Bendix Commercial Vehicle Systems TU-FLO 1000 User Manual
®
Bendix® TU-FLO® 400, 500, 1000 Air Compressors
SD-01-326
TU-FLO® 400 Air Compressor TU-FLO® 500 Air Compressor
TU-FLO
®
1000 Air Compressor
1
DESCRIPTION AND OPERATION
GENERAL
The function of the air compressor is to build up and maintain
the air pressure required to operate air powered devices in
air brake or air auxiliary systems.
DESCRIPTION
Tu-Flo® Type 400, 500, and 1000 compressors are single
stage, reciprocating piston type compressors. Tu-Flo
(Fig. 1) and 500 (Fig. 2) compressors have two cylinders
while the Tu-Flo
®
1000 compressor (Fig. 3) is a V-type
design having four cylinders. The rated capacity of all Bendix
compressors is their piston displacement in cubic feet per
minute when operating at 1,250 RPM. The rated capacity
of the Tu-Flo® 400 compressor is 7-1/4 cubic feet per minute.
®
The Tu-Flo
minute and the Tu-Flo
500 compressor is rated at 12 cubic feet per
®
1000 compressor has a rating of 24
cubic feet per minute.
Tu-Flo® type compressors have automatic type inlet valves.
Their unloading mechanisms are located in the cylinder block
®
400
and they have no external moving parts. Both air and water
cooled type compressors are available. V arious mounting
and drive adaptations are used as required by different vehicle
engine designs (Fig. 4).
FIGURE 1 - TU-FLO® 400 AIR COMPRESSOR
FIGURE 2 - TU-FLO® 500 AIR COMPRESSOR
FIGURE 3 - TU-FLO® 1000 AIR COMPRESSOR
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FIGURE 4 - VARIOUS COMPRESSOR MOUNTINGS
Compressors are either engine or self-lubricated. The
majority used are the engine lubricated types (Fig. 5) which
obtain the oil necessary to lubricate their moving parts from
the engines on which they are mounted. To meet the
requirements of some manufacturers and for field
installations, self-lubricated types (Fig. 6) are available. They
are compressors having a self-contained oil supply and
pumping system.
The method of lubricating the moving parts of the compressor
is the same in either type. Oil is forced through the oil
passage in the crankshaft and out around each connecting
rod journal. The turning motion of the crankshaft throws the
oil that is forced out at the journals, against the cylinder
bores and crankcase walls, lubricating the bores and
crankshaft bearings.
The wrist pins and wrist pin bushings are lubricated in two
ways depending upon the type connecting rods used. Older
design compressors had forged steel rifle-drilled rods through
which oil was forced to the wrist pin bushings. Later versions
FIGURE 5
ENGINE LUBRICA TED TYPE
FIGURE 6
SELF-LUBRICATED TYPE
had either die cast aluminum, cast ductile iron, or forged
steel rods which were not rifle drilled but were drilled at the
top of the rod. The wrist pins and bushings are lubricated
by oil dripping from a drip-boss on the piston into a
“catch-funnel” at the top of the rod and through the drilled
passage to the bushings and pins. (SEE FIG. 7)
PISTON WRIST PIN
LOCK WIRE
WRIST PIN
BUSHING
OPERATION
GENERAL
All compressors run continuously while the engine is running,
but actual compression of air is controlled by a governor,
which stops or starts the compression of air by loading or
unloading the compressor in conjunction with its unloading
mechanism. This is done when the air pressure in the system
reaches the desired maximum or minimum pressures.
TO RESERVOIR
DISCHARGE
VALVE
PISTON
INLET VALVE
UNLOADER PLUNGER
INTAKE
STRAINER
TO GOVERNOR
WRIST PIN
OIL
PASSAGE
OLD DESIGN
WRIST PIN
BUSHING
NEW DESIGN
FIGURE 7- PISTONS & CONNECTING RODS
CONNECTING
“CATCH FUNNEL”
CAST IRON
PISTON
STEEL
ROD
DIE CAST
PISTON
DIE CAST
CONNECTING ROD
A nameplate is attached to the crankcase of all compressors.
It shows the piece number, type and serial number (Fig. 8).
A nameplate with a black background denotes a new
compressor, whereas a nameplate with a red background
designates that the compressor is a factory reconditioned
unit. All compressors are identified by the piece number
which is the number to use when reference is made to a
particular compressor. The type and serial number is
supplementary information.
STROKE
INTAKE
FIGURE 9
INT AKE AND COMPRESSION (Loaded)
During the down stroke of the piston, a slight vacuum created
above the piston causes the inlet valve to move off its seat.
Atmospheric air is drawn in through the compressor intake,
by the open inlet valve, and on top of the piston (Fig. 9). As
the piston starts its upward stroke, the air that was drawn in
on the down stroke is being compressed. Now, air pressure
on top of the inlet valve plus the force of its spring, returns
the inlet valve to its seat. The piston continues the upward
stroke and compresses the air sufficiently to overcome the
discharge valve spring and unseat the discharge valve. The
compressed air then flows by the open discharge valve, into
the discharge line and on to the reservoirs (Fig. 10).
TO RESERVOIR
DISCHARGE
VALVE
PISTON
INLET VALVE
UNLOADER PLUNGER
INTAKE
STRAINER
FIGURE 8 - COMPRESSOR NAMEPLATE
TO GOVERNOR
STROKE
COMPRESSION
FIGURE 10
3
As the piston reaches the top of its stroke and starts down,
the discharge valve spring returns the discharge valve to its
seat. This prevents the compressed air in the discharge
line from returning to the cylinder bore as the intake and
compression cycle is repeated.
NON-COMPRESSION (Unloaded)
When the air pressure in the reservoir reaches the high
pressure setting of the governor, the governor opens, allowing
air to pass from the reservoir through the governor and into
the cavity beneath the unloader pistons. This lifts the
unloader pistons and plungers. The plungers move up and
hold the inlet valves off their seats (Fig. 1 1).
TO RESERVOIR
DISCHARGE
VALVE
PISTON
STROKE
FIGURE 1 1
INLET VALVE
UNLOADER
PLUNGER
INTAKE
STRAINER
TO GOVERNOR
UNLOADING
With the inlet valves held off their seats by the unloader
pistons and plungers, air is merely pumped back and forth
between the two cylinders. When air is used from the
reservoir and the pressure drops to the low pressure setting
of the governor, the governor closes, and in doing so,
exhausts the air from beneath the unloader pistons. The
unloader saddle spring forces the saddle, pistons and
plungers down and the inlet valves return to their seats.
Compression is then resumed.
COMPRESSOR & THE AIR BRAKE SYSTEM
GENERAL
The compressor is part of the total air brake system, more
specifically, the charging portion of the air brake system. As
a component in the overall system its condition, duty cycle,
proper installation and operation will directly affect other
components in the system.
Powered by the vehicle engine, the air compressor builds
the air pressure for the air brake system. The air compressor
is typically cooled by the engine coolant system, lubricated
by the engine oil supply and has its inlet connected to the
engine induction system.
As the atmospheric air is compressed, all the water vapor
originally in the air is carried along into the air system, as
well as a small amount of the lubricating oil as vapor. If an
air dryer is not used to remove these contaminants prior to
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entering the air system, the majority , but not all, will condense
in the reservoirs. The quantity of contaminants that reach
the air system depends on several factors including
installation, maintenance and contaminant handling devices
in the system. These contaminants must either be eliminated
prior to entering the air system or after they enter .
DUTY CYCLE
The duty cycle is the ratio of time the compressor spends
building air to the total engine running time. Air compressors
are designed to build air (run "loaded") up to 25% of the
time. Higher duty cycles cause conditions that affect air
brake charging system performance which may require
additional maintenance. Factors that add to the duty cycle
are: air suspension, additional air accessories, use of an
undersized compressor, frequent stops, excessive leakage
from fittings, connections, lines, chambers or valves, etc.
Refer to T able A in the Troubleshooting section for a guide to
various duty cycles and the consideration that must be given
to maintenance of other components.
COMPRESSOR INST ALLATION
While the original compressor installation is usually
completed by the vehicle manufacturer, conditions of
operation and maintenance may require additional
consideration. The following presents base guidelines.
DISCHARGE LINE
The discharge line allows the air, water-vapor and oil-vapor
mixture to cool between the compressor and air dryer or
reservoir. The typical size of a vehicle's discharge line, (see
column 2 of T able A in the Troubleshooting section) assumes
a compressor with a normal (less than 25%) duty cycle,
operating in a temperate climate. See Bendix and/or other
air dryer manufacturer guidelines as needed.
The discharge line must maintain a constant slope down
from the compressor to the air dryer inlet fitting or reservoir
to avoid low points where ice may form and block the flow . If,
instead, ice blockages occur at the air dryer or reservoir
inlet, insulation may be added here, or if the inlet fitting is a
typical 90 degree fitting, it may be changed to a straight or
45 degree fitting. Shorter discharge line lengths or insulation
may be required in cold climates.
While not all compressors and charging systems are
equipped with a discharge line safety valve this component
is recommended. The discharge line safety valve is installed
in the cylinder head or close to the compressor discharge
port and protects against over pressurizing the compressor
in the event of a discharge line freezeup.
DISCHARGE LINE TEMPERA TURE
When the temperature of the compressed air that enters
the air dryer is within the normal range, the air dryer can
remove most of the charging system oil. If the temperature
of the compressed air is above the normal range, oil as oilvapor is able to pass through the air dryer and into the air
system. Larger diameter discharge lines and/or longer
discharge line lengths can help reduce the temperature.
Discharge
Line
Optional “Ping” T ank
Air Dryer
The Air Brake Charging System supplies the
compressed air for the braking system as well as other air
accessories for the vehicle. The system usually consists
of an air compressor, governor, discharge line, air dryer ,
and service reservoir.
Compressor
Governor
(Governor plus Synchro valve
for the Bendix
FIGURE 12A - SYSTEM DRAWING
THREAD
FIGURE 12B - DISCHARGE LINE SAFETY VALVE
®
DuraFlo™ 596
Compressor)
HOLE
Optional Bendix® PuraGuard® QC
™
Oil Coalescing Filter
Service Reservoir
(Supply Reservoir)
Reservoir Drain
PREVENTIVE MAINTENANCE
Regularly scheduled maintenance is the single most
important factor in maintaining the air brake charging system.
Refer to T able A in the Troubleshooting section for a guide to
various considerations that must be given to the maintenance
of the compressor and other related charging system
components.
If the compressor is a self-lubricated type, its oil level should
be checked daily . The oil level should be kept between the
bottom of the dipstick threads and the bottom of the dipstick
(Fig. 13). Every 8,000 miles or 300 operating hours, the oil
should be drained and refilled with SAE 10-20-30.
The air dryer contains a filter that collects oil droplets, and a
desiccant bed that removes almost all of the remaining water
vapor. The compressed air is then passed to the air brake
service (supply) reservoir. The oil droplets and the water
collected are automatically purged when the governor
reaches its "cut-out" setting.
For vehicles with accessories that are sensitive to small
amounts of oil, we recommend installation of a Bendix
PuraGuard® QC™ oil coalescing filter, designed to minimize
the amount of oil present.
COOLING
Tu-Flo® 400, 500 or 1000 compressors may be air-cooled or
water- cooled and in some instances will have air-cooled
blocks and water-cooled heads. The air-cooled versions
are easily recognized by the external fins. The water-cooled
versions are cooled by vehicle coolant.
®
FIGURE 13 - OIL LEVEL - SELF-LUBRICATED
COMPRESSOR
POL YURETHANE SPONGE STRAINER (Fig. 14)
Remove and wash all of the parts. The strainer element
should be cleaned or replaced. If the element is cleaned, it
should be washed in a commercial solvent or a detergent
and water solution. The element should be saturated in
clean engine oil, then squeezed dry before replacing it in
the strainer. Be sure to replace the air strainer gasket if the
entire air strainer is removed from the compressor intake.
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