learn more about fire apparatus brake systems It was not developed to make firefighters into functions of components and parts of a brake

Transcription

1 Fire Apparatus Braking Systems This video was developed to help firefighters learn more about fire apparatus brake systems and wheels. It was not developed to make firefighters into Technicians, but to help them understand the functions of components and parts of a brake systems and wheel ends. Pictures and illustrations from Arvin Meritor Maintenance Manuals MM4, MM1, MM4m available from; aspx

2 Fire Apparatus Braking Systems Although the braking systems on fire apparatus function the same way as all other heavy trucks, fire apparatus brakes have several important differences. Brake shoe and disc pad linings are very aggressive Brake drums are harder either ductile or grey iron Disc brake rotors are also ductile or grey iron Rotors can not be turned or machined

3 Brake Systems Requirements NFPA 1911 requires 1 major and 1 minor brake inspection annually Required annual brake test Brake test also required after brake repairs Required annual parking brake test Required performance tests listed in NFPA 1911 NFPA 1911, Standard for the Inspection, Maintenance, Testing and Retirement of In Service Automotive ti Fire Apparatus

4 Brake Adjustments Modern fire apparatus with s cam drum brakes and ADB disc brakes have automatic slack adjusters (ASA) ASA slack adjusters do not need to be adjusted. If brakes are not stopping correctly and / or the slack adjusters are out of adjustment, there is something wrong TAKE THE UNIT OUT OF SERVICE Have a qualified technician inspect the brake systems

5 Brake Types

6 S Cam Drum brakes

7 Disc Brakes ADB

8 Disc Brakes EX225 new system

9 Wheels Two types of wheels are used on fire apparatus Aluminum Steel Two types of mounting Hub Pilot mount newer apparatus Wheel stud mount

10 Wheels Aluminum Thicker then steel wheels Can mount either by stud or pilot Stud mounting requires hardware designed d for aluminum wheels. Can get corrosion in bead area and cause leaks. Lighter then steel wheels

11 Wheel Aluminum

12 Wheel Steel Mount either by studs or pilot Heavier then aluminum wheels Can rust over time Thinner then aluminum wheels Can crack in between stud holes. Will bend if curbed or from hitting objects.

13 Wheel Steel

14 Wheel Mounting Stud type mounting wheel nuts and studs are tapered with no flange Hub Piloted wheel nuts have flanges

15 Wheel Mounting Any shinny areas around wheel nuts indicate looses wheel nuts Any finger tight (turns by hand) wheel nut must be torqued to proper specifications Wheel simulators must be removed periodically to inspect wheels and nuts Qualified technician to inspect and repair defects

16 Air Brake System Pressure Air brake system pressure should be near 120 psi when full. Compressor should start filling thetanks tanks when air pressure is approximately 85 psi Some units have one gauge with ihdual needles One red and one green Red needle is Primary Rear brakes Green needle is secondary front brakes

17 Air Brake System Pressure All new fire apparatus have air dryers installed. Many fire apparatus do not have pull cables to drain tanks. Tanks may have petcock drains or automatic moisture ejectors Check for moisture in air tanks or oil Check air dryer ejector valve for oil

18 Anti lock Brake System ABS Purpose is to stop the vehicle in as straight a line as possible. ABS brakes sense wheel spin and can apply and release the brakes on each wheel as needed to avoid skidding If a wheel stops spinning and the other wheels are still turning the ABS system will momentarily release and apply the brakes for the wheel that is not turning.

19 Anti lock Brake System ABS Driver feels the sensation of the brakes being pumped even though he is holding down on thebrake pedal. Stopping distances are not extended with ABS systems ATC Traction control system part of the ABS system

20 Know Your Vehicle Driver training should be done under different road conditions Testing the ABS system should be done in designated area. ABS light is on and does not go off when driving, get unit diagnosed for fault code

21 Auxiliary Braking systems Jake Brake engine brake Exhaust Brake engine brake Transmission i retarder di driveline brake Telma retarder driveline brake Know when to use the auxiliary brake system Normally recommended to be shut off in slippery conditions Check with chassis manufacturer

22 Conclusion This video is designed to help firefighters become more familiar with the braking systems used on fire apparatus. It was not intended to replace training and qualifications required by NFPA standards NFPA 1911 contains the requirements for daily / weekly operational checks which this video can help firefighters meet. NFPA 1911, Standard for the Inspection, Maintenance, Testing and Retirement of In Service Automotive Fire Apparatus