Air Brakes Flashcards
Why must air tanks be drained?
because water and compressor oil will start to build up and can cause brake failure
What is a supply pressure gauge used for?
used to measure how much pressure is in the air tanks
What are air storage tanks used for?
air storage tanks are used to hold compressed air. The tanks hold enough air to allow brakes to be used several times even after the compressor stops working
all vehicles with air brakes must have a low air pressure warning signal?
TRUE
Front wheel brakes are good under all conditions?
TRUE
what are spring brakes?
an alternate power source for emergency and parking brakes that will activate when air pressure is gone
how do you know your vehicle is equipped with antilock brakes?
THE VEHICLE WILL HAVE A YELLOW ABS MALFUNCTION LAMP
purpose of air government control?
controls when the air compressor will pump air into the air storage tanks
what is cut-out and cut-in pressure levels and how does it work?
cut out level is around 125 psi. Air compressor governor will stop the compressor from pumping air.
Cut in level is around 100 psi and the air compressor governor will allow the compressor to start pumping again
Purpose of alcohol evaporator?
helps to reduce the risk of ice in air brake valves and other parts during cold weather
what two types of air drains?
manual and automatic
what is the purpose of a safety relief valve
purpose is to protect air tank and rest of system from too much pressure. Valve is usually set to open at 150 psi
what is a dual air brake system?
SYSTEM HAS TWO SEPARATE AIR BRAKE SYSTEMS, WHICH USE A SINGLE SET OF BRAKE CONTROLS. ONE SYSTEM OPERATES THE REGULAR BRAKES ON THE REAR AXLE OR AXLES WHILE THE OTHER OPERATES ON THE FRONT AXLE. Both systems supply air to trailer (if there is one)
what are slack adjusters?
Slack adjusters are mechanical links between the brake-chamber push rod and the camshaft on cam type brakes.
how can you check slack adjusters?
release parking brake so you can move them and pull them
how can you test low pressure warning signal?
turn engine off when you have enough air pressure. Turn electrical power on and press on and off the brake pedal. The low air pressure warning signal should come on around 60 psi
what is application pressure gauge (not on all trucks)
a gauge that measures how much air pressure you are applying to the brakes.
how can you check that the spring brakes come on automatically?
lower air pressure by stepping on and off brake pedal. The tractor protection valve and parking brake valve should close (pop out) when air pressure falls to 20-45 psi
what are the maximum leak rates?
4 pounds in one minute with combination vehicle
3 pounds in one minute with single vehicle
what does the braking power of spring brakes depend on?
the adjustment of the brakes
what are service brakes?
the foot pedal that you use to apply brakes while traveling up and down the road
how does s-cam brakes work
when the brake is applied, air pressure pushes slack adjuster which turns the s-cam and forces brake shoes to press against the inside of the brake drum
purpose of front brake limiting valve? (used for vehicles made before 1975)
limiting valve cuts the “normal” air pressure to the front brakes by half effectively reducing braking power of front brakes
when engine is at operating rpms what psi range and how long should it take for the pressure to build?
pressure should build from 85-100 psi within 45 seconds in dual air systems
