Bendix Commercial Vehicle Systems DRM DRYER RESERVOIR MODULE 3/07 - Manual (Page 8)

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3. “Fan” the service brakes to reduce system air pressure
to governor cut-in. Note that the system once again
builds to full pressure and is followed by a purge at the
AD-IS
® air dryer exhaust.
4. It is recommended that the total air system be tested for
leakage to assure that the AD-IS ® air dryer will not cycle
excessively.
See Bendix publication BW-5057 “Air Brake Handbook.”
BRAKING SYSTEM PROTECTION
The DRM ™ dryer module allows the system to maintain
one brake circuit up to about 100 psi even after a pressure
loss in the other brake circuit. This allows a vehicle to be
moved (in an emergency), but with reduced braking capacity.
Compare this to a conventional system where a loss of
pressure in one service tank leaves the vehicle with a limited
number of reduced braking capacity applications before the
parking brakes automatically apply and stay on.
ROADSIDE INSPECTION
In the event of a roadside inspection the system behavior
will be as follows: When the system is charged to governor
cut out, and then one reservoir drain valve is opened,
initially both reservoir gauges will fall, however, the AD-IS
®
air dryer's primary and secondary pressure protection valves
will close at pressures above 70 psi, protecting the remaining
brake circuit from further loss of pressure.
TEMPORARY AIR DRYER BYPASS
To temporarily bypass the air dryer, the following procedure
needs to be followed.
Follow the Maintenance Precautions outlined elsewhere in
this document.
Make sure that all residual pressure has been released,
then remove the air supply line from the compressor to
the inlet port (1 IN). Remove the safety valve from the
AD-IS
® air dryer body (see Figure 1 for location) and install
a T-fitting into the port. Using any adapters necessary,
re-install the safety valve in one of the branches of the
T-fitting. Using any adapters necessary, install the air supply
line into the remaining T-fitting port. After testing the
T-fitting for any air leakage, using a soap solution after
charging system pressure (a 1” bubble in 10 seconds is
acceptable), the vehicle may be returned to temporary
service.
Note: This is a temporary bypass of the air dryer, and
full repair of the unit must be carried out at the earliest
opportunity. With the air dryer removed from the system,
contaminants will be entering the air system: reservoirs
will need to be manually drained daily until the repairs are
completed. At end of each working day, park vehicle and
slowly drain pressure through the drain valves – leave open
to the atmosphere, for several hours if possible. When
repairs are carried out, be sure to check that all reservoirs
(including the purge reservoir incorporated into the secondary
reservoir) are emptied of all contaminants.
If after bypassing the dryer reservoir module the system
pressure still does not build, use the following procedure to
remove, clean and reinstall the delivery check valve.
DELIVERY CHECK VALVE CLEANING PROCEDURE
(Note: This is only required if system pressure does not
build after temporary bypass is completed.)
See Figure 7 throughout this procedure. Depressurize
the air brake system following the general safety
precautions outlined elsewhere in this document.
This procedure does not require removal of the AD-IS ® air
dryer from the vehicle.
1. Remove line from governor and mark for easy
reinstallation.
2. Remove bolts attaching the governor to the AD-IS ® air
dryer and retain for reassembly.
3. Remove governor and the adapter’s o-ring.
4. The spring/delivery check valve can now be removed.
(Note: The spring/delivery check valve may be a
previous design. See Figure 7.)
5. Remove o-ring from check valve body.
CLEANING & INSPECTION
1. Use a suitable solvent to clean all metal parts, and use
a cotton swab to clean the bore (Note: Do not use
abrasives or tools to clean the bore: any scratches
caused may necessitate replacing the AD-IS
® air dryer.)
Superficial external corrosion and/or pitting is
acceptable.
2. Clean the o-rings with a clean dry cloth. Do not use
solvents.
3. Inspect for physical damage to the bore and the check
valve seat. If the bore is damaged (by scratches etc.
that would prevent delivery check valve from seating),
replace the AD-IS
® air dryer.
4. Inspect the delivery check valve, o-rings, etc. for wear or
damage. Replace if necessary using the check valve
replacement kit available at authorized Bendix parts
outlets.
5. Inspect all air line fittings for corrosion and replace as
necessary.