TRUCK SERVICE MANUAL
BRAKES-AIR
CHAPTER XIV
AIR DRYER
Fig. 1. AD-1 Air Dryer
Fig .
2.
AD-2 Air Dryer
DESCRIPTION
The safety valve protects against excessive pressure
The air dryer function is to collect and remove
buildup within the housing.
moisture and contaminants before air reaches the first
reservoir, thus providing "super dry" air for the air brake
The desiccant sealing plate is located midway in the
system. Daily draining of the air system reservoirs is no
housing assembly and houses a replaceable single type
longer necessary with an air dryer and air brake system
check ball and a purge orifice. The desiccant cartridge
maintenance is considerably reduced when compared to
and paper pleated oil filter are removable and comprise a
an air brake system without an air dryer.
complete serviceable unit.
The air dryer is installed in the discharge line
The desiccant beads, referred to as the "drying bed,
between the air compressor and supply reservoir. The
" are a drying substance which has the unique property
unit is mounted vertically, usually on the frame of the
of exposing a tremendous surface area in proportion to
vehicle.
its bulk. Desiccant beads weighing .454 km (1 lb.) have
about 186, 000 m2 (two million square feet) of absorptive
The housing assembly consists of two cylindrical
area made up of a large number of submicroscopic
steel stampings welded together. The housing on the
cavities in each bead. Each bead absorbs or extracts
AD-2 Air Dryer incorporates two inlet ports, one reservoir
moisture from the compressed air.
port and one purge volume port. The side outlet port of
the AD-2 has an integral single check valve with the top
The desiccant beads are held in place in the
port used for the addition of purge volume.
cartridge with steel perforated plates and filter cloths.
The top plate is held in place by a spring, while the
The AD-1 Air Dryer has two inlet and three outlet
bottom plate rests on a shoulder about 3 mm (1/8") from
ports, but is not equipped with a single check valve in
the bottom of cartridge housing.
any of the three outlet ports.
The end cover assembly is retained by
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