PUMP - OIL 4597099 - Caterpillar

Destroking
Illustration 3 g00497741
Pump and compensator valve (destroking) (11) Margin spool (12) Line (signal oil from control valves) (13) Chamber (14) Line (pump oil to control valves) (15) Passage for small actuator piston (16) Small actuator piston (17) Suction line to tank (18) Springs (19) Passage (20) Passage (pump oil to margin spool) (21) Passage (pressure cutoff spool) (22) Passage (pressure cutoff spool) (23) Outlet for the pump oil (24) Swashplate (25) Line (case drain to tank) (26) Large actuator piston (27) Passage (large actuator piston) (28) Piston (29) Pressure cutoff spool (30) Spring (AA) High pressure oil (EE) Signal oil (LL) Tank oilDestroking means that the pump is decreasing the displacement (output). Destroking occurs when signal oil pressure decreases from lower loads. Destroking also occurs when all of the control valves are in the HOLD position and signal oil pressure decreases to 0 kPa (0 psi). The lower signal oil pressure in chamber (13) causes the higher pump oil pressure in passage (19) to move margin spool (11) to the right. The spool movement allows pump oil pressure to flow through passages (21) and (27) to large actuator piston (26). The pump oil pressure that is behind large actuator piston (26) is now higher than the force of the actuator spring and the pump oil pressure that is behind small actuator piston (16). Therefore, the angle of the swashplate decreases. Pump output decreases until the pump pressure is not adequate to maintain system pressure. When system pressure approaches 2100 kPa (305 psi) (margin pressure over signal oil pressure), margin spool (11) moves to the left and the spool begins to meter oil at the large actuator piston to case drain (25) .When system pressure approaches 0 kPa (0 psi) (low pressure standby), margin spool (11) moves to the left and the spool begins to meter oil at the large actuator piston to case drain (25). Signal oil pressure is zero when the control valves are in the HOLD position. Swashplate (24) maintains a slight angle that is sufficient to make up for system leakage. Also, the swashplate angle maintains the lower required pressure.Low Pressure Standby
Illustration 4 g00497800
Pump and compensator valve (low pressure standby) (11) Margin spool (12) Line (signal oil from control valves) (13) Chamber (14) Line (pump oil to control valves) (15) Passage for small actuator piston (16) Small actuator piston (17) Suction line to tank (18) Springs (19) Passage (20) Passage (pump oil to margin spool) (21) Passage (pressure cutoff spool) (22) Passage (pressure cutoff spool) (23) Outlet for the pump oil (24) Swashplate (25) Line (case drain to tank) (26) Large actuator piston (27) Passage (large actuator piston) (28) Piston (29) Pressure cutoff spool (30) Spring (AA) High pressure oil (LL) Tank oilWhen the engine is running with the control valves in the HOLD position, there is no signal oil pressure in line (12) to chamber (13). Without signal oil pressure in chamber (13), pump oil pressure in passage (19) moves the margin spool to the right