Bendix Commercial Vehicle Systems AD-9si Oil Coalescing Air Dryer - Manual (Page 3)

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DESCRIPTION
The function of both the Bendix ® AD-9si ™ air dryer and the
Bendix ® AD-9si ™ PuraGuard ® oil coalescing air dryer is to
collect and remove air system contaminants in solid, liquid,
and aerosol form before they enter the brake system. The
AD-9si includes a spin-on style cartridge for easy servicing,
and most include a fully integrated governor to control air
system charging.
The air dryer provides clean, dry air to the components of
the brake system, which increases the life of the system
and reduces maintenance costs. The need for daily manual
draining of the reservoirs is eliminated.
The Bendix AD-9si PuraGuard oil coalescing air dryer has
an identical appearance to the standard Bendix AD-9si air
dryer, but contains a coalescing media at the inlet of the
desiccant bed. This coalescing media provides a higher
level of oil removal over the standard AD-9si air dryer.
The AD-9si PuraGuard oil coalescing air dryer has all of
the same functions as the standard AD-9si air dryer and is
used in applications where lower oil concentration levels
are required.
IMPORTANT! When servicing, note that standard AD-9si
air dryers or air dryer cartridges may be serviced with
PuraGuard oil coalescing air dryers or cartridges, however,
PuraGuard oil coalescing air dryers or cartridges MUST
only be serviced with like replacements.
Note: Unless otherwise stated in this document, AD-9si
air dryer refers to both the standard and PuraGuard oil
coalescing air dryer.
The AD-9si air dryer consists of a “spin on” desiccant
cartridge secured to a base assembly. The base assembly
contains a delivery check valve assembly, safety valve,
heater and thermostat assembly, integrated governor (in
most assemblies), threaded air connections, internal purge
volume, and purge valve assembly.
The removable purge valve assembly incorporates the
purge valve mechanism and a turbocharger cut-off feature
that is designed to prevent loss of engine “turbo” boost
pressure during the purge cycle of the AD-9si air dryer. For
ease of maintenance, all replaceable assemblies should
be serviceable without removal of the air dryer from its
mounting on the vehicle — provided adequate clearance
exists between the air dryer and the vehicle components.
Refer to the Preventive Maintenance section of this
document.
Air
Connection
Port ID
Function/
Connection
Quantity
IN 1 Inlet Port (air in) 1
OUT 21 Delivery Port Out 2
PT 22 Extended Purge 1
CON 2-4 Governor Unloader 1
3 Governor Exhaust 1
TABLE 1 - PORT DESIGNATIONS
BENDIX AD-9si AIR DRYER OPERATION:
GENERAL (Refer to Figures 2 through 5.)
The Bendix AD-9si air dryer is designed to receive
compressed air from the vehicle air compressor, clean and
dry the air, deliver air to the vehicle’s air reservoirs and
control the compressor/dryer charge cycle. The AD-9si
air dryer is available with an internal governor (Figures 2
and 3) or without an internal governor (Figures 4 and 5).
AIR DRYER OPERATION: GENERAL
The Bendix AD-9si air dryer alternates between two modes
or “cycles” during operation: the Charge Cycle and the
Purge Cycle. The following describes these “cycles” of
operation.