Service - Air Dryer - Allied Systems Company

Service - Air Dryer - Allied Systems Company
4-3
Section
Service - Air Dryer
UPPER
BRACKET
UPPER
BRACKET
OUTER
SHELL
OUTER
SHELL
LOWER
BRACKET
LOWER
BRACKET
END COVER
CONTROL
PORT
END COVER
PORT
CONTROL
SUPPLY
PORT
CHECK
VALVE
ASSEMBLY
DELIVERY PORT
WIRING HARNESS
CONNECTION
EXTENDED PURGE AIR DRYER
CHECK
VALVE
ASSEMBLY
SUPPLY
PORT
DELIVERY PORT
WIRING HARNESS
CONNECTION
STANDARD AIR DRYER
FIGURE 1 - AIR DRYER MODELS
DESCRIPTION
The function of the Air Dryer is to collect and remove air system contaminants in solid, liquid and vapor
form before they enter the brake system. It provides clean,
dry air to the components of the brake system which increases the life of the system and reduces maintenance
costs. Daily manual draining of the reservoirs is eliminated.
The Air Dryer consists of a desiccant cartridge and a
die cast aluminum end cover secured to a cylindrical steel
outer shell with eight cap screws and nuts. The end cover
contains a check valve assembly, a safety valve, three
threaded air connections and the purge valve housing
assembly. The removable purge valve housing assembly
incorporates a purge valve mechanism and a turbo charger
cut-off feature that is designed to prevent loss of engine
“turbo” boost pressure during the purge cycle of the
80-705
air dryer. For ease of serviceability, the desiccant cartridge
and discharge check valve assembly are screw in type.
The purge valve housing assembly, which includes the
heater and thermostat assembly, and the discharge check
valve assembly, is serviceable from the exterior of the air
dryer, while servicing the screw-in desiccant cartridge requires removal of the air dryer assembly from the vehicle.
The a i r d r y e r has three female pipe thread air
connections and each is identified as follows:
Port l.D.
Function/Connection
CON 4 .............. Control Port
(purge valve control and turbo cut-off).
SUP 11 ............. Supply Port (air in).
DEL 2 ............... Delivery Port (air out).
1
CHECK
VALVE
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¬
¬
¬
¬
¬
¬
¬
DESSICANT
CARTRIDGE
ORIFICE
¬
¬
¬
¬
¬
DESSICANT
BED
¬
¬
¬
PURGE
VALVE
¬
¬
¬
¬
¬
¬
¬
RESERVOIR
¬
¬
¬
¬
SUPPLY
PORT
¬
EXHAUST HEATER
ELEMENT
¬
¬
¬
¬
¬
¬
ENGINE
TURBO
¬
¬
¬
COMPRESSOR
¬ ¬
¬
¬
¬
GOVERNOR
¬
CONTROL
PORT
¬
OIL
SEPARATOR
¬
¬
PURGE
VOLUME
SUMP
CHECK
VALVE
ASSEMBLY
DELIVERY
PORT
FIGURE 2 - CHARGE CYCLE
OPERATION OF THE AIR DRYER
The air dryer alternates between two operational
modes or “cycles” during operation: the charge cycle and
the purge cycle. The following description of operation is
separated into these “cycles” of operation.
CHARGE CYCLE (refer to Figure 2)
When the compressor is loaded (compressing air) compressed air, along with oil, oil vapor, water and water vapor
flows through the compressor discharge line to the supply
port of the air dryer end cover. As air travels through the
end cover assembly, its direction of flow changes several
times, reducing the temperature, causing contaminants to
condense and drop to the bottom or sump of the air dryer
end cover.
After exiting the end cover, the air flows into the desiccant
cartridge. Once in the desiccant cartridge air first flows
through an oil separator which removes water in liquid form
as well as oil, oil vapor and solid contaminants.
Air exits the oil separator and enters the desiccant drying
bed. Air flowing through the column of desiccant becomes
2
progressively dryer as water vapor adheres to the desiccant material in a process known as “adsorption”. The
desiccant cartridge using the adsorption process typically
removes 95% of the water vapor from the pressurized air.
The majority of dry air exits the desiccant cartridge through
its integral single check valve to fill the purge volume between the desiccant cartridge and outer shell. Some air
will also exit the desiccant cartridge through the purge orifice adjacent to the check valve.
Dry air flows out of the purge volume through the single
check valve assembly and out the delivery port to the first
(supply) reservoir of the air system.
The air dryer will remain in the charge cycle until air brake
system pressure builds to the governor cutout setting.
PURGE CYCLE (refer to Figure 3)
When air brake system pressure reaches the cutout setting of the governor, the compressor unloads (air
compression stopped) and the purge cycle of the air dryer
begins. When the governor unloads the compressor, it
pressurizes the compressor unloader mechanism and line
80-705
Section
CHECK
VALVE
ORIFICE
¬
¬
¬
¬
¬
¬
¬
DESSICANT
BED
¬
¬
¬
DESSICANT
CARTRIDGE
PURGE
VOLUME
¬
¬
¬
¬
¬
¬
OIL
SEPARATOR
¬
¬
¬
¬
¬
¬
¬
¬
¬
COMPRESSOR
¬¬
¬
CONTROL
PORT
SUPPLY
PORT
¬
¬
¬
¬
¬
¬
ENGINE
TURBO
RESERVOIR
TURBO
CUTOFF
PISTON
PURGE
VALVE
¬
¬
GOVERNOR
4-3
EXHAUST
HEATER
ELEMENT
SUMP
CHECK
VALVE
ASSEMBLY
DELIVERY
PORT
FIGURE 3 - PURGE CYCLE
connecting the governor unloader port to the end
cover control port. The purge piston moves in response to
air pressure causing the purge valve to open to atmosphere
and (partially) closing off the supply of air from the compressor, this will be further discussed in the section covering
the turbo cut-off feature. Contaminants in the end cover
sump are expelled immediately when the purge valve
opens. Also, air which was flowing through the desiccant
cartridge changes direction and begins to flow toward the
open purge valve. Oil and solid contaminants collected by
the oil separator are removed by air flowing from the desiccant drying bed to the open purge valve.
The initial purge and desiccant cartridge decompression
lasts only a few seconds and is evidenced by an audible
burst of air at the exhaust.
The actual reactivation of the desiccant drying bed begins
as dry air flows from the purge volume through the desiccant cartridge purge orifice and into the desiccant drying
bed. Pressurized air from the purge volume expands after
passing through the purge orifice; its pressure is lowered
and its volume increased. The flow of dry air through the
drying bed reactivates the desiccant material by remov-
80-705
ing the water vapor adhering to it. Generally 15-30 seconds are required for the entire purge volume of a standard
air dryer to flow through the desiccant drying bed.
The end cover single check valve assembly prevents air
pressure in the brake system from returning to the air dryer
during the purge cycle. After the 30 second purge cycle is
complete, the air dryer is ready for the next charge cycle
to begin.
The purge valve will remain open after the purge cycle is
complete and will not close until air brake system pressure is reduced and the governor signals the compressor
to charge.
TURBO CUT-OFF FEATURE (Refer to Figure 4)
The primary function of the turbo cut-off valve is to prevent loss of engine turbocharger air pressure through the
air dryer in systems where the compressor intake is connected to the engine turbocharger. The turbo cut-off valve
also reduces the “puffing” of air out the open exhaust
when a naturally aspirated, single cylinder compressor
equipped with an inlet check valve is in use.
3
¬
¬
UPPER
BRACKET
STRAP
¬
¬
¬
¬
¬
¬
DESSICANT
BED
HOUSING
LOWER
BRACKET
CONTROL
PORT
PURGE
VALVE
EXHAUST
CHECK
DISCHARGE
VALVE
LINE
ASSEMBLY
FIGURE 4 - TURBO CUTOFF
At the onset of the purge cycle, the downward travel of the
purge piston is stopped when the turbo cut-off valve (tapered portion of purge piston) contacts its mating metal
seat in the purge valve housing. With the turbo cut-off
valve seated (closed position), air in the discharge line
and inlet port is restricted from entering the air dryer.
While the turbo cut-off effectively prevents loss of turbo
charger boost pressure to the engine, some “seepage” of
air may be detected under certain conditions of compressor engine and turbo charger operation, even so there will
always be low pressure trapped in the discharge line.
PREVENTIVE MAINTENANCE
Important: Review the warranty policy before performing
any intrusive maintenance procedures. An extended warranty may be voided if intrusive maintenance is performed
during this period.
Because no two vehicles operate under identical conditions, maintenance and maintenance intervals will vary.
Experience is a valuable guide in determining the best
maintenance interval for any one particular operation.
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.
4
DESSICANT
CARTRIDGE
OIL
SEPARATOR
¬
¬
¬
TURBO
CUTOFF
PISTON
¬
SUPPLY
PORT
¬
UPPER
BRACKET
SUPPLY
PORT
TURBO
CUTOFF
PISTION
CHECK
VALVE
ASSEMBLY
PURGE VALVE
HOUSING
ASSEMBLY
PURGE
VALVE
DISCHARGE
PORT
FIGURE 5 - AIR DRYER SECTIONAL VIEW
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.
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 air dryer On Vehicle sect.
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.
2. Check mounting bolts for tightness. Retorque to 270385 inch pounds.
80-705
Section
4-3
3. Perform the Operation & Leakage Tests listed in this
publication.
Every 10,800 hours; 300,000 miles or 36 months:
1. Rebuild the air dryer including the desiccant cartridge.
Note: The desiccant change interval may vary from vehicle to vehicle. Although typical desiccant cartridge life is
three years, many will perform adequately for a longer
period of time. In order to take maximum advantage of
desiccant life and assure that replacement occurs only
when necessary, it is important that Operation & Leakage
Tests be performed.
LOWER
MOUNTING
BRACKET
AIR DRYER
END COVER
FEMALE
CONNECTOR
MALE
CONNECTOR
LATCH MUST BE
INSERTED UNTIL
IT SNAPS OVER
TAB ON MATING
CONNECTOR
OPERATION & LEAKAGE TESTS
1. Test the outlet port check valve assembly by building
the air system to governor cut-out and observing a test
air gauge installed in the #1 reservoir. A rapid loss of
pressure could indicate a failed outlet port check valve.
This can be confirmed by bleeding the system down,
removing the check valve assembly from the end
cover, subject air pressure to the unit and apply a soap
solution to the check valve side. Leakage should not
exceed a 1 inch bubble in 1 second.
2. Check for excessive leakage around the purge valve.
With the compressor in loaded mode (compressing air),
apply a soap solution to the purge valve housing assembly exhaust port and observe that leakage does
not exceed a 1 inch bubble in 1 second. If the leakage
exceeds the maximum specified, service the purge
valve housing assembly.
3. Close all reservoir drain cocks. Build up system pressure to governor cut-out and note that purges
with an audible escape of air. “Fan” the service brakes
to reduce system air pressure to governor cut-in. Note
that the system once again builds to full pressure and
is followed by a purge.
4. Check the operation of the safety valve by pulling the
exposed stem while the compressor is loaded (compressing air). There must be an exhaust of air while
the stem is held and the valve should reseat when the
stem is released.
5. Check all lines and fittings leading to and from the air
dryer for leakage and integrity.
6. Check the operation of the end cover heater and thermostat assembly during cold weather operation as
follows:
A. Electric Power to the Dryer
With the ignition or engine kill switch in the ON
position, check for voltage to the heater and thermostat assembly using a voltmeter or test light.
Unplug the electrical connector at the air dryer and
place the test leads on each of the pins of the male
80-705
SIDE VIEW
END VIEW
A two lead, 12 inch, wire harness with attached weather
resistant connector is supplied with all retrofit and
replacement Air Dryers. Connect one of the two
leads of the wire harness to the engine kill or ignition
switch. The remaining lead of the wire harness must
be connected to a good vehicle ground. A fuse should
be installed in the power carrying wire; install a 10 amp
fuse for 12 volt heaters and a 5 amp fuse for a 24 volt
heater.
Use 14 AWG wire if it is necessary to lengthen the wire
harness provided.
Make certain all wire splices are waterproofed.
Tie wrap or support all electrical wire leading to the.
FIGURE 6 - HEATER AND THERMOSTAT CONNECTOR
connector. If there is no voltage, look for a blown
fuse, broken wires, or corrosion in the vehicle wiring harness. Check to see if a good ground path
exists.
B. Thermostat and Heater Operation
Turn off the ignition switch and cool the end cover
assembly to below 40 degrees Fahrenheit. Using
an ohmmeter, check the resistance between the
electrical pins in the female connector. The resistance should be 1.5 to 3.0 ohms for the 12 volt
heater assembly and 6.8 to 9.0 ohms for the 24
volt heater assembly. Note: Some early models of
the air dryer will have resistance readings of 1.0 to
2.5 ohms for the 12 volt heater assembly and
4.8 to 7.2 ohms for the 24 volt heater assembly.
If the resistance is higher than the maximum stated, replace the purge valve housing assembly,
which includes the heater and thermostat assy.
Warm the end cover assembly to over 90 degrees
Fahrenheit and again check the resistance. The
5
resistance should exceed 1000 ohms. If the resistance values obtained are within the stated limits,
the thermostat and heater assembly is operating
properly. If the resistance values obtained are outside the stated limits, replace the purge valve
housing assembly, which includes the heater and
thermostat assembly.
REBUILDING THE AIR DRYER
GENERAL
If, after completing the routine operation and leakage tests,
it has been determined that one or more components of
the air dryer requires replacement or maintenance, refer
to the following list to find the appropriate kit(s).
When rebuilding or replacing components of the air dryer
use only genuine parts. For ease in servicing the
air dryer desiccant cartridge assembly, it is recommended
that the air dryer be removed from the vehicle.
MAINTENANCE KITS AVAILABLE:
240658 Purge Valve Housing Maintenance Kit
This kit contains the parts necessary to rebuild
the air portion of the purge valve housing and does
not include the heater and thermo.
Desiccant Cartridge Replacement Kit
This kit contains the parts necessary to change
the desiccant cartridge only.
240662 Remanufactured Desiccant Cartridge
Replacement Kit
This kit contains the parts necessary to change
the desiccant cartridge only.
240660 End Cover Check Valve Assembly Replacement
3/4 inch thread size.
End Cover Check Valve Assembly Replacement
1/2 inch thread size.
Service New or Remanufactured Exchange
Purge Valve Housing Assembly
(w/heater and thermo.) 12 volt system.
Service New or Remanufactured Exchange Purge
Valve Housing Assembly
(w/heater and thermo.) 24 volt system.
240661 Complete Mounting Bracket Kit
This kit contains the upper and lower brackets as
well as the necessary hardware items to mount
them.
IMPORTANT! PLEASE READ
When working on or around a vehicle, the following
general precautions should be observed:
1. Park the vehicle on a level surface, apply the parking brakes, and always block the wheels.
2. Stop the engine when working around the vehicle.
6
3. If the vehicle is equipped with air brakes, make
certain to drain the air pressure from all reservoirs
before beginning ANY work on the vehicle.
4. Following the vehicle manufacturer’s recommended procedures, deactivate the electrical
system in a manner that removes all electrical
power from the vehicle.
5. When working in the engine compartment the engine should be shut off. Where circumstances
require that the engine be in operation, EXTREME
CAUTION should be used to prevent personal injury resulting from contact with moving, rotating,
leaking, heated, or electrically charged components.
6. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a
component or plug unless you are certain all system pressure has been depleted.
7. Never exceed recommended pressures and always
wear safety glasses.
8. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended procedures. Use only the proper tools and observe all
precautions pertaining to use of those tools.
9. Use only genuine replacement parts, components,
and kits. Replacement hardware, tubing, hose,
fittings, etc. should be of equivalent size, type,
and strength as original equipment and be
designed specifically for such applications and
systems.
10. Components with stripped threads or damaged
parts should be replaced rather than repaired. Repairs requiring machining or welding should not
be at tempted unless specifically approved and
stated by the vehicle or component manufacturer.
11. Prior to returning the vehicle to service, make certain all components and systems are restored to
their proper operating condition.
REMOVAL
1. Park the vehicle on a level surface and prevent movement by means other than the brakes.
2. Drain all reservoirs to 0 p.s.i. (0 kPa).— Caution:
Compressor discharge line may still contain residual
pressure.
3. Identify and disconnect the three air lines from the end
cover and note the position of end cover ports relative
to the vehicle.
4. Unplug the vehicle wiring harness from the heater and
thermostat assembly connector on the purge valve
housing assembly.
80-705
Section
4-3
25
26
28
29
22
27
24
21
19
23
17
SAFETY
VALVE
1
20
END
COVER
17
15
6
5
31
17
14
33
18
10
13
8
30
3
11
2
32
4
7
16
NOTE: NUMBERS 9 AND 12
NOT USED
1
2
3
4
5
6
7
8
10
11
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
O-RING
EXHAUST DIAPHRAGM
1/4" TAPPING SCREW
PURGE VALVE LOCK NUT
O-RING
O-RING
O-RING
PURGE VALVE ASSEMBLY
O-RING
PURGE VALVE
SPRING
O-RING
CHECK VALVE ASSEMBLY
3/8" CAP SCREW
3/8" SPECIAL WASHER
3/8" CAP SCREW (LONG)
LOCK NUT
LOWER MOUNTING BRACKET
O-RING
DESICCANT CARTRIDGE
COMPLETE
O-RING
HOUSING
5/16" X 4-1/2" UPPER BRACKET
CAP SCREW
UPPER BRACKET STRAP
UPPER MOUNTING BRACKET
5/16" LOCK WASHER
5/16" LOCK NUT
EXHAUST COVER
TORX HEAD BOLT
EXHAUST DIAPHRAGM WASHER
PURGE PISTON
FIGURE 7 - AIR DRYER ASSEMBLY
80-705
7
5. Loosen the 5/16" X 4-1/2" hex bolt securing the upper
mounting strap.
6. Remove, retain and mark the two 3/8" end cover cap
screws, lock nuts and four special washers that retain
the lower mounting bracket to the end cover, also mark
these two holes of the end cover. (These bolts are
longer than the other 6 bolts.)
7. Remove the air dryer from its mounting brackets
on the vehicle.
DISASSEMBLY
The following disassembly and assembly procedure is presented for reference purposes and presupposes that a
major rebuild of the air dryer is being undertaken.
Several replacement parts and maintenance kits are
available which do not require full disassembly. The instructions provided with these parts and kits should be
followed in lieu of the instructions presented here. Refer
to Figure 7 during disassembly.
Caution: While performing service on the air dryer,
it is not recommended that a clamping device (vise, Cclamp, etc.) be used to hold any die cast aluminum
component as damage may result. To hold the end cover,
install a pipe nipple in the supply port and clamp the nipple
into a vise.
1. Using an adjustable wrench or an 1-3/4" socket, remove the delivery, check valve assembly (15) and
o-ring. Remove the o-ring from the check valve assembly.
2. Remove the three 1/4" self tapping screws (3) that secure
the purge valve housing assembly to the end cover
assembly. Pull the purge valve housing assembly out of
the end cover assembly. Remove the three o-rings (5,6
& 7) from the exterior of the purge valve housing
assembly. Note: O-rings 5 and 6 may be lodged in the
end cover bores, if so, they must be removed
3. Purge Valve Disassembly:
Note: In most cases a flat (non-extended) exhaust
cover (30) is used. This cover should be left intact while
servicing the purge valve housing assembly. However,
if an extended type exhaust cover is in use to
accommodate the attachment of an exhaust hose, the
exhaust cover must be carefully peeled off the purge
valve housing. Use a thin flat blade to pry the
exhaust cover off, taking care not to damage the
potting material (RTV sealant) under the cover. To
remove the piston from the purge valve housing
assembly requires a special Torx head socket or a
twelve point 1/4" socket to hold the head of the purge
valve bolt (31).
A. Remove the 1/4" nut (4) from the bottom of the
purge valve housing assembly using a 9/16" socket
8
wrench and a Torx head socket to hold the head of
the bolt (31). Remove the diaphragm washer (32)
(if present), and the diaphragm (2) (if present), and
the purge valve (11) from the purge valve housing.
B. Remove the 1/4" Torx head bolt (31) from the opposite end, then the purge piston (33), the return
spring (13) and two o-rings (10 & 14); one on the
O.D. and the other in the inside of the purge piston.
C. Heater and Thermostat Assembly Replacement.
Caution: Do not attempt to remove this assembly,
as it will be damaged during the removal process
and is not available as a service part. If the heater
and thermostat are defective, replace the entire
purge valve housing assembly which includes these
items.
4. Remove the remaining six 3/8" cap screws (16), lock
nuts (19) and twelve special washers (17) that secure
the end cover to the housing (24). Separate the end
cover and desiccant cartridge (22) from the housing (24).
5. Remove the end cover to outer housing o-ring (23).
6. Do not remove the safety valve from the end cover
unless it has been proven defective. If replacement is
required, apply thread sealant or teflon tape on the
threads of the replacement valve and torque to 120400 in. Ibs.
7. Place a strap or chain wrench around the desiccant
cartridge (22) so that it is approximately 2-3 inches
away from the end cover. Rotate the cartridge counterclockwise until it completely separates from the end
cover. Note: A substantial torque (up to 50 lb. ft.) may
be required to perform this disassembly.
8. Remove the desiccant cartridge o-ring (21) from the
end cover.
CLEANING & INSPECTION
1. Using mineral spirits or an equivalent solvent, clean
and thoroughly dry all metal parts.
2. Inspect the interior and exterior of all metal parts that
will be reused for severe corrosion, pitting and cracks.
Superficial corrosion and or pitting on the exterior portion of the upper and lower body halves is acceptable.
3. Inspect the bores of both the end cover and the purge
valve housing for deep scuffing or gouges.
4. Make certain that all purge valve housing and end cover
passages are open and free of obstructions.
5. Inspect the pipe threads in the end cover. Make certain they are clean and free of thread sealant.
6. Inspect the purge valve housing bore and seats for
excessive wear and scuffing.
7. Inspect the purge valve piston seat for excessive wear.
80-705
4-3
Section
8. Inspect all air line fittings for corrosion. Clean all old
thread sealant from the pipe threads.
9. All o-rings removed should be discarded and replaced
with new o-rings provided in appropriate kit(s).
Any component exhibiting a condition described in step 1
to 8 should be replaced.
ASSEMBLY
Prior to assembly, coat all o-rings, o-ring grooves, and
bores with a generous amount of barium base lubricant.
Refer to Figure 7 during assembly unless otherwise
advised.
1. Purge Valve Housing Assembly
A. Install the o-ring (14) in its groove on the O.D. of
the purge piston. Place the return spring (13) in the
bore of the purge valve housing. Place the o-ring
(10) into its recess in the bore of the purge piston.
Install the 1/4" Torx head bolt (31) into the l.D. of
the purge piston. Insert the purge piston (33) into
the l.D. of the spring (13). Using a Torx head wrench,
push the purge piston into the piston housing until
it bottoms.
B. While depressing the purge piston with the Torx
head wrench, install the following parts over the
purge valve bolt (31) from the opposite end of the
purge valve housing; the purge valve (11) with its
rubber side first, followed by the diaphragm (2) (if
present), the diaphragm washer (32) (if present) or
the flat washer and finally the 1/4" hex nut (4).
Torque the purge valve nut and bolt (4 & 31) to
between 60-80 in. Ibs.
C. Install the three o-rings (5, 6 & 7) on the purge valve
housing placing each in its appropriate location. If
the exhaust cover (30) was removed during disassembly, install it on the purge valve housing
assembly making certain the “bubble” portion is
positioned over the thermostat. Install the assembled purge valve housing in the end cover
making certain to orient both parts such that the
connector is approximately 10 degrees clockwise
from the supply port, while making certain the purge
valve housing is fully seated against the end cover.
Secure the purge valve housing to the end cover
using the three 1/4" self-tapping screws (3). Start
all three screws by hand then torque to 50-80 in.
Ibs.
2. Install the o-ring on the check valve assembly (15),
then install the assembly in the end cover.
Screw the desiccant cartridge into the end cover until
contact is made between it and the o-ring. Using a
strap or chain wrench positioned 2-3" from the bottom
of the cartridge, turn the desiccant cartridge clockwise
180-225 degrees beyond the position where initial contact was made between the cartridge and end cover
o-ring. Torque should not exceed 50 ft. Ibs.
4. Install the end cover outer housing o-ring (23) on the
shoulder in the end cover. Place the housing (24) over
the desiccant cartridge and align the holes. Install the
six 3/8" cap screws (16), lock nuts (19) and twelve special washers (17) making certain they are in the proper
position as marked during disassembly. The two longer
3/8" cap screws (18) will be used to secure the air dryer
to its mounting bracket. Tighten the six cap screws
and nuts in a star pattern in a fashion similar to
Figure 8; depending on lower bracket location.
Torque to 270-385 in. Ibs. (Refer to Fig. 8.) Note: The
two remaining bolt holes in the end cover and two
3/8" cap screws must be the ones marked during
disassembly to assure proper orientation of the ports and
adequate length of the cap screws.
6
2
4
5
3
1&9
7
8
FIGURE 8 - END COVER TO HOUSING TORQUE PATTERN
3. Install the desiccant cartridge o-ring (21) in its groove
in the end cover. Using a light coat of barium grease,
lubricate the bottom of the desiccant cartridge in the
area that will contact the o-ring (21) and end cover.
80-705
9
AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS
1. Dryer is constantly
“cycling” or purging.
CAUSE
A. Excessive system
leakage.
REMEDY
A. Test for excessive system leakage.
Allowable leakage:
Pre-121 vehicles, single vehicles - 2 psi/
minute.
Tractor trailer - 3 psi/minute.
121 vehicles, single vehicle - 1 psi/minute per
service reservoir.
Tractor trailer - 3 psi/minute per service
reservoir.
10
B. Excessive leakage in
fitting, hoses and tubing
connected to the
compressor, air dryer
and first reservoir.
B. Using soap solution, test for leakage at fittings,
drain valve (if any) and safety valve in first
reservoir. Repair or replace as necessary.
C. Defective check valve
assembly in air
dryer end cover.
C. Remove check valve assembly from end
cover. Subject air pressure to delivery side of
valve. Apply soap solution at opposite end and
check for leakage. (Permissible leakage - 1inch
bubble in five seconds) If excessive leakage,
replace check valve assembly.
D. Defective governor.
D. Test governor for proper cut-in and cut-out
pressures and excessive leakage in both
positions.
E. Leaking purge valve
housing assembly and/
or o-rings in air
dryer end cover.
E. With the supply port open to atmosphere, apply
120 psi at the control port. Apply a soap
solution to the supply port and exhaust port
(purge valve seat area). Permissible leakage 1 inch bubble in five seconds.
F. Compressor unloader
mechanism leaking
excessively.
F. Remove air strainer or fitting from compressor
inlet cavity. With compressor unloaded, check
for unloader piston leakage. Slight leakage
permissible.
G. Holset “E” type
compressor.
G. Test Air Dryer system using Product
Bulletin entitled “Troubleshooting
The Holset E compressor system With
Air Dryer.”
H. Rapid cycling of the
governor due to air
starvation at the RES
port of the governor.
H. With gauge installed at RES port of governor,
pressure should not drop below “Cut-In”
pressure at the onset of the compressor
“Unloaded” cycle. If pressure drops, check for
“kinks” or restrictions in line connected to RES
port. Line connected to RES port on governor
must be same diameter, or preferably larger
than, lines connected to UNL port(s) on
governor.
80-705
Section
4-3
AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS
2. Water in vehicle
reservoir.
CAUSE
REMEDY
A. Desiccant requires
replacement - excessive
contaminants in
desiccant cartridge
assembly.
A. Replace desiccant cartridge.
B. Improper discharge line
length or improper line
material. Maximum air
dryer inlet temperature
is exceeded.
B. Refer to section entitled “Connecting the Air
Lines” and check “Discharge Line” size and
length.
C. Air system charged
from outside air source
(outside air not passing
through air dryer).
C. If system must have outside air fill provision,
outside air should pass through air dryer. This
practice should be minimized.
D. Air dryer not purging
(see Symptom #5).
D. See cause and remedy for Symptom #5.
E. Purge (air exhaust) time
insufficient due to
excessive system
leakage (see causes for
Symptom #1).
E. Check causes and remedies for Symptom #1.
F. Excessive air usage Air dryer/vehicle
application requires
additional purge
volume. Air dryer not
compatible with vehicle
air system requirement
(Improper air dryer/
vehicle application).
F. Charge Cycle Time - The air dryer is designed
to provide clean, dry air for the brake system.
When a vehicle’s air system is used to operate
non-brake air accessories it is necessary to
determine that during normal, daily operation
the compressor should recover from governor
“cut-in” to governor “cut-out” (usually 100 psi to
120 psi) in 90 seconds or less at engine RPM’s
commensurate with the vehicle vocation. If the
recovery time consistently exceeds this limit, it
may be necessary to “bypass” the air accessory
responsible for the high air usage. An example
of where a by-pass system would be required is
when the compressor is used to pressurize a
tank trailer for purposes of off-loading product.
Consult your local authorized parts
outlet or sales representative for additional
information.
Purge Cycle Time - During normal vehicle
operation, the air compressor must remain
unloaded for a minimum of 20 seconds for
the standard AD-9 or 30 seconds for the
Extended Purge Model. These minimum
purge times are required to ensure complete
regeneration of the desiccant material. If the
purge time is consistently less than the
minimum, an accessory by-pass system must
80-705
11
AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS
CAUSE
2. Water in vehicle
reservoir (continued).
REMEDY
be installed. Consult your local authorized
parts outlet or sales representative for
additional information.
European Air Brake Systems - Brake systems
that incorporate compressors without integral
unloading mechanisms and/or utilize a
compressor discharge line unloader valve have
special air dryer installation requirements.
Consult your local authorized parts
outlet or sales representative for additional
information.
Air Compressor Size - Although the air dryer
can be used in conjunction with larger
compressors, it was designed primarily for
units rated for up to 17 CFM. It is
recommended that when using the air dryer
with a compressor which has a rated displacement exceeding 17 CFM that an authorized
parts outlet or marketing representative
be contacted for assistance.
G. Air by-passes desiccant
cartridge assembly.
G. Replace desiccant cartridge/end cover/o-ring.
H. Purge time is
significantly less than
minimum allowable.
H. Replace desiccant cartridge/end cover o-ring.
Check to make sure desiccant cartridge
assembly is properly installed.
Check to make sure desiccant cartridge
assembly is properly installed.
Replace desiccant cartridge assembly.
3. Safety valve on air
dryer “popping off” or
exhausting air.
12
A. Desiccant cartridge
plugged.
A. Check compressor for excessive oil passing
and/or correct compressor installation. Repair
or replace as necessary. Rebuild or replace
cartridge.
B. Defective discharge
check valve in end
cover of the air dryer.
B. Test to determine if air is passing through
check valve. Repair or replace.
C. Defective fittings, hose
or tubing between air
dryer and first reservoir.
C. Check to determine if air is reaching first
reservoir. Inspect for kinked tubing or hose.
Check for undrilled or restricted hose or tubing
fittings.
D. Excessive pressure
pulsations from
compressor. (Typical
single cylinder type).
D. Increase volume in discharge line. Added
length or size of line, or add a ping tank.
E. Safety valve setting
lower than the
maximum system
pressure.
E. Reduce system pressure or obtain a higher
setting safety valve.
80-705
Section
4-3
g
AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS
4. Constant exhaust of air
at air dryer purge valve
exhaust or unable to
build system pressure.
(Charge mode.)
5. Air dryer does not
purge or exhaust air.
6. Desiccant material
being expelled from air
dryer purge valve
exhaust (may look like
whitish liquid or paste
or small beads.)
- OR Unsatisfactory
desiccant life.
80-705
CAUSE
REMEDY
A. Air dryer purge valve
leaking excessively.
A. With compressor loaded, apply soap solution
on purge valve exhaust, to test for excessive
leakage. Repair purge valve as necessary.
B. Defective governor.
B. Check governor for proper “cut-in”, “cut-out”
pressure and excessive leakage in both
positions. Repair or replace as necessary.
C. Purge control line
connected to reservoir
or exhaust port of
governor.
C. Purge control line must be connected to
unloader port of governor.
D. Purge valve frozen
open - faulty heater and
thermostat, wiring,
blown fuse.
D. Test heater and thermostat as described in
Step 7 of Preventative Maintenance Section.
E. Inlet and outlet air
connections reversed.
E. Compressor discharge to inlet port. Reconnect
lines properly.
F. Kinked or blocked
(plugged) discharge
line.
F. Check to determine if air passes through
discharge line. Check for kinks, bends,
excessive carbon deposits.
G. Excessive bends in
discharge line (water
collects and freezes).
G. Discharge line should be constantly sloping
from compressor to air dryer with as few bends
as possible.
H. Excessive system
leakage.
H. See Symptom #1’s Causes and Remedies.
I. Purge valve stays open
- supply air leaks to
control side.
I. Replace purge valve housing assembly o-rings.
A. Broken, kinked, frozen,
plugged or disconnected
purge control line.
A. Test to determine air flows through purge
control line when compressor unloaded. Check
for undrilled fittings. (See Symptom #4,
Remedy C.)
B. See Causes B, E, G for
Symptom #4.
B. Refer to Remedies B, E, G for Symptom #4.
A. This symptom is almost
always accompanied by
one or more of
Symptoms 1, 2, 3, 4 and
5. See related causes
for these Symptoms
above.
A. See Causes and Remedies for Symptoms 1, 2,
3, 4 and 5.
B. Air dryer not securely
mounted. (Excessive
vibration.)
C. Defective cloth covered
perforated plate in air
dryer.
B. Vibration should be held to minimum. Add
bracket supports or change air dryer mounting
location if necessary.
C. Replace desiccant cartridge assembly.
13
AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS
6. (Continued.)
7. “Pinging” noise
excessive during
compressor loaded
cycle.
CAUSE
REMEDY
D. Compressor passing
excessive oil.
D. Check for proper compressor installation; if
symptoms persist, replace compressor.
E. Desiccant cartridge not
assembled properly to
end cover. (Loose
attachment)
E. Check the torque on the desiccant cartridge to
end cover attachment. Refer to assembly
section of this data sheet.
A. Single cylinder
compressor with high
pulse cycles.
A. A slight “pinging” sound may be heard during
system build up when a single cylinder
compressor is used. If this sound is deemed
objectionable, it can be reduced substantially
by increasing the discharge line volume.
This can be accomplished by adding an
additional four feet of discharge line or adding
a 90 cubic inch reservoir between the
compressor and the air dryer.
8. Constant seepage of
air at air dryer purge
valve exhaust (noncharging mode.)
9. The air dryer purge
piston cycles rapidly in
the compressor
unloaded
(noncompressing)
mode.
14
A. Inlet of air compressor
pressurized by
turbocharger from
engine.
A. Some leakage of pressure past the metal seat
of the turbo cutoff feature of the air dryer is to
be expected also may be audible. This slight
loss of air will not effect the engine or turbo
performance.
B. Defective check valve
assembly in air
dryer end cover.
B. Refer to Remedy C, Symptom #1.
A. Compressor fails to
“unload”.
A. Faulty governor installation; no air line from
governor to compressor or line is “kinked” or
restricted. Install or repair air line.
80-705
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