BC Air Brake Knowledge Test flashcards
BC Air Brake Knowledge Test · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Governor
- A valve that senses reservoir pressure and controls compressor loading and unloading, maintaining system air pressure within the designed operating range.
- Treadle valve
- The driver-operated foot valve that delivers graduated air pressure to the service brake chambers; releasing it exhausts air and releases the brakes.
- Brake chamber
- A device that converts compressed air pressure into mechanical force, moving a push rod to apply the foundation brake at a wheel.
- Slack adjuster
- A lever between the brake chamber push rod and the brake camshaft; it converts linear push-rod motion into rotary motion and adjusts clearance.
- Spring brake
- A brake chamber containing a strong spring that applies the brake when air pressure is released, providing parking and emergency braking.
- Wet reservoir
- The first reservoir after the compressor; it collects moisture and oil and has a drain for removing contaminants before air reaches other tanks.
- Safety valve
- A pressure-relief device on the air system that releases air if reservoir pressure exceeds a safe limit, protecting against governor failure.
- Air dryer
- A device that removes moisture and oil vapor from compressed air before it enters the reservoirs, using a desiccant cartridge and purge cycle.
- Compressor
- An engine-driven pump that compresses atmospheric air and supplies it to the reservoirs; the governor controls when it loads and unloads.
- Reservoir drain
- A valve at the bottom of an air tank used to remove accumulated water and oil; it must be closed fully after draining.
- Static leak test
- With the engine off and service brakes released, after pressure stabilizes, reservoir pressure should not drop more than 2 psi in one minute.
- Applied leak test
- With the engine off and service brake applied and held, air pressure should not drop more than 3 psi in one minute.
- Low pressure warning
- A buzzer or light that must activate before reservoir pressure falls below about 60 psi, warning that spring brakes may soon apply.
- Push rod travel
- The distance a brake chamber push rod moves when the brakes are applied; excessive travel indicates bad adjustment or a component fault.
- Slack adjuster check
- Inspection of free play and push-rod stroke against the manufacturer's limit; automatic slack adjusters must not be used to hide excessive stroke.
- Compressor build-up test
- A check that the compressor raises reservoir pressure from 85 to 100 psi within 45 seconds at fast idle in a typical dual-circuit system.
- Snub braking
- A downhill braking method: apply the service brakes firmly to reduce speed, then release them to allow cooling, repeating as needed.
- Brake fade
- Loss of braking force caused by overheating of drums, shoes, or pads; it may require stopping to cool and using a lower gear.
- Trailer hand valve
- A control that applies only the trailer service brakes; it is not a parking brake and cannot hold a parked combination.
- Parking brake control
- A valve that exhausts air from spring brake chambers to apply them for parking; it is not used for normal service braking.
- Tractor protection valve
- A valve that closes the tractor's air supply to the trailer if a line separates or pressure drops, helping protect tractor air.
- Emergency line separation
- If the trailer emergency line separates, the tractor protection valve closes and the trailer spring brakes apply automatically.
- Spring brake application
- As air pressure falls below the spring brake threshold, mechanical springs apply the brakes automatically; the vehicle should be stopped safely.
- Caging spring brake
- Mechanically compressing and locking a spring brake to release it; this disables parking and emergency braking on that wheel.
- Low air loss response
- If the low-pressure warning activates, stop safely, secure the vehicle, and find the cause; continued driving may cause automatic spring brake application.
- Emergency stop control
- A parking or emergency control that applies spring brakes; some vehicles have a modulated control for a controlled stop.
- Compressor failure
- If pressure does not build, check the compressor drive, governor, leaks, and gauge; the vehicle must not be driven until repaired.
- Governor failure
- A governor that fails to unload can cause overpressure; the safety valve releases air, and the system needs repair.
- Air leak check
- Listen for escaping air and apply soapy water to fittings and hoses; bubbles show a leak that can cause pressure loss.
- Frozen air line
- Moisture in an air line can freeze and block airflow; use the air dryer and alcohol evaporator, never an open flame.
- Dragging brake
- A brake that stays applied can overheat, smell, smoke, and reduce power; stop, cool, and inspect before continuing.
- Wheel chocks
- Blocks placed against wheels to prevent movement; use them before working under a vehicle because air pressure alone is not reliable.