BRAKE SHUTTLE VALVE
Shuttle valve maintenance is generally limited to
repairing leakage. External leakage may usually be
repaired by tightening the end caps. If this does not
stop the leakage, the end cap O-ring should be
replaced.
Internal leakage can usually be repaired by
removing and flushing the unit with clean, hydraulic
fluid. Excessive heating is a good indication of
internal leakage through a shuttle valve. Excessive
cycling of the emergency system pump is also an
indication of a leaky shuttle valve.
After an emergency system has been operated, all
emergency system pressure should be bled off as soon
as possible and the normal system restored to
operation.
AUTOMATIC BRAKE ADJUSTER VALVE
Tests are not required on the individual adjuster
valve parts. After disassembly, cleaning, inspection,
repair or parts replacement, and complete reassembly
have been accomplished, perform a bench test to
Figure 14-23.--Rod packing, cylinder leakage, and pumping
determine whether the brake adjuster valve satisfies
function test.
the required minimum specifications.
harness it at the midstroke position with 25-psi
Disassembly
hydraulic pressure applied at the brake port. There
should be no external leakage. Leakage at the reservoir
The brake adjuster valve should be disassembled
in accordance with instructions contained in the MIM
port should not exceed 1 drop per minute for 2 minutes
and/or 03 manual. Check the safety wiring before
after a 1-minute waiting period. If the unit tests
disassembly to expedite rewiring after reassembly.
satisfactorily at this stage, the pressure should be
increased to 2,000 psi. There should be no external
Cleaning
leakage, and leakage at the reservoir port should not
exceed 1 drop per minute for 2 minutes after a 1-minute
Clean all parts except the nylon insert and O-rings
with P-D-680 cleaning solvent. The insert and O-rings
waiting period.
will normally be replaced upon each disassembly of
When the foregoing test is completed, the unit is
the valve. Dry parts with dry, clean, filtered,
ready to receive a rod packing, cycling leakage, and
compressed air.
pumping function test. With the unit extended and
installed in the actuating fixture, a reservoir should be
WARNING
connected to the reservoir port and a 200- to 400-psi
Do not inhale solvent vapors or direct
relief valve should be connected to the brake port. See
compressed air against the skin. Failure to observe
figure 14-23. Operation of the manual lever through
proper safety precautions could result in injury to
five full strokes should pump hydraulic fluid through
personnel.
the relief valve. Leakage at the piston rod gland should
not exceed 1 drop at this time. Not less than 0.75 cubic
inch of fluid should flow from the relief valve during
Inspection
any one complete stroke cycle of the manual lever.
Perform inspections under a strong light and with
There should be no evidence of binding at any time
magnification. Inspect all threads for crossed, filled, or
during these tests.
14-23
