BRADEN PD12C Series Installation Maintenance And Service Manual page 33

5. Remove the damper piston from the spool. The pis-
ton will come out slowly, because of a partial vac-
uum formed as it is removed. Use extreme care to
avoid damaging the polished surfaces of the piston
or spool.
6. Remove the check valve spring retainer, spring and
check valve poppet. Check spring free length. Re-
place spring if less than 1-1/2 in. (38.1 mm) long.
CLEAN AND INSPECT
1. Discard all O-rings and back-up rings. Clean all
parts in solvent and blow dry. Inspect polished sur-
faces of spool and damper piston for damage that
may cause binding or leakage. Inspect spool bore
in valve housing for damage or scoring. Inspect
check valve seat in valve housing and check valve
poppet. If the spools, bores or valves are damaged,
the entire valve must be replaced as these parts are
not serviced separately.
2. Inspect the .020 inch (.5 mm) orifi ce in the end of
the spool and the pilot orifi ce to be certain they are
open.
ASSEMBLY
1. Install new O-rings on the plug and spring retainers.
2. Install new O-rings and back-up rings on the spool
and damper piston as shown. It is important that
each back-up ring is on the correct side of its O-ring.
Take care not to cut the O-rings during assembly.
Let the spool and damper piston set for ten minutes
before installing them in their respective bores. This
will allow the O-rings to return to their original size
after being stretched.
3. Lubricate the spool and damper piston O-rings with
hydraulic oil. Carefully install the damper piston into
the spool.
4. Lubricate the spool bore and spool O-rings with hy-
draulic oil. Carefully install the spool into the valve
housing. Always install the spool from the plug end
as shown to minimize the possibility of damaging
the O-ring. Install the plug, spool spring and spring
retainer.
5. Install the check valve poppet, spring and check
valve spring retainer.
6. Install the motor drain check ball, spring and elbow
fi tting.
7. Install the pilot orifi ce into the valve housing.
8. The brake valve is complete and ready to be in-
stalled on hoist motor.
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