JLG 110HX ANSI Service Manual - Manual (Page 33)

SECTION 2 - PROCEDURES
3120636 – JLG Lift – 2-9
2. Lubrication: One of the most important but often
overlooked factors is adequate lubrication. In addi-
tion to reducing internal friction, maintaining a film of
oil on all chain surfaces will inhibit rusting and corro-
sion. This is important as corrosion of highly
stressed, hardened steel chain components can
cause a major reduction in the load capacity of leaf
chain and result in link plate cracking.
NOTE: The need for lubrication can be determined by the
presence of rust on the exposed portions of chain.
3. Rust and Corrosion: Rust and corrosion will cause
a major reduction in the load carrying capacity of the
chain, because these are primary reasons for side
plate cracking. The initial lubrication at the factory is
applied in a hot dip tank to assure full penetration
into the joint. Do not steam clean or degrease
chains. At time of chain installation, factory lube
must be supplemented by a maintenance program
to provide a film of oil on the chains at all times.

If chains are corroded, they must be inspected,
especially the outside plates, for cracks in-line with
the pins. If cracks are found, replace the chain; if no
cracks are discovered, lubricate the chains by dip-
ping in heated oil, and reinstall on the machine.
Keep chains lubricated.
4. Fatigue Cracks: Fatigue is a phenomenon that
affects most metals, and is the most common cause
of chain plate failures. Fatigue cracks are found
through the link holes, perpendicular (90 degrees)
from the pin in-line position. Inspect chains carefully
after long time use and heavy loading for this type of
crack. If any cracks are discovered, replace all
chains, as seemingly sound plates are on the verge
of cracking. Fatigue and ultimate strength failures on
JLG Lifts are incurred as a result of severe abuse as
design specs are well within the rated lifting capacity
of these chains.
5. Tight Joints: All joints in the roller chain should flex
freely. On roller chain, tight joints are usually caused
by rust/corrosion, or the inside plates “walking” off
the bushing. Limber up rusty/corroded chains (after
inspecting carefully) 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 lubrication. Tight
joints on leaf chain are generally caused by:

1. Bent pins or plates.
2. Rusty joints.
3. Peened plate edges.

Oil rusty chains, and replace chains with bent or
peened chain components. Keep chains lubricated.
6. Protruding or Turned Pins: Chains operating with
inadequate lube generate tremendous friction
between the pin and plates (pin and bushing on
roller 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.
7. Stress Corrosion Cracking: The outside link
plates, which are heavily press-fitted to the pins, are
particularly susceptible to stress corrosion cracking.
Like fatigue cracks, these initiate at the point of high-
est stress (aperture) but tend to extend in an arc-like
path, often parallel to the rolling grain of the material.
Table 2-1.Chain Stretch Tolerance
Chain Size
Pin to Pin
Measurement
Allowable Stretch
0.50 in. (1.27 cm) pitch 14 in. (36 cm) or 28 pitches 0.42 in. (1.07 cm)
0.625 in. (1.59 cm) pitch 15 in. (38 cm) or 24 pitches 0.45 in. (1.14 cm)
0.75 in. (1.91 cm) pitch 15 in. (38 cm) or 20 pitches 0.45 in. (1.14 cm)
1 in. (2.54 cm) pitch 14 in. (36 cm) or 14 pitches 0.42 in. (1.07 cm)
1.25 in. (3.18 cm) pitch 15 in. (38 cm) or 12 pitches 0.45 in. (1.14 cm)
TIGHT JOINTS