BENDIX DD-3 Manual - Page 5

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16. (SD-3

Actuator) Install diaphragm, pressure plate, and

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clamping ring.

17. (DD-3

Actuator) The DD-3

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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

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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

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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

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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

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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

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