Bendix Commercial Vehicle Systems AD-9si Oil Coalescing Air Dryer User Manual
®
Bendix® AD-9si™ and AD-9si™ PuraGuard® Oil Coalescing Air Dryer
DESICCANT
CARTRIDGE
(PURAGUARD® OIL
COALESCING SHOWN)
SD-08-2433
DELIVERY
CHECK VALVE
COVER
OUT 21
DELIVERY PORTS (2)
PT 22
EXTENDED PURGE
PORT
MOUNTING
HOLES
(3 PER SIDE)
HEATER /
THERMOSTAT
GOVERNOR
(GOVERNOR CUT-OUT
PRESSURE STAMPED
ON COVER)
GOVERNOR
EXHAUST
3
IN 1
SUPPLY FROM
COMPRESSOR
CON 2-4
UNLOADER TO
COMPRESSOR
SAFETY VALVE
PURGE
VALV E
PURGE
VALV E
OUT 21
DELIVERY PORTS (2)
FIGURE 1 - BENDIX® AD-9si™ AND AD-9si™ PURAGUARD® OIL COALESCING AIR DRYER
BOTTOM
VIEW
1
GENERAL SAFETY GUIDELINES
WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS
TO AVOID PERSONAL INJURY OR DEATH:
When working on or around a vehicle, the following guidelines should be observed AT ALL TIMES:
▲ Park the vehicle on a level surface, apply the
parking brakes and always block the wheels.
Always wear personal protection equipment.
▲ Stop the engine and remove the ignition key
when working under or around the vehicle.
When working in the engine compartment,
the engine should be shut off and the ignition
key should be removed. Where circumstances
require that the engine be in operation, EXTREME
CAUTION should be used to prevent personal
injury resulting from contact with moving,
rotating, leaking, heated or electrically-charged
components.
▲ Do not attempt to install, remove, disassemble
or assemble a component until you have read,
and thoroughly understand, the recommended
procedures. Use only the proper tools and
observe all precautions pertaining to use of those
tools.
▲ If the work is being performed on the vehicle’s
air brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure
from all reservoirs before beginning ANY work
on the vehicle. If the vehicle is equipped with a
Bendix® AD-IS® air dryer system, a Bendix® DRM™
dryer reservoir module, or a Bendix® AD-9si™ air
dryer, be sure to drain the purge reservoir.
▲ Following the vehicle manufacturer’s
recommended procedures, deactivate the
electrical system in a manner that safely removes
all electrical power from the vehicle.
▲ Never exceed manufacturer’s recommended
pressures.
▲ Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove
a component or plug unless you are certain all
system pressure has been depleted.
▲ Use only genuine Bendix
®
brand replacement
parts, components and kits. Replacement
hardware, tubing, hose, fi ttings, etc. must be of
equivalent size, type and strength as original
equipment and be designed specifi cally for such
applications and systems.
▲ Components with stripped threads or damaged
parts should be replaced rather than repaired.
Do not attempt repairs requiring machining or
welding unless specifi cally stated and approved
by the vehicle and component manufacturer.
▲ Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
▲ For vehicles with Automatic Traction Control
(ATC), the ATC function must be disabled (ATC
indicator lamp should be ON) prior to performing
any vehicle maintenance where one or more
wheels on a drive axle are lifted off the ground
and moving.
▲ The power MUST be temporarily disconnected
from the radar sensor whenever any tests USING
A DYNAMOMETER are conducted on a Bendix
®
Wingman® Advanced™-equipped vehicle.
▲ You should consult the vehicle manufacturer's operating and service manuals, and any related literature,
in conjunction with the Guidelines above.
2
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.
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.
Air
Connection
Port ID
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
Function/
Connection
Quantity
3
COMPRESSOR
OIL
COALESCING
FILTER
DESICCANT
BED
Note 1:
The Bendix® AD-9si™ air dryer purge piston has
a purge control channel drain. This allows any
condensation in this area to ow past a diaphragm
in the top of the purge piston and out through a
channel in the middle of the central bolt of the purge
assembly to be drained. During the purge cycle this
drain is closed.
CONTROL
PORT
TURBO
CUT-OFF
VALVE
(OPEN)
SUPPLY
PORT
SAFETY
VALV E
CONTROL
LINE
PURGE
VALV E
EXHAUST
EXHAUST
GOVERNOR
PURGE
ORIFICE
PURGE AIR
EXTENDED
PURGE
PORT
DELIVERY
CHECK
VALV E
REAR
RESERVOIR
FRONT
RESERVOIR
DELIVERY
PORT
FIGURE 2 - BENDIX® AD-9si™ AIR DRYER WITH GOVERNOR—CHARGE CYCLE
CHARGE CYCLE (Refer to Figures 2 and 4)
When the compressor is running loaded (compressing air),
compressed air ows through the compressor discharge
line to the inlet (IN 1) port of the air dryer body. The
compressed air often includes contaminates such as oil,
oil vapor, water and water vapor.
Traveling through the discharge line and into the air dryer,
the temperature of the compressed air falls, causing
some of the contaminants to condense and drop to the
bottom of the air dryer and purge valve assembly. These
contaminants are ready to be expelled at the next purge
cycle. The air then flows through the inlet tube and
into the desiccant cartridge, where it ows through an
oil separator — or coalescing lter if equipped with a
Bendix® PuraGuard® oil coalescing cartridge — which
removes water in liquid form as well as liquid oil and solid
contaminants.
4
Air then ows into the desiccant drying bed and becomes
progressively more dry as water vapor adheres to the
desiccant material in a process known as adsorption.
Dry air exits the desiccant cartridge, through the outlet tube,
then ows to the delivery check valve. Some air exiting
the desiccant cartridge is diverted through the orice into
the purge volume area. The delivery check valve opens,
supplying air to the two delivery ports. The purge reservoir
lls, storing air that will be used to regenerate the desiccant
during the purge cycle.
The air dryer will remain in the charge cycle until the air
brake system pressure builds to the governor cut-out
setting of approximately 130 psi.
DESICCANT
BED
COMPRESSOR
CONTROL
PORT
TURBO
CUT-OFF
VALVE
(CLOSED)
SUPPLY
PORT
SAFETY
VALV E
OIL
COALESCING
FILTER
CONTROL
LINE
PURGE
VALV E
EXHAUST
EXHAUST
GOVERNOR
PURGE
ORIFICE
PURGE AIR
EXTENDED
PURGE
PORT
REAR
RESERVOIR
DELIVERY
CHECK
VALV E
FRONT
RESERVOIR
DELIVERY
PORT
FIGURE 3 - BENDIX® AD-9si™ AIR DRYER WITH GOVERNOR—PURGE CYCLE
PURGE CYCLE (Refer to Figures 3 and 5)
When air brake system pressure reaches the cut-out
setting of the governor, the integral governor unloads the
compressor by supplying a pressure signal through the
control port (CON 2-4). This signal activates the purge
cycle of the air dryer.
The governor unloads the compressor by allowing air
pressure to ll the line leading to the compressor unloader
mechanism. This suspends the delivery of compressed
air to the Bendix® AD-9si™ air dryer.
Similarly, the governor also supplies this air pressure signal
to the purge valve. The pressure moves the air dryer purge
piston down, opening the purge valve to atmosphere and
closing off the compressor air supply to the turbo cut-off
valve (described in the "Turbo Cut-off Feature" section of
this document). Water and contaminants captured are
expelled immediately when the purge valve opens. In
addition, air — which was owing through the desiccant
cartridge — changes direction and begins to ow from the
purge volume toward the open purge valve. Contaminants
collected by the air dryer lters and desiccant are removed
by air owing from the purge volume through the desiccant
drying bed to the open purge valve.
The initial purge and desiccant cartridge decompression
lasts only a few seconds, evidenced by an audible burst
of air at the air dryer exhaust.
5
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