JLG 4017PS Service Manual - Manual (Page 71)

3-33 3706PS, 3707PS, 4014PS, 4017PS, 33.7, 37.6, 37.7
Boom
11. Measure the distance between the top of both
extend chains and the bottom of the second and
third boom sections at the center of each section.
12. The distance between the top of the extend chains
and the bottom of the third boom section (E) should
measure 120 mm ± 2 mm (4.724 in ± 0.078 in).
13. The distance between the top of the extend chains
and the bottom of the second boom section (F)
should measure 180 mm ± 2 mm (7.0 in ± 0.078 in).
14. Loosen the locknuts on the extend chains and adjust
if necessary. Tighten locknuts to 120 Nm (86 lb-ft).
15. Start the machine and cycle the extend/retract
cylinder to verify the boom extends and retracts
properly.
3.16 BOOM EXTEND AND RETRACT
CHAINS - 4014PS & 4017PS
3.16.1 Boom Chain Inspection
Under normal operating conditions the boom chains will
need to be inspected every
250 hours of operation. The
retract chains need to be exposed and inspected every
1000 hours of operation. Refer to the Service Manual for
the proper procedure. Environmental conditions and
dynamic impulse/shock loads can drastically affect
normal operating conditions and require more frequent
inspection intervals.
Environments in which material handling vehicles
operate can vary widely from outdoor moisture to
temperature to mildly corrosive or highly corrosive
industrial atmospheres, in addition to abrasive
exposures such as sand and grit. Some effects can be
as follows:
• Moisture - Corrosive rusting reduces chain
strength by pitting and cracking.
• Temperature - Low temperature reduces chain
strength by embrittlement. Going in and out of
cold storage results in moisture from
condensation.
• Chemical Solutions or Vapors - Corrosive attack
on the chain components and/or the mechanical
connections between the chain components.
Cracking can be (and often is) microscopic.
Going from microscopic cracking to complete
failure can be either abrupt or may require an
extended period of time.
• Abrasives - Accelerated wearing and scoring of
the articulating members of the chain (pins and
plates), with a corresponding reduction in chain
strength. Due to the inaccessibility of the bearing
surfaces (pin surfaces and plate apertures),
wear and scoring are not readily noticeable to
the naked eye.
Following are some examples of dynamic shock loading
which can impose abnormal loads above the endurance
limit of a leaf chain.
MY5290
F E
WARNING
Worn pins, stretched or cracked links or corrosive
environments can cause chain failure. A chain failure
could result in uncontrolled boom movement, loss of
load or machine instability.