BENDIX BW5057 User Manual
DRIVING SAFER
DOESN’T HAPPEN BY ACCIDENT.
Our nation’s roadways are increasingly busy, and the need has
never been greater for solutions to help commercial vehicle
drivers respond to the situations they encounter every
day – especially in today’s CSA (Compliance, Safety,
Accountability) environment. Bendix is leading the way
to improved highway safety with an ever-increasing
portfolio of road-tested, advanced commercial
vehicle technologies that are affordable
and effective.
We offer robust active and supportive safety
technologies that help fleets:
» improve stability
» reduce collisions
» increase stopping power
» strengthen driver performance
with actionable data
Our solutions are driving
in a new era of safety.
Learn more.
Call 1.800.247.2725 or visit bendix.com today. Follow us on Twitter @Bendix_CVS.
©Bendix Commercial Vehicle Systems LLC, a member of the Knorr-Bremse Group. All Rights Reserved. 06/12
The Air Brake Handbook
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
1
Device Index
Alphabetic Device Index
AutoVue® by Bendix CVS
Lane Departure Warning (LDW) System . . . . . 50
Bendix® A-18™ Controller Assy . . . . . . . . . . . . . . 44
Bendix® ACom® Diagnostic Software . . . . . . . . . . . 48
Bendix® Brand Actuators. . . . . . . . . . . . . . . . . . 20
Bendix® AD-2®, AD-9®, AD-9si™, AD-IP® Air Dryers . . . . 13
Bendix® AD-IS® Air Dryer Module . . . . . . . . . . . . . 13
Bendix® AD-SP® Air Dryer . . . . . . . . . . . . . . . . . 15
Bendix® AF-3™ In-line Air Filter. . . . . . . . . . . . . . . 15
Bendix® Brand Air Disc Brakes . . . . . . . . . . . . . . 23
Bendix® ASA-5® Automatic Slack Adjuster . . . . . . . . 24
Bendix® BA-921®, BA-922® Air Compressors . . . . . . 10-11
Bendix® BASIC™ Test Kit . . . . . . . . . . . . . . . . . . .11
Bendix® BP-R1® Bobtail Proportioning Relay Valve . . . . 26
Bendix® BVA-85™ Brake Valve Actuator . . . . . . . . . . 30
Bendix® BX-2150™ Air Compressor . . . . . . . . . . . . 10
Bendix® Converter Dolly Brakes . . . . . . . . . . . . . . 36
Bendix® Cyclone DuraDrain® Trailer Water Separator . . . 15
Bendix® D-2® Governor . . . . . . . . . . . . . . . . . . 12
Bendix® DC-4® Double Check Valve. . . . . . . . . . . . 17
Bendix® Dryer Reservoir Module . . . . . . . . . . . . . 14
Bendix® DS-2™ Double Check Valve & Stop Light Switch . 17
Bendix® DuraFlo 596™ Air Compressor . . . . . . . . . 10-11
Bendix® E-10™, E-10P™ Brake Valve . . . . . . . . . . . 19
Bendix® E-10PR™ Retarder Control Brake Valve . . . . . 19
Bendix® E-6® , E-7™, E-8P® Brake Valves . . . . . . . . . 19
Bendix® EC-30™, EC-60™ ABS/ATC Controller . . . . . . 39
Bendix® ESP® Functionality . . . . . . . . . . . . . . . . 41
Bendix® EverFlow® Module . . . . . . . . . . . . . . . . 14
Bendix® Inlet Check Valve . . . . . . . . . . . . . . . . . 12
Bendix® Inlet Regulating Valve. . . . . . . . . . . . . . . 12
Bendix® LP-3™ Low Pressure Indicator . . . . . . . . . . 16
Bendix® LQ-4™ Ratio Valve, LQ-2™, LQ-5™ Limiting Valves 25
Bendix® M-32™ and M-32QR™ Modulators. . . . . . . . . 38
Bendix® MV-3® Dash Control Module . . . . . . . . . . . 32
Bendix® PP-1® and PP-3™ Valves . . . . . . . . . . . . . 27
Bendix® PP-5™ Push-Pull Control Valve . . . . . . . . . . 30
Bendix® PP-7™, PP-8™ Control Valves . . . . . . . . . . . 27
Bendix® PP-DC® Park Control Valve . . . . . . . . . . . 31
Bendix® PR-2™, PR-4™ Pressure Protection Valves . . . . 17
Bendix® PR-3™ Reservoir Control Valve . . . . . . . . . . 37
Bendix® PuraGuard® QC™ Oil Coalescing Filter . . . . . . 15
Bendix® QR-1®, QR-1C® , QR-L™, QRN™
Quick Release Valves . . . . . . . . . . . . . . . 25
Bendix® R-12DC® Relay Valve . . . . . . . . . . . . . . 26
Bendix® R-12P™ Relay Valve . . . . . . . . . . . . . .26-36
Bendix® R-12®, R-14®, R-6™ Relay Valves . . . . . . . . . 26
Bendix® R-7™ Modulating Valve . . . . . . . . . . . . . . 25
Bendix® R-8P™ Relay Valve . . . . . . . . . . . . . . . . 26
Bendix® RD-3™ Control Valve . . . . . . . . . . . . . . . 30
Bendix® RDU™ (Remote Diagnostic Unit) . . . . . . . . . 47
Bendix® RE-6NC™ Relay Emergency Valve . . . . . . . . 37
Bendix® Reservoirs . . . . . . . . . . . . . . . . . . . . 16
Bendix® RV-1™, RV-3™ Pressure Reducing Valve . . . . . 17
Bendix® Foundation Drum Brakes . . . . . . . . . . . . . 22
Bendix® SC-3™Single Check Valve . . . . . . . . . . . . 16
Bendix® SC-PR™ Valve . . . . . . . . . . . . . . . . . . 15
Bendix® SL-4™ and SL-5™ Stop Lamp Switches . . . . . . 29
Bendix® Spring Brake Actuators . . . . . . . . . . . . . . 20
Bendix® SR-2™, SR-4™, SR-5™ Spring Brake Valve . . . . 34
Bendix® SRC-7000™ Trailer Spring Brake Valve . . . . . 34-35
Bendix® ST-1™, ST-3™ and ST-4™, Safety Valves . . . . . 16
Bendix® SV-1™ Synchro Valve . . . . . . . . . . . . . . . 30
Bendix® SV-4™ Synchro Valve . . . . . . . . . . . . . 30, 36
Bendix® System-Guard® Trailer Air Dryer . . . . . . . 15, 61
Bendix® TABS-6, TABS-6 Advanced Trailer ABS . . . . . 45
Bendix® TABS-6 Advanced MC Trailer ABS . . . . . . . . 46
Bendix® TC-2™, TC-6™, TCS-9000™ Trailer Control Valves 32
Bendix® TE-1™ Trailer Emergency Stop Light . . . . . . . 35
Bendix® TP-3®, TP-3DC™,
TP-5™ Tractor Protection Valves . . . . . . . . . 33
Bendix® TR-3™ Valve. . . . . . . . . . . . . . . . . . . . 30
Bendix® Trailer Control (TC) Valves . . . . . . . . . . . . 32
Bendix® TRDU™ (Trailer Remote Diagnostic Unit) . . . . . 47
Bendix® Tu-Flo® 400, 500, 501, 550, 700,
and 750 Air Compressors . . . . . . . . . . . . 10-11
Bendix® TW-1™, TW-2™, TW-3™ Control Valves . . . . . . 29
Bendix® TW-11™, TW-12™ Valve . . . . . . . . . . . . . . 29
Bendix® Versajust®. . . . . . . . . . . . . . . . . . . . . 24
Bendix® Wingman® Advanced . . . . . . . . . . . . . . . 49
Bendix® WS-24™ Wheel Speed Sensors . . . . . . . . . 38
Bendix® Yaw Stability . . . . . . . . . . . . . . . . . . . 41
SmarTire® Tire Pressure Monitoring System (TPMS)
by Bendix CVS . . . . . . . . . . . . . . . . . . 50
Bendix Commercial Vehicle Systems LLC and Bendix Spicer Foundation Brake LLC now provide both on-line and
in-person Bendix Brake Training Schools.
• The Bendix On-line Brake School is your complete resource for web-based technical training. Keep your skills
sharp with a comprehensive menu of ever-evolving instructional videos and interactive modules.
• The In-Person Bendix Brake Training School is conducted by the veteran ASE-certifi ed Bendix team, this allinclusive course of classroom lectures is available at locations around the country.
• To enroll, visit www.bendix.com, click on the "Services & Support" tab, select "Brake School" from the menu on the
left side of the page, and then choose the type of school you wish to participate in.
2
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
Handbook Section Index
How to use the Air Brake Handbook
This twelve-section handbook provides an introduction to the use and operation of Bendix air brake systems and
devices.
Components are introduced and shown with typical system diagrams to depict where they are used. As new components
are introduced and their function explained, they gradually build up to a complete functioning air brake system refl ected
in the schematics at the close of this handbook.
Partial system-drawings, displayed throughout the manual, assist in explaining the use of the components. See section
12 for examples of vehicle system schematics.
Contents
Air Brake Handbook Section Page No.
Index and Precautions
Device Index 2
Handbook Section Index 3
General Precautions 4
Glossary 72-76
Section 1: Introduction
An Introduction 6-7
Section 2: The Charging, Air Treatment and Storage System
The Charging, Air Treatment and Storage System 8
Compressors 9-11
Governors, Etc. 12
Air Dryers 13-15
Reservoirs, Etc. 16
Misc. Components 17
Section 3: The Control System
The Control System: Dual Circuit Brake Valves 19
Actuators 20
Foundation Brakes: Drum Brakes (aka S-Cam) 21
Foundation Drum Brakes 22
Air Disc Brakes 23
Slack Adjusters 24
Quick Release, Ratio & Modulating Valves 25
Relay Valves 26
Push-Pull Control Valves 27
Spring Brake Valves 28
Lever-Operated Control Valves 29
Additional Control Valves 30
DIN symbols are used in this handbook.
Air Brake Handbook Section Page No.
Section 4: Tractor Parking, Trailer Charging/ Parking and
Emergency Systems
Tractor/Trailer Parking and Emergency Systems 31
Park Control Valves 31
Dash Control Valves 32
Tractor Protection Valves 33
Trailer Spring Brake Valves 34-35
Section 5: Convertor Dolly Brakes
Trailer/Converter Dolly Brakes 36-37
Section 6: Antilock Braking System
Antilock Braking Systems: Components 38
Truck and Tractor ABS Operation; ATC 39-40
Advanced ABS 41
Advanced ABS Operation and Features 42-43
Trailer ABS Components and Operation 44
PLC, Troubleshooting 45
Advanced Trailer ABS Operation and Features 46
Troubleshooting ABS 47-48
Section 7: Additional Systems and Components
Additional Systems and Components 49-50
Section 8: The Fundamentals of Air Braking
Air Brake System Fundamentals 51-62
Section 9: Air Brake System Troubleshooting Test
Air Brake System Troubleshooting Tests 63-68
Section 10: Bendix Literature and Contact Information
Downloading and Ordering Literature 69-70
Contacting Bendix 69
Section 11: About Bendix
About Bendix Commercial Vehicle Systems LLC 71
Section 12: Typical Air Brake System Schematics
Examples of Air Brake System Schematics 81-89
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
3
General Precautions
The systems presented in this manual are intended for illustrative purposes
only and are not intended to be used for actual vehicle piping.
Air Brake System General Precautions
WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS
When working on or around a vehicle, the following guidelines should be observed AT ALL TIMES:
▲ Park the vehicle on a level surface, apply the
parking brakes and always block the wheels.
Always wear personal protection equipment.
▲ Stop the engine and remove the ignition key
when working under or around the vehicle.
When working in the engine compartment,
the engine should be shut off and the ignition
key should be removed. Where circumstances
re qu ire th at t he eng ine b e i n op er ati on , EXTR EM E
CAUTION should be used to prevent personal
injury resulting from contact with moving,
rotating, leaking, heated or electrically-charged
components.
▲ 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 per taining to use of those
tools.
▲ If the work is being performed on the vehicle’s
air brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure
from all reservoirs before beginning ANY work
on the vehicle. If the vehicle is equipped with a
®
Bendix
AD-IS® air dryer system, a Bendix® DRM™
dryer reser voir module, or a Bendix
dryer, be sure to drain the purge reservoir.
▲ Following the vehicle manufacturer’s
recommended procedures, deactivate the
el ec tric al sys tem i n a m an ner th at s af ely remo ves
all electrical power from the vehicle.
▲ You should consult the vehicle manufacturer's operating and service manuals, and any related literature,
in conjunction with the Guidelines above.
IMPORTANT
GENERAL SAFETY GUIDELINES
TO AVOID PERSONAL INJURY OR DEATH:
▲ Never exceed manufacturer’s recommended
pressures.
▲ 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.
▲ Use only genuine Bendix
parts, components and kits. Replacement
hardware, tubing, hose, fi ttings, etc. must be of
equivalent size, type and strength as original
equipment and be designed specifi cally for such
applications and systems.
▲ Components with stripped threads or damaged
parts should be replaced rather than repaired.
Do not attempt repairs requiring machining or
welding unless specifi cally stated and approved
by the vehicle and component manufacturer.
▲ Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
▲ For vehicles with Automatic Traction Control
(ATC), the ATC function must be disabled (ATC
indicator lamp should be ON) prior to performing
any vehicle maintenance where one or more
®
AD-9si™ air
wheels on a drive axle are lifted off the ground
and moving.
▲ The power MUST be temporarily disconnected
from the radar sensor whenever any tests USING
A DYNAMOMETER are conducted on a Bendix
Wingman® Advanced™-equipped vehicle.
®
brand replacement
®
4
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
:KHQ<RX:DQW,W:KHUH<RX1HHG,WZZZEUDNHVFKRROFRP
The Bendix Online Brake School is your complete resource for web-based technical
training, straight from the experts. Keep your skills sharp with a comprehensive menu
of ever-evolving instructional videos and interactive modules.
Home to e-training on a full range of Bendix products and industry hot topics,
www.brake-school.com offers courses on:
• Air Dryers and Compressors
• Valves
• Disc and Drum Brakes
• Vehicle Stability
• Electronics
• Air Brake System training and more!
Visit www.brake-school.com, register for your secure account and take
the course(s) that you need. Each course is accompanied by a brief quiz
to test your knowledge.
Put yourself to the test. Bendix
Online Brake School... where
you need it, when you
need it, and on the topics
that matter most to
advancing your skill set.
BW2948 © 2013 Bendix Commercial Vehicle Systems LLC, a member of the Knorr-Bremse Group • 03/13 • All Rights Reserved
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
5
Introduction
Section 1: An Introduction
Air Supply
The vehicle’s compressor takes in fi ltered air — either at
atmospheric pressure from the outside or already at an
increased pressure from an engine turbocharger — and
compresses it. The compressed air is delivered to the air
dryer where water and a small amount of oil is removed.
The air then travels into the air reservoirs (“air tanks”). It
is typically delivered to a rear brake system reservoir and
a front brake system reservoir, as well as any attached
trailer reservoirs. For each system, the air pressurizes
the reservoir and the air hoses all the way to the next
control valve, where the air pressure remains, ready to
use.
A vehicle may use compressed air for many tasks. Some
examples are: to provide force for braking, to deliver air
to a particular component, to off-load bulk goods, etc.
Normal Braking
When the driver applies the foot brake, a plunger within
the foot brake valve moves, opening channels within the
valve that allow the air pressure waiting there to pass
through and be delivered to the rear and front brake
systems. The pressure quickly increases in the brake
chambers and applies force to the push rod, transferring
the force to the air disc brake (or via a slack adjuster, to
a foundation drum brake). (See page 21 for more about
foundation brakes, and government-mandated stopping
distances.) Frictional forces slow the wheels and the
vehicle comes to a stop. When the brakes are released,
the air in the brake chambers is quickly released, enabling
the vehicle to drive away.
Vehicle Parking
Vehicles are parked using powerful springs, which are
part of the spring brake assembly, to engage the brakes
and hold the vehicle in position. When the driver prepares
to move away and releases the parking brake, the spring
force is countered by the introduction of air pressure.
An anti-compounding valve in the system design helps
prevent the application of both the spring and service
brakes together.
Emergency Braking
In emergency situations where system air pressure is
reduced or lost, government regulations require vehicles
to meet specifi ed stopping distances. As an example,
some straight truck system designs use modulated
parking-brake applications to bring the vehicle to a stop.
Electronically-Controlled Braking
The following systems enhance the air brake system by
adding electronic sensors and controllers to modify the
vehicle’s braking characteristics.
• Antilock Braking Systems (ABS)
Most commercial vehicles use electronic Antilock
Braking Systems (ABS) to help improve braking
when excessive wheel slip, or wheel lock-up, is
detected. Bendix® Electronic Control Units (ECUs)
use patented technology to monitor wheel speeds
(on all wheels equipped with speed sensors) and use
ABS modulator valves to adjust, or pulse, the braking
force being applied. These valves operate multiple
times per second during an ABS event. ABS typically
improves stability and steerability, and also helps
reduce stopping distances on most surfaces.
I n ad dit i on t o th e AB S fe a tur e s ab ove, s o me a dvan c ed
ECUs have a drag torque control feature which helps
reduce drive-axle wheel slip (due to driveline inertia)
by communicating with the engine’s controller and
increasing the engine torque.
Automatic Traction Control
In addition to the ABS function, many Bendix ECU
models provide an Automatic Traction Control (ATC)
feature which can help improve vehicle stability and
traction during vehicle acceleration at low speeds.
• Hill Start Feature
For vehicles with the optional Bendix hill start feature
(often referred to as Hill Start Assist/Assistance or
HSA), the system interfaces between the transmission
and the braking system to help the driver prevent the
vehicle from rolling downhill when moving up a steep
incline from a stationary position.
6
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
Introduction, continued
Electronically-Controlled Braking (continued)
• Bendix® Electronic Stability Program/
Full Stability Program
The ESP®* functionality of the Bendix advanced ABS
system responds to a wide range of low- to highfriction surface scenarios including rollover, jackknife
and loss-of-control. It is the recommended system for
all power vehicles and especially critical for tractors
pulling trailers.
In the case of vehicle slide (over-steer or under-steer
situations), the system will reduce the throttle and
then brake one or more of the “four corners of vehicle”
(in addition to potentially braking the trailer), thus
applying a counter-force to better align the vehicle
with an appropriate path of travel.
In the case of a potential roll event, the system
reduces the throttle and quickly applies the brakes to
slow the vehicle combination below the threshold.
Bendix® Wingman® Advanced™ — A Collision
Mitigation Technology
The Bendix® Wingman® Advanced™ system — which uses
a radar sensor mounted on the front of the vehicle — is an
integrated combination of three features: adaptive cruise
control with braking; alerts (several different types); and
collision mitigation technology.
The adaptive cruise control with braking feature is an
additional upgrade of ordinary cruise control. When
using cruise control, the Wingman Advanced system will
maintain the set vehicle speed, and will also intervene, as
needed, to help maintain a set following distance behind
a detected forward vehicle.
The Bendix Wingman Advanced system also assists by
giving audible and visual alerts, whether or not cruise
control is on.
The collision mitigation technology feature is designed to
be ready to react to the presence of moving vehicles in
front of the vehicle (whether or not cruise control is set).
AutoVue® Lane Departure Warning (LDW) by
Bendix CVS
The AutoVue® Lane Departure Warning (LDW) system
detects when a vehicle drifts across a lane marking. When
this occurs and the turn signal is not activated, the unit
automatically emits a distinctive “rumble strip” or other
warning (using speakers or – if a non-audible warning is
preferred – a vibrating seat), alerting the driver to make
a correction.
The AutoVue LDW system utilizes a camera with a
60-degree fi eld of view that tracks visible lane markings,
including both solid and dashed shoulder lines,
centerlines, and lines between lanes – even if they are
heavily faded. It works effectively both day and night
and in most weather conditions, like rain or fog, where
visibility is limited. Even in snowy conditions, if the driver
can see the lane markings, the AutoVue LDW system
can as well.
SmarTire® Tire Pressure Monitoring System (TPMS)
by Bendix CVS
Bendix offers a wireless approach to tire pressure
monitoring. Using a sensor/transmitter mounted
securely inside each tire, a wireless receiver and a dashmounted display, the SmartWave® TPMS system actively
measures the air pressure and temperature within the
tires. T h i s infor m a t ion is t h en s ent wire l e ssly to a r e c eiver
mounted on the vehicle, or a hand-held display, and
alerts the driver of a loss of air pressure or dangerously
high tire temperature.
Driving Vehicles Equipped with Bendix® Advanced Technologies
The driver is always responsible for the control and safe operation of the
vehicle at all times. Even with Bendix® advanced technologies such as the
Bendix® ESP® stability system and Bendix® Wingman® Advanced™, the need
for a skilled, alert professional driver, reacting appropriately and in a timely
manner, and using safe driving practices, remains the most important factor in
road safety.
*ESP is a registered trademark of Daimler and is used by BCVS under license.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
7
The Charging, Air Treatment and Storage System
Section 2: The Charging, Air Treatment and Storage System
Traditional Air Charging System
Low Pressure
Indicator
Safety
Valve
Air Compressor
Air Dryer
Governor
Drain Valve
Purge
Valve
The charging, air treatment and storage system
consists of:
• An air compressor, to pressurize the system;
• A governor, to control when the compressor needs to
build, or stop building, air for the system and also to
control the air dryer purge cycle;
• An air dryer, to remove water and oil droplets from
the air;
• Reservoirs (or “air tanks”) to store air to be used for
vehicle braking, etc.;
To Front Axle To Rear Axle
Note: A three-
Check
Valves
Supply
Reservoir
Safety Valve
Primary
(Rear Axle)
Reservoir
reservoir system
is shown here. See
below for a system
using an integrated
air dryer/reservoir.
• Safety valves to protect against excessive pressure
in the system in the event that a charging system
component malfunction occurs (e.g. a line blockage);
• Single check valves to maintain a one-way fl ow of
air into the reservoirs. This arrangement protects the
contents from being drained in the event of an upstream
loss of pressure; and
• Low pressure indicators to alert the driver whenever
a reservoir has less than a pre-set amount of air
available.
Integrated Air Dryer/Reservoir System
Integrated Air Dryer Housing Also Includes:
Safety Valve; Check Valve; Purge Valve;
Delivery Check Valves
Governor
Safety
Valve
Air
Compressor
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
8
Purge
Reservoir
PuraGuard®
To Front Axle To Rear Axle
Secondary
(Front Axle)
Reservoir
Bendix
QC™ Filter
®
Primary
(Rear Axle)
Reservoir
To Vehicle Accessories
Sensitive to
Oil Carryover
To Vehicle
Accessories
The Charging, Air Treatment and Storage System: Compressors
Bendix Air Compressors
The air compressor is the source of energy for the air
brake system.
Usually driven 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 and lubricated by the engine oil supply. (Certain
models have self-lubricated and/or air-cooled versions
available.) Note: Air compressor shafts can rotate in
either direction.
The vehicle’s compressor draws in fi ltered air — either
naturally aspirated (at atmospheric pressure) from
the outside (or already at an increased pressure from
the engine turbocharger where permitted) — and
compresses it until system pressure is achieved.
To function, the brake system needs a supply of
compressed air within a preset maximum and minimum.
The governor (along with a synchro valve for certain
Bendix® air compressors) monitors the air pressure in
the supply reservoir and monitors when the compressor
needs to pump air into the air system (also known
as the “air build cycle” — where the compressor is
“running loaded”). When the system has suffi cient air,
the compressor can simply turn over without building
pressure (“running unloaded”). It also monitors when
the air pressure becomes greater than that of the preset
“cut-out”, the governor controls the unloader mechanism
of the compressor, stops the compressor from building
air and causes the air dryer to purge. As the service
reservoir air pressure drops to the “cut-in” setting of the
governor, the governor returns the compressor back to
building air and cycles the air dryer back to air drying
mode.
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 compressor lubricating oil)
as vapor.
The duty cycle is the ratio of time the compressor spends
building air, relative 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
(such as higher compressor head temperatures) that may
adversely affect air brake charging system performance.
These conditions may require additional maintenance
due to a higher amount of oil vapor droplets being passed
along into the air brake system. Factors that add to the duty
cycle are: air suspension, additional air accessories, use
of an undersized compressor, frequent stops, excessive
Air Dryer — Typically with
Safety
Valve
Compressor
Air Treatment System
Discharge Line
Air
Governor
a Bendix® PuraGuard® Oil
Coalescing Filter
Purge
Valve
Supply Reservoir
Safety
Valve
Drain Valve
leakage from fi ttings, connections, lines, chambers or
valves, etc. See page 11 for compressor maintenance
and usage guidelines. Use the Bendix
®
BASIC
™
test (p/n
5013711) where the amount of oil present in the air brake
system is suspected to be above normal.
The discharge line allows the air, water vapor and oil vapor
mixture to cool between the compressor and air dryer.
The typical size of a vehicle’s discharge line, (se e ta bl e
on page 10) assumes a compressor with a normal (less
than 25%) duty cycle, operating in a temperate climate.
See Bendix and/or the vehicle or air dryer manufacturer
guidelines as needed.
Air dryer inlet temperatures play a key role in air system
cleanliness and air dryer performance. 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 discharge line must maintain a constant slope
down from the compressor to the air dryer inlet fi tting
to avoid low points where ice may form and block the
fl ow. If, instead, ice blockages occur at the air dryer
inlet, insulation may be added here — or if the inlet fi tting
is a typical 90-degree fi tting — it may be changed to a
straight, or 45-degree fi tting, to prevent moisture build-
up and freezing. For more information on how to help
prevent discharge line freeze-ups , see Bendix Bulletins
TCH-008-021 and TCH-008-022. Conversely, shorter
discharge line lengths (or insulation) may be required in
extreme cold climates to maintain proper dryer operation.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
9
The Charging, Air Treatment and Storage System: Compressors
Bendix® Single-
Cylinder Compressors
BA-921® Air
Compressor
BX-2150
Air Compressor
™
Bendix® Two-Cylinder
Compressors
Tu- Flo® 700 Air
Compressor
Tu -F lo® 550 Air
Compressor
or Tu -F lo® 750 Air
Compressor
(exterior view is
the same.)
Tu- Flo® 501 Air
Compressor
BA-922® Air Compressor (shown)
or DuraFlo 596™ Air Compressor
(exterior view is very similar.)
Tu- Flo® 500 Air
Compressor
Tu- Flo® 400 Air
Compressor
Bendix® Four-Cylinder CompressorsCompressor Comparison by Displacement
Displacement CFM
at 1250 RPM
Tu-Flo® 400 Compressor 7.25 2 Both Both Y
™
BX-2150
Tu-Flo
Tu-Flo
Tu-Flo
Tu-Flo
BA-921
Tu-Flo
Tu-Flo
DuraFlo
BA-922
Tu-Flo
Compressor 9.5 1 Eng. Water Y**
®
500 Compressor 12 2 Eng. Water Y
®
501 Compressor 12 2 Both Both Y
®
550 Compressor 13.2 2 Eng. Water Y
®
700 Compressor 15.5 2 Eng. Water Y
®
Compressor 15.8 1 Eng. Water Y**
®
750 Compressor 16.5 2 Eng. Water Y
®
1000 Compressor* 24 4 Both Both Y
596™ Compressor 27 2 Eng. Water N
®
Compressor 31.6 2 Eng. Water N
®
1400 Compressor* 32 4 Eng. Water Y
*Special use (e.g. Tank trailer pump-off)
***Uses an Inlet Regulating Valve
lubricated available?
Is Engine / self-
Is Water / air-
cooled available?
Cylinders
**Uses Inlet Check Valve
Turbo inlet option?
***
For compressor Service Data Sheet downloads, visit the document library on www.bendix.com.
To order paper copies, visit the Literature Center at the same site.
Tu- Flo® 1000 Air
Compressor
®
1400 Air
Tu- Flo
Compressor
10
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
The Charging, Air Treatment and Storage System: Compressors
2
Discharge Line
Length
1
Air Compressor
Spec’d
4
Air Dryer
Maintenance
Schedule
Reservoir
3
Draining
Low Air Use
e.g. Line haul single
trailer without air
suspension; air over
hydraulic brakes.
Compressor with less
than 15% duty cycle
(builds air pressure during 15% or
less of the engine r unning time.)
Maintenance Schedule and Usage Guidelines
Regularly scheduled maintenance is the single most important factor in
maintaining the air brake charging system.
Depending on the vehicle’s air use, the table below shows examples of
compressors spec’d, and typical discharge line lengths and maintenance
intervals. See your compressor and/or air dryer Service Data Sheet for
more information.
Very High
Air Use
e.g. City transit
bus, refuse, bulk
unloaders, low boys,
urban region coach,
central tire infl ation.
Compressor with up
to 25% duty cycle
Medium
Air Use
e.g. Line haul
single trailer with
air suspension, RV,
school bus.
Compressor with less
than 25% duty cycle
(builds air pressure during 25% or
less of the engine r unning time.)
High Air Use
e.g. Double/triple
trailer, open highway
coach, (most) pick-up &
delivery, yard or terminal
jockey, off-highway,
construction, loggers,
concrete mixer, dump
truck, fi re truck.
Compressor with up
to 25% duty cycle
(5 or less axles) (5 or less axles) (8 or less axles) (12 or less axles)
Examples of Typical Compressors Spec’da :
1
Discharge line:
6 ft. @ ½ in. Inner Diameter
2
3
4
Passing
Concerns?
Use the BASIC
Tes t K i t :
Bendix P/N
5013711
a. Compressor and/or air dryer upgrades are recommended in cases
where duty cycle is greater than the normal range (for the examples
above). For certain vehicles/applications, where turbo-charged inlet
air is used, a smaller size compressor may be permissible.
b. To counter above normal temperatures at the air dryer inlet (and
resultant oil-vapor passing upstream in the air system), replace the
discharge line with either a larger diameter and/or longer length
line. This helps reduce the temperature of the discharged air. If
(oil carry-over control
suggested upgradeb: 9 ft.
Drain Reservoirs Every Month to 90 Days
Replace Air Dryer Cartridge Every 3 Years
Oil
Bendix® Tu-Flo® 550 air compressor
@ 5/8 in.)
BASIC Test acceptable range:
Bendix® BA-921® air compressor
Discharge line:
9 ft. @ ½ in. Inner Diameter
(oil carry-over control suggested
upgradeb: 12 ft. @ 5/8 in.)
c
≤ 3 oil units per month.
Bendix® Tu-Flo® 750 air compressor
Bendix® BA-922® air compressor
Bendix® DuraFlo 596
Discharge line:
12 ft. @ ½ in. Inner Diameter
(oil carry-over control suggested
upgradeb: 15 ft. @ 5/8 in.)
15 ft. @ 5/8 in. Inner Diameter
(oil carry-over control suggested
™
air compressor
Discharge line:
upgradeb: 15 ft. @ ¾ in.)
Drain Reservoirs Every Month
Replace Every 2 Years
c
Replace Every Year
c
BASIC Test acceptable range:
≤ 5 oil units per month.
suffi cient cooling occurs, the oil-vapor condenses and can be
removed by the air dryer. Discharge line upgrades are not covered
under warranty. Note: To help prevent discharge line freeze-ups,
shorter discharge line lengths, or insulation, may be required in cold
climates. See Bendix Bulletins TCH-008-021 and TCH-008-022,
for more information.
c. With increased air demand, the air dryer cartridge needs to be
replaced more often.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
11
The Charging, Air Treatment and Storage System: Governors, Etc.
Governors and Components
The Governor monitors the air pressure in the supply
reservoir and operates the compressor unloading
mechanism to control whether or not the compressor
builds air pressure.
The Bendix® D-2® governor is an adjustable pistontype valve. It is available preset to a choice of pressure
settings. Note: The pressure range between the cut-in
and cut-out pressure is designed into the governor and
is not adjustable. The D-2 governor may be directmounted to the compressor or remote-mounted as
desired. Specialized governors are available for vehicles
needing a governor adapted to abnormally high or low
temperatures, as well as a “weatherproof” model. For
example:
• The Bendix® D-2A™ governor is a non-adjustable
version of the D-2® governor.
• The D-2®/SV-1™ governor module is a special com-
bination device used with the Bendix® DuraFlo 596™
air compressor to provide the fast-rising unloader signal needed by this compressor.
Safety Valves are used in an air brake system to protect
against excessive air pressure build-up and to sound
an audible alert. Safety valves are available in both
adjustable (e.g. the Bendix® ST-1™ valve) and nonadjustable (e.g. Bendix® ST-3™, and ST-4™ valve) styles,
in a variety of pressure settings, and for a variety of port
sizes. Maximum service system air pressure allowed by
government regulation is typically 150 psi. A variety of
safety valve settings are used at different points in the
charging and treatment system.
Specifi cally designed for use in compressors, ST-4
safety valves are installed — in an extra compressor
head discharge port, if available or in the discharge line
near the compressor — to prevent compressor damage
in the event of discharge line blockage.
Bendix®
™
D-2A
Governor
Bendix® ST-1™, ST-3™
and ST-4™ Safety Valves
Exhaust Port
Inlet Regulating
Valve
Inlet Check
Valves
Shown With
Breather Valve
Bendix
®
D-2®/SV-1™
Bendix
Governor Module
Installed
®
D-2
Governor
®
An Inlet Regulating Valve (or “IRV”) is typically used
on multi-cylinder compressors which receive their
input air supply from the pressurized side of the engine
turbocharger. The IRV, which is generally mounted to
the compressor inlet, is designed to regulate compressor
inlet pressure to 10 psi or less. The outlet fl ange of the
IRV can be mounted to all Bendix® Tu- Flo® compressors
except the Tu-Flo 300 compressor. The IRV may not be
used in conjunction with single cylinder compressors.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
12
Inlet Check Valves (or “ICV” valves) are used on naturally
aspirated compressors to prevent oil mist from entering
the inlet line during the unloaded cycle. The inlet check
valve either mounts to the intake side of the compressor
(and must be used in conjunction with an inlet valve stop
or inlet adapter), or may be mounted remotely.
Visit the Bendix website at www.bendix.com for more
information, including the Advanced Compressor
Troubleshooting Guide (BW1971) and compressor
Service Data sheets.
Integrated
Purge
Reservoir
Bendix
AD-IS®
Air Dryer
Governor
The Charging, Air Treatment and Storage System: Air Dryers
®
The Bendix
Medallion - Indicates the presence of a
PuraGuard Oil Coalescing Cartridge
®
PuraGuard® Graphics and
Bendix
®
Bendix
®
AD-IP
Air Dryer
Cartridge
Special Discharge Port
Fitting with Feedback Line
Connection
®
AD-IS®
Air Dryer
Module
Bendix®
AD-IP® DI Air
Dryer
(“Drop-in”
version)
Feedback
Line
Bendix®
AD-9
Air Dryer
Bendix®
AD-9si
Air Dryer
®
™
AD-2®Air Dryer
Air Dryer
Cartridge
Bendix
Bendix®
®
AD-9
®
Air Dryers
The air dryer is an in-line fi ltration system that removes
both water vapor and oil droplets from the compressor
discharge air after it leaves the compressor. This results
in cleaner, drier air being supplied to the air brake system,
and aids in the prevention of air line and component
freeze-ups in winter weather.
As the air passes into the air dryer, most of the oil droplets
are removed by the oil separator. The air then moves
through the desiccant material which removes most of
the water vapor before the compressed air is passed to
the air brake service (supply) reservoir. The oil droplets,
and the water collected, are automatically purged at the
dryer when the governor reaches its “cut-out” setting.
For vehicles with accessories that are sensitive to small
amounts of oil, Bendix® PuraGuard® oil coalescing
air dryers are used. Similar in appearance to standard
air dryers (with different graphics and an added center
medallion symbol), PuraGuard oil coalescing air dryer
cartridges contain a coalescing media at the inlet of the
desiccant bed that provides a high level of oil removal.
clean dry air
Air passes through the oil separator
and then the desiccant material.
Important! When servicing, note that standard
Bendix® brand air dryers or air dryer cartridges may
be serviced with Bendix PuraGuard oil coalescing
air dryers or cartridges, however, Bendix PuraGuard
oil coalescing air dryers or cartridges must only be
serviced with like replacements.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
13
The Charging, Air Treatment and Storage System: Air Dryers
Purge Cycles, Purge Volume
When the air pressure in the supply air tank reaches the
required level, the governor makes the compressor stop
building air and allows the air dryer’s “purge cycle” to
begin. During the purge cycle, the desiccant material is
regenerated (its ability to remove water is renewed) by a
reversal of the saturation process. A small amount of dry
air passes back through the desiccant material and the
water that has been collected, as well as any oil droplets
collected by the oil separator, are purged out through the
base of the dryer. It is normal to see a small amount of
oil around the purge valve.
The Bendix® AD-2®, AD-9®, AD-9si™, and AD-IP® air
dryers are designed with an internal storage (“purge
volume”) of dry air for the purge cycle.
“Extended Purge” air dryers — such as the Bendix
AD-IP EP air dryer — are designed with an extra amount
of air storage internally that is used to assist in the purge
cycle.
Air dryer end covers are typically equipped with an integral
(12- or 24-volt) heating element for winter operation.
Integrated Air Dryer Modules
Technology advances in the charging, treatment and
storage, have resulted in the availability of integrated air
supply systems.
For example, the Bendix® Dryer Reservoir Module —
featuring the Bendix® AD-IS® (Integrated Solution) air
dryer — provides heavy vehicles with integrated purge
and supply reservoirs, an air dryer, governor and a
number of the charging valve components, including four
pressure protection valves.
®
Bendix® EverFlow® Modules
Bendix® EverFlow® air dryer modules are used for air
dryer systems where a vehicle needs a continuous fl ow
of air, such as for bulk unloaders and central tire infl ation.
As stated earlier, air dryers need to initiate a purge cycle
periodically to refresh the moisture-removing desiccant
material. Bendix EverFlow air dryer modules have two
air dryers plumbed in parallel that take turns supplying
air, resulting in a continuous, uninterrupted supply.
Bendix
AD-IP® EverFlow
Bendix
EverFlow
Module
®
®
Bendix
AD-9® EverFlow
Air Dryer
Assembly
Air Dryer Assembly
Bendix
AD-IS® EverFlow
Air Dryer
Assembly
®
®
®
®
®
®
Bendix® AD-IS® Air Dryer
(This example features a Bendix®
PuraGuard® Oil Coalescing Cartridge)
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
14
Reservoir
Dryer
Reservoir
Module
The Charging, Air Treatment and Storage System: Air Dryers
Special Use Air Dryers
Several Bendix air dryers are available in specialized
“Drop-in” versions designed especially for air systems
that use either the Holset (Cummins) Type E, or QE,
air compressor. These Holset compressors use an
unloading system that requires that air pressure remain
in the discharge line during the entire unloaded cycle of
the compressor. For example, the Bendix® AD-IP® air
dryer “Drop-in” version is shown on page 13.
®
Bendix
®
Bendix
AD-SP® Air Dryer
(installation uses
SC-PR™ valve)
SC-PR™
Valve
Bendix® Cyclone
DuraDrain
Trailer Water
Separator
®
Bendix® AF-3
In-line Air Filter
Bendix®
PuraGuard® QC™
Oil Coalescing
Filter
™
Bendix
®
AD-SP® air dryers use a small amount of air
from the supply and front axle (secondary) reservoirs to
perform the purge function. Because of this difference,
the AD-SP air dryer is smaller and lighter than air dryers
that have their purge volume within the dryer canister.
A Bendix
®
SC-PR™ Single Check Protection Valve is
used in conjunction with the AD-SP air dryer. The SCPR single check protection valve is a combination of two
separate devices — a single check valve and a pressure
protection valve that allows limited fl ow in the opposite
direction. It helps to protect the air pressure in the front
axle service reservoir. This is because it will only allow
its air supply to be used to help purge the Bendix AD-SP
air dryer if the pressure is above a certain preset level.
Trailer Air Dryer Systems
The Bendix
®
Cyclone DuraDrain® trailer water
separator is installed in the trailer control and/or
supply lines near the gladhands. It self-purges liquid
contaminates, contains solid contaminants and improves
the life of the trailer system components.
The Bendix
®
AF-3™ in-line air fi lter screens out foreign
material from trailer air lines.
High Air-Use Vehicles
For high air-use vehicles — such as transit buses and
refuse trucks — the technology used in Bendix
Guard air dryers is also available by using Bendix®
PuraGuard® QC™ oil coalescing fi lters. Installed
downstream of the air dryer, these fi lters use a replaceable
fi lter element mounted within a sump housing to remove
oil aerosols before they can enter the air system. A drain
valve allows periodic maintenance.
®
System-
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
15
The Charging, Air Treatment and Storage System: Reservoirs, Etc.
Reservoirs, Etc.
Reservoirs (or “air tanks”) serve the air brake system
as a storage tank for compressed air. The reservoir size
is selected by the vehicle manufacturer to provide an
adequate amount of air for use by the braking system
and other control devices.
Bendix reservoirs are built in accordance with Society
of Automotive Engineers (SAE) specifi cations and
are available in a variety of sizes in both single and
double compartment design confi gurations. They are
certifi ed to comply with government regulations (such as
FMVSS 121).
Reservoir draining devices are installed in air brake
reservoirs, and allow liquid contaminants collected to be
drained off. Vehicles with Bendix® brand desiccant air
dryers should be drained every 30-90 days — See the
chart on page 10 for more information.
The presence of water may indicate that the air dryer
cartridge may need to be replaced. Other potential
sources of water in the reservoirs are: when shop air has
been used to fi ll the system, an excessive duty cycle (see
page 11), or excessive air leakage.
Vehic les wi thout air dryers are normally drained each
day.
Manual draining devices are drain cocks which require
manual operation at the point at which they are installed.
Drain cocks are available in a variety of styles and pipe
thread sizes. Always drain the contents slowly for the
best results.
Reservoirs are
available in many
confi gurations.
®
Bendix
™
SC-3
Single Check
Valves
Bendix
LP-3™ Low
Pressure
Indicator
Drain
Cock
®
Single Check Valves
In-line single check valves allow air fl ow in one direction
only. Several sizes and confi gurations are available to
accommodate a variety of piping arrangements. Single
check valves are used in air brake systems to prevent
loss of remaining system pressure if another reservoir, or
hose etc. — upstream in the system — fails.
For double check valves and pressure protection valves,
see the Miscellaneous Components section.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
16
Low Pressure Indicators
Low pressure indicators are pressure-operated electropneumatic switches. They are designed to complete
an electrical circuit and actuate a warning light and/
or buzzer to inform the driver in the event that the air
pressure in the service brake system is below a minimum
level for normal operation. Low pressure indicators are
not adjustable, but are available in a variety of pressure
settings.
The Charging, Air Treatment & Storage System: Misc. Components
Miscellaneous Components
A double check valve is used in the air system when a
single function or component must receive air from, or
be controlled by, the higher of two pressure sources. An
internal disc, or shuttle, moves in response to the higher
air pressure and allows the air source to fl ow out of the
delivery port. It is recommended that double check
valves are always mounted so that the shuttle (or disc)
operates horizontally.
While not strictly part of the charging system, in some
vehicle brake systems, the Bendix® DS-2™ double
check valve and stop light switch (shown on this page)
is used to detect air pressure from either brake circuit
source. It will operate the stop lamp switch, illuminating
the stop lamps.
Pressure Protection Valves
The Pressure Protection Valve is a normally-closed
pressure sensitive control valve. These valves can be
used in many different applications but are most often
used:
(a) To protect or isolate one reservoir from another, by
closing automatically at a pre-set pressure. Pressure
protection valves can be used to allow air to be “shared”
between two reservoirs above the closing setting of the
valve. The sharing ceases when pressure drops below
the closing pressure of the valve and the reservoirs are
then isolated from each other.
(b) To delay the fi lling of one, or more, auxiliary reservoirs
until a pre-set pressure is achieved in the primary, or
braking, reservoirs.
(c) To delay supplying auxiliary components and systems
(e.g. air actuated wipers, air suspension) until the
braking system reservoirs have reached a pre-defi ned
minimum pressure suffi cient for braking purposes. Once
the braking system has reached the pre-set minimum,
the pressure protection valves open to supply the
auxiliary systems.
The Bendix® PR-2™ pressure protection valve is
externally adjustable, while the Bendix® PR-4™ pressure
protection valve (shown) has a fi xe d s et tin g. Bo th va lve s
are available in a variety of factory pre-set pressure
settings. The Bendix® PR-3™ pressure protection
valve differs from the two valves previously mentioned
since its design includes a check valve preventing air
return. The Bendix® AD-IS® Integrated system air
dryers have a set of pressure protection valves internal
to the design.
RV-1
®
Pressure
Protection
Valve
Auxiliary
™
Bendix® DS-2
Double Check
Valve and Stop
Light Switch
®
PR-4
Bendix
Pressure
Protection Valve
Bendix® RV-3
™
™
™
Pressure
Reducing
Valve
Bendix® DC-4
Double Check
Bendix® PR-3
Pressure
Protection Valve
Bendix
Pressure
Reducing
Valve
™
®
Valve
Pressure Reducing Valves
Pressure reducing valves are used in a variety of
applications where a constant set air pressure (lower
than supply pressure) is required. A typical application is
an air-operated accessor y that requires less than system
pressure for operation. The Bendix® RV-1™ pressure
reducing valve (shown) is available in a wide range of
pressure settings and can be manually adjusted. The
Bendix® RV-3™ pressure reducing valve is available
only with factory pre-set pressure settings and cannot be
manually adjusted.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
17
The Control System: Dual Circuit Brake Valves
Section 3: The Control System
The control system typically consists of:
• A foot brake valve and, often, an additional hand-
operated trailer brake control valve;
• Brake actuators or rotochambers, to change the
applied air pressure into a push rod force which
operates the foundation brakes (air disc, foundation
drum brakes, etc.);
• Quick release valves to assist in releasing the brakes
quickly;
Tra i l e r B r a kes
May Also Use
a Bendix
QR-1® Valve
®
Secondary
Delivery to
Brake
Chamber
Modulator
Delivery to
Front Brakes
Primary
Delivery to
Tra i l e r B r a kes
Dual Circuit
Brake
Valve
• Vehicle parking using push-pull hand-operated
valves and spring brakes;
• An anti-compounding system design to prevent
both the service brakes and the parking brakes from
being applied at the same time; and
• Proportioning valves to adjust braking when a
tractor is not pulling a trailer.
Typical Foot Brake Application Delivery System
See the fi nal
section of this
handbook for more
sample system
schematics in color.
PRIMARY
SECONDARY
Primary Reservoir
Secondary Reservoir
18
Modulator
(See the ABS
section for
more about
modulators)
Brake
Chamber
Delivery to
Rear Brakes
Vehicle Maintenance
Optimal system braking requires a properly maintained air brake system, including:
• Low system air leakage, with a maintained air dryer, compressor and valve components
• Regularly maintained foundation brakes (drum, wide-drum, or air disc) which meet
appropriate safety standards and regulations
• A fully-functioning ABS system without any active ABS Diagnostic Trouble Codes (DTCs)
• Properly sized and infl ated tires, with a safe tread depth
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
Note: Brake valve
replacements are typically
supplied without the foot
pedal components. For
illustration, full assemblies
are shown here.
The Control System: Dual Circuit Brake Valves, continued
Bendix® E-7™
Bendix® E-8P®
Brake Valve
Brake Valve
®
Bendix® E-10P™
Brake Valve
®
Bendix
E-10™
Brake Valve
Bendix® E-6
Brake Valve
Dual Circuit Brake Valves
When the driver applies the service brakes using the
brake pedal/treadle, a two-part plunger within the brake
valve moves.
The moving parts close the valve’s exhaust and allow air
pressure from the primary and secondary reservoirs to
pass through and be delivered to the rear and front brake
systems. There, the pressure in the brake chambers
rises and applies force to the push rod, transferring the
fo r c e to the air di sc brake s o r foundation dr u m brakes (via
the slack adjuster). Frictional forces slow the wheels and
the vehicle comes to a stop. When the driver removes
all force from the brake valve, the internal plunger returns
to the original position and allows air in the valve, and
delivery lines, to vent to the atmosphere through the
exhaust port.
Bendix® E-10PR™
Brake Valve
The Bendix® E-6®, E-8P®, E-10™ and E-10P™ dual
circuit brake valves are typically fl oor-mounted and
treadle-operated, while the Bendix® E-7™ dual circuit
brake valve is a bulkhead-mounted, suspended pedal
valve.
Mostly used in the transit (bus/coach) industry, the
Bendix® E-10PR™ retarder control brake valve has
circuitry that is used to communicate with retarder
systems installed on automatic transmission vehicles extending the life of brake system components.
Hand-operated Brake Valves
For information on trailer contro l hand-operated valves,
see Section 4.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
19
The Control System: Actuators
Actuators
During service braking, actuators convert the air pressure
being produced by the driver pushing on the brake pedal
into a mechanical push rod force acting on the foundation
brakes. Air enters the actuator and pressurizes a chamber
containing a rubber diaphragm. The air pushes against
the diaphragm, pushing against the service return spring
and moving the push-plate (and push rod) forward. See
the Section 8 for information about the physics behind
how actuators work.
Brake chambers are available in many sizes, providing
a wide range of output forces and stroke lengths.
Different size brake chambers are identifi ed by numbers
which specify the effective area of the diaphragm. For
example, a “type 30” brake chamber has 30 square
inches of effective area.
Spring brake actuators are composed of separate air
and mechanical actuators in a single housing. Mounted
at the wheel of the axle it serves, they function as service,
parking and emergency brakes.
Service Brake
Chamber
(No Spring Brake)
Threaded Push Rod
The service chamber portion of a spring brake actuator
functions the same as described at the start of this
section.
The parking/emergency brake housing side of the spring
brake actuator contains a powerful spring that — when
engaged — holds a parked vehicle in position. When the
driver prepares to move away and releases the parking
brake, the spring force is countered by the introduction of
air pressure into a chamber within the spring brake portion
of the actuator.
A spring brake, therefore, contains two actuators which
use air pressure in opposite ways. The service actuator
requires air pressure to apply the brakes, while the park
(or emergency actuator) uses air pressure to release the
brakes.
In an emergency, the air pressure restraining the
powerful spring can be released and the spring brakes
can be used to help stop the vehicle. A feature — called
anti-compounding — helps to prevent the simultaneous
application of both the spring and service brakes.
Air Disc Brake Actuator
Welded Clevis
(uses ADB-style
push rod)
Bendix® NG-3™ Piston-Style
Spring Brake Chamber
Diaphragm
Dust Cap installed
(Spring brake components are not serviceable, and are shown here for informational purposes only.)
20
T-Bolt
Non-Pressure
Housing
Service Return
Spring
Service
Push Rod
Yok e
Release
Tool
Dust Cap
removed
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
Clamp
Band
Service
Chamber
Storage
Pocket
Service
Diaphragm
Parking/ Emergency
Brake Housing
Non-Serviceable
Section Permanently
Sealed
Non-Serviceable
Parking Diaphragm
Release Tool T-Bolt
(Used during brake
service to restrain the
power spring.)
Non-serviceable
Power Spring
The No Touch™
Power Spring shown
here — designed to
prevent spring corrosion
— is used in Bendix®
EverSure® Spring Brakes.
The Control System: Foundation Brakes
Foundation Brakes: Drum Brakes (aka S-Cam) and Air Disc Brakes
S-CAM FOUNDATION
DRUM BRAKE
Automatic
Slack Adjuster
CAM
Fric tion Material
Replacement Kit
Brake Chamber
Fric tion Material
Spider
Axle
Shoe
The foundation brake is the actual braking mechanism
located at each end of the axle that provides the primary
retardation for controlling vehicle speeds. It generally
consists of an air service and/or spring brake chamber,
AIR DISC BRAKE
Rotor
Brake Pads
Fric tion
Material
Replacement
Kit
a mechanical brake mechanism and friction material.
Two main types of foundation brakes are in use: S-Cam
foundation drum actuated brakes (traditional and newer
wide-brake versions) and Air Disc Brakes.
The Importance of High Performance Friction to Maintain Braking Performance and Safety
In August 2011, the National Highway Traffi c Safety Administration (NHTSA) mandated a 30 percent reduction
in stopping distance for new three-axle tractors with Gross Vehicle Weight Ratings (GVWRs) up to 59,600 lbs.
Reduced Stopping Distance (RS D) is meant to sig ni fi cantly improve safety, avoid highway fatalities, and reduce the
number of rear-end collisions . Phase two of the mandate (Aug. 1, 2013), adds tractors with two axles, as well as
severe service tractors with GVWRs above 59,600 lbs.
In the new RSD era, Bendix completed stopping-distance testing and analysis of RSD compliant brakes relined with
a range of aftermarket friction products.
Bendix compared the 60 mph stopping distance of an RSD-compliant vehicle equipped with high performance brakes
and linings against several pre-RSD OE brake linings. The RSD-compliant vehicle used Bendix® High Performa nce E S™
(Extended Service) Brakes. Bendix® brand High Performance Friction had a stopping distance of 215 feet, well under the
250-foot limit established by the federal mandate. None of the comparison friction used in the relining of the RSD brakes
met the stopping distance requirement. The worst-performing friction material, a popular aftermarket lining, had a stopping
distance of 311 feet, a 45 percent dec rease in per formance fr om the Bendix fric tion. The 96 - foot dif ference represents
approximately fi ve passenger car lengths.
Delivering lower fade and better thermal management, High Performance (HP) Friction from Bendix performs at high
heat better than any previous OE drum brake linings, resulting in signifi cantly shorter stopping distances.
For more information about Bendix High Performance Friction, visit www.foundationbrakes.com.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
21
The Control System: Foundation Drum Brakes
Foundation Drum Brakes
Brake
Block
S-Cam Foundation Drum Brake and
Examples of Friction Material
Brake Lining
In an S-Cam type foundation drum brake, the pneumatic
system is linked by an air line to the air service and/or
spring brake chamber, which is then connected to the
arm of a slack adjuster by a push rod and clevis. The
slack adjuster is installed on the spline of the forged brake
cam shaft. The slack adjuster acts as a lever, converting
the linear force of the chamber push rod into a torsional
force needed to apply the brakes.
When torque is applied to the cam shaft, the “S” shape on
one end of the cam spreads the brake shoes, forcing the
brake lining into contact with the brake drum, therefore
retarding and/or stopping the vehicle.
Foundation drum brakes (aka S-Cam) are offered in
a variety of drum diameters to meet vehicle braking
requirements, with the most common being the 16½
inch version. The cam brake has a “leading-trailing”
shoe design with one or more fi xed anchor points for the
shoes, opposite the cam end of the shoe.
The structure of the S-Cam-actuated brakes generally
consists of stamped steel brake shoes and spiders for
standard duty applications, and cast shoes and spiders
for heavy-duty applications.
Foundation Drum Brake Linings
When cam - actuated drum brakes are applied, the friction
material contacts the brake drum. The friction between
the lining and drum effectively converts the kinetic energy
of the vehicle into thermal energy, heating up the brake
drum and lining.
The friction material used in the brake must have the
capability of withstanding the heat until dissipated. It
takes the right combination of ingredients to provide all
the desirable characteristics: including a torque output
suffi cient to stop the vehicle, long lining life, long drum life
and noise reduction.
All friction material is identifi ed by stenciled codes on its
edge. These codes consist of the name or brand of the
manufacturer, the formula identifi cation, the specifi c part
number and usually two letters designating the lining’s
general friction level (examples: EF, FG). It should be
noted that these stenciled letters are not considered to
be accurate enough for choosing replacement linings.
To ensure proper braking, always use either genuine
original equipment linings, or an approved material with
direct performance comparison.
22
See the section on page 21 of this handbook for
more information about selecting fr iction materials
that meet the requirements of the Reduced Stopping
Distance (RSD) mandates.
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
Air Disc Brakes
The Control System: Air Disc Brakes
Rotor
Brake
Chamber
Bendix® Air Disc Brake
Bendix air disc brakes are a “fl oating caliper” design for
use as a foundation brake on all axles of heavy commercial
vehicles and trailers. In terms of performance and ease
of service, Bendix® air disc brakes compare favorably to
traditional foundation drum brakes. They are available
in models with or without a combination spring brake
chamber.
Bendix air disc brakes convert air pressure into braking
force. When the foot brake is applied, air from the vehicle
brake system enters the service brake chamber through
the supply port, applying pressure to the diaphragm. The
pressure pushes the diaphragm, moving the pressure
plate and push rod against a cup in the lever. The lever
pivots on an eccentric bearing and transfers motion to
the actuating beam. Moving against return spring force,
the actuating beam moves two threaded tubes and
Air Disc Brake
Cut-away View
Actuator
Rod
Lever
Supply Port
Brake Pad
Fric tion
Material
tappets, which force the inner brake pad into contact with
the brake rotor. Further movement of the actuating beam
forces the caliper — sliding on two stationary guide pins
— away from the rotor, which pulls the outer brake pad
into the rotor. The clamping action of the brake pads on
the rotor applies braking force to the wheel.
Releasing the foot brake releases pressure in the
service brake chamber. With no pressure in the service
brake chamber, return springs force the air disc brakes
into a neutral, non-braked position. The non-braked
position is mechanically controlled by a brake adjuster
mechanism in the caliper. The caliper contains a brake
adjuster mechanism that turns threaded tubes to set
a gap (running clearance) between the rotor and the
brake pads. When operated manually with the adjuster
shaft, the adjuster mechanism sets the system’s nonbraked position. The adjuster mechanism also operates
automatically, whenever the brakes are activated, to
compensate for rotor and brake pad wear and to keep
the running clearance constant.
The rotor-friction couple is carefully designed for optimal
performance and durability. It is recommended that only
approved replacement disc pads or rotors be used to
prevent damage to disc brake components (e.g. cracked
rotors) or premature or uneven pad wear, which can
adversely affect braking performance.
Outer
Brake Pad
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
Inner Brake
Pad
Rotor
Actuating
Beam
Eccentric
Bearing
23
The Control System: Slack Adjusters
Slack Adjusters
Slack adjusters are used on foundation drum brakes to
link the brake chamber or actuator and the camshaft. Its
arm is fastened to the push rod with a yoke and its spline
is installed on the foundation brake camshaft. The slack
adjuster transforms and multiplies the force developed
by the chamber into a torque which applies the brakes
via the brake camshaft.
To compensate for the gradual wear on the brake block
lining, automatic slack adjusters are equipped with an
adjusting mechanism. For many years now, the required
standard has been an automatically-adjusting design.
Slack adjuster models are designated by a number
which represents its maximum torque rating (e.g. a type
20 unit is rated for a maximum of 20,000 inch-pounds of
torque). Slack adjusters are available in a variety of arm
confi gurations, lengths and spline types.
The entire slack adjuster operates as a unit, rotating as a
lever with the brake cam shaft, as the brakes are applied
Bendix®
Versajust®
Federal
Regulations require
that commercial motor
vehicles manufactured
after October 20, 1994,
and equipped with air
brakes, have automatic
brake (slack) adjusters
and brake adjustment
indicators (push rod).
Yok e
®
Bendix
ASA-5®
Automatic Slack
Adjuster
Adjustment
Mechanism
Spline
Automatic Slack
Adjuster
or released. The most effi cient braking action is obtained
when the slack adjuster arm travel is approximately
90-degrees and in the recommended range of the
chamber. All Bendix® slack adjusters incorporate a
grease fi tting and/or a tapped hole for a lube fi tting.
Automatic Slack Adjusters
Automatic slack adjusters automatically adjust for lining
wear. Bendix brand automatic slack adjusters monitor the
brake-lining-to-brake-drum-clearance, thus eliminating
the possibility of over-adjustment.
The automatic slack adjuster does not require periodic
manual adjustment; however, the unit does provide for
manual adjustment for use in the initial installation and
brake relining.
Important: Extract from Bendix® Technical Bulletin
Bulletin No: TCH-005-014
Subject: Automatic Slack Adjusters Not For Manual
Adjustment
The automatic slack adjuster is not des igned to function
as a manual adjuster once it is unable to maintain
adjustment automatically.
Automatic slack adjusters should not be manually
adjusted in an effort to correct excessive push rod stroke,
because this condition indicates that a problem exists
with the automatic adjuster, with the installation of the
adjuster, or with related foundation brake components,
which manual adjustment will not fi x.
WARNING: The manual adjustment of automatic slack
adjusters is a dangerous practice that could have serious
consequences, becaus e it can give the operator a false
sense of security ab out the effectiveness of the brakes,
which are likely to go out of adjustment again s oon. Do
not make manual adjustments of an automatic slack
adjuster once it can no longer automatically adjust the
brakes. Manual adjustment DOES NOT fi x the underlying
wheel end adjustment. As soon as possible, have the
vehicle inspected by a qualifi ed technician or consult the
manufacturer’s troubleshooting guidelines to locate and
fi x the actual adjustment problem.
Examples of
Off-set and
Straight Arm
Styles
24
Manual Slack Adjusters
Lube
Fitting
Manual Slack
Adjuster
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
Legacy manual slack adjusters require periodic
adjustment to remain within vehicle specifi cations.
The Control System: Quick Release, Ratio and Modulating Valves
Quick Release, Ratio and Modulating
Valves
Quick Release Valves
The function of quick release valves is to speed up the
exhaust of air from the air chambers. They are mounted
close to the chambers they serve.
Typically, these valves are designed to deliver within
one psi of control pressure to the controlled device;
however for special applications, the valve is available
with greater differential pressure designed into the valve
by the inclusion of a spring or spring seat.
Several styles of quick release valves are available and are
functionally the same. The Bendix
quick release valves have die cast metal bodies. The
Bendix® QRN™ quick release valve is a nonmetallic version.
The Bendix® QR-L™ quick release valve is an inline device.
Ratio Valves
Historically, valves such as the Bendix® LQ-4™ ratio
valves (and Bendix® LQ-2™ and LQ-5™ limiting valves
not shown) were used in the front axle delivery line of
vehicles. During normal service brake applications, these
valves were used to automatically reduce application
pressure to the front axle brakes. As brake application
pressure was increased, the percentage of reduction
was decreased until approximately 60 psi (depending
upon valve design) full pressure was delivered.
®
QR-1® and QR-1C®
Bendix® QR-1® Quick
Release Valve
Bendix® QRN™
Quick Release
Valve
Bendix ® QR-L
Inline Quick
Release Valve
Bendix ® LQ- 4™
Front Axle Ratio
Bendix® QR-1C®
Quick Release Valve
™
Valve
Bendix® R-7™ Modulating Valve
Spring Brake Actuator
The Bendix
®
R-7™ Modulating Valve is used in dual circuit
brake systems and performs four functions: during normal
operation, it limits hold-off pressure to the spring brakes; it
provides quick release of air pressure from the spring cavity
of the spring brake actuator allowing
a fast application of the spring brake
Bendix ® R-7™
Modulating Valve
Park
Control
Valve
Bendix ® R-7™
Modulating Valve
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
actuators; it modulates spring brake
actuator application should a failure
occur in the service brake system;
and it prevents compounding of
service and spring forces.
25
The Control System: Relay Valves
Relay Valves
Relay valves are primarily used on vehicles to apply and
release rear axle(s) service or parking brakes.
When the driver applies the brakes, air travels through
the delivery (in this case, signal) line to the relay valve
and moves an internal piston down. This closes the
exhaust and opens the delivery of air to the brakes.
The primary benefi ts of using a relay valve is that the
high capacity of air needed for braking is delivered
directly and does not have to travel up to the brake valve
and then all the way to the brakes. The brake force is
adjustable and when released, the relay valve exhausts
to the atmosphere. Relay valves are generally mounted
close to the chambers they serve and are available in
both remote- and reservoir-mount designs. The inlet/
exhaust valve cartridge can be replaced without line
removal.
In order to design braking systems with good brake timing
— that is, where brake application occurs in the correct
sequence — some relay valve models are available in
multiple “crack pressures”. The crack pressure value for
a particular valve varies by the use of different strength
return springs within the valve (which the air pressure
signal must overcome before air begins to be delivered
to the brake chambers).
The Bendix® R-14® relay valve incorporates both
an integral double check valve, with a balance port
connection which provides both an anti-compounding or
quick-exhaust feature, depending upon vehicle.
The Bendix® BP-R1® bobtail proportioning relay
valve is a combination of two valves in a single housing.
The lower portion contains a “standard” service brake
relay valve, which functions as a relay station to speed up
brake application and release. The upper portion houses
a brake proportioning valve which reduces normal
service brake application pressure when the tractor is not
towing a trailer (bobtail operation). The control port on
the Bendix BP-R1 valve is connected to the trailer supply
valve delivery and signals bobtail operation application.
The anti-compound feature is used when these valves
are used to control spring-actuated parking features.
Bendix®R-12P
Relay Valve
(0 crack pressure for
long wheelbase trailers
and dollies)
Bendix
R-8P
Relay Valve
(0 crack pressure for
long wheelbase trailers
and dollies)
™
®
™
®
Bendix
Relay Valve
Bendix
R-14
Relay Valve
(Anti-compounding)
Bendix® BP-R1® Bobtail
Proportioning Relay Valve
R-12
®
®
®
Bendix
R-12DC
Relay Valve
(Straight
Bendix
Relay Valve
trucks)
R-6
®
®
®
™
26
For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)
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