Bendix Commercial Vehicle Systems AD-9 IPC AIR DRYERS 4/11 - Manual (Page 4)

4
AD-9 CHARGE MODE
BW
The initial purge and desiccant cartridge decompression
lasts only a few seconds and is evidenced by an audible
burst of air at the Bendix
® AD-9 ® or AD-9 ® IPC air dryer
exhaust.
The actual reactivation of the desiccant drying bed begins
as dry air fl ows from the purge volume through the desiccant
cartridge purge orifi ce and into the desiccant drying bed.
Pressurized air from the purge volume expands after
passing through the purge orifi ce; its pressure is lowered
and its volume increased. The fl ow of dry air through the
drying bed reactivates the desiccant material by removing
the water vapor adhering to it. Generally 15–30 seconds are
required for the entire purge volume of a standard Bendix
AD-9
or AD-9 IPC air dryer to fl ow through the desiccant
drying bed.
The end cover single check valve assembly prevents air
pressure in the brake system from returning to the air dryer
during the purge cycle. After the 30 second purge cycle is
complete, the air dryer is ready for the next charge cycle
to begin.
The purge valve will remain open after the purge cycle is
complete, and will not close until air brake system pressure
is reduced and the governor signals the compressor to
charge.
TURBO CUT-OFF FEATURE (Refer to Figure 4)
The primary function of the turbo cut-off valve is to prevent
loss of engine turbocharger air pressure through the
Bendix AD-9 and AD-9 IPC air dryers in systems where the
compressor intake is connected to the engine turbocharger.
The turbo cut-off valve also reduces the “puffi ng” of air out
the open exhaust when a naturally aspirated, single cylinder
compressor equipped with an inlet check valve is in use.
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 discharge line and air
dryer inlet port is restricted from entering the air dryer. While
the turbo cut-off effectively prevents loss of turbocharger
boost pressure to the engine, some “seepage” of air may
be detected under certain conditions of compressor engine
and turbocharger operation. Even so, there will always be
low pressure trapped in the discharge line.
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.
FIGURE 4 - BENDIX ® AD-9 ® AND AD-9 ® IPC AIR DRYER
TURBO CUT-OFF
UPPER
BRACKET
CHECK
VALVE
ASSEMBLY
SUPPLY
PORT


 

 



 
UPPER
BRACKET
STRAP
DESICCANT
CARTRIDGE
LOWER
BRACKET
HOUSING
CHECK
VALVE
ASSEMBLY

DISCHARGE
LINE
TURBO
CUT-OFF
PISTON
EXHAUST
PURGE
VALVE
TURBO
CUT-OFF
PISTON PURGE VALVE
HOUSING
ASSEMBLY
PURGE
VALVE
DISCHARGE
PORT
FIGURE 5 - BENDIX ® AD-9 ® AND AD-9 ® IPC AIR DRYER
CROSS SECTION
DESICCANT
BED
OIL
SEPARATOR
CONTROL
PORT
SUPPLY
PORT