SkyTrak 3606 Service Manual - Manual (Page 288)

Section 9
9-94
9.10.3 Extend/Retract Cylinder
The extend/retract cylinder (Fig. 9– 66) is located within
the inner boom.
a. Extend/Retract Cylinder Removal
Procedures for replacing the extend/retract cylinder
appear in Section 3.2.1 Inner Boom Replacement.
b. Extend/Retract Cylinder Disassembly
Note: An additional O-ring may be included at the base
of the cylinder rod. This additional O-ring may be
discarded, as it served only in a temporarily protective
role to keep paint off the rod while the cylinder was
painted at the factory.
1. Clean the extend/retract cylinder (Fig. 9– 66) with a
suitable cleaner. Remove all dirt, debris and grease
from the cylinder.
2. Secure the extend/retract cylinder in a soft-jawed
vise or other acceptable holding equipment if
possible. DO NOT damage the tube (19).
Note: Significant pressure may be trapped inside the
cylinder. Exercise caution when removing the counter-
balance valves (18) from the cylinder.
3. Remove both counterbalance valves (18) from the
rod weldment (17).
IMPORTANT: DO NOT tamper with or attempt to reset
the counterbalance valve cartridges. If adjustment or
replacement is necessary, replace a counterbalance
valve with a new one.
4. Extend the rod weldment (17, Fig. 9– 66) as required
to allow access to the base of the cylinder.
5. Using a pin spanner wrench, unscrew the head gland
(14) from the tube (19). The gland was originally
torqued to 250-300 lb/ft (339-407 Nm), so a
considerable amount of force is required. Slide the
gland down along the rod toward the eyelet end,
away from the cylinder tube (19).
IMPORTANT: Protect the finish on the rod at all times.
Damage to the surface of the rod can cause seal failure.
6. Carefully pull the rod (17) with all attachments
straight out of the tube (19).
IMPORTANT: When sliding the rod and piston assembly
in the tube, prevent the threaded end of the tube from
damaging the piston (4). Keep the rod centered within the
tube to help prevent binding.
7. Fasten the rear of the rod in a soft-jawed vise and put
a padded support below and near the threaded end
of the rod to help prevent damage to the rod.
8. Remove the locking insert (15) from its hole in the
head gland threads. Pry or drill out the insert as
required. DO NOT damage the head gland threads. A
new locking insert will be required for reassembly.
9. Remove the 5/16-18 UNC x 0.63 set screw (5) from
the piston (4). The set screw is used to provide a
secondary lock on the piston.
10. Remove the piston (4) from the rod spacer (8) and
rod weldment (17). The piston was installed with
Loctite #271 (red) and torqued to 1500-1700 lb/ft
(2034-2305 Nm).
Note: It may be necessary to apply heat to break the
bond of the sealant between piston (4) and the rod (17)
before the piston can be removed. Some parts of cylin-
ders are sealed with a special organic sealant and lock-
ing compound. Before attempting to disassemble these
parts, remove any accessible seals from the area of the
bonded joint. Wipe off any hydraulic oil and heat the joint
uniformly to break the bond. A temperature of 300° to
400° F (149° to 204° C) will destroy the bond. Avoid over-
heating or the parts may become distorted or damaged.
Apply sufficient torque or pressure for removal while the
parts are still hot. Breakdown of sealant will leave a
white, powdery residue on threads and parts. Clean the
residue away with a soft brass wire brush prior to reas-
sembly, and wipe with Loctite T cleaner before reinstalla-
tion.
11. Remove the rod spacer (8).
12. Remove both precision wearbands (6) and the
capped T-seal (7) from the piston (4).
Note: The T-seal actually consists of four components; a
wide, flexible inner band, the flexible T-seal band itself,
and two supportive split caps that mount on either side of
the “T” itself.
13. Remove the O-ring (9), backup ring (10) and O-ring
(11) from the head gland (14). Slide the rings over
the rod spacer (8) and piston (4) to remove them
from the rod weldment (17).
14. Remove the precision wearband (12) and deep Z-
seal with rod backup (13) from the head gland (14).
15. From within the head gland (14), remove the
precision wearbands (12), the deep Z-seal with
backup (13), and, from the other end, remove the
sealed outside diameter heavy-duty rod wiper (16).
16. From within the piston (4), remove the hytrel backup
rings (2) and the small O-ring (3).
Model 3606 • Origin 10/99