering control valve. (4) Check valve. (5) Diverter valve. (6) Check valve. (7) Relief valve. (8) Dual check valves. (9) Pressure reducing valve. (10) Secondary steering pump. (11) Right neutralizer valve. (12) Left neutralizer valve. (13) Steering oil pressure sensor. (14) Pilot control valve. (15) Pressure control and selector valve. (16) Steering pump. (17) Hydraulic tank.
The secondary steering system supplies the steering oil only if the following conditions exist. The primary steering pump fails, or the engine stops while the machine is still moving.The following components make up the secondary steering system: Hydraulic oil tank (17) for the steering systems , secondary steering pump (10), secondary steering relief valve (7) and diverter valve (5).Note: Diverter valve (5) and secondary steering relief valve (7) are part of steering control valve (3).During normal machine operation, steering pump (16) draws oil from hydraulic tank (17). The pump then sends the oil through check valve (6). Check valve (6) is located in steering control valve (3). The oil then flows to pressure reducing valve (9), and steering cylinders (1) and (2).As the machine starts to move, oil begins to flow from secondary steering pump (10). Secondary steering pump (10) is a ground driven pump that is attached to the output transfer gears of the transmission. If the machine is moving forward or backward, the pump will provide oil flow.With secondary steering pump (10) in operation, oil flows into diverter valve (5). If steering pump (16) maintains a steady pressure, that pressure remains greater than the pressure from secondary steering pump (10). This keeps the check valve (4) against the seat. This also keeps the spool in diverter valve (5) in the DOWNWARD position.With the spool in diverter valve (5) in the DOWNWARD position, the oil from secondary steering pump (10) flows back to hydraulic tank (17).When steering pump (16) does not maintain adequate system pressure, and if the machine is in motion, a spring on the bottom of the diverter valve spool forces the spool upward. The oil from secondary steering pump (10) now flows through diverter valve (5). The oil then flows through check valve (4). Then oil flows to check valve (6).Because primary steering pump (16) has stopped working, or because the engine has stopped, the secondary steering oil forces check valve (6) to seat. This stops the flow of oil from secondary steering pump (10) from flowing to steering pump (16).This forces the pressurized oil to flow to pressure reducing valve (9), and to steering cylinder (1) and steering cylinder (2).Pressure reducing valve (9) changes the pressure of the secondary steering oil to pilot pressure. The pilot oil then flows through steering pilot valve (14). From steering pilot valve (14), the pilot oil flows through steering neutralizer valve (11) and steering neutralizer valve (12). The pilot oil then flows through the neutralizer check valves (8). Then oil flows to the steering control valve (3).The