Oshkosh JLG 1500SJ, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
3121262 – JLG Lift – 5-93
Jib Telescope Cylinder
USE CARE IN REMOVAL OF ANY, AND ALL, COMPONENTS
AS COUNTERBALANCE VALVES MAY RETAIN CONSIDER-
ABLE PRESSURE WITHIN THE CYLINDER ASSEMBLY. USE
EXTREME CARE REMOVING PLUGS, VALVES, AND/OR THE
ROD ASSEMBLY TO ENSURE THE INTERNAL CYLINDER
PRESSURE HAS BEEN RELIEVED.
NOTE: The jib telescope cylinder weighs approximately 130.5 lbs.
(59.2 kg).
DISASSEMBLY
1. Retract cylinder and support equipment to allow for cyl-
inder removal. Relieve system pressure to the cylinder.
Clean any debris from around both ports and remove
the hydraulic lines. Plug/cap both ports and remove cyl-
inder from equipment.
2. The cylinder assembly should be secured in such a way
as to prevent movement of the barrel assembly while
removing the rod assembly. (Such as in a vise with pipe
jaws.) Caution should be used to avoid damaging the
rod surface and to avoid excessive deformation of the
barrel, which could permanently damage the unit. Provi-
sions must also be made to support the rod assembly
during its removal.
3. Remove all dirt, grease, and other contaminants from
around the ports and the head gland. Drain all oil from
the unit. Extending and retracting the rod manually can
help purge the bulk of remaining oil.
4. Mark the orientation of the rod, gland, pad support, and
barrel with a permanent marker or paint pen.
Do not
paint the chromed surface of the rod! Remove the cap
screws retaining the head gland from the cylinder
assembly.
NOTE: The threads are “locked” with a non-permanent thread
adhesive during assembly; a quick tug on the wrench may
be necessary to release the thread adhesive.
5. Remove the rod assembly from the barrel using care not
to damage the threads or any other components sur-
face.
6. Clamp the rod mount and support the rod assembly
with the chrome surface protected. Remove the piston
assembly by unthreading the piston itself from the rod
using a spanner wrench.
INSPECTION
1. Inspect all seals, backup rings, wipers, and wear rings for
tears, grooves, foreign matter, and excessive wear. Deep
grooves may be an indication of damage to the barrel
bore, rod chrome, or the presence of large particle con-
tamination.
2. Remove the seals, backup rings, wipers, and wear rings
using a soft metal tool (brass or aluminum) with
rounded edges. Use care not to nick or score the sur-
faces of any component, especially the seal grooves.
3. Wipe all components clean with a lint-free cloth. Plug
the barrel opening with a lint-free cloth. Remove any
adhesive remnants from the head gland, barrel, rod, and
piston threads (where applicable) using a soft wire
brush. Use care not to scratch or otherwise damage the
critical surfaces of any component including seal
grooves, barrel bore, rod chrome, etc.
4. Inspect the piston and head gland for excessive wear,
cracks, scoring, or any other damage. If wear is present
on the O.D. of the piston or the I.D. of the head gland,
check to ensure that the circularity of both dimensions
are within 0.007”. Beyond this limit the seal performance
is compromised and the components must be replaced.
5. The stop tube should be inspected for cracking and
excessive flaring of the ends.
6. Closely inspect the chrome surface of the rod. Any nicks,
gouges, or scratches that penetrate the chrome plating
or result in a sharp edge, which may damage seals, are
cause for rod assembly replacement.
7. Flush the barrel and fluid tube (if equipped), drain, and
wipe dry with a lint-free cloth. Closely inspect bore for
nicks, gouges, or scratches. Replace barrel assembly if
any of these are present.