JLG 340AJ Service Manual - Manual (Page 154)

SECTION 4 - BOOM & PLATFORM
4-22 – JLG Lift – 3121259
Greasing Thrust Washers
1. After the actuator is assembled but before it is put into
service, the thrust washer area must be packed with
Lithium grease.
There are two grease ports located on both the shaft
flange and the end cap. They are plugged with cap
screws (113) or set screws. Remove the grease port
screws from the shaft flange and end cap. (See exploded
view)
IF A HYDRAULIC TEST BENCH IS NOT AVAILABLE, THE ACTUATOR CAN BE
ROTATED BY HAND, OPEN THE PRESSURE PORTS AND USE A PRY BAR WITH
CAP SCREWS INSERTED INTO THE SHAFT FLANGE TO TURN THE SHAFT IN THE
DESIRED DIRECTION.
Insert the tip of a grease gun into one port and apply
grease to the shaft flange. Continue applying until
grease flows from the opposite port. Cycle the actuator
five times and apply grease again. Repeat this process
on the end cap. Insert the cap screws into the grease
ports and tighten to 25 in-lbs. (2.8 Nm).
Installing Counterbalance Valve
Refer to Figure 4-8., 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 a counterbalance valve, plug
the valve ports. Connect the hydraulic lines to the housing
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.