Air Brake Systems Flashcards
7 cards from real CLP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Air Brake Systems flashcards as text
What is a 'modulating control valve' and in what situation would a driver use it?
Answer: A hand-operated valve that lets a driver gradually apply spring brakes when service brakes fail
A modulating control valve allows the driver to manually and gradually apply spring brakes if the service brakes fail, providing a controlled stop.
What effect does cold weather have on air brake systems, and how should drivers prepare?
Answer: Moisture in the system can freeze, blocking valves and lines — drivers should drain tanks and use alcohol evaporators or air dryers
Moisture that collects in air tanks and lines can freeze in cold weather, blocking air flow — draining tanks daily and ensuring the air dryer works properly prevents this.
What is the correct maximum push rod stroke for a Type 30 brake chamber before adjustment is required?
Answer: 2.0 inches
For a Type 30 brake chamber, the maximum allowable push rod stroke before adjustment is 2 inches; exceeding this reduces braking effectiveness.
What does it mean when the brake pedal feels 'spongy' or requires more travel than usual on an air brake vehicle?
Answer: Brakes are out of adjustment or there is a problem such as air in the hydraulic portion of a system
A spongy pedal or excessive travel often indicates out-of-adjustment brakes or a mechanical problem that prevents brakes from applying with normal pedal movement.
How do antilock braking systems (ABS) affect air brake operation on commercial vehicles?
Answer: ABS monitors wheel speed and modulates air pressure to prevent wheel lockup while keeping maximum braking force
ABS sensors detect wheel lockup and automatically modulate brake pressure to restore rotation, helping drivers maintain steering control during hard stops.
When inspecting air brake hoses and lines during a pre-trip inspection, what conditions should cause you to take the vehicle out of service?
Answer: Hoses that are cracked, chafed, worn through, crimped, or leaking air
Air brake hoses with cracks, chafing, visible wear, crimps, or active air leaks must be repaired before the vehicle is operated, as these indicate potential failure.
What is the significance of the 'cut-in' and 'cut-out' pressures of the air compressor governor?
Answer: Cut-in (~100 psi) is when the compressor starts building pressure; cut-out (~125 psi) is when it stops to prevent over-pressurization
The governor controls the compressor to maintain air pressure between approximately 100 psi (cut-in) and 125 psi (cut-out) to keep the system in the safe operating range.