Hydraulic system

5.7Dipper arm check valve (load retaining valve)

• Rod side dipper arm cylinder

A pilot-operated load retaining valve is used to prevent spool leakage, which allows the cylinder to retain its home position.

Retracting the dipper arm

The oil opens the check valve and flows to the rod side of the dipper arm cylinder.

Extending the dipper arm

The load on the check valve is reduced by means of the pilot control line and a piston (return to tank). This allows the base side oil to flow back via the check valve.

5.8Secondary pressure limiting valv es for the auxiliary hydraulics (option)

The limiting valve provides over-pressure protection for components in the secondary circuit (e.g., hydraulic hammer).

IMPORTANT!

The attachment manufacturer (e.g., hammer, offset bucket, etc.) is responsible for attachment over-pressure protection. Mustang is not liable for damage to attachments.

Problem

The secondary circuit is also protected by the primary pressure limiting valve if the spool valve is enabled. There is no protection if the spool valve is not enabled.

Ensuring protection with the spool valve disabled requires two secondary pressure limiting valves instead of the plugs.

Adjusting the secondary pressure limiting valves

The pressure limiting valves must be set at 4061 psi (280 bar) while adjusting the limiting valves.

Short-term pressure peaks can be reduced with this setting.

follow the following should the pressure limiting valves be set to less than 4061 psi (280bar):

• Have the pressure setting performed by a hydraulic systems technical specialist.

• The pump's high flow rate, and the fact that the pressure peaks are now reduced by the secondary pressure limiting valve cartridges at the auxiliary hydraulics section, may cause the hydraulic oil to overheat.

• Reset the pressure setting to the initial 4061 psi (280 bar) when changing attachment.

Location

See Pressure limiting valves on page5-11.

Hydraulic system

5.9Pilot valves

Joystick

• Pilot valve for bucket, boom, dipper arm and rotation.

• Consists of a lever and four pressure-reducing valves.

Numbering for right-hand side joystick. Left-hand side joystick: 31-2-4

Ref. Description

Ref. Description (left joystick) Description (right joystick)

AControl lever1Dipper arm extension controlBoom cylinder extension control

BRubber collar2Left-hand side rotation controlBucket cylinder extension control

CLinkage3Dipper arm retraction controlBoom cylinder retraction control

DUniversal joint4Right-hand side rotation controlBucket cylinder retraction control

EGuide platePSupply from pilot oil supply unitSupply from pilot oil supply unit FTappetTTank lineTank line

• Pedal with hydraulic damping.

• Consists of two pedals and four pressure-reducing valves.

Pilot valve for auxiliary hydraulics

• Pilot valve with pedals for remote control of directional valves.

• Consists of a pedal and two pressure-reducing valves.

MA = 7 lbf.-ft. (10 Nm)

MA = 37 lbf.-ft. (50 Nm)

Ref. Description

A Pedal

Ref. Description

Hydraulic system

Pilot valve for dozer blade

• Pilot valve with pedals for remote control of directional valves consists of a pedal and two pressure-reducing valves.

5.10Valves

7/3 directional valve (changeover valve)

Switches from auxiliary hydraulics (valve de-energized) to boom swivel and vice versa (valve energized).

Electric control by using push button on left-hand side joystick.

Hydraulic system

4/3 directional valve

• Used for electrical auxiliary hydraulics and 3rd control circuit.

• Valve is located in pilot control branch and is controlled by using tip switches on lefthand side joystick.

The high slewing torque during swivel unit start-up causes pump P4 to be switched directly to the tank to reduce engine droop.

Further rotation reduces the pressure to under 2393 psi (165 bar) and the second P4 pump is automatically turned on for a higher upper carriage rotation speed. Location: • In the engine compartment over the hydraulic pump unit.