BRADEN CH400B Installation Maintenance And Service Manual page 33

binding or leakage. Inspect spool bore in valve hous-
ing 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.
Check the free length of the main piston spring. For
the 1-1/4-inch valve, replace if less than 1-15/16 inches
(49.2 mm) long. For the 1-1/2-inch valve, replace if
less than 3-7/16 inches (87.3 mm) long. Check the
free length of the check valve spring. Replace if less
than 1-1/2 inches (38.1 mm) long.
1-1/4-inch valve
1-1/2-inch valve
2. Inspect the 0.020-inch (0.5 mm) orifice in the end of the
spool to be certain it is open. On the 1-1/4-inch valve,
also inspect the pilot orifice to be certain it is open.
ASSEMBLY
1. Install new O-rings on the plug and spool retainers.
1-1/4-inch valve
O-RING
BACK-UP RING
1-1/2-inch valve
BACK-UP RING
O-RING
2. Install new O-rings and backup rings on the spool and
damper pistons as shown. It is important that each
backup ring is on the correct side of its O-ring. Take
care not to cut the O-rings during assembly. Let the
spool and 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.
1-1/4-inch valve
1-1/2-inch valve
3. Lubricate the spool and damper piston O-rings with
hydraulic oil. Carefully install the damper piston into the
spool. Carefully install the spool into the valve housing.
On either valve, always install the spool into the valve
body so the O-ring enters the bore first, or the plug end
of the valve body. Install the plug. On the 1-1/4-inch-
valve, install the spool spring and spring retainer. On
the 1-1/2-inch valve, install the spring seat, spool
spring, damper piston extension and spring retainer.
4. Install the check valve poppet, spring and check valve
spring retainer.
5. Install the motor drain check ball, spring and fitting.
6. On the 1-1/4-inch valve only, install the pilot orifice into
the brake release port on the valve housing.
7. The brake valve is now complete and ready to be in-
stalled on the hoist motor.
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