JLG GRADALL 522D Owner's/Operator's Manual page 68

OPEN CENTER HYDRAULIC BRAKE VALVE
SLIDING PISTON DESIGN
(Refer to Figure 12)
Disassembly
1.
Remove boot (item 1) and
pressure regulating spring
assembly (item 2).
CAUTION: Pressure regulating
spring assembly has
been set at the fac-
tory and should
never be disas-
sembled.
2.
Separate end cap (item 20) from
housing (item 3).
CAUTION: Care must be taken
as end cap is under
tension of spring
(item 18).
Remove gasket (item 6).
Remove piston & poppet
3.
assembly (item 15), spring (item
18) and residual valve (item 19)
from end cap (item 20).
Remove cap screw (item 5) from
4.
under side of housing (item 3).
Remove o-ring (item 4) from cap
screw.
5.
Remove sleeve &
assembly (item 14) from housing
(item 3). Remove cup (item 12)
and piston ring (item 13) from
sleeve & piston assembly (item
14).
6. Remove retaining ring (item 7)
carefully with a small flat tool. Do
not scratch bore of sleeve & piston
assembly (item 14).
7.
Remove push rod (item 8), spool
(item 10) and spring (item 11) from
sleeve & piston assembly (item
14). Remove cup (item 9) from
spool (item 10).
Inspection
Clean and inspect all component
parts for scratches, cracks or wear.
Replace any par ts that are
excessively worn or damaged.
CAUTION: If spool (item 10),
sleeve (item 14) or
bore of housing (item
3) are in any way
damaged, scratched
(12)
or broken, the entire
assembly must be
replaced. These parts
are select-fitted and are
not interchangeable or
replaceable
service items.
Assembly
1.
Install new cup (item 12) and new
piston ring (item 13) on sleeve &
piston assembly (item 14).
CAUTION: Lips on cup (item
12) should be away
from end of sleeve
(item 14).
2.
Install new cup (item 9) on spool
(item 10).
Lips on cup (item 9)
CAUTION:
should be away from
end of spool (item
10).
3.
Insert spool (item 10) and push
rod (item 8) into sleeve & piston
assembly (item 14). Secure with
piston
retaining ring (item 7).
4.
Carefully install sleeve & piston
assembly (item 14) into housing
(item 3).
CAUTION:
Make sure that
groove on sleeve
will engage screw
(item 5).
5. Install new o-ring (item 4) on cap
screw (item 5) and install in
housing (item 3).
6. Install new o-ring (item 16) and
new ring seal (item 17) on new
piston & poppet assembly (item
15).
7.
Place residual valve (item 19),
spring (item 18) and piston &
poppet assembly (item 15) in end
cap (item 20).
NOTE: Residual valve must be
checked for proper
seating in end cap.
CAUTION: Extreme care must be
taken so as not to
scratch ring seal (item
17) when installing
piston
with assembly (item 15) in
end cap (item 20).
8.
Place new gasket (item 6) on
mounting face of end cap (item
20) and assembly, with its
components, to housing (item 3).
Install lock washers (items 21)
9.
and bolts (items 22). Torque 16
to 18 ft. lbs.
Install pressure regulating spring
10.
assembly (item 2) on push rod
(item 8). Install new boot (item 1).
SEE BLEEDING SECTION FOR
COMPLETE BLEEDING
INSTRUCTIONS
PARTS LIST
ITEM DESCRIPTION
1 •
BOOT
2
PRESSURE REGULATING
SPRING ASSEMBLY
3
HOUSING
4 • O-RING
5
CAP SCREW
6
• GASKET
7
RETAINING RING
8
PUSH ROD
9
CUP
•
10
SPOOL
11
SPRING
12 • CUP
13
PISTON RING
•
14
SLEEVE & PISTON
ASSEMBLY
15 •
PISTON & POPPET
ASSEMBLY
16
O-RING
•
17 •
RING SEAL
18 SPRING
19 •
RESIDUAL VALVE
20
END CAP
21
LOCKWASHERS
22 BOLTS
& poppet
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