Bendix Commercial Vehicle Systems AD-IS AIR DRYER AND RESERVOIR SYSTM - Manual (Page 6)

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The actual regeneration of the desiccant drying bed begins
as dry air from the purge reservoir flows through the purge
orifice into the desiccant bed. Pressurized air from the
purge reservoir expands after passing through the purge
orifice; its pressure lowers and its volume increases. The
flow of dry air through the drying bed regenerates the
desiccant material by removing any water vapor adhering
to it. Approximately 30 seconds are required for the entire
contents of the purge reservoir of a Bendix ® AD-IS ® air
dryer and reservoir system to flow through the desiccant
drying bed.
The delivery check valve assembly prevents air pressure
in the brake system from returning to the air dryer during
the purge cycle. After the purge cycle is complete, the air
dryer and reservoir system is ready for the next charge
cycle to begin.
TURBO CUT-OFF FEATURE (Refer to Figure 3.)
The primary function of the turbo cut-off valve is to prevent
loss of engine turbocharger air pressure through the
AD-IS air dryer when the dryer is in the purge mode.
At the onset of the purge cycle, the downward travel of the
purge piston is stopped when the turbo cut-off valve (the
tapered portion of purge piston) contacts its mating metal
seat in the purge valve housing. With the turbo cut-off
valve seated (in the closed position), air in the compressor
discharge line—as well as the AD-IS air dryer inlet port—
cannot enter the air dryer. By completing these actions,
the turbo cut-off effectively maintains turbo charger boost
pressure to the engine.
PREVENTIVE MAINTENANCE
Important: Review the warranty policy before performing
any intrusive maintenance procedures. An extended
warranty may be voided if intrusive maintenance is
performed during this period. Purge valve maintenance
is permissible during the warranty period only when using
a genuine Bendix ® purge valve kit.
Because no two vehicles operate under identical
conditions, maintenance and maintenance intervals will
vary. Experience is a valuable guide in determining the best
maintenance interval for any one particular operation.
Every 900 operating hours, or 25,000 miles, or three
(3) months:
1. Check for moisture in the air brake system by opening
reservoir drain valves and checking for the presence
of water. If moisture is present, the desiccant cartridge
may require replacement; however, the following
conditions can also cause water accumulation and
should be considered before replacing the desiccant:
A. An outside air source has been used to charge the
system. This air did not pass through the drying
bed.
B. Air usage is exceptionally high and not normal for
a highway vehicle.
This may be due to accessory air demands or some
unusual air requirement that does not allow the
compressor to load and unload (compressing and
non-compressing cycle) in a normal fashion. Check
for high air system leakage. If the vehicle vocation
has changed, it may be necessary to upgrade the
compressor size. Refer to Bendix Specification
BW-100-A / Appendix D, to determine if any changes
are necessary. Specification BW-100-A is available
from the Bendix TechTeam at 1-800-247-2725 or
www.bendix.com.
C. The location of the air dryer and reservoir system
is too close to the air compressor. Refer to Bendix
Specification BW-110-A / Appendix B, for discharge
line lengths.
D. In areas where more than a 30 degree range of
temperature occurs in one day, small amounts
of water can temporarily accumulate in the air
brake system due to condensation. Under these
conditions, the presence of small amounts of
moisture is normal.
For Bendix ® AD-IS ® air dryers: Preventive Maintenance
is as easy as 1-2-3
Adhering to a preventive maintenance schedule is crucial
to keeping a vehicle’s air system clean and ensuring
superior performance of all components that utilize system
air— such as brakes, emissions equipment and automated
manual transmissions. Depending on vocation, Bendix
recommends a 1, 2 or 3-year air dryer cartridge replacement
on vehicles equipped with a Bendix ® compressor.
For severe service application—such as residential refuse
trucks or school buses—the air dryer cartridge should
be replaced every year or 100,000 miles; for pick-up
and delivery operations, or for double- and triple-trailer
line haul trucks, every two years or 200,000 miles is the
recommendation. Line-haul operations using a single trailer
should swap the filter out every three (3) years or 300,000
miles. The recommended intervals for trucks equipped with
non-Bendix compressors are 6 months (50,000 miles),
one year (100,000 miles) and two years (200,000 miles),
respectively.
More frequent intervals may be required depending
on a vehicle’s age, its compressor condition, use of a
non-Bendix compressor, the operating environment, the
vehicle’s vocation, and its usage. In conjunction with these
guidelines, fleets can determine the functionality of their
filters by checking for moisture in the air brake system
monthly. If moisture is present, the air dryer cartridge may
require replacement. Reference the Bendix Service Data
Sheet of the specific air dryer for additional information.