JLG 19AMI (3120758) Service Manual - Manual (Page 20)

SECTION 2 - SERVICE PROCEDURES
2-6 – JLG Lift – 3120758
Bolt Usage and Torque Application
Use bolts of proper length. A bolt which is too long will
bottom before the head is tight against its related part. If a
bolt is too short, there will not be enough thread area to
engage and hold the part properly. When replacing bolts,
use only those having the same specifications of the origi-
nal, or one which is equivalent.
Unless specific torque requirements are given within the
text, standard torque values should be used on heat-
treated bolts, studs, and steel nuts, in accordance with
recommended shop practices. (See Torque Chart, Sec-
tion-1.)
Hydraulic Lines and Electrical Wiring
Clearly mark or tag hydraulic lines and electrical wiring, as
well as their receptacles, when disconnecting or removing
them from the unit. This will assure that they are correctly
reinstalled.
Hydraulic System
Keep the system clean. If evidence of metal or rubber par-
ticles is found in the hydraulic system, drain and flush the
entire system.
Disassemble and reassemble parts on clean work sur-
face. Clean all metal parts with non-flammable cleaning
solvent. Lubricate components, as required, to aid assem-
bly.
Lubrication and Servicing
Components and assemblies requiring lubrication and
servicing are shown in the Lubrication Chart, (See Sec-
tion-1). Service applicable components with the amount,
type, and grade of lubricant recommended in this manual,
at the specified intervals. When recommended lubricants
are not available, consult your local supplier for an equiva-
lent that meets or exceeds the specifications listed.
Batteries
Clean batteries, using a non-metallic brush and a solution
of baking soda and water. Rinse with clean water. After
cleaning, thoroughly dry batteries and coat terminals with
an anti-corrosion compound.
Mast Chain Inspection Procedure
Inspect mast chains for the following conditions:
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 wear very gradually.
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 2-3 for
proper chain specifications and allowable stretch toler-
ances. Peening and wear of chain plate edges are caused
by the chain sliding over a chain worn contact face of a
sheave, or unusually 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 misalign-
ment 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.
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 crack-
ing. 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 installa-
tion, factory lube must be supplemented by a mainte-
nance 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 dipping in heated
oil, and reinstall on the machine. Keep chains lubricated.
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 dis-
covered, 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 lift-
ing capacity of these chains.
Tight Joints: All joints in the leaf chain should flex freely.
On leaf chains, tight joints are usually caused by rust/cor-
rosion, or the inside plates “walking” off the bushing. Lim-
ber up rusty/corroded chains (after inspecting carefully)
with a heavy application of oil (preferably a hot oil dip). Tap
Table 2-3. Chain Stretch Tolerance
Chain Size
Pin to Pin
Measurement
Allowable Stretch
.50" pitch 12" or 24 pitches .24 in./12 in. span
.625 pitch 15" or 24 pitches .30 in./15 in. span