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16. (SD-3
Actuator) Install diaphragm, pressure plate, and
™
clamping ring.
17. (DD-3
Actuator) The DD-3
™
two different diaphragm constructions. Figure 1 shows
one construction with a metal separator between the
service and auxiliary diaphragms. The separator snaps
over a bead on the service diaphragm. The service
diaphragm piece number for this assembly is 246371
for the type 30 and 246365 for the type 24.
An alternate design eliminates the separator in the type
30 and substitutes service diaphragm 292711 with a
special surface lubricant which eliminates the need for
the separator. This design has not been produced in
the type 24.
Still a third design was used for certain customers for a
short period, in which the service diaphragm and
separator were riveted together as an assembly. If this
construction is encountered, the diaphragm and
separator assembly should be discarded. The new
surface lubricated diaphragm 292711 may then be
installed, without a separator. A kit, piece number
265071, is available which includes one of the new
surface lubricated service diaphragm 292711 and one
auxiliary diaphragm 246675.
18. Install service diaphragm and separator (if used), service
pressure plate, and clamping ring.
19. Install auxiliary diaphragm, auxiliary pressure plate, and
clamping ring.
20. Tighten bolts on both clamping rings evenly and securely.
21. Install exhaust check valve.
22. If push rod was removed, replace with new rod and
new locking ring. Pack shaft cavity with BW 204-M
barium lubricant (piece number 240176 or piece number
246671). Install lock ring in groove on rod and press
rod in shaft cavity, making certain rod is locked in place
in shaft.
23. Install new gasket on non-pressure plate.
24. Install boot over cap assembly. Install splash plate over
boot.
OPERATING AND LEAKAGE CHECKS
OPERATING - DD-3
ACTUATOR
™
With the actuator in the released position, make several
brake applications and note that actuators apply and release
properly.
Operate parking control valve and observe that actuators
apply. While actuators are in a parking position, drain air
supply to auxiliary diaphragm and note that actuators remain
applied.
actuators are supplied with
™
Replenish air supply to auxiliary diaphragm. Operate control
valve to release parking application, then make a full service
application to complete release of actuators. The magnitude
of the service brake application to release the brakes may
vary on different vehicles due to compressor governor
settings. Normally a service application of approximately
70 psi should release the brakes.
OPERATING SD-3
ACTUATOR
™
With actuator in the released position, make several brake
applications and note that actuator applies and releases
properly.
Make a parking application, air pressure released from lock
port. Release air pressure from service diaphragm and
observe that actuators remain applied. Apply full reservoir
pressure on service diaphragm and on lock port. Release
application on service diaphragm and observe that actuator
releases properly.
LEAKAGE - SD-3
AND DD-3
™
With system pressure up and actuators in the released
position, check drain slot and around the push rod boot
with a soapy solution to detect possible leakage past the
locking piston grommet.
Make and hold a service brake application and again check
the actuator drain slot or exhaust check valve for service
diaphragm leakage. Continue to hold the service application
and coat around the service and auxiliary diaphragm
clamping rings with the soapy solution to detect seal leakage.
DD-3
ACTUATOR ONLY
™
Operate the park control valve to apply a park or emergency
application on the auxiliary diaphragm. Remove the hose
connection at the service diaphragm port and observe for
leakage which would indicate a failed auxiliary diaphragm.
The auxiliary diaphragm clamp should again be checked
for leakage while the auxiliary diaphragm is pressurized.
Should leakage be detected at the clamping rings in either
of the above tests, the clamping ring nuts should be tightened
evenly but only enough to stop leakage.
If the safety actuator does not function as described or
leakage is excessive, it is recommended that it be returned
to the nearest Bendix authorized distributor for a factory
reconditioned actuator under the repair exchange plan. If
this is not possible, the actuator can be repaired with genuine
Bendix parts.
ACTUATOR
™
5
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