This section contains the general safety precautions whi ch
must be o bser ved du ring m ainten anc e of the ae rial pla tform. It is of utmost importance that maintenance personnel pay strict attention to these warnings and precautions
to avoid possible injury to themselves or others , or damage to the equipment. A maintenance program must be
followed to ensure that the machine is safe to operate.
MODIFICATION OF THE MACHINE WITHOUT CERTIFICATION BY
A RESPONSIBLE AUTHORITY THAT THE MACHINE IS AT LEAST
AS SAFE AS ORIGINALLY MANUFACTURED, IS A SAFETY VIOLATION.
The sp ecific precau tion s to be o bser ved d uring main tenance are inserted at the appropriate point in the manual.
These precautions are, for the most part, those that apply
when servicing hydraulic and larger machine component
parts.
Your safety, and that of other s, is th e first cons iderati on
when engaging in the maintenance of equipment. Always
be conscious of weight. Never attempt to move heavy
parts without the aid of a mechanical device. Do not allow
heavy objects to rest in an unstable position. When rai sing
a portion of the equipment , ensure tha t adequa te sup port is
provided.
feed lines to system components c an then be disconnected
with minimal fl uid loss.
A.C MAINTENANCE
FAILURE TO COMPLY WITH SAFETY PRECAUTIONS LISTED IN
THIS SECTION MAY RESULT IN MACHINE DAMAGE, PERSONNEL
INJURY OR DEATH AND IS A SAFETY VIOLATION.
• NO SMOKING IS MANDATORY. NEVER REFUEL DURING ELECTRICAL STORMS. ENSURE THAT FUEL
CAP IS CLOSED AND SECURE AT ALL OTHER
TIMES.
• REMOVE ALL RINGS, WATCHES AND JEWELRY
WHEN PERFORMING ANY MAINTENANCE.
• DO NOT WEAR LONG HAIR UNRESTRAINED, OR
LOOSE-FITTING CLOTHING AND NECKTIES WHICH
ARE APT TO BECOME CAUGHT ON OR ENTANGLED
IN EQUIPMENT.
• OBSERVE AND OBEY ALL WARNINGS AND CAUTIONS ON MACHINE AND IN SERVICEMANUAL.
• KEEP OIL, GREASE, WATER, ETC. WIPED FROM
STANDING SURFACES AND HAND HOLDS.
• USE CAUTION WHEN CHECKING A HOT, PRESSURIZED COOLANT SYSTEM.
• NEVER WORK UNDER AN ELEVATED BOOM UNTIL
BOOM HAS BEEN SAFELY RESTRAINED FROM ANY
SINCE THE MACHINE MANUFACTURER HAS NO DIRECT CONTROL OVER THE FIELD INSPECTION AND MAINTENANCE,
SAFETY IN THIS AREA RESPONSIBILITY OF THE OWNER/OPERATO R.
A.B HYDRAULIC SYSTEM SAFETY
It shou ld be n ote d that the ma chin es hy drau lic s yst ems
operate at ext rem ely high potentia lly dangerous press ures.
Every effort should be made to relieve any system pr essure prior to disconnecting or removing any portion of the
system.
MOVEMENT BY BLOCKING OR OVERHEAD SLING,
OR BOOM SAFETY PROP HAS BEEN ENGAGED.
• BEFORE MAKING ADJUSTMENTS, LUBRICATING OR
PERFORMING ANY OTHER MAINTENANCE, SHUT
OFF ALL POWER CONTROLS.
• BATTERY SHOULD ALWAYS BE DISCONNECTEDDURING REPLACEMENT OF ELECTRICAL COMPONENTS.
• KEEP ALL SUPPORT EQUIPMENT AND ATTACHMENTS STOWED IN THEIR PROPER PLACE.
• USE ONLY APPROVED, NONFLAMMABLE CLEANING
SOLVENTS.
Relieve system pressure by cycling the applicable control
several times with the engine stopped and ignition on, to
direct any line pressure back into the reservoir. Pressure
3120240– JLG Li ft –a
EFFECTI VITY CHANGES
REVISON LOG
Aug, 1985-Original Issue
Nov. 1985-Revised
Oct. 1998-Revised
Aug. 1999-Revised
October 11, 2001-Revised
b– JLG Li ft –3120240
TABLE OF CONTENTS
SUBJECT - SECTION, PARAGRAPHPAGE NO.
SECTION A - INTRODUCTION - MAINTENANCE SAFETY PRECAUTIONS
0° F to +180° F (-18°C. to 83°C.)10W
0° F to +210° F (-18° C to 99° C)10W-20/10W-30
50° F to 210° F (10° C to 99° C)20W-20
NOTE: Hydraulic oils must have anti-wear qualities at least
to API Service Classification GL-3, and sufficient
chemical stability for mobile hydraulic system service. JLG Industries recommends Mobilfluid 424
hydraulic oil, which has an SAE viscosity of 10W-30
and viscosity index of 152.
When temperatures remain consistently below +20°
F. (-7° C.), an amount of no. 2 diesel fuel, not to
exceed 20% of system capacity, may be added to
the hydraulic oil reservoir. This diesel fuel will “thin”
the hydraulic oil for easier cold weather operation,
and will almost completely dissipate from the hydraulic system over a several month period of time. When
cold weather is past, it may be necessary to drain
and refill the hydraulic system to rid the system of
any remaining diesel fuel.
Aside from JLG recommendations, it is not advisable
to mix oils of different brands or types, as they may
not contain the same required additives or be of
comparable viscosities. If use of hydraulic oil other
than Kendall Hyken 052 is desired or Mobilfluid 424,
contact JLG Industries for proper recommendations.
Use SAE
Viscosity Number
Use SAE
Viscosity Number
SAE Viscosity
Grade
1-4– JLG Lift –3120240
SECTION 1 - SPECIFICATIONS
Figure 1-1. Torque Chart.
3120240– JLG Lift –1-5
SECTION 1 - SPECIFICATIONS
Figure 1-2. Lubrication Chart. (Sheet 1 of 2)
1-6– JLG Lift –3120240
SECTION 1 - SPECIFICATIONS
INDEX
NO.
1.Wheel Drive HubFill Plug/1/2 FullEPGL (SAE - 90)*50/2 years
*Check oil level after every 50 hours of operation. Change oil after every 2 years (1200 hrs.) of operation.
**Check oil level after every 10 hours of operation. Change oil after every 3 months (150 hrs.) of operation.
***Replace filter element after first 40 hours of operation, then after every 6 months (300 hrs.) of operation thereafter.
****Check oil level after every 10 hours of operation.Change oil after every 2 years(1200 hrs.) of operation.
*****It will be necessary to swing the boom over side of frame and remove the frame shield to gain access to
the grease fitting.
NOTE: Lubrication intervals are based on machine operations under normal conditions. for machines used in multi shift opera-
tions and /or exposed to hostile environments or conditions, lubrication frequencies must be increased accordingly.
A serial number plate is affixed to the left rear front of the turntable. If the serial number plate is damaged or missing, the
machine serial number is stamped on the left side of the frame between front and rear wheels, below turntable bearing. In
addition, the last five digits of the serial number are stamped on top of the fly and base end of the boom and on the left side
of the turntable.
1-10– JLG Lift –3120240
SECTION 1 - SPECIFICATIONS
Figure 1-3. Serial Number Locations.
3120240– JLG Lift –1-11
SECTION 1 - SPECIFICATIONS
intentional blank page
1-12– JLG Lift –3120240
SECTION 2. PROCEDURES
SECTION 2 - PROCEDURES
2.1GENERAL.
This section provides information necessary to perform
maintenance on the aerial platform. Descriptions, techniques and specific procedures are designed to provide
the safest and most efficient maintenance for use by personnel responsible for ensuring the correct installation
and operation of machine components and systems.
WHEN AN ABNORMAL CONDITION IS NOTED AND PROCEDURES
CONTAINED HEREIN DO NOT SPECIFICALLY RELATE TO THE
NOTED IRREGULARITY, WORK SHOULD BE STOPPED AND
TECHNICALLY QUALIFIED GUIDANCE OBTAINED BEFORE WORK
IS RESUMED.
The maintenance procedures included consist of servicing and component removal and installation, disassembly
and assembly, inspection, lubrication and cleaning. Information on any special tools or test equipment is also provided where applicable.
2.2SERVICING AND MAINTENANCE
GUIDELINES.
General.
The following information is provided to assist you in the
use and application of servicing and maintenance procedures contained in this chapter.
Safety and Workmanship.
Your safety, and that of others, is the first consideration
when engaging in the maintenance of equipment. Always
be conscious of weight. Never attempt to move heavy
parts without the aid of a mechanical device. Do not allow
heavy objects to rest in an unstable position. When raising
a portion of the equipment, ensure that adequate support
is provided.
2. At any time when air, fuel, or oil lines are disconnected, clear adjacent areas as well as the openings
and fittings themselves. As soon as a line or component is disconnected, cap or cover all openings to
prevent entry of foreign matter.
3. Clean and inspect all parts during servicing or maintenance, and assure that all passages and openings
are unobstructed. Cover all parts to keep them
clean. Be sure all parts are clean before they are
installed. New parts should remain in their containers until they are ready to be used.
Components Removal and Installation.
4. Use adjustable lifting devices, whenever possible, if
mechanical assistance is required. All slings (chains,
cables, etc.) should be parallel to each other and as
near perpendicular as possible to top of part being
lifted.
5. Should it be necessary to remove a component on
an angle, keep in mind that the capacity of an eyebolt or similar bracket lessens, as the angle between
the supporting structure and the component
becomes less than 90 degrees.
6. If a part resists removal, check to see whether all
nuts, bolts, cables, brackets, wiring, etc., have been
removed and that no adjacent parts are interfering.
Component Disassembly and Reassembly.
When disassembling or reassembling a component, complete the procedural steps in sequence. Do not partially
disassemble or assemble one part, then start on another.
Always recheck your work to assure that nothing ha s b ee n
overlooked. Do not make any adjustments, other than
those recommended, without obtaining proper approval.
Pressure-Fit Parts.
When assembling pressure-fit parts, use an “anti-seize” or
molybdenum disulfide base compound to lubricate the
mating surface.
Cleanliness.
Bearings.
1. When a bearing is removed, cover it to keep out dirt
1. The most important single item in preserving the
long service life of a machine is to keep dirt and foreign materials out of the vital components. Precautions have been taken to safeguard against this.
Shields, covers, seals, and filters are provided to
keep air, fuel, and oil supplies clean; however, these
items must be maintained on a scheduled basis in
order to function properly.
3120240– JLG Lift –2-1
and abrasives. Clean bearings in nonflammable
cleaning solvent and allow to drip dry. Compressed
air can be used but do not spin the bearing.
2. Discard bearings if the races and balls (or rollers)
are pitted, scored, or burned.
3. If bearing is found to be serviceable, apply a light
coat of oil and wrap it in clean (waxed) paper. Do not
SECTION 2 - PROCEDURES
unwrap reusable or new bearings until they are
ready to install.
4. Lubricate new or used serviceable bearings before
installation. When pressing a bearing into a retainer
or bore, apply pressure to the outer race. If the bearing is to be installed on a shaft, apply pressure to the
inner race.
Gaskets.
Check that holes in gaskets align with openings in the
mating parts. If it becomes necessary to hand-fabricate a
gasket, use gasket material or stock of equivalent material
and thickness. Be sure to cut holes in the right location, as
blank gaskets can cause serious system damage.
Bolt Usage and Torque Application.
1. 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 original, or one which is
equivalent.
2. 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 Figure 1-1.)
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.
Battery.
Clean battery, using a non-metallic brush and a solution of
baking soda and water. Rinse with clean water. After
cleaning, thoroughly dry battery and coat terminals with
an anti corrosion compound.
Lubrication and Servicing.
Components and assemblies requiring lubrication and
servicing are shown in Figures 1-2.
2.3LUBRICATION INFORMATION.
Hydraulic System.
1. The primary enemy of a hydraulic system is contamination. Contaminants enter the system by various
means, e.g., using inadequate hydraulic oil, allowing
moisture, grease, filings, sealing components, sand,
etc., to enter when performing maintenance, or by
permitting the pump to cavitate due to insufficient
system warm-up or leaks in the pump supply (suction) lines.
2. The design and manufacturing tolerances of the
component working parts are very close, therefore,
even the smallest amount of dirt or foreign matter
entering a system can cause wear or damage to the
components and generally results in faulty operation. Every precaution mst be taken to keep hydraulic oil clean, including reserve oil in storage.
Hydraulic system filters should be checked,
cleaned, and/or replaced as necessary, at the specified intervals required in Figure 1-2. Always examine
filters for evidence of metal particles.
1. Keep the system clean. If evidence of metal or rubber particles are found in the hydraulic system, drain
and flush the entire system.
2. Disassemble and reassemble parts on clean work
surface. Clean all metal parts with non-flammable
cleaning solvent. Lubricate components, as
required, to aid assembly.
Lubrication.
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 equivalent
that meets or exceeds the specifications listed.
3. Cloudy oils indicate a high moisture content which
permits organic growth, resulting in oxidation or corrosion. If this condition occurs, the system must be
drained, flushed, and refilled with clean oil.
4. It is not advisable to mix oils of different brands or
types, as they may not contain the same required
additives or be of comparable viscosities. Good
grade mineral oils, with viscosities suited to the
ambient temperatures in which the machine is operating, are recommended for use.
NOTE: Metal particles may appear in the oil or filters of new
machines due to the wear-in of meshing components.
2-2– JLG Lift –3120240
SECTION 2 - PROCEDURES
Hydraulic Oil.
5. Refer to Table 1-1 for recommendations for viscosity
ranges.
6. JLG recommends Mobilfluid 424 hydraulic oil, which
has an SAE viscosity of 10W-30 and a viscosity
index of 152.
NOTE: Start-up of hydraulic system with oil temperatures
below -15° F. is not recommended. If it is necessary
to start the system in a sub-zero environment, it will
be necessary to heat the oil with a low density,
100VAC heater to a minimum temperature of -15° F.
7. The only exception to the above is to drain and fill
the system with Mobil DTE 11 oil or its equivalent.
This will allow start up at temperatures down to 20°F. However, use of this oil will give poor performance at temperatures above 120° F. Systems using
DTE 11 oil should not be operated at temperatures
above 200°F. under any condition.
Changing Hydraulic Oil.
8. Use of any of the recommended crankcase or
hydraulic oils eliminates the need for changing the
oil on a regular basis. However, filter elements must
be changed after the first 40 hours of operation and
every 250 hours thereafter. If it is necessary to
change the oil, use only those oils meeting or
exceeding the specifications appearing in this manual. If unable to obtain the same type of oil supplied
with the machine, consult local supplier for assistance in selecting the proper equivalent. Avoid mixing petroleum and synthetic base oils. JLG
Industries recommends changing the hydraulic oil
annually.
9. Use every precaution to keep the hydraulic oil clean.
If the oil must be poured from the original container
into another, be sure to clean all possible contaminants from the service container. Always clean the
mesh element of the filter and replace the cartridge
any time the system oil is changed.
10. While the unit is shut down, a good preventive maintenance measure is to make a thorough inspection
of all hydraulic components, lines, fittings, etc., as
well as a functional check of each system, before
placing the machine back in service.
Lubrication Specifications.
Specified lubricants, as recommended by the component
manufacturers, are always the best choice, however,
multi-purpose greases usually have the qualities which
meet a variety of single purpose grease requirements.
Should any question arise, regarding the use of greases in
maintenance stock, consult your local supplier for evalua-
tion. Refer to Table 1-2 for an explanation of the lubricant
key designations appearing in the Lubrication Chart.
2.4CYLINDERS - THEORY OF OPERATION.
Systems Incorporating Double Acting
Cylinders:
Cylinders are of the double-acting type. Systems incorporating double-acting cylinders are as follows: Lift, Telescope, Platform Leveling, Steer and Lockout. A double
acting cylinder is one that requires oil flow to operate the
cylinder rod in both directions. Directing oil (by actuating
the corresponding control valve to the piston side of the
cylinder) forces the piston to travel toward the rod end of
the barrel, extending the cylinder rod (piston attached to
rod). When the oil flow is stopped, movement of rod will
stop. By directing oil to the rod side of the cylinder, the
piston will be forced in the opposite direction and the cylinder rod will retract.
Holding valves are used in the Lift, Telescope, Slave Level
and lockout circuits to prevent retraction of the cylinder
rod, should a hydraulic line rupture or a leak develop
between the cylinder and its related control valve.
2.5VALVES - THEORY OF OPERATION.
Solenoid Control Valves (Bang-Bang).
Control valves used are four-way three-position solenoid
valves of the sliding spool design. When a circuit is activated and the control valve solenoid energizes, the spool
is shifted and the corresponding work port opens to permit oil flow to the component in the selected circuit with
the opposite work port opening to reservoir. Once the circuit is deactivated (control returned to neutral) the valve
spool returns to neutral (center) and oil flow is then
directed through the valve body and returns to reservoir. A
typical control valve consist of the valve body, sliding
spool, and two solenoid assemblies. The spool is
machine fitted in the bore of the valve body. Lands on the
spool divide the bore into various chambers, which when
the spool is shifted, align with corresponding ports in the
valve body open to common flow. At the same time other
ports would be blocked to flow. The spool is spring loaded
to center position, therefore when the control is released,
the spool automatically returns to neutral, prohibiting any
flow through the circuit.
3120240– JLG Lift –2-3
SECTION 2 - PROCEDURES
Proportional Control Valve - Vickers.
CMX series valves provide a power output matching that
required by the load. A small line connected to a loadsensing port feeds load pressure back to the pump. The
pump senses the difference between the load and pump
outlet pressures, and varies the pump displacement to
keep the difference constant. This differential pressure is
applied across the valves meter-in spool, with the effect
that pump flow is determined by the degree of spool
opening, independent of load pressure. Return lines are
connected together simplifying routing of return flow and
to help reduce cavitation. Load sensing lines connect
through shuttle valves to feed the highest load signal back
to the pump. Integral actuator port relief valves, anti cavitation check valves, and load check valves are standard.
The load drop check prevents any drop of a suspended
load before upward movement.
Relief Valves.
Main relief valves are installed at various points with the
hydraulic system to protect associated systems and components against excessive pressure. Excessive pressure
can be developed when a cylinder reaches its limit of
travel and the flow of pressurized fluid continues from the
system control. The relief valve provides an alternate path
for the continuing flow from the pump, thus preventing
rupture of the cylinder, hydraulic line or fitting. Complete
failure of the system pump is also avoided by relieving circuit pressure. The relief valve is installed in the circuit
between the pump outlet (pressure line) and the cylinder
of the circuit, generally as an integral part of the system
valve bank. Relief pressures are set slightly higher than
the load requirement, with the valve diverting excess
pump delivery back to the reservoir when operating pressure of the component is reached.
2. Torque fly boom retract chains, adjust to
28 ft. lbs. (38 NM).
3. Torque fly boom extend chains, adjust to
28 ft. lbs. (38 NM).
4. Cycle boom (extend at least three feet and
return to the fully retracted position).
JLG Industries, Inc. requires a complete boom disassembly, per instructions outlined in the 2-11 boom disassembly, every two years. All boom chains and related
components (i.e., sheaves, pins, sprockets, wear pads,
etc.) must also be inspected and replaced (as necessary)
during this disassembly.
A more frequent disassembly of the boom assembly and
inspection of the boom chains and related components is
required if 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. Such a disassembly is required if either debris has
accumulated inside the boom assembly or an inspection
of the boom chain and related components, in accordance with the INSPECTION PROCEDURES in this section, reveals any discrepancies to the boom chain or
related components.
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:
Relief Valves.
Crossover relief valves are used in circuits where the actuator requires an operating pressure lower than that supplied to the system. When the circuit is activated and the
required pressure at the actuator is developed, the crossover relief diverts excess pump flow to the reservoir, individual, integral reliefs are provided for each side of the
circuits.
2.6BOOM CHAINS. (SEE FIGURE 2-1)
1. Erratic boom operation or unusual noise exists, due
to discrepancies listed in the INSPECTION PROCEDURES in this section, to the boom chains or related
components. See troubleshooting section in Service
Manual for probable causes.
2. Chain adjustment is required more often than specified in Service Manual or links need to be removed
(chain shortened) to make adjustment.
3. Machine is idle for an extended period (6 months or
longer.)
4. Boom is overloaded or sustained a shock load.
Adjusting Procedures.
FAILURE TO DISASSEMBLE THE BOOM ASSEMBLY AND PROP-
ENSURE MACHINE IS ON A FIRM AND LEVEL SURFACE.
1. Fully retract boom in the horizontal position.
2-4– JLG Lift –3120240
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-
SECTION 2 - PROCEDURES
NENTS. DAMAGE AND/OR BREAKAGE OF THESE ITEMS COULD
RESULT IN UNCONTROLLED EXTENSION OR RETRACTION OF
Figure 2-1. Typical Three Section Boom Assembly.
Inspection Procedures.
5. Inspect boom chains for the following condition:
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 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 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
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.
THE BOOM ASSEMBLY AND COULD CAUSE SERIOUS INJURY OR
DEATH TO PERSONNEL OPERATING THE JLG BOOM LIFT.
a film of oil on all chain surfaces will inhibit rusting
and corrosion. 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.
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 this lubricant on chains. A
grade of SAE 30 or 40 weight, non detergent
motor oil should be used as a supplemental lubricant and a film of this oil should be constantly
maintained on the surfaces and internal joints. 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 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
Lubrication: One of the most important but often
overlooked factors is adequate lubrication. In
addition to reducing internal friction, maintaining
3120240– JLG Lift –2-5
common cause of chain plate failures.
Fatigue cracks are found through the link
holes, perpendicular (90 degrees) from the
SECTION 2 - PROCEDURES
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.
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 care fully) 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.
extend in an arc-like path, often parallel to the rolling grain of the material.
Also, more then one crack can often appear on a
link plate. In addition to rusting, this condition can
be caused by exposure to an acidic or caustic
medium or atmosphere. Stress corrosion is an
environmentally assisted failure. Two conditions
must be present - corrosive agent and static
stress. In the chain, static stress is present at the
aperture due to the press fit pin.
No cycle motion is required and the plates can
crack during idle periods. The reactions of many
chemical agents (such as battery acid fumes) with
hardened metals liberate hydrogen which attacks
and weakens the metal grain structure.
Oil rusty chains, and replace chains with bent or
peened chain components. Keep chains lubricated.
Protruding or Tur ned P i ns: 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.
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 highest stress (aperture) but tend to
Chain Anchors, Sheaves and Pins: An inspection of the chain must include a close examination
of chain anchors, sheaves and pins. Check chain
anchors for wear breakage and misalignment.
Anchors with worn or broken fingers should be
replaced. They should also be adjusted to eliminate twisting the chain for an even load distribution.
Sheaves should be inspected for worn flanges,
which would indicate misalignment, and wear on
the outside diameter of the sheave. A worn
sheave can mean several problems, as follows:
1. Chains too tight.
2. Sheave bearings/pin bad.
3. Bent/misaligned chains.
2.7WEAR PADS.
1. Shim up wear pads within 1/16 in. (1.59 mm) tolerance between wear pad and adjacent surface.
2. Replace wear pads when worn within 1/8 in. (3.18
mm) of threaded insert.
2-6– JLG Lift –3120240
Table 2-1. Chain Stretch Tolerance.
SECTION 2 - PROCEDURES
Chain
Size
0.50 in. (1.27 cm) pitch14 in. (36 cm) or 28 pitches0.42 in. (1.07 cm)
0.625 in. (1.59 cm) pitch15 in. (38 cm) or 24 pitches0.45 in. (1.14 cm)
0.75 in. (1.91 cm) pitch15 in. (38 cm) or 20 pitches0.45 in. (1.14 cm)
1 in. (2.54 cm) pitch14 in. (36 cm) or 14 pitches0.42 in. (1.07 cm)
1.25 in. (3.18 cm) pitch15 in. (38 cm) or 12 pitches0.45 in. (1.14 cm)
1.75 in. (4.45 cm) pitch14 in. (36 cm) or 8 pitches0.42 in. (1.07 cm)
2 in. (5.08 cm) pitch14 in. (36 cm) or 7 pitches0.42 in. (1.07 cm)
2.8CYLINDER CHECKING PROCEDURE.
NOTE: Cylinder checks must be performed any time a cylin-
der component is replaced or when improper system
operation is suspected.
Cylinders Without Counterbalance Valves.
Steer Cylinder and Master Cylinder.
3. Using all applicable safety precautions, activate
engine and fully extend cylinder to be checked. Shut
down engine.
4. Carefully disconnect hydraulic hose from retract port
of cylinder. There will be initial weeping of hydraulic
fluid which can be caught in a suitable container.
After the initial discharge there should be no further
leakage from the retract port.
Pin To Pin
Measurement
Allowable
Stretch
Cylinders With Single Counterbalance
Valve.
Lift Cylinder, Telescope Cylinder and Extend- A-Reach Lift
Cylinder.
OPERATE ALL FUNCTIONS FROM GROUND CONTROLS.
1. Using all applicable safety precautions, activate
hydraulic system.
WHEN WORKING ON THE LIFT CYLINDER, RAISE THE BOOM TO
HORIZONTAL AND PLACE A BOOM PROP APPROXIMATELY 1
INCH (2.50 CM) BELOW THE BOOM. DO NOT WORK ON THE CYLINDER WITHOUT A SUITABLE PROP IN PLACE. REFER TO FIGURE 2-2.
5. Activate engine and extend cylinder.
6. If cylinder retract port leakage is less than 6-8 drops
per minute, carefully reconnect hose to port and
retract cylinder. If leakage continues at a rate of 6-8
drops per minute or more, cylinder repairs must be
made.
7. With cylinder fully retracted, shut down engine and
carefully disconnect hydraulic hose from cylinder
extend port.
8. Activate engine and retract cylinder. Check extend
port for leakage.
9. If extend port leakage is less than 6-8 drops per
minute, carefully reconnect hose to extend port,
then activate cylinder through one complete cycle
and check for leaks. If leakage continues at a rate of
6-8 drops per minute or more, cylinder repairs must
be made.
2. After completing the above, shut down hydraulic
system and allow machine to sit for 10-15 minutes.
Turn IGNITION SWITCH to ON, move control switch
or lever for applicable cylinder in each direction,
then turn IGNITION SWITCH to OFF. This is done to
relieve pressure in the hydraulic lines. Carefully
remove hydraulic hoses from appropriate cylinder
port block.
3. There will be initial weeping of hydraulic fluid, which
can be caught in a suitable container. After the initial
discharge, there should not be any further leakage
from the ports. If leakage continues at a rate of 6-8
drops per minute or more, the following cylinder
repairs must be made. If the retract port is leaking,
the piston seals are defective and must be replaced.
If the extend port is leaking, the counterbalance
valve is defective and must be replaced.
4. If no repairs are necessary or when repairs have
been made, carefully reconnect hydraulic hoses to
the appropriate ports.
3120240– JLG Lift –2-7
SECTION 2 - PROCEDURES
Figure 2-2. Boom Positioning and Support, Cylinder Repair.
2-8– JLG Lift –3120240
SECTION 2 - PROCEDURES
5. If used, remove boom prop from beneath boom,
activate hydraulic system and run cylinder through
one complete cycle to check for leaks.
Cylinders With Dual Counterbalance Valves.
Platform Slave Level Cylinder, Lockout Cylinder
and Extend-A-Reach Level Cylinder.
OPERATE ALL FUNCTIONS FROM GROUND CONTROL STATION
ONLY.
1. Using all applicable safety precautions, activate
hydraulic system.
2. When working on the platform slave level cylinder,
stroke platform slave level cylinder forward until platform sits at a 45° angle.
3. Shut down hydraulic system and allow machine to
sit for 10-15 minutes. If machine is equipped with a
bang-bang or proportional control valves, turn IGNITION SWITCH to ON, move control switch or lever
for applicable cylinder in each direction, then turn
IGNITION SWITCH to OFF. If machine is equipped
with hydraulic control valves, move control lever for
applicable cylinder in each direction. This is done to
relieve pressure in the hydraulic lines. Carefully
remove hydraulic hoses from appropriate cylinder
port block.
4. There will be initial weeping of hydraulic fluid which
can be caught in a suitable container. After the initial
discharge, there should not be any further leakage
from the ports. If leakage continues at a rate of 6-8
drops per minute or more, the counterbalance valve
is defective and must be replaced.
5. To check piston seals, carefully remove the counterbalance valve from the retract port. After initial discharge there should not be any further leakage from
the ports. If leakage occurs at a rate of 6-8 drops per
minute or more, the piston seals are defective and
must be replaced.
6. If no repairs are necessary or when repairs have
been made, replace counterbalance valve and carefully connect hydraulic hoses to cylinder port block.
2.9CYLINDER REPAIR.
NOTE: The following are general procedures that apply to
all of the cylinders on this machine. Procedures that
apply to a specific cylinder will be so noted.
Disassembly.
DISASSEMBLY OF THE CYLINDER SHOULD BE PERFORMED ON
A CLEAN WORK SURFACE IN A DIRT FREE WORK AREA.
1. Connect a suitable auxiliary hydraulic power source
to the cylinder port block fitting.
DO NOT FULLY EXTEND CYLINDER TO THE END OF STROKE.
RETRACT CYLINDER SLIGHTLY TO AVOID TRAPPING PRESSURE.
2. Operate the hydraulic power source and extend the
cylinder. Shut down and disconnect the power
source. Adequately support the cylinder rod, if applicable.
CYLINDERS WITH DOUBLE HOLDING VALVES. BEFORE REMOVING HOLDING VALVES CRACK BLEEDERS TO RELEASE PRESSURE.
3. If applicable, remove the cartridge-type holding
valve and fittings from the cylinder port block. Discard o-rings.
4. Place the cylinder barrel into a suitable holding fixture. Tap around outside of cylinder head retainer
with a suitable hammer to shatter loctite.
5. Using a suitable spanner wrench, loosen the cylinder head retainer, if applicable, and/or cylinder head
gland, and remove from cylinder barrel.
6. Attach a suitable pulling device to the cylinder rod
port block end or cylinder rod end, as applicable.
7. If used, remove lifting device from upright or remove
prop from below boom, activate hydraulic system
and run cylinder through one complete cycle to
check for leaks.
EXTREME CARE SHOULD BE TAKEN WHEN REMOVING THE CYLINDER ROD, HEAD, AND PISTON. AVOID PULLING THE ROD OFFCENTER, WHICH COULD CAUSE DAMAGE TO THE PISTON AND
CYLINDER BARREL SURFACES.
3120240– JLG Lift –2-9
SECTION 2 - PROCEDURES
7. With the barrel clamped securely, apply pressure to
the rod pulling device and carefully withdraw the
complete rod assembly from the cylinder barrel.
8. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
9. Remove the set screw (s), if applicable, and nut
which attach the piston to the rod, and remove the
piston. Discard self-locking set screws.
10. Remove the piston rings.
11. Remove and discard the piston o-rings, seal rings,
and backup rings.
12. Remove the set screw, if applicable, piston spacer,
and wear ring, if applicable, from the rod.
13. Remove the rod from the holding fixture. Remove
the cylinder head gland and retainer, if applicable.
Discard the o-rings, back-up rings, rod seals, and
wiper seals.
Cleaning and Inspection.
1. Clean all parts thoroughly in an approved cleaning
solvent.
2. Inspect the cylinder rod for scoring, tapering, ovality,
or other damage. If necessary, dress rod with
Scotch Brite or equivalent. Replace rod if necessary.
3. Inspect threaded portion of rod for excessive damage. Dress threads as necessary.
4. Inspect inner surface of cylinder barrel tube for scoring or other damage. Check inside diameter for
tapering or ovality. Replace if necessary.
5. Inspect threaded portion of barrel for damage. Dress
threads as necessary.
6. Inspect piston surface for damage and scoring and
for distortion. Dress piston surface or replace piston
as necessary.
7. Inspect seal and o-ring grooves in piston for burrs
and sharp edges. Dress applicable surfaces as necessary.
11. Inspect cylinder head outside diameter for scoring
or other damage and ovality and tapering. Replace
as necessary.
12. If applicable, inspect thread ring for scoring or other
damage. Dress threads or applicable surfaces as
necessary.
13. If applicable, inspect seal grooves in thread ring for
burrs and sharp edges. Dress applicable surfaces
as necessary.
14. If applicable, inspect rod and barrel bushings for
signs of correct lubrication and excessive wear.
Replace as necessary.
15. Inspect travel limiting collar or spacer for burrs and
sharp edges. If necessary, dress inside diameter
surface with Scotch Brite or equivalent.
16. If applicable, inspect port block fittings and holding
valve. Replace as necessary.
17. Inspect the oil ports for blockage or the presence of
dirt or other foreign material. Repair as necessary.
18. If applicable, inspect piston rings for cracks or other
damage. Replace as necessary.
NOTE: Steps (19) through (22) apply to the 3 Section Boom
telescope cylinder only.
19. Inspect chain sheave bushings for scoring, tapering,
ovality and for excessive wear and evidence of correct lubrication. Replace bushing as necessary.
20. Inspect sheave chain groove for damage. Replace
sheave assembly as necessary.
21. Inspect sheave attach pin for scoring or other damage and for evidence of correct lubrication. Dress
pin surface with Scotch Brite or equivalent or
replace pin as necessary.
22. Inspect sheave pin lubrication drilling and fitting for
blockage or the presence of dirt or other foreign
material. Repair as necessary.
Assembly.
NOTE: Prior to cylinder assembly, ensure that the proper
cylinder seal kit is used. See your JLG Parts Manual.
8. Inspect cylinder head inside diameter for scoring or
other damage and for ovality and tapering. Replace
as necessary.
9. Inspect seal and o-ring grooves in head for burrs
and sharp edges. Dress applicable surfaces as necessary.
10. If applicable, inspect cylinder head retainer or end
cap for surface or thread damage. Repair or replace
as necessary.
WHEN INSTALLING ‘POLY-PAK’ PISTON SEALS, ENSURE SEALS
ARE INSTALLED PROPERLY. REFER TO FIGURE 2-3 FOR CORRECT SEAL ORIENTATION. IMPROPER SEAL INSTALLATION
COULD RESULT IN CYLINDER LEAKAGE AND IMPROPER CYLINDER OPERATION.
Apply a light film of hydraulic oil to all components
prior to assembly.
2-10– JLG Lift –3120240
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