JLG 4017PS Service Manual - Manual (Page 72)

Boom
3-34 3706PS, 3707PS, 4014PS, 4017PS, 33.7, 37.6, 37.7
• High velocity movement of load, followed by
sudden, abrupt stops.
• Carrying loads in suspension over irregular
surfaces such as railroad tracks, potholes, and
rough terrain.
• Attempting to “inch” loads which are beyond the
rated capacity of the vehicle.
The above load cycles and environmental conditions
make it impossible to predict chain life. It is therefore
necessary to conduct frequent inspections until
replacement life can be predicted.
The boom chain’s normal life expectancy can be
expressed as a maximum percent of elongation. This is
generally 3%. As the chain flexes back and forth over the
sheave, the bearing joints (pins and inside link plates)
gradually incur wear due to articulation.
3.16.2 Inspection Guidelines - 4014PS
a. Retract Chain
1. Park the machine on a firm, level surface, raise the
boom to a horizontal (level) position, place the
transmission control lever in (N) NEUTRAL, engage
the park brake switch.
2. Fully extend the boom until the retract chain is taut.
Shut the engine off.
3. The retract chain will be visible for inspection with
the vehicle in this state.
4. While doing the chain inspection, check all chain
clevis ends, pins for distortion or cracking and
sheaves for bearing wear or grooving from the chain.
b. Extend Chains
1. Park the machine on a firm, level surface, raise the
boom to a horizontal (level) position, place the
transmission control lever in (N) NEUTRAL, engage
the park brake switch.
2. Fully retract the boom. Shut the engine off.
3. Both extend chain clevises and pins will be visible
for inspection with the vehicle in this state.
4. Limited visual inspection of the extend chains is
possible. For complete extend chain inspection, the
extend chains must be removed from the boom. For
extend chain removal, refer to Section 3.7.3, “Extend
Chain Removal,” and Section 3.7.4, “Extend Chain
Installation.”
5. Inspect the extend and retract chains every 250
hours of operation.
6. Inspect the chains for the following conditions:
Edge Wear
Check the chain for wear on the link plate edges
caused by running back and forth over the sheave.
The maximum reduction of material should not
exceed 5%. Measure and compare to a normal link
plate height by measuring a portion of chain that
does not run over the sheave. If the measured plate
height (1) is 5% less than the normal plate height (2),
discard and replace the chain.
Elongation
It is important to measure the chain in the section
that moves over the sheaves because it receives the
most frequent articulation. Measuring the chain near
its clevis terminals could give an inaccurate reading.
The ends of the chains, near the clevis terminal, will
not have flexed as frequently, if at all, as the middle
of the chains.
It is best to measure in 12 pin increments from pin
center to pin center. For example, if the links are
25 mm (1 in) from pin center to pin center, the
distance should be 305 mm (12 in). If the links are
19 mm (.75 in) apart, the distance after 12 pins
should be 229 mm (9 in).
If the distance measured (3) is 3% greater than the
normal length (4), discard and replace the chain.
MZ1463
2 1
MY1360
3
4