XVIII. Propel Circuit
59
FIGURE 66
PILOT PROPEL & MOTOR DRAIN CIRCUIT BLOCK DIAGRAM
Center Pin
The center pin also known as (hydraulic swivel) is positioned in the center of the upperstructure and undercarriage. It
is the component that carries hydraulic fluid to the undercarriage from the upperstructure. This design allows for 360°
continous upperstructure rotation. All ports are identified by numbers and letters. Ports 1, 2, 3, 4 are for main
control valve propel fluid. Ports A, C, & E are not used on the XL 4200 and XL 5200 crawler mounted Excavators.
Port D carries fluid to the two speed (hi/lo) section of the propel motors. Ports B and F carry motor case oil
drain oil to tank. Main components and their function are:
Center Pin
Fastened to the crawler carbody. Has fluid ports machined in it to carry oil undercarriage.
Housing
Fastened to the upperstructure and fits around the center pin. Has ports machined in it to carry fluid to correct
location to match ports of the center pin.
Top gland
Located at top of center pin. Has machined ports to carry pilot and drain fluid.
Seals
Located at all port areas. Keeps fluid trapped in individual ports.
Bearings
Located at top and bottom of assembly. Reduces rotation forces against center pin assembly.
B, D, F - Center Pin Pon
FWD - Forward Travel
REV - Reverse Travel
A, B - Control Valve Main Pump Ports
T - Tank
P - Pressure
Left
Travel
Motor
Right
Travel
Motor
2 Speed
(Hi/Lo)
Valve
12 Volt
Left
Travel
Pedal
Right
Travel
Pedal
Travel
Alarm
Switch 12
Volt
Left Track
Right Track
Boom
To Tank
Center Pin
Pilot Line
Motor Case Drain
Pressure
Tank
XL 4200/XL 5200 HYDRAULIC SYSTEM OPERATIONS MANUAL
Form No. 29704
Summary of Contents for XL4000
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