Bendix Commercial Vehicle Systems BX2150 User Manual
®
Bendix® BX-2150™ Air Compressor
AIR OUTLET (2)
(1 NOT SHOWN)
WATER
OUTLET
UNLOADER
STOP
SD-01-331
WATER INLET
(NOT SHOWN)
AIR
INLET
WATER
OUTLET
UNLOADER
PORTS
INLET VALVE
AIR INTAKE
PISTON
CONNECTING
ROD
CRANKSHAFT
OIL SEAL
ROLLER
BEARING
UNLOADER
PISTON
AIR OUTLET
DISCHARGE
VALVE
PISTON
RINGS
REAR END
COVER
OIL INLET
SLEEVE
BEARING
CRANKSHAFT OIL PASSAGE
BX-2150™ AIR COMPRESSOR BELT DRIVE MODEL
DESCRIPTION
GENERAL
The function of the air compressor is to provide and maintain
air under pressure to operate devices in the air brake and/or
auxiliary air systems.
DESCRIPTION
The BX-2150™ compressor is a single cylinder, single stage
reciprocating compressor with a rated displacement of 9.5
cubic feet per minute at 1250 R.P.M. The BX-2150
compressor is constructed from two major assemblies, the
cylinder head and the crankcase. The cylinder head is an
iron casting containing the inlet, discharge and unloader
valving. It is installed on the crankcase and is secured using
four cap screws symmetrically placed. The cylinder head
can be, therefore installed in any one of four different positions
which are 90° apart.
Two governor mounting surfaces, adjacent to the single
rectangular inlet cavity, provide a convenient means of
mounting the governor to the cylinder head. One eighth inch
™
1
1/2” P.T.
WATER
PORT (3)
OUTLET WATER
ONLY
1/2” P.T. AIR
DISCHARGE
(2)
PART NUMBER
SERIAL NUMBER
TYPICAL NAMEPLA TE
1/8” P.T.
GOVERNOR
PORT 2 PLACES
BX-2150™ COMPRESSOR CYLINDER HEAD
AIR INLET
1/2” P.T.
WATER
PORT
pipe threads in each of the two governor mounting pads
allow plugging of the unused port or the installation of a
tubing fitting for remote governor mounting. Three 1/2” N.P .T.
ports provide the means for the connection of coolant lines
and are labeled WATER. Two 1/2” N.P.T. discharge ports
are located on the top and side of the cylinder head and are
labeled AIR OUT.
The various mounting and drive configurations required by
the numerous vehicle engine designs are accommodated
by different crankcase castings and crankshafts.
Two methods for cooling the BX-2150™ compressor are
employed. The cylinder head is water cooled using the
engine’s cooling system, while external fins on the crankcase
provide a means for efficient air cooling in that area.
All BX-2150™ compressors utilize the engine’s pressurized
oil system to lubricate internal moving parts.
A nameplate attached to the compressor crankcase identifies
the compressor model and is stamped to indicate the Bendix
part number and serial number.
compression of air is controlled by the compressor unloading
mechanism and the governor. The governor is generally
mounted on the compressor and maintains the brake system
air pressure between a preset maximum and minimum
pressure level.
INT AKE AND COMPRESSION OF AIR (LOADED)
During the down stroke of the piston, a slight vacuum is
created between the top of the piston and the head, causing
the flat circular inlet valve to move off its seat. (Note the flat
square discharge valve remains on its seat.) Atmospheric
air is drawn into the intake cavity and flows past the open
inlet valve and into the cylinder (See Figure 1). As the piston
begins its upward stroke, the air that was drawn into the
cylinder on the down strike is compressed . Air pressure on
the inlet valve plus the force of its spring, returns the inlet
valve to its seat. As the piston continues its upward stroke,
air is compressed and forces the discharge valve away from
its seat. Air flows past the open discharge valve into the
discharge line and on to the reservoirs. (See Figure 2)
As the piston reaches the top of its stroke and starts down,
the discharge valve spring and air pressure in the discharge
line returns the discharge valve to its seat. This prevents the
compressed air in the discharge line from returning to the
OPERATION
GENERAL
The compressor is driven by the vehicle engine and is
operating continuously while the engine is running. Actual
COMPRESSOR MOUNTING/DRIVE CONFIGURATIONS
2
UNLOADER
PISTON
INTAKE
INLET
VALVE
VIEW
FIGURE 1
VALVE
STOP
TO
RESERVOIR
DISCHARGE
VALVE
PISTON
INTAKE CYCLE
UNLOADER
PISTON
INLET
INLET
VALVE
FIGURE 2 - COMPRESSION/DISCHARGE CYCLE
VALVE
STOP
TO
RESERVOIR
DISCHARGE
VALVE
PISTON
cylinder bore as the intake and compression cycle is
repeated.
NON-COMPRESSION OF AIR (UNLOADED)
When air pressure in the reservoir reaches the cut-out setting
of the governor, the governor allows air to flow from the
reservoir into the unloader piston cavity .
The unloader piston moves, in response to air pressure and
drives the inlet valve away from its seat and holds it against
its stop.
With the inlet valve held away from its seat, air compression
is stopped and air is free to move back and forth past the
inlet valve in response to piston travel. System pressure will
eventually drop to the cut-in pressure setting of the governor
due to air usage. When the cut-in pressure is reached, the
governor responds by exhausting air from the unloader piston
cavity . Spring force moves the unloader piston away from
the inlet valve and compression is resumed as the inlet valve
returns to its seat.
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
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.
UNLOADER
PISTON
INLET
INLET
VALVE
FIGURE 3 - UNLOADED CYCLE
VALVE
STOP
TO
RESERVOIR
DISCHARGE
VALVE
PISTON
COMPRESSOR INST ALLA TION
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,
3
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 4A - SYSTEM DRAWING
®
DuraFlo™ 596
Compressor)
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.
Optional Bendix® PuraGuard® QC
™
Oil Coalescing Filter
Service Reservoir
(Supply Reservoir)
Reservoir Drain
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.
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.
HOLE
THREAD
FIGURE 4B - DISCHARGE LINE SAFETY VALVE
4
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.
LUBRICATION
All BX-2150™ compressors are connected to the engine’s
pressurized oil system and a continuous flow of oil is provided
to the compressor, which is eventually returned to the engine.
Oil is fed into the compressor in various ways, for example;
through the rear end cover or the drive end of the crankshaft.
An oil passage in the crankshaft conducts pressurized oil
to the precision sleeve main bearings and to the connecting
rod bearing.
®
The cylinder bore, connecting rod wrist pin bushing and ball
type main bearing, where used, are splash lubricated. Splash
lubrication is obtained as oil is forced out around the
crankshaft journals by engine oil pressure. See the tabulated
technical data in the back of this manual for specific
requirements.
COOLING
Air flowing through the engine compartment from the action
of the engine’s fan and the movement of the vehicle assists
in cooling the crankcase. Coolant flowing from the engine’s
cooling system through connecting lines enters the head
and passes through the head’s water jacket and back to the
engine. Proper cooling is important in maintaining discharge
air temperatures below the maximum 400°F recommended.
Figure 5 illustrates the various approved coolant flow
directions. See the tabulated technical data in the back of
this manual for specific requirements.
PLUG
IN
OLD STYLE HEAD
ADAPTER REQUIRED
GASKET 243430
INLET ADAPTER 297871
INLET CHECK
VALVE KIT 104670
FAILURE TO INSTALL ADAPTER 297871
WHEN USING AN INLET CHECK VALVE
WITH THIS STYLE HEAD... WILL
RESULT IN COMPRESSOR DAMAGE
NEW STYLE HEAD
ADAPTER
NOT REQUIRED
IDENTIFY NEW HEAD BY NOTING
PRESENCE OF PLUGGED BOSS
HERE
OUT
PLUG
OUT
FIGURE 5 - WA TER CONNECTIONS/FLOW
PLUG
IN
OUT
IN
AIR INDUCTION
GENERAL
There are three methods of providing clean air to the BX-2150
compressor;
1. Naturally aspirated Local Air Strainer - Compressor
utilizes its own attached air strainer (polyurethane sponge
or pleated paper dry element).
2. Naturally aspirated Engine Air Cleaner - Compressor inlet
is connected to the engine air cleaner or the vacuum
side (engine air cleaner) of the supercharger or
turbocharger.
3. Pressurized induction - Compressor inlet is connected
to the pressure side of the supercharger or turbocharger.
See the tabulated technical data in the back of this manual
for specific requirements for numbers 2 and 3 above.
INLET CHECK VALVE KIT 104670
FIGURE 6
INLET CHECK VALVE
An inlet check valve is used on some naturally aspirated
BX-2150™ compressors (never with pressurized induction,
see #3 above) to prevent inlet oil misting during the unloaded
cycle.
The new style BX-2150™ compressor head (See Figure 6)
can be identified by the plugged boss on the upper right
hand side. This head only requires kit 104670 to install an
inlet check valve. All other old style BX-2150™ compressor
heads (See Figure 6) require the use of the inlet adapter
™
297871 and inlet gasket 243430 in addition to the kit 104670.
WARNING!
FAILURE TO INSTALL ADAPTER 297871 WHEN
REQUIRED WILL RESUL T IN COMPRESSOR DAMAGE.
The inlet check valve consists of three parts, the inlet gasket,
the inlet check valve reed and the inlet check valve seat
(See Figure 6) during the compression cycle, the inlet check
valve reed is drawn away from its seat uncovering three inlet
holes which allows air to flow into the compressor inlet cavity .
A machined stop in the cylinder head inlet cavity or in the
inlet adapter 297871 limits the travel of the inlet check valve
reed. In the unloaded cycle, the inlet check valve reed rests
on its seat covering the three inlet holes. Air from within the
compressor is prevented from exiting the inlet cavity .
5
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