SkyTrak 3606 Service Manual - Manual (Page 293)

Hydraulic System
9-99
c. Hoist/Lower Cylinder Cleaning
1. Remove all hydraulic fluid, dirt and debris from the
inner surface of the cylinder tube (3, Fig. 9– 67).
2. Discard all seals, backup rings, O-rings, etc. Replace
with new items from a complete seal kit to help
ensure proper cylinder function.
3. Clean all metal parts with an approved cleaning
solvent such as trichlorethylene. Carefully clean
cavities, grooves, threads, etc.
Note: If a white, powdery residue is present on threads
and parts, it can be removed. Clean the residue away
with a soft brass wire brush prior to reassembly, and wipe
with Loctite “T” cleaner before reinstallation.
d. Hoist/Lower Cylinder Inspection
1. Inspect internal surfaces and all parts for wear,
damage, etc. If inner surface of the tube (3,
Fig. 9– 67) does not display a smooth finish, or is
scored or damaged in any way, replace the tube.
Most often, dirty hydraulic fluid causes failure of
internal seals and damage to the smooth surface
within the tube. Remove slight scratches on the
piston, rod, or inner surface of the tube with very fine
grit emery cloth. Use the emery cloth in a rotary
motion to polish out and blend the scratch(es) into
the surrounding surface.
2. Clean parts with trichlorethylene.
3. Check that the rod (18) is straight. If it is bent, install
a new rod.
e. Hoist/Lower Cylinder Assembly
Note: Follow Section 9.12 c. General Assembly Instruc-
tions.
1. Install a new small O-ring (8, Fig. 9– 67) into the
piston (6).
2. Install the capped T-seal (7) and both precision
wearbands (5) onto the piston (6).
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.
3. Install the deep Z-seal with backup (13) and the
precision wearbands (12) into the forward end of the
head gland (14), and, at the rear end, install the
sealed outside diameter heavy-duty rod wiper (16).
4. Install a new O-ring (9), backup ring (10) and O-ring
(11) onto the head gland (14).
5. 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.
6. Carefully slide the head gland (14) onto the rod
weldment (18).
7. Carefully slide the piston (6) onto the rod weldment
(18).
8. Apply Loctite Threadlocker #271 (red) to the threads
of the 2.00-12 UN locknut (4). Thread the lock nut
onto the rod weldment (18). Torque to 1550-1750 lb/ft
(2102-2373 Nm). The threads will deform upon
tightening, locking the nut in place.
9. Install two new locking inserts (15) into their holes in
the head gland threads.
10. Secure the hoist/lower cylinder in a soft-jawed vise or
other acceptable holding equipment if possible. DO
NOT damage the tube (3).
11. Lubricate the inside of the tube (3) and outside of the
piston (6) and head gland (14) with clean, filtered
hydraulic oil.
12. Apply a compression sleeve or other suitable tool to
the head and piston in order to compress the O-rings,
backup rings and seals while inserting the assembled
piston, rod and head into the tube (3). Carefully insert
the rod (18) with all attachments straight into the tube
(3).
IMPORTANT: When sliding the rod (18) and piston
assembly in the tube, prevent the threaded end of the
tube from damaging the piston (6). Keep the rod centered
within the tube to help prevent binding. Protect the finish
on the rod at all times. Damage to the surface of the rod
can cause seal failure.
13. Using a pin spanner wrench, thread the head gland
(14) into the tube (3). Torque the gland to 300-400 lb/
ft (407-542 Nm).
14. Lubricate the counterbalance valve (2) with clean,
filtered hydraulic oil. Thread the counterbalance valve
into tube (3). Torque to 45-50 lb/ft (61-68 Nm).
IMPORTANT: DO NOT tamper with or attempt to reset
the counterbalance valve cartridge. If adjustment or
replacement is necessary, replace a counterbalance
valve with a new one.
15. Test the cylinder at low operating pressure (100 psi or
6,9 bar). Verify that the piston and the rod move
freely in both directions.
16. Increase the operating pressure to the maximum
amount for the cylinder (4000 psi, or 276 bar) and
again check for free movement in both directions.
17. Retract the rod fully into the tube and cap and plug
the hydraulic hose ports.
18. If the self-align bearing (17) needs replacement,
support the rod (18) in a soft-jawed vise or other
suitable holding device. Carefully press a new
bearing into the rod eyelet.
Model 3606 • Origin 10/99