JLG 600SC_660SJC Service Manual - Manual (Page 67)

SECTION 4 - CAT CHASSIS (PRIOR TO S/N 0300128000)
3121157 – JLG Lift – 4-5
RESULT OF INCORRECT ASSEMBLY
The slipping of the rubber toric ring on the housing ramp
or on the seal ring ramp may result in uneven pressure on
the seal face. Uneven pressure on the seal face causes
galling, scoring, and leakage.
If the rubber toric ring slips at one location but not all the
way around the seal ring, the toric ring will twist.
The twisted toric ring could be cocked. Seals that are
cocked will cause uneven pressure on the seal face. Seals
that are cocked may also cause possible galling, scoring,
and leakage.
The twisted toric ring could oscillate when the ring is
rotated. Seals that oscillate may allow dirt into the seal
joint. This is caused by the pumping action that is created
by the toric ring that is oscillating.
The illustration below shows a toric ring that is assembled
incorrectly. The upper housing is stationary. The lower
housing is rotating.
The illustration below shows the same seal after the lower
housing has rotated 180 degrees. In this position, there
will be high pressure at Point (B) and at Point (X). These
points of high pressure may result in galling of the toric
rings. There will be low pressure at Point (A) and at Point
(Y) which will result in possible leakage.
4.2 SYSTEM PRESSURE - RELEASE
Procedure for Releasing Pressure
The release of hydraulic pressure in a hydraulic circuit is
required before service is performed to that hydraulic cir-
cuit. Release the pressure in the following hydraulic cir-
cuits before any hydraulic lines are disconnected or
removed from that hydraulic circuit.
• Boom hydraulic circuit
• Swing hydraulic circuit
• Drive hydraulic circuit
• Pilot hydraulic circuit
• Return hydraulic circuit
NOTE: Refer to the applicable section in this manual for
additional information concerning service of the com-
ponents of specific hydraulic circuits.