BENDIX SD-08-2418, Manual

Page: 5 / 16

5
Similarly, the governor also supplies air pressure to the
air dryer. The pressure also 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 ( covered in the Turbo Cut-off Valve 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 toward
the open purge valve. Contaminants collected by the air
dryer are removed by air flowing from the purge reservoir
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.
Figure 3 - Bendix
®
AD-IS
®
Air Dryer & Reservoir System Purge Cycle
Diagram shows all pressure
protection valves open
.
Compressor
Governor
Desiccant
Bed
Delivery
Check
Valve
(open)
Primary
Port (PRI)
Purge
Valve
(Open)
Turbo
Cut-Off
Valve
(Closed)
Engine
Turbo
Unloader
Port
Supply
Port
Primary
Reservoir
Pressure
Protection
Valves
Exhaust
Safety
Valve
Purge
Reservoir
Drain Valve
Secondary
Reservoir
Purge
Orifice
Oil Coalescing Filter
(Bendix
®
AD-IS
®
PuraGuard
®
oil
coalescing air dryer)
A
D C
B
Purge
Control
Channel
accessories. If the pressure protection valves are pre-set
to different values, the valves will open – in order of lowest
setting to highest setting – when charging a flat system.
The air dryer and purge reservoir will remain in the charge
cycle until the air brake system pressure builds to the
governor cut-out setting of approximately 130 psi.
PURGE CYCLE
(Refer to Figure 3.)
When air brake system pressure reaches the cut-out setting
of the governor, the governor unloads the compressor
activating the purge cycle of the air dryer & reservoir.
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-IS
®
air dryer & reservoir system.
Auxiliary Ports
(To Accessories)
Secondary
Port (SEC)
Purge
Reservoir