Bendix Commercial Vehicle Systems AD-SP SYSTEM PURGE AIR DRYER 10/04 - Manual (Page 7)

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For Bendix AD-IP 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 applications — 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.
(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.)
FIGURE 6 - BENDIX ® AD-IP ® AND AD-IP DLU AIR DRYER PURGE VALVES
At the onset of the purge cycle, the downward travel of
the purge piston is stopped when the turbo cut-off valve
(tapered portion of purge piston) contacts its mating metal
seat in the purge valve housing. With the turbo cut-off valve
seated (closed position), air in the compressor discharge
line and Bendix ® AD-IP ® air dryer inlet port cannot enter
the air dryer. In this manner the turbo cut-off effectively
maintains turbocharger boost pressure to the engine.
DISCHARGE LINE UNLOADER (Refer to Figure 6)
The Bendix AD-IP air dryers are available as a standard air
dryer and as a Discharge Line Unloader (DLU-style) . The
functions of these air dryers (Standard vs. DLU) and their
internal components are different. The standard air dryer
cuts off the supply air from compressor to the air dryer
when the compressor is in the unloaded mode, while the
DLU air dryer utilizes a purge valve to bleed off the excess
air instead of unloading the compressor. Externally the
standard and DLU versions of each air dryer configuration
are identical in appearance; however the DLU-style air
dryer often has a silencer on the exhaust port.
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. Note: It is acceptable for
the purge valve to be maintained as necessary, i.e., the
installation of a purge valve maintenance kit, without
voiding the warranty.
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.
STANDARD
PURGE VALVE
DLU
PURGE VALVE
3 O-RING
GROOVES
2 O-RING
GROOVES
PURGE VALVE
HOUSING