1. Copyright © by Circle “B” Inc. 2008 All Rights Reserved
Presents
Copyright © by Circle “B” Inc All Rights Reserved

2. “ The Quality Training Company “
AIR BRAKES
Dual Air Brake System
Boyd-One In-Service & Training
“ The Quality Training Company “

3. CERTIFIED CALIFORNIA DEPARTMENT OF EDUCATION
BUS DRIVER INSTRUCTOR AND TRAINER
Steve T. Boyd – Instructor & Trainer

4. DUAL AIR BRAKE SYSTEM

5. DUAL AIR BRAKE SYSTEM SECONDARY SYSTEM OR FRONT BRAKES
PRIMARY SYSTEM OR REAR BRAKES
EMERGENCY STOPPING SYSTEM

6. AIR BRAKE SYSTEM
All applicants for a California Special Certificate must have a through knowledge of the air brake system, when operating a vehicle with a dual air brake system. Unfamiliarity with the system will result in a failure of the brake system test given by the California Highway Patrol.
Air brakes use compressed air to make the brakes work and must be well maintained and used correctly.
Air brake systems are three systems combined:
Service Brake System: Applies and releases the brakes when you use the brake pedal
during normal driving.
Parking Brake System: Applies and releases the parking brakes when you use the
parking brake control.
Emergency Brake System: Uses parts of the service and parking brake systems to stop
the vehicle in the event of a brake failure.
A full service brake application must deliver to all brake chambers not less than 90 percent of
the air reservoir pressure remaining with the brakes applied.
Air compressor : Pumps air into the air storage tanks.
Allow for tanks to build up to a minimum of 100 p.s.i. in both primary and
secondary systems.
Air Governor : Controls when the air compressor will pump air into the air storage tanks.
Air Governor “cut-out” (no higher than 130 p.s.i.)
Air governor “cut-in” (nor lower than 85 p.s.i.)

7. AIR BRAKE SYSTEM - CONTINUED
Alcohol evaporator: Helps reduce the risk of ice in air brake valves and other parts during cold weather. Check and fill up as necessary.
Safety valve: Installed in first tank air is pumped into. Protects the tank and rest of the system from to much air. Usually set to open at 150 p.s.i.
Brake pedal: The harder you push down on the pedal, the more air pressure is applied from the storage tanks to brake chambers.
Drum brakes: The most common type is the S-cam drum brake. Brake drums are located on each end of the vehicle’s axle.
S-cam: Air pressure pushes the rod our, moving the slack adjuster, twisting the brake cam shaft, turning the S-cam.
One-way check valve: Allows air to flow in one way only.
Air supply gauge: Tells how much air pressure is in the air tanks.
Application gauge: Shows how much air pressure is applied to the brakes (some vehicles do not have this gauge).
Low air warning device: Visible and audible. Must activate when air supply pressure drops below a fixed pressure.
Modulated – not more than 75 p.s.i., nor less than 55 p.s.i.
Dual Air System – before 60 p.s.i.
Another type of warning device is the “wig wag”

8. AIR BRAKE SYSTEM - CONTINUED
Stop light switch: An electric switch that turns on the brake lights, works by air pressure. When air pressure is removed, the springs put on the brakes.
Parking brake control: A diamond shape, yellow, push-pull knob. On older vehicles, a red lever.
Dual air brake system: Has two separate air brake systems which use a single set of brake controls. Each system has its own air tank, Hoses, lines, etc. One system operates the regular brakes on the rear axle or axles (primary system). The other system operates the regular brakes on the front axle, and rear axle (secondary system).
Air Brake tests:
1) Cut-out pressure (before 130 psi).
2) Cut-in pressure (before 85 psi).
3) Static air loss (2 psi or less in 1 min. / Brake applied).
4) Applied air loss (3 psi or less in 1 min / Brake released).
5) Low air warning devices (audible and visual).
6) Spring brake (must activate between 40 and 20 psi).
7) Parking brake.
8) Service brakes (2 at about 5 mph).
Air tank drains: Drain daily, to remove moisture and oil.

9. BRAKE CHECK:
Air Governor Cut-In - before 85psi / Cut Out - Before 130psi
Static Air – Not more than 2psi in 1 minute – Break Applied
Applied Air – Not more than 3psi in 1 minute – Break Released
Low Air Warning – 2 audible & visual – Before 60 on DAS
Emergency Stopping System – between 40 and 20 psi
Parking Brake – Bus MUST NOT roll / Build up to about 90psi – Stop Bus With Brake Knob
Brake Check – 2 at about 5 MPH – NOT pulling to left or right

10. CLICK MOUSE BUTTON TO CONTINUE
AIR BRAKE QUESTIONS
A. How do you activate the emergency stopping system?
By applying the _______________ brake.
B. What happens when you loose the front brake system?
There is air in the _______________ brake system to stop the vehicle.
C. What happen when you loose the rear brake system?
D. If you loose air in both systems, how do you stop the vehicle?
There is enough air in the _______________ system to make one stop.
E. What are the steps you take when you notice an air loss?
Air gauge will start to drop.
Turn on right turn signal, and start to pull of the roadway.
When air pressure drops to ____, the low air warning devices will activate.
When air pressure reaches _____, the spring brakes will activate.
NOTE: You want to be off the roadway before the spring brakes activate.
F. What is a supply air pressure gauge for?
Tell the air supply in the _______________ and _______________ systems.
G. How do you check slack adjusters?
Check the _______________
CLICK MOUSE BUTTON TO CONTINUE

11. CLICK MOUSE BUTTON FOR ANSWERS
AIR BRAKE (continued)
H. Do air brakes work instantly, like hydraulic brakes?
No. It takes time for _______________ to go from the tanks to the brake _______________ .
I. How often do you drain the air tanks? _______________
J. What are spring brakes? _______________ used to apply brakes when there is
a __________ of air.
K. Name the air brake systems?
Front brake or _______________, rear brake or _______________,
and _______________ brake system.
L. What is a one-way check valve?
A valve that allows air to flow in _______________ direction only.
M. What is the air applied gauge?
Tell how much air is applied on _______________.
N. What is the front brake limiting valve?
Reduces the chance of _______________ wheel skids.
O. What will be affected if the brakes are not adjusted properly?
Neither the _______________ nor _______________ brakes will work properly.
CLICK MOUSE BUTTON FOR ANSWERS

12. AIR BRAKE ANSWERS SERVICE BRAKE REAR BRAKES FRONT BRAKES AUXILLARY
60PSI / 40 – 20PSI
FRONT / REAR
BRAKE LAG
AIR / CHAMBERS
DAILY, BEFORE DRIVING
HEAVY SPRINGS / AIR
SECONDARY / PRIMARY / AUXILLARY
ONE
FRONT WHEEL

13. Boyd-One In-Service & Training
Thank You !
FOR TAKING THE
Boyd-One In-Service & Training
AIR BRAKE TRAINING COURSE
FOR ADDITIONAL INFORMATION ON BOYD-ONE TRAINING VISIT OUR WEB-SITE:
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