TM 5-3805-260-24
Air Dryer Check (Models 613BSNS1 and 613BSS1)
Put a new or rebuilt desiccant cartridge in the air
dryer when the desiccant in the cartridge does not have
enough water absorption ability. First, make the checks
that follow.
NOTE: The check for water may be made at 250 service
hours but it is not expected that maintenance of the
desiccant will be required for at least 1000 service hours.
1. Check for water in the air tanks. Open the drains on
the tanks. In areas where there is more than 300 F
(170 C) change in ambient temperature, there can be
water in the air tanks because of condensation. A
small amount of water from condensation is normal
and is not an indication that the air dryer is not in
operation. Steps A, B and C are probable causes of
too much water in the air tanks.
A.
Air from another machine without an air dryer
was put in the air reservoirs and did not go
through an air dryer.
B.
Too much air has been used for a long time and
the air compressor has not been let to load and
unload in a normal way (abnormal usage of air
compressor).
C.
The air dryer has been installed on a machine
that did not have one before. This type of
system will be saturated with moisture and
several weeks of operation may be needed to
dry it out.
2.
Check all bolts that hold the air dryer to see
that they are tight. Check all air and electrical
connections.
3.
Check the operation of the check valve in the
discharge opening of the air dryer. Install an air pressure
gauge in the line between the air dryer discharge and the
air tanks. With the system air pressure at governor cut-
out pressure and the engine not running, check the air
pressure gauge. If there is a fast drop in air pressure, it
could be an indication of a check valve with a defect.
This can be checked by an inspection of the purge-valve
exhaust. The purge valve will be open when the air
pressure has gone up to governor cut-out pressure. Let
two minutes go by for a complete purge cycle. If there is
a constant flow of air from the purge valve exhaust with
the engine shut off and if the air pressure on the test
gauge went down, it is an indication there is an air leak in
the check valve.
4.
With the compressor loaded (compressing air),
put a mixture of liquid soap and water on the
exhaust of the purge valve to see if there is an air
leak in the valve.
5.
Pull on the stem of the relief valve while the air
compressor is loaded (compressing air). There
must be an exhaust of air from the valve and it
must stop when the stem of the valve is released.
6.
Check all lines and fittings that go to and from the
air dryer for leakage.
7.
Check the operation of the heater and the
thermostat during cold weather operation.
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