Airbrakes Flashcards
Why are airbrakes, rather than hydraulic brakes, used on heavy commercial vehicles?
if properly maintained, air brake systems will never be depleted
What are the five components of a simple airbrake system?
-Air compressor.
-Reservoir.
-Foot valve.
-Brake chamber
-Brake shoes and drums
What prevents total loss of air pressure in the service brake system in the event of an airline rupture between the compressor and the supply reservoir
One-way check valve
How can you tell how much air pressure is in the main reservoir
Reservoir air pressure gauge
What must you do if the low pressure warning indicator activates?
A low air warning switch is installed after the supply reservoir to alert you when air pressure drops below a safe level 60 psi (414 kPa). If the low air warning system activates, you must stop and determine the cause.
What’s one advantage of a dual airbrake system?
Even if one or the other system totally fails, the driver is able to make a controlled stop using only the foot valve.
In a dual air brake system, if an airline in the secondary braking system ruptures, how would you know? What would happen if you’ve been made a break application?
The low air warning system will activate when pressure and any reservoir falls below 60 psi. When you apply the brakes, you’ll be able to make a controlled stop, but only braking on the rear axle would be maintained, the steering axle brakes would not operate.
How does a spring parking brake work
Spring breaks will apply if air pressure falls beneath a certain level, but their effectiveness in stopping the vehicle or holding a parked vehicle depends on how well the brakes have been kept in adjustment. The brakes are applied and remain applied by mechanical spring pressure, not by air pressure. If air pressure falls beneath the amount needed to keep the spring compressor, the spring pushes against the pushrod in the service brake chamber, pushing the pushrod out against the slack adjuster to apply the foundation breaks.
What are the two ways that the spring in a spring parking brake chamber can be held in the released position?
Using the parking brake control valve or by manually releasing “caging” the brake
Park brake control valve
“Caging”
Why should you avoid compounding the brakes?
It can damage/gestures, s-cams, brake chamber mounting bolts, brake shoe rollers, shoes and brake drums
Why are spring parking brakes are reliable type of parking break?
Because they are unaffected by loss of air pressure
What is the purpose of the tractor protection system on a tractor?
To prevent the tractor air from being depleted too unsafe levels.
If a driver makes a 20 pound break application with the hand valve, what’s the application pressure at the tractor brakes?
Only the trailer brakes will be applied.
What would happen if the control line to the trailer becomes disconnected while you’re driving the tractor trailer combination?
Nothing will happen until the trailer brakes are applied. When that happens, the tractor protection system will activate to protect the tractor air supply.
How does a wedge break work?
When the brakes are applied, air pressure in the brake chamber pushes the wedge part of the pushrod between two rollers, forcing the brake linings out to contact the brake drum.
