Bendix Commercial Vehicle Systems AD-RP PuraGuard Oil Coalescing Remote Purge Air Dryers - Manual (Page 3)

3
OPERATION
GENERAL
The AD-RP air dryer alternates between two operational
modes or “cycles” during operation: the Charge Cycle and
the Purge Cycle. What follows is a description of operation
separated into these “cycles”.
CHARGE CYCLE (Refer to Figure 3.)
When the compressor is loaded (compressing air)
compressed air — along with oil, oil vapor, water and water
vapor — fl ows through the compressor discharge line to the
supply port of the air dryer body. Air entering the supply
port immediately encounters the “turbo cut-off” valve. With
no air pressure in the control port, the turbo cut-off piston
moves the valve away from its seat in the body, allowing
the supply air to enter the body. As air travels through the
end cover assembly, its direction of fl ow changes several
times, reducing the temperature, causing contaminants
to condense and drop to the bottom (or sump) of the air
dryer body. After exiting the end cover, the air fl ows into the
desiccant cartridge where an oil separator — or coalescing
fi lter, if equipped with a Bendix
® PuraGuard ® oil coalescing
The aluminum body of the Bendix ® AD-RP ™ air dryer
contains the following serviceable components or
assemblies: the turbocharger cut-off valve; the heater and
thermostat assembly; a delivery check valve assembly;
and the combined purge and relief valve assembly. All
service and replacement can be accomplished from the
exterior of the dryer without removing it from the vehicle.
The spin-on desiccant cartridge is removed and installed
using a “strap wrench.”
The AD-RP air dryer has four female pipe thread air
connections identifi ed as follows: (Also refer to Figure 1.)
Air Connection Port ID Function/Connection
CON 4
Control Port (purge valve control
& turbo cut-off)
SUP 1 Supply Port (air in)
DEL 2 Delivery Port (air out)
PT 22
(not identifi ed on
the air dryer)
Remote Purge Port
DESICCANT
DELIVERY
CHECK
VALVE
DELIVERY
PORT
TURBO
CUT-OFF
CONTROL
PORT
GOVERNOR
COMPRESSOR
PURGE
VALVE
FRONT
RESERVOIR
REAR
RESERVOIR
ENGINE
TURBO
EXHAUST
PORT
SUPPLY
PORT
OIL
COALESCING
FILTER
PURGE
ORIFICE
SAFETY
VALVE
REMOTE
PURGE
PORT
REMOTE
PURGE
RESERVOIR
PURGE
CONTROL LINE
FIGURE 3 - BENDIX ® AD-RP ™ AIR DRYER SYSTEM - CHARGE CYCLE