JLG 680S, Service And Maintenance Manual

Page: 329 / 530

SECTION 4 - BOOM & PLATFORM
3121234 4-65
Greasing Thrust Washers
5. After the actuator is assembled but before it is put into
service, the thrust washer area must be packed with
Lithium grease.
6. There are two grease ports located on both the shaft
flange and the end cap. They are plugged with cap-
screws (6) 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
CAPSCREWS INSERTED INTO THE SHAFT FLANGE TO TURN THE SHAFT IN THE
DESIRED DIRECTION.
7. 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 capscrews into the grease
ports and tighten to 25 in. lbs. (2.8 Nm).
Testing the Actuator
If the equipment is available, the actuator should be tested on a
hydraulic test bench. The breakaway pressure — the pressure at
which the shaft begins to rotate — should be approximately
400 psi (28 bar). Cycle the actuator at least 25 times at 3000 psi
(207 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 opposite 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 (207 bar) and
maintain pressure. Remove the hydraulic line from the non-pres-
surized side.
Continuous oil flow from the open housing port indicates inter-
nal 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.