CW12 Pneumatic Compactor Machine Systems Caterpillar

Illustration 1	g06266438
Right Side of Machine (1) Steering manifold

Steering manifold (1) is located in the pump compartment on the right side of the machine. The right side compartment door provides access to the valve.

Steering manifold (1) contains components used to control the steering system.

Illustration 2	g06266441
Steering Control Manifold (2) Compensator spool (3) Directional solenoid (4) Directional solenoid (5) Counterbalance valves (6) Main relief valve (7) Shunt solenoid (8) Warmup solenoid (9) Margin spool

The steering control valve is controlled by the machine ECM. This valve is controlled by two solenoids. Directional solenoid (4) causes the machine to turn right. Directional solenoid (3) causes the machine to turn left. The steering control valves direct oil to one end of the steering cylinder while opening the other end to the hydraulic tank.

Counterbalance valves (2) ensure that the steering cylinder will not move unless pressurized oil is in one end of the cylinder. When steering oil is made available to one end of the steering cylinder, pressure shifts the counterbalance valve on the other end of the cylinder. This shift opens the other end of the steering cylinder to the hydraulic tank.

Main relief valve (6) limits steering system pressure to 18350 ± 2661 kPa (2661 ± 386 psi). When the main relief valve is open, steering oil flows into the hydraulic tank.

Steering shunt solenoid (7) enables and disables the steering system. The machine ECM energizes the shunt solenoid to enable the steering system. In this condition, the shunt valve is closed and oil from the steering pump is routed to the steering control valve.

When shunt solenoid (7) is not energized, the shunt valve opens and sends oil from the pump directly to the hydraulic tank. In this condition, the steering system is disabled. The machine ECM disables the steering system when the machine electronic control system registers a level-3 fault.

When the hydraulic oil temperature is less than 20 °C (68 °F), the machine ECM energizes warmup solenoid (8). When this happens, the valve directs supply pressure to the network of shuttle valves that monitor the system demand pressures. This action closes margin spool (9). With the margin spool closed, system pressure increases. Pressure will increase until it reaches the set point of main relief valve (6) at 18350 ± 2661 kPa (2661 ± 386 psi). The flow of hydraulic oil through the relief valve rapidly heats the hydraulic oil.

Margin spool (9) regulates the flow of supply oil to the steering system. When the flow of supply oil into the system is greater than demand, the margin spool directs unused oil to the hydraulic tank.

Shuttle valves located inside the manifold compare pressure requirements and send the highest pressure requirement to the margin spool. One shuttle valve compares the pressure at the rod end of the cylinder and the pressure at the head end of the cylinder. A second shuttle valve compares the highest pressure in the steering cylinder and the external load-sensing pressure signal.

A check valve also located inside the manifold is installed in parallel with each counterbalance valve. This check valve prevents hydraulic oil from flowing out of the steering cylinder unless the corresponding counterbalance valve is open.