Air Dryer Sectional View; Appendix A, Table A And The Column Entitled Vehicle - BENDIX AD-4 AIR DRYER Manual

CHECK VALVE
ASSEMBLY
NUT
WASHER
END COVER
SPECIAL
WASHER
HEX HEAD
SCREW
™
FIGURE 4 - AD-4

AIR DRYER SECTIONAL VIEW

Every 900 operating hours or 25,000 miles or every three
(3) months:
1. Check for moisture in the air brake system by opening
reservoirs, drain cocks, or valves and checking for
presence of water. If moisture is present, the desiccant
may require replacement; however, the following
conditions can also cause water accumulation and
should be considered before replacing the desiccant:
A. An outside air source has been used to charge the
system. This air did not pass through the drying bed.
B. Air usage is exceptionally high and not normal for a
highway vehicle. This may be due to accessory air
demands or some unusual air requirement that does
not allow the compressor to load and unload
(compressing and non-compressing cycle) in a
normal fashion. Check for high air system leakage.
If the vehicle vocation has changed it may be
necessary to upgrade the compressor size. Refer to

Appendix A, Table A and the column entitled Vehicle

Vocation.
4
CHECK
VALVE
DESICCANT
CARTRIDGE
DELIVERY
PORT
PURGE
VALVE
PURGE PISTON
EXHAUST
EXHAUST
COVER
DIAPHRAGM
C. The air dryer has been installed in a system that
has been previously used without an air dryer. This
type system will be saturated with moisture and
several weeks of operation may be required to dry it
out.
D. Location of the air dryer is too close to the air
compressor. Refer to Locating AD-4
Vehicle section and Appendix A, Table A, column 2
for discharge line length.
E. In areas where more than a 30 degree range of
temperature occurs in one day, small amounts of
water can accumulate in the air brake system due
to condensation. Under these conditions, the
presence of small amounts of moisture is normal
and should not be considered as an indication that
the dryer is not performing properly.
Note: A small amount of oil in the system may be normal
and should not, in itself, be considered a reason to
replace the desiccant; oil stained desiccant can function
adequately.
PURGE
ORIFICE
PURGE VOLUME
DESICCANT
BED
PERFORATED PLATE
OIL SEPARATOR
SEALING RING
SEALING RING
SEALING RING
SEALING RING
SUPPLY
PORT
SPRING
O-RING
™
Air Dryer On