JLG Skytrak 6036 Service Manual page 159

Section 9. Hydraulic System
1. Cotter Pin
2. Retaining Pin
3. Locknut
4. Washer
5. Capscrew
6. Main Control Valve
7. Linkage
The relief valve setting is determined by the
compression of the pilot spring as set by the
adjustment screw. When the pressure exceeds
the relief setting, the pilot poppet acts against the
poppet spring to unseat. The fluid then flows
around the pilot poppet through cross-drilled holes
in the plug to the reservoir; some pressure is
relieved.
Due to the reduced pressure, the piston seats
against the pilot poppet. This shuts off fluid flow
through the valve and causes a low pressure area
PISTON
RELIEF VALVE
POPPET
CHECK VALVE
POPPET
Model 6036 S/N 9B0499 and Before
6
5
4
Fig. 9.23 Main Control Valve Installation
TO
RESERVOIR
Fig. 9.24 Relief Valve Sectional View
3
internally. The differential pressure between the
supply pressure and the internal pressure causes
the relief valve poppet to unseat and fluid flows to
the reservoir thus relieving the pressure.
If low supply pressure should occur due to pump
cavitation, the check valve poppet will unseat and
allow fluid to flow back to the supply from the
reservoir.
Refer to paragraph 9.1 for information on relief
valve functions and testing.
PILOT
POPPET
RELIEF
PLUG
AREA
7
1
FRAME
PILOT
SPRING
ADJUSTMENT
SCREW
2
MA0641
MA0652
9-46