Hydraulic Circuit Fig. WH 169
NOTE: 1 Bar is equal to 100 kPa; 1 Bar is equal to 14.5 psi; 1 psi is equal to 6.9 kPa.
(1) Variable double pump with total capacity controller
(2) 4-element valve bank. left, with 300 bar (30 000 kPa) main relief valve
Connections:
(P) Pressure line from hydraulic pump
(T) Return line to tank
(A1) Retract bucket cylinder
(B1) Extend bucket cylinder
(A2) Retract boom cylinders
(B2) Extend boom cylinders
(A3) Variable-displacement hydraulic motor for running gear - reverse
(B3) Variable-displacement hydraulic motor for running gear - forward
(A4) Series connection extend stick cylinder and e.g. rotate grab
(B4) e.g. rotate grab
(X1), (Y1), (X2), (Y2), (X3), (Y3) Pilot pressure oil
- cut-in 6.5 bar (650 kPa)
- cut-out 15 bar (1500 kPa)
(X4), (Y4) Pilot pressure oil -
- cut-in 18 bar (1800 kPa)
- cut-out 26 bar (2600 kPa)
*See also topic Spring Exchange 4th section left valve bank. WH111.
(3) 4-element valve bank, right, with 300 bar (30 000 kPa) main relief valve
Connections:
(P) Pressure line from hydraulic pump
(T) Return line to tank
(A1) Hydraulic motor for swing gear - CCW swing
(B1) Hydraulic motor for swing gear - CW swing
(A2) Extend stick cylinder
(B2) Retract stick cylinder
(A3) Extend stabilizer cylinder for stabilizing lower chassis (or grader cylinder)
(B3) Retract stabilizer for stabilizing lower chassis (or grader cylinder)
(A4) Series connection extend bucket cylinder
(B4) Series connection extend boom cylinders
(X1), (Y1), (X2), (Y2), (X3), (Y3) Pilot pressure oil -
- cut-in 18 bar (1800 kPa)
- cut-out 26 bar (2600 kPa)
(4) Pilot-control valve, left (with electric contact)
Connections:
(A1) Retract stick cylinder
(A2) CW swing
(B1) CCW swing
(B2) Extend stick cylinder
(5) Pilot-control valve, right
Connections:
(A1) Retract boom cylinders
(A2) Retract bucket cylinder
(B1) Extend bucket cylinder
(B2) Extend boom cylinders
(6) 4-way electromagnetic directional valve
a. In the pilot-control lines for CW swing and series connection, stick cylinder or for optional hydraulic attachment function (e.g. rotate grab CW). Controlled by electric contact of pilot-control valve, right, Item 5.
b. In the pilot-control lines for CCW swing or for optional hydraulic attachment function (e.g. rotate grab CCW). Controlled by electric contact of pilot-control valve, right, Item 5.
c. In the pilot-control lines for forward and reverse travel. Controlled by pressure switch (3 bar; 300 kPa) of compressed air unit.
Energized - float position for third section of valve bank, left. Thus, the running gear can be cut out when the pilot-control valve, center. Item 23 (handbrake switch) is switched on. If the air pressure on the spring-loaded handbrake cylinder drops below 3 bar (300 kPa) (air line is vented), the (3 bar: 300 kPa) pressure switch transmits current simultaneously to the 4-way electro-magnetic valve and the handbrake fault light in the driver's cab. This provides visual warning of an applied handbrake and prevents travel with the handbrake applied.
(7) Bucket cylinder
(8) Boom cylinder
(9) Variable flow axial piston motor for running gear
(10) Axial piston fixed displacement motor for swing gear
(11) Stick cylinder
(12) Stabilizer cylinder for lower chasis or grader cylinder, both with pilot-controlled check valves (hose rupture protection)
(13) Cut-off valve for boom cylinder (operated from driver's cab)
(14) Throttle check valve for boom cylinders
(15) Throttle check valve for stick cylinder
(16) Hydraulic oil cooler
(17) Check valves as back-pressure valves
(18) Return filter with bypass valve
(19) Cut-off valve in service hydraulic circuit, stick cylinder series connection:
Cut-off valve open - stick cylinder series connection
Cut-off valve shut - for optional hydraulic function. e.g. rotate grab
(20) Optional hydraulic function, e.g. rotate hydraulic motor for grab with line relief valves
(21) Cut-off valve in the pilot-control line
Cut-off valve open - stick cylinder series connection
Cut-off valve shut - for optional hydraulic function. e.g. rotate grab
(22) Check valve
a. For bucket cylinder series connection
b. For boom cylinder series connection
(23) Pilot-control valve, center
Connections:
(A1) Reverse travel
(A2) Forward travel
(B1) Retract stabilizer cylinder for lower chassis (or grader cylinder)
(B2) Extend stabilizer cylinder for lower chassis (or grader cylinder)
(24) 4/3-way electromagnetic directional valve
Connected to the pilot-control unit. Controlled by combination switch on steering column in driver's cab.
Connection A pressurized - high ratio of power-shift gearbox
Connection B pressurized - low ratio of power-shift gearbox
Neutral position (no current) - power-shift gearbox in neutral
(25-27) Not applicable
(28) Breather filter (with inlet and discharge valve)
Inlet valve opens at max. 0.35 bar (35 kPa)
Discharge valve opens at 0.03 bar (3 kPa) (vacuum)
(29) Hydraulic oil reservoir, pressurized at max. 0.35 bar (35 kPa)
(30) Cut-off valve
a. Cut-off valve for emergency lowering of boom cylinders
b. Cut-off valve for overload warning pressure switch, if equipped
(31) Pressure switch for overload warning device (with pressure gauge connection), when equipped