RACE 4M8794 - Caterpillar

Illustration 1 g01107864
(S/N: BXY1-3999) Steering system schematic
(1) Left steering cylinder
(2) Right steering cylinder
(3) Steering control valve
(4) Shuttle valve
(5) Backup relief valve
(6) Steering cylinder crossover relief valve
(7) Makeup valves
(8) Steering control valve spool
(9) Pressure reducing valve
(10) Check valve
(11) Steering pump
(12) Hydraulic tank
(13) Main hydraulic tank
Illustration 2 g02053976
(S/N: BXY4000-Up) Steering system schematic
(1) Left steering cylinder
(2) Right steering cylinder
(3) Steering control valve
(4) Shuttle valve
(5) Backup relief valve
(6) Steering cylinder crossover relief valve
(7) Makeup valves
(8) Steering control valve spool
(9) Pressure reducing valve
(10) Check valve
(11) Steering pump
(12) Hydraulic tank
(13) Main hydraulic tank
(14) Crossover line relief valve The steering pump (11) provides high pressure oil for the steering system. The steering pump can also supply supplemental pilot oil for the pilot oil system.During normal operation, steering pump (11) withdraws oil from hydraulic tank (12). High pressure oil from the steering pump is then sent through three circuits.High pressure oil can also flow to backup relief valve (5) and pressure reducing valve (9). The maximum allowable system pressure is controlled by the backup relief valve. The backup relief valve is set to 27600 kPa (4000 psi). Backup relief valve (5) sends oil back to the hydraulic tank if the oil pressure increases to 27600 kPa (4000 psi). The pump cutoff pressure is set to 24100 kPa (3500 psi). Under normal operations, the steering pump will not allow the oil pressure to rise above the pump cutoff pressure of 24100 kPa (3500 psi). The backup relief valve prevents damage to the steering system if the steering pump fails to limit the system pressure to 24100 kPa (3500 psi).Pressure reducing valve (9) allows the steering pump to supply supplemental pilot oil for the pilot oil system. The pressure reducing valve lowers the high pressure steering oil to approximately 1650 kPa (240 psi).When the operator moves the pilot control valve, pilot oil shifts valve spool (8). High pressure steering oil is then allowed to flow through valve spool (8) to steering cylinders (1) and (2). The machine will then articulate. Makeup valves (7) are present in order to prevent cavitation in the steering cylinders. Additional oil from the tank may be pulled through the makeup valves, if necessary.An increase in pressure will occur if an outside force tries to steer the machine. The increase in pressure will open steering cylinder crossover relief valve (6) and (14). The steering cylinder crossover relief valve prevents the pressure in the steering cylinders from exceeding specifications.Shuttle valve (4) allows high pressure oil to travel through a load sensing line. The load sensing line travels back to the steering pump.