SPOOL 9W6577 - Caterpillar

Hydraulic System for Implements and for Steering
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Location of components (1) Ripper lift cylinder (2) Steering motor (3) Counterbalance valve (4) Hydraulic pump for implements and for steering (5) Oil cooler pump (6) Quick-drop valve (7) Bulldozer lift cylinders (8) Bulldozer tilt cylinder (9) Bulldozer and steering control valve group (10) Tank and filters for the hydraulic oilThe hydraulic system controls the steering, the bulldozer, and the ripper (if equipped). The hydraulic system is a load sensing, pressure compensated system that is manually operated.In a load sensing, pressure compensated system, oil flow does not change according to the load conditions. Cylinder speeds remain constant under all load conditions.
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Bulldozer blade control lever
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Ripper control lever
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Steering control (12) LeverThe implement control levers and the steering control lever are the controls for the hydraulic system. When one of the control levers is moved to an operating position, pressure in the system increases to the required amount for movement of the load or for completion of the turn.
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Hydraulic components (4) Hydraulic pump (5) Oil cooler pump (13) Compensator valveHydraulic pump (4) is a slipper type, variable piston pump that is load sensing and pressure compensated.The pump provides oil for all implement circuits and for all steering circuits. When the implement circuits and the steering circuits are not active, the pump is destroked. The destroked pump emits only enough oil in order to compensate for system leakage. Also, the destroked pump maintains an approximate line pressure of 3000 kPa (435 psi).If an implement circuit is activated, the compensator valve (part of the pump) senses the load increase through the signal system for the control valve. The signal causes the pump to upstroke. The pump continues to upstroke until the pump pressure is approximately 2100 kPa (305 psi) higher than the load signal from the control valve. Pressure limiters in the implement control valves control the maximum pressure in the circuit.If the steering circuit is activated, the pump upstrokes in the same manner. However, pressure in the circuit is controlled by the cutoff spool in the compensator valve. When the steering circuit pressure reaches an approximate pressure of 38500 kPa (5600 psi), the pump destrokes enough to maintain the pressure until the system pressure decreases. A main relief valve in the system limits the pressure increases (spikes) over approximately 41500 kPa (6000 psi).
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Bulldozer and steering control valve group (14) Bulldozer tilt control valve (15) Bulldozer lift control valve (16) Steering control valve (17) Inlet manifold (18) Main relief valveThe bulldozer and steering control valve group has an inlet manifold and an end cover. The bulldozer and steering control valve group can have as many as three control sections: a steering control valve, a bulldozer lift control valve and a bulldozer tilt control valve. Also, a main relief valve is installed on the inlet manifold. When the control levers are in the HOLD position, pump oil flows to the inlet manifold, through all the control valves, and to the end cover.