Bendix Commercial Vehicle Systems AD-9si Oil Coalescing Air Dryer - Manual (Page 5)

5
COMPRESSOR
GOVERNOR
DESICCANT
BED
DELIVERY
CHECK
VALVE
PURGE
VALVE
TURBO
CUT-OFF
VALVE
(CLOSED)
CONTROL
PORT
SUPPLY
PORT
FRONT
RESERVOIR
SAFETY
VALVE
REAR
RESERVOIR
PURGE
ORIFICE
OIL
COALESCING
FILTER
CONTROL
LINE
PURGE AIR
EXTENDED
PURGE
PORT
EXHAUST
EXHAUST
DELIVERY
PORT
FIGURE 3 - BENDIX ® AD-9si ™ AIR DRYER WITH GOVERNOR—PURGE CYCLE
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 flowing through the desiccant
cartridge — changes direction and begins to flow from the
purge volume toward the open purge valve. Contaminants
collected by the air dryer filters and desiccant are removed
by air flowing 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.
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 fill 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