JLG 1350SJP Service Manual - Manual (Page 322)

SECTION 4 - BOOM & PLATFORM
4-88 – JLG Lift – 3121142
Installing Counterbalance Valve
Refer to Figure 4-37., Rotator Counterbalance Valve.
1. Make sure the surface of the actuator is clean, free of any
contamination and foreign debris including old Loctite.
2. Make sure the new valve has the O-rings in the counter-
bores of the valve to seal it to the actuator housing.
3. The bolts that come with the valve are grade 8 bolts.
New bolts should be installed with a new valve. Loctite
#242 should be applied to the shank of the three bolts at
the time of installation.
4. Torque the 1/4-inch bolts 110 to 120 inch pounds (12.4
to 13.5 Nm). Do not torque over 125 inch pounds (14.1
Nm). Torque the 5/16-inch bolts 140 inch pounds (15.8
Nm). Do not torque over 145 inch pounds (16.3 Nm).
Testing the Actuator
If the equipment is available, the actuator should be tested on
a hydraulic test bench. The breakaway pressure — the pres-
sure at which the shaft begins to rotate — should be approxi-
mately 400 psi (28 bar). Cycle the actuator at least 25 times at
3000 psi (210 bar) pressure. After the 25 rotations, increase the
pressure to 4500 psi (315 bar) to check for leaks and cracks.
Perform the test again at the end of the rotation in the oppo-
site direction.
TESTING THE ACTUATOR FOR INTERNAL LEAKAGE
If the actuator is equipped with with a counterbalance valve,
plug the valve ports. Connect the hydraulic lines to the hous-
ing ports. Bleed all air from the actuator (see Installation and
Bleeding) Rotate the shaft to the end of rotation at 3000 psi
(210 bar) and maintain pressure. Remove the hydraulic line
from the non-pressurized side.
Continuous oil flow from the open housing port indicates
internal leakage across the piston. Replace the line and rotate
the shaft to the end of rotation in the opposite direction.
Repeat the test procedure outlined above for the other port. If
there is an internal leak, disassemble, inspect and repair.
Bleeding After Installation
NOTE: Bleeding will be necessary if excessive backlash is displayed
after the actuator is installed. To do this, bleeder valves
must be installed in the actuator at the locations shown
below. The following steps are recommended when a mini-
mum of two gallons (8 liters) is purged.
1. Connect a 5 foot (1.5 m) long 3/16" inside diameter, 5/
16" outside diameter clear vinyl drain tube to each of
the two bleeder valves. Secure the tubes in place with
hose clamps.
2. Place the end of the tubes in a clean 5 gallon (19 L) con-
tainer to collect the purged oil. The oil can be returned
to the reservoir when the procedure is complete.
3. Open both bleeder valves 1/4 turn. Using the hydraulic
system, rotate the platform to the end of rotation and
maintain hydraulic pressure. Oil with small air bubbles
should be seen flowing through the tubes. Allow 1/2
gallon (2 L) of oil to be purged from the actuator.
4. Keep the bleeder valves open and rotate the platform in
the opposite direction to the end of rotation. Maintain
hydraulic pressure until an additional 1/2 gallon (2 L) of
oil is pumped out.
5. Repeat steps 3 and 4. After the last 1/2 gallon (2 L) of oil
is purged, close both bleed nipples before rotating away
from the end of rotation.