JLG 20VP (3120728) Service Manual - Manual (Page 21)

SECTION 2 - SERVICE PROCEDURES
3120728 – JLG Lift – 2-3
Tight Joints: All joints in the leaf chain should flex freely.
On leaf chain, tight joints are usually caused by rust/corro-
sion, or the inside plates “walking” off the bushing. Limber
up rusty/corroded chains (after inspecting care fully) with
a heavy application of oil (preferably a hot oil dip). Tap
inside “walking” plates inward; if “walking” persists,
replace the chain. This type of problem is accelerated by
poor lubrication maintenance practice, and most tight
joint chains have been operated with little or no lubrica-
tion. Tight joints on leaf chain are generally caused by:
a. Bent pins or plates.
b. Rusty joints.
c. Peened plate edges.
Oil rusty chains, and replace chains with bent or peened
chain components. Keep chains lubricated.
Protruding or Turned Pins: Chains operating with inade-
quate lube generate tremendous friction between the pin
and plates (pin and bushing on leaf chain). In extreme
cases, this frictional torque can actually turn the pins in
the outside press-fit plates. Inspect for turned pins, which
can be easily spotted as the “V” flats on the pin heads are
no longer in line. Replace all chains showing evidence of
turned or protruding pins. Keep chains lubricated.
Chain Anchors and Sheaves: An inspection of the chain
must include a close examination of chain anchors and
sheaves. Check chain anchors for wear breakage and
misalignment. Anchors with worn or broken fingers should
be replaced. They should also be adjusted to eliminate
twisting the chain for an even load distribution.
Inspect the sheaves, sheave bearings, sheave grooves
and pins for extreme wear, replace as necessary. A worn
sheave can mean several problems, as follows:
a. Chains too tight.
b. Sheave bearings/pin bad.
c. Bent/misaligned chains.
Mast Cable Inspection Procedure
MAST CABLES ARE TO BE INSPECTED EVERY THREE MONTHS
OR MORE FREQUENTLY AS DESCRIBED FOLLOWING.
WEAR PROTECTIVE GLOVES TO PROTECT HANDS WHEN HAN-
DLING CABLE.
The periodic inspection shall cover the entire length of the
cable. The inspection frequency shall be based on such
factors as expected cable life as determined by experi-
ence on the particular application or similar installations,
severity of environment, percentage of capacity lifts, fre-
quency rates of operation, and exposure to shock loads.
Inspection should be more frequent as cables approach
the end of their useful lives.
Only the surface wires of the cable require inspection, do
not attempt to open the cable. Any deterioration resulting
in any loss of original strength, such as described below,
shall be noted, and then a determination made if further
use would constitute a hazard.
Mast cables must be replaced after machine has been in
service for five (5) years, regardless of cable condition, or
sooner if conditions dictate.
Conditions such as the following shall be sufficient reason
for questioning continual use of the [cable] or increasing
the frequency of inspection:
1. In running ropes, six randomly distributed broken
wires in one lay or three broken wires in one strand
in one lay.
2. One outer wire broken at the point of contact with
the core of the rope which has worked its way out of
the rope structure and protrudes or loops out from
the rope structure. Additional inspection of this sec-
tion is required.
3. Wear of one-third the original diameter of outside
individual wires.
4. Kinking, crushing, birdcaging or any other damage
resulting in distortion of the rope structure.
5. Evidence of any heat damage from any cause.
6. Reductions from nominal diameter of more than;
a. 1/64th in. (0.4mm) for diameters up to and
including 5/16th in. (8mm);
NOTE: A good indicator of a stretched extend/retract cable
is if the adjusting nuts are bottomed out. If no adjust-
ment remains the cables have stretched and need
replacement.
Also check for cracked, bent, worn, severely corroded, or
improperly installed cable ends.
Inspect sheaves, sheave grooves, and sheave pins for
excessive wear, replace as necessary.
2.3 LUBRICATION INFORMATION
Hydraulic System
The primary enemy of a hydraulic system is contamina-
tion. Contaminants enter the system by various means,
e.g., using inadequate hydraulic oil, allowing moisture,
grease, filings, sealing components, sand, etc., to enter
when performing maintenance, or by permitting the pump
to cavitate due to insufficient system warm-up or leaks in
the pump supply.
The design and manufacturing tolerances of the compo-
nent working parts are very close, therefore, even the
smallest amount of dirt or foreign matter entering a system