SkyTrak 6036 Service Manual - Manual (Page 115)

Section 9. Hydraulic System
Model 6036 S/N 9B0499 and Before 9-2
oil from the base end of the cylinder to return
through ports A to D, Fig. 9.1, of the directional
control valve to the return filter and reservoir. If
supply pressure reaches 3,000 ± 50 psi (206,7 ±
3,4 bar), the main relief valve, Fig. 9.2, will open,
allowing hydraulic oil to return to the reservoir. If
the return filter becomes clogged, hydraulic oil will
bypass the filter when the pressure reaches 10 to
15 psi
(0,7 to 1,03 bar).
The counterbalance valve in each boom hoist
cylinder serves as a safety device. The counter-
balance valve functions as follows:
Should any of the hydraulic lines going to
either hoist cylinder fail, there will be a loss of
hydraulic system pressure to the cylinder(s).
Example: If there was a hydraulic line failure
in the pressurized lowering line during lower-
Fig. 9.1 Boom Hoist Circuit
STRAINER
RESERVOIR
MAIN RELIEF
VALVE
port relief valve, Fig. 9.2, will open allowing
hydraulic oil to return to the reservoir.
Return oil from the top end of the boom hoist
cylinder piston is directed back to the directional
control valve through ports B to D, Fig. 9.1, to the
return filter and reservoir. If the filter becomes
clogged, hydraulic oil will bypass the filter when
the pressure reaches 10 to 15 psi
(0,7 to 1,03 bar).
Lower Position
When the joystick is placed in the lower position,
the directional control valve spool is shifted so that
supply pressure is directed through ports E to B,
Fig. 9.1, to the rod (top) end of both left and right
boom hoist cylinder pistons. This supply pressure
also pilots open the counterbalance valve, Fig.
9.1. The open counterbalance valve allows return
COUNTERBALANCE
VALVES
A B C A B C A B C
D E F D E F D E F
LOWER
CENTER
TO FRAME TILT
CYLINDER
TO GRILLE TILT AND
SLAVE CYLINDERS
MAIN CONTROL
VALVE
DIRECTIONAL CONTROL
VALVE POSITIONS
RETURN
FILTER
TO BOOM EXTEND/
RETRACT CYLINDER
RIGHT BOOM
HOIST CYLINDER
LEFT BOOM
HOIST CYLINDER
BOOM HOIST
RELIEF VALVE
0-4000 psi
PRESSURE
GAUGE
RAISE
15
GPM
30
GPM
TANDEM
PUMP
MA0421
LOWER
RAISE