JLG DVSP Series Service Manual - Manual (Page 98)

SECTION 5 - MAST COMPONENTS
5-10 – JLG Lift – 3121136
rod wiper. Damage to the seal grooves, particularly on the
sealing surfaces, is unacceptable. In the event that an unac-
ceptable condition occurs, the head should be replaced.
Piston
Visually inspect the outside surface for scratches or polish-
ing. Deep scratches are unacceptable. Polishing indicates
uneven loading and when this occurs, the diameter should
be checked for out-of-roundness. If out-of-roundness
exceeds 0.007", this is unacceptable. Check the condition of
the dynamic seals and bearings looking particularly for
metallic particles embedded in the bearing and in the piston
seal surface. Remove the seals and bearings. Damage to
the seal grooves, particularly on the sealing surfaces, is
unacceptable. In the event that an unacceptable condition
occurs, the piston should be replaced.
Tube Assembly
Visually inspect the inside bore for scratches and pits. There
should be no scratches or pits deep enough to catch the fin-
gernail. Scratches that catch the fingernail but are less than
0.5 inch long and primarily in the circumferential direction
are acceptable provided they cannot cut the piston seal. The
roughness of the bore should be between 10 and 20 µ
inches RMS. Significant variation (greater than 8 µ inches
difference) are unacceptable. In the event that an unaccept-
able condition occurs, the tube assembly should be
repaired or replaced.
Cylinder Assembly
(See Figure 5-4.)
1. Rinse the inside of the tube with hydraulic fluid and
allow to drain. A high-pressure rinse followed by a
wipe with a lint-free rag is preferable. Clean all inter-
nal components of any foreign material.
2. Lubricate the head and all seals with hydraulic fluid
prior to installation. Install the seal, wiper, o-ring,
back-up ring, and retraining ring to the cylinder
head.
3. Lubricate the piston and all components with
hydraulic fluid. Install the seal and wear ring to the
piston.
NOTE: Re-check that seals are not twisted or pinched and
are properly seated.
4. Place the rod on a clean table. Install the static pis-
ton o-ring seal into the groove on the piston end of
the rod.
5. Install the head followed by the piston onto the rod
noting the proper orientation of each component.
Torque the piston nut to 100-120 ft. lbs.
1. Cylinder Rod 6. Apply Anti-Seize 10. Piston
2. Cylinder Head 7. Cylinder Tube 11. Wear Ring
3. Rod Wiper 8. Spacer 12. Piston O-Ring
4. Rod Seal 9. Piston Seal 13. Piston Lock Nut (a)
5. O-Ring
Note: (a) - Torque 100 - 120 ft. lbs.
Figure 5-4. Lift Cylinder Component Cross-Section
(DVL/DVSP).
1
3
4
5
6
8
9
12
10
11
13
2
7