325C L & 325C LN Excavator CRB00001-UP (MACHINE) POWERED ...

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Product: EXCAVATOR
Model: 325C EXCAVATOR CRB01180
Configuration: 325C L & 325C LN Excavator CRB00001-UP (MACHINE) POWERED BY 3126 Engine

Systems Operation
325C Excavator Hydraulic System
Media Number -RENR5364-02 Publication Date -01/11/2003 Date Updated -21/11/2003

i01827505

Pilot Hydraulic System

SMCS - 5050

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Illustration 1 g00932427

(1) Swing parking brake

(2) Displacement change valve (left travel motor)

(3) Displacement change valve (right travel motor)

(4) Line (pilot oil from swing parking brake solenoid valve)

(5) Travel pilot control valve

(6) Pilot line (BOOM LOWER)

(7) Pilot line (boom drift reduction valve)

(8) Pilot line (STICK IN)

(9) Pilot line (stick drift reduction valve)

(10) Stick drift reduction valve

(11) Main control valve

(12) Boom drift reduction valve

(13) Solenoid valve (straight travel)

(14) Pilot line (pilot pressure to left travel pressure switch)

(15) Pilot line (pilot oil to travel pilot control valve)

(16) Right travel control valve

(17) Boom I control valve

(18) Straight travel control valve

(19) Travel pressure switch (left)

(20) Pilot line (pilot pressure to right travel pressure switch)

(21) Travel pressure switch (right)

(22) Pilot line (pilot oil to pilot control valve for the stick and swing)

(23) Pilot line (pilot oil to pilot control valve for the boom and bucket)

(24) Left travel control valve

(25) Pilot control valve for stick and swing

(26) Pilot control valve for boom and bucket

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(27) Variable swing priority valve

(28) Pilot line (STICK OUT)

(29) Pilot line (STICK IN)

(30) Pilot line (SWING RIGHT)

(31) Pilot line (SWING LEFT)

(32) Pilot line (BUCKET CLOSE)

(33) Pilot line (BOOM RAISE)

(34) Pilot line (BOOM LOWER)

(35) Pilot line (BUCKET OPEN)

(36) Pilot line (pilot oil from boom pilot control valve)

(37) Pilot line (BOOM RAISE)

(38) Pilot line (pilot oil to the pressure reducing valve for boom priority)

(39) Pilot line (pilot pressure to implement/swing pressure switch)

(40) Implement/swing pressure switch

(41) Pilot line (pilot pressure to displacement change valves)

(42) Pilot line (pilot oil to pressure reducing valve for swing priority)

(43) Pilot line (pilot oil to pilot control valves)

(44) Pilot line (pilot oil to straight travel control valve)

(45) Swing parking brake solenoid valve

(46) Valve (hydraulic activation)

(47) Pressure reducing valve for swing priority

(48) Pressure reducing valve for boom priority

(49) Left pump

(50) Passage (power shift pressure)

(51) Pilot manifold

(52) Travel speed solenoid valve

(53) Passage

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(54) Hydraulic activation solenoid valve

(55) Passage

(56) Passage

(57) Passage

(58) Right pump

(59) Pilot pump

(60) Pilot line (pilot oil flow to pilot oil manifold)

(61) Pilot filter

(62) Passage (power shift pressure)

(63) Proportional reducing valve (power shift pressure)

(64) Pilot relief valve

(65) Passage

(66) Pilot line (pilot oil flow from pilot pump to pilot oil filter)

(67) Pilot line (pilot oil flow to pump regulators)

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Illustration 2 g00746504

Ports and solenoids at the pilot manifold

(45) Swing parking brake solenoid valve

(46) Valve (hydraulic activation)

(52) Travel speed solenoid valve

(54) Hydraulic activation solenoid valve

Pilot Oil Circuit

The pilot circuit pressure is limited by pilot relief valve (64) .

The oil delivery from pilot pump (59) performs the following main functions:

• Create pilot oil pressure in order to control the output flows of the main pumps.

• Provide pilot oil pressure to the pilot control valves for implements, swing and
travel in order to perform machine operations.

• Create pilot oil pressure in order to automatically operate the control devices.

Note: Each pilot circuit performs one of the functions above.

The pilot circuit is classified into the following circuits:

• Power shift pressure system

• Pilot control valve circuit

• Pressure switch circuits

• Straight travel valve circuit

• Swing parking brake

• Boom priority

• Swing priority

• Automatic travel speed change

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Power Shift Pressure System

Illustration 3 g00746518

(49) Left pump

(58) Right pump

(63) Proportional reducing valve (PS pressure)

(59) Pilot pump

(68) Engine and pump controller

(69) Monitor

(70) Engine speed dial

(71) Right pump pressure sensor

(72) Left pump pressure sensor

(73) Feedback sensor

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(74) Governor actuator

(75) Engine speed sensor (flywheel housing)

During machine operation, engine and pump controller (68) receives input signals from
the following components:

• Engine speed dial (70)

• Engine speed sensor (75) that is located on the flywheel housing

• Right pump pressure sensor (71)

• Left pump pressure sensor (72)

• Monitor in the cab (69)

• Feedback sensor (73) at governor actuator (74)

The engine and pump controller (68) continually monitors all of the input signals. The
input signals are processed by the engine and pump controller and an output signal is
sent to proportional reducing valve (63) at the right pump regulator. The proportional
reducing valve assists in controlling the output flow of right pump (58) and left pump
(49) .

The oil delivery from pilot pump (59) flows through the pilot filter to proportional
reducing valve (63) at the right pump regulator. The electrical signal that is sent from
engine and pump controller (68) causes proportional reducing valve (63) to regulate the
pilot pressure to a reduced pressure. This reduced pressure is called power shift pressure
(PS). The proportional reducing valve sends the reduced pilot oil pressure through the
right pump regulator and through the left pump regulator. The output flow of right pump
(58) and left pump (49) is controlled in accordance with the power shift pressure. The
power shift pressure is used to regulate the maximum allowable hydraulic pump output.

The output signal that is sent from the engine and pump controller to the proportional
reducing valve will change when the engine and pump controller detects a change in any
of the input signals. The power shift pressure that is sent to the regulators at the right
pump and the left pump will change in order to regulate the maximum allowable
hydraulic pump output. The desired engine speed is maintained.

A decrease in engine speed increases the power shift pressure. An increase in power
shift pressure causes destroke condition of the right pump and the left pump. The
maximum allowable hydraulic power output is decreased.

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An increase in engine speed decreases the power shift pressure. A decrease in power
shift pressure causes an upstroke condition of the right pump and the left pump. The
maximum allowable hydraulic power output is increased.

Note: For more information concerning the operation of the engine and pump
controller, refer to Systems Operation/Testing and Adjusting, "Engine and Pump
Electronic Control System".

Pilot Control Valve Circuits

Oil from pilot pump (59) flows through pilot line (66), pilot filter (61) and pilot line (60)
to pilot manifold (51). When the hydraulic activation control lever is shifted to the
UNLOCKED position, the engine and pump controller energizes the hydraulic
activation solenoid valve (54). The pilot oil then shifts valve (46). The pilot oil now
flows through valve (46) and pilot line (43). The pilot oil now flows to pilot control
valves (5), (25) and (26) for implements, swing and travel in order to perform machine
operations. When the joysticks and/or travel levers/pedals are moved, the pilot oil flows
to main control valve (11) in order to control the machine functions.

Illustration 4 g00932058

Pilot lines at the main control valve (top view)

When joystick (25) and/or joystick (26) are operated, the pilot control valves send pilot
pump oil through the pilot lines to pilot ports at the main control valve in order to shift
the spools in the main control valve. Refer to Illustration 4 and Table 1 for the location
of the pilot lines and machine operations.

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Table 1
Pilot line Control Valve Machine Operation
(76) Boom I control valve BOOM LOWER
(77) Bucket control valve BUCKET CLOSE
(78) Swing control valve SWING LEFT
(79) Boom II control valve BOOM RAISE
(80) Stick II control valve STICK IN
(81) Right travel control valve REVERSE RIGHT TRAVEL
(82) Left travel control valve REVERSE LEFT TRAVEL
(83) Stick I control valve STICK IN

Pilot oil from the pilot control valves flows through pilot lines to the ports on the bottom
of the main control valve in order to perform the opposite operation.

The following example is given for the BOOM LOWER operation and the BOOM
RAISE operation. Machine operations for a stick operation, bucket operation, travel
operation and swing operation are accomplished in the same manner as the boom
operation.

When the joystick for the boom is moved to the BOOM RAISE position, pilot oil from
pilot control valve (26) flows through pilot line (37) to boom I control valve (17). The
pilot pressure shifts the boom I control valve. The oil delivery from the right pump
flows to the head end of the boom cylinders in order to perform the BOOM RAISE
operation.

When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from
pilot control valve (26) flows through pilot line (6) to boom I control valve (17). The
pilot pressure shifts the boom I control valve. The pilot oil also flows through pilot line
(7) in order to open boom drift reduction valve (12). The return oil from the head end of
the boom cylinders flows through the boom drift reduction valve and the boom I control
valve to the hydraulic tank. The BOOM LOWER operation is now performed.

Pressure Switch Circuits

Pressure switches (19) and (21) are connected to travel pilot control valve (5). Pressure
switch (40) is connected to pilot control valve (25) and pilot control valve (26). When
all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, the pilot

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oil pressure to the pressure switches is low. Pressure switches (19), (21) and (40) are
OFF. The engine and pump controller recognizes the OFF condition of all of the
pressure switches. The AEC system is activated in order to lower the engine rpm.

If any of the joysticks and/or travel levers/pedals are moved from the NEUTRAL
position, the increased pilot oil pressure is sent to the pressure switches. If pressure
switch (19), (21) and/or (40) is ON, the engine and pump controller activates the AEC
system in order to increase the engine rpm.

Straight Travel Valve Circuit

When a swing operation and/or implement operation is performed during a travel
operation, the increase of pilot pressure in pilot line (39) activates implement/swing
pressure switch (40). The implement/swing pressure switch sends an electrical signal to
the engine and pump controller. The engine and pump controller energizes straight
travel solenoid (13). Pilot pressure now activates straight travel control valve (18). The
straight travel control valve maintains straight travel even though there is a swing
operation or an implement operation during travel. For more information concerning the
operation of the straight travel control valve, refer to Systems Operation, "Control Valve
(Straight Travel)".

Swing Parking Brake

When the hydraulic activation control lever is placed in the UNLOCKED position, pilot
oil in passage (57) flows through valve (46) and passage (53) to swing parking brake
solenoid valve (45). When any of the joysticks are moved from the NEUTRAL position,
the increase of pilot pressure in pilot line (39) activates implement/swing pressure
switch (40). The implement/swing pressure switch sends an electrical signal to the
engine and pump controller. An electrical signal from the engine and pump controller
energizes the swing parking brake solenoid valve (45). Pilot oil in line (4) flows to
swing parking brake (1). This oil releases the swing parking brakes. For more
information concerning the operation of the swing parking brake, refer to Systems
Operation, "Pilot Valve (Swing Parking Brake)".

Boom Priority
During combined operations of BOOM RAISE and STICK IN, the pilot oil pressure in
pilot line (36) and pilot line (38) activates the pressure reducing valve for boom priority.
The pressure reducing valve for boom priority allows priority flow to the head end of
the boom cylinders during these combined hydraulic operations by disabling the stick II

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control valve. For more information concerning the pressure reducing valve for boom
priority, refer to Systems Operation, "Boom Hydraulic System".

Swing Priority
During a swing operation, pilot oil flows from pilot control valve (25) to the pressure
reducing valve for swing priority (47). The pressure reducing valve for swing priority
shifts. The pilot oil flow in pilot line (42) from pilot oil manifold (51) is blocked by the
pressure reducing valve for swing priority. Most of the left pump delivery flow goes to
the swing motor. For more information concerning the pressure reducing valve for
swing priority, refer to Systems Operation, "Swing Hydraulic System".

Automatic Travel Speed Change Valve

Pilot oil in passage (56) flows to travel speed solenoid valve (52). When the travel speed
switch on the right console is set at the HIGH SPEED position, the travel speed solenoid
valve opens. This allows pilot oil to flow through travel speed solenoid valve (52) and
through line (41). The oil then flows to the displacement change valve for the left travel
motor (2) and the displacement change valve for the right travel motor (3). As the
displacement change valve operates, the travel speed is maintained at the HIGH SPEED
position.

When the travel speed switch on the right console is set at the HIGH SPEED position,
the pressure sensors for the pump delivery pressure control the travel speed in
accordance with the travel load. For example, low speed during a high load condition
and high speed during a low load condition.

For more information concerning the operation of the displacement change valves, refer
to Systems Operation, "Displacement Change Valve".

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