JLG 120HX ANSI Service Manual - Manual (Page 26)

SECTION 2 - PROCEDURES
2-6 – JLG Lift – 3120686
An immediate disassembly of the boom assembly and
inspection of the boom chains and related components is
required if any of the following conditions occur:
1. After machine is exposed to hostile environments or
conditions (i.e., extreme cold, dust, sand, blasting
grit, salt, chemicals, etc.) which could adversely
affect boom operation.
2. Erratic boom operation or unusual noise exists.
Refer to troubleshooting tables in Section 3.
3. Chain adjustment is required more often than speci-
fied in this Section or links need to be removed
(chain shortened) to make adjustment.
4. Machine is idle for an extended period (6 months or
longer).
5. Boom is overloaded or has sustained a shock load.
FAILURE TO DISASSEMBLE THE BOOM ASSEMBLY AND PROP-
ERLY INSPECT AND/OR REPLACE THE BOOM CHAINS AND
RELATED COMPONENTS (I.E., SHEAVES, PINS, SPROCKETS,
WEAR PADS, ETC.) COULD RESULT IN THE DAMAGE AND/OR
BREAKAGE OF THE BOOM CHAINS AND/OR RELATED COMPO-
NENTS. DAMAGE AND/OR BREAKAGE OF THESE ITEMS COULD
RESULT IN UNCONTROLLED EXTENSION OR RETRACTION OF
THE BOOM ASSEMBLY AND COULD CAUSE SERIOUS INJURY OR
DEATH TO PERSONNEL OPERATING THE JLG BOOM LIFT.
Inspection Procedure
BOOM CHAINS TO BE INSPECTED AT TIME OF NEXT BOOM
OVERHAUL AND WHEN DEEMED NECESSARY BY MACHINE
OWNER, BUT NOT TO EXCEED 2 YEARS OF MACHINE OPERA-
TION.
1. Inspect boom chains for the following conditions:
a. Wear: Always inspect that segment of chain that
operates over a sheave. As the chain flexes over
the extend/retract sheaves, joints and plate
edges very gradually wear. Chain “stretch” can
be measured using a manufacturers wear scale
or steel tape. When chains have elongated 3%
they must be removed and replaced. Refer to
Table 2-1 for proper chain specifications and
allowable stretch tolerances. Peening and wear
of chain plate edges are caused by sliding over
a chain worn contact face of a sheave, or unusu-
ally heavy loads. All of the above require
replacement of the chain and correction of the
cause. Chain side wear, noticeable when pin
heads and outside plates show a definite wear
pattern, is caused by misalignment of the
sheave/chain anchors and must be corrected
promptly. Do not repair chains; if a section of
chain is damaged, replace the entire chain set.
Figure 2-2. Typical Boom Assembly