JLG 40RTS Service Manual - Manual (Page 19)

SECTION 2 - PROCEDURES
3120826 – JLG Sizzor – 2-3
NOTE: Metal particles may appear in the oil or filters of new
machines due to the wear-in of meshing compo-
nents.
Hydraulic Oil
1. Refer to Section 1 for recommendations for viscosity
ranges.
2. JLG recommends Mobilfluid 424 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 -26° C (-15° F). is not recommended. If it is
necessary to start the system in a sub-zero environ-
ment, it will be necessary to heat the oil with a low
density, 100VAC heater to a minimum temperature of
-26° C (-15° F).
3. 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 -29°
C (-20 ° F). However, use of this oil will give poor per-
formance at temperatures above 49° C (120° F). Sys-
tems using DTE 11 oil should not be operated at
temperatures above 94° C (200° F). under any con-
dition.
Changing Hydraulic Oil
1. 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 50 hours of operation and
every 300 hours thereafter. If it is necessary to
change the oil, use only those oils meeting or
exceeding the specifications appearing in this man-
ual. If unable to obtain the same type of oil supplied
with the machine, consult local supplier for assis-
tance in selecting the proper equivalent. Avoid mix-
ing petroleum and synthetic base oils. JLG
Industries recommends changing the hydraulic oil
annually.
2. 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 contami-
nants from the service container. Always clean the
mesh element of the filter and replace the cartridge
any time the system oil is changed.
3. While the unit is shut down, a good preventive main-
tenance 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 Section 1 for an explanation of the lubricant
key designations appearing in the Lubrication Chart.
2.4 CYLINDERS - THEORY OF OPERATION
Cylinders are of the double acting type. The Lift and Steer
systems incorporate double acting cylinders. 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 the rod
will stop. By directing oil to the rod side of the cylinder, the
piston will be forced in the opposite direction and the cyl-
inder rod will retract.
NOTE: The lift cylinder is a single acting cylinder which
takes hydraulic pressure to extend and gravity to
retract.
A holding valve is used in the Lift circuit to prevent retrac-
tion of the cylinder rod should a hydraulic line rupture or a
leak develop between the cylinder and its related control
valve.
2.5 VALVES - 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 acti-
vated and the control valve solenoid energizes, the spool
is shifted and the corresponding work port opens to per-
mit oil flow to the component in the selected circuit, with
the opposite work port opening to reservoir. Once the cir-
cuit 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 consists 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, pro-
hibiting any flow through the circuit.