National Crane Published 5-27-2018 Control # 039-06 6-3
800D REPAIR
TELESCOPE CYLINDER
Telescope Cylinder Disassembly
1. After cylinder has been removed from boom, place on
supports and place drain pan under holding valve and
cylinder head area.
2. Using hydraulic power (porta power or crane circuit)
extend cylinder approximately 12 in (30 cm). Relieve
any trapped hydraulic pressure which might remain in
the cylinder.
3. Using a special drive tool, drive the packing gland into
the barrel assembly to expose the round cross section
retaining ring. Then use a small needle nose locking
plier to clamp the round cross section retaining ring to
prevent from rotating in the groove. Use two straight
blade screw drivers; one to pry the end of the ring out of
the groove and the other to pry the ring out of the barrel
assembly.
4. Deburring groove edge. Failure to do so will damage
packing gland and or barrel assembly when packing
gland is removed.
5. Plug retract port in the cylinder holding valve with SAE
#8 O-Ring boss plug and pull on the rod assembly to
force packing gland out of the barrel assembly.
6. If step 5 fails to break packing gland loose from the
barrel assembly, remove the plug from the retract port
and plug the extend port in the cylinder holding valve
(SAE #8 O-Ring boss). Apply retract pressure to cylinder
to break packing gland loose. Remove pressure and pull
packing gland out by hand.
7. As soon as the packing gland is sufficiently loosened,
properly support the rod assembly and carefully remove
it. Place rod assembly on supports. Caution must be
exercised in the support and removal of the rod
assembly as damage to the chrome surface will
necessitate rod assembly replacement.
8. Remove the two locking setscrews from piston.
9. Using proper spanner wrench loosen and remove
threaded piston.
10. Remove piston, stop tube, packing gland and round ring.
Replace any damaged or worn metal parts.
11. Replace all seals and bearings.
12. Wipe and inspect all cylinder internal and external
surfaces for damage.
13. Inspect wear pad on barrel assembly and replace as
required.
Telescope Cylinder Assembly
1. Debur ring groove edge in barrel assembly and inspect
all internal and external surfaces for damage.
2. Reassemble round ring, packing gland and stop tube on
shaft assembly.
3. Install piston on shaft assembly and torque piston to 200
lb-ft (271 Nm). Loctite® should not be used on
threaded piston.
4. Apply Loctite® 243 to two setscrews and install in piston.
Torque setscrews to 8 lb-ft (11 Nm).
5. Grease piston assembly and install the shaft assembly
with piston, stop tube, packing gland and round ring into
barrel assembly.
6. Using special drive tool, drive the packing gland into the
barrel assembly.
7. Insert one end of round ring into groove in barrel
assembly and spiral ring into groove with straight blade
screw driver.
8. Cycle test cylinder to ensure no leaks exist. Support end
of cylinder as it extends and retracts.
Boom Retract
Boom Extend
9396
Fo
r
Reference
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