Free BC Air Brake Exam Flashcards

Compressed air can generate very high braking force for heavy loads, and the compressor continuously replenishes the air supply, unlike a fixed hydraulic fluid volume.

A compressor with a governor to control it, air lines, a reservoir to store compressed air, a foot valve (brake pedal) to direct air to the brakes, and foundation brakes to apply mechanical force.

Air pressure actuates a hydraulic pressure intensifier, and hydraulic pressure then applies the foundation brakes. Most air-over-hydraulic vehicles require a B.C. air brake endorsement (code 15), just like fully air-braked vehicles.

Within three minutes, at a fast idle of about 1,000 to 1,200 rpm, per ICBC's Driving Commercial Vehicles guide.

Most systems operate at a maximum of about 125 psi (range 105-135 psi across vehicles). The governor stops ("unloads") the compressor once maximum pressure is reached and restarts it once pressure drops enough, keeping roughly a 20 psi spread between cut-out and cut-in.

The governor must cause the compressor to resume building air before pressure drops below 80 to 85 psi.

It protects reservoirs from bursting if the governor fails to unload the compressor. It is normally set to vent excess pressure at approximately 150 psi. If it releases, the governor or compressor needs service.

Compressed air from the compressor carries water vapour, oil mist, and carbon particles; most contaminants condense and settle in the supply reservoir before air moves on to the primary and secondary reservoirs.

The primary section (closest to the pedal in the dual foot valve) usually operates the drive (rear) axle brakes. The secondary section usually operates the steering (front) axle brakes.

A one-way check valve between the supply reservoir and each service reservoir allows air to flow in only one direction, preventing the primary and secondary reservoir air from flowing backward and being lost.

Below 60 psi (414 kPa), per ICBC's Driving Commercial Vehicles guide. The warning may activate above 60 psi on some systems, but it must not activate later than 60 psi.

No more than the 80 psi available in the reservoir — brake application pressure can never exceed the pressure stored in the reservoir supplying it.

Spring brakes may begin to drag below about 60 psi and may automatically fully apply at about 20 to 45 psi, depending on the system.

On the rear axles only — not on the steering axle — in the common spring parking brake arrangement.

Block the wheels first, because caging mechanically removes the spring's parking force at that wheel and the vehicle could roll.

Loss of supply-line pressure causes the trailer spring brake valve to exhaust air from the spring brake chambers, automatically applying the trailer's spring parking brakes.

The mechanical wheel-end brake parts operated by the air system: brake chambers, pushrods, slack adjusters, drums or rotors, and linings or pads.

It acts as a lever between the pushrod and the s-cam, rotating the s-cam to apply the brake, and it also serves as the adjustment point used to keep pushrod travel within tolerance.

1/2 to 3/4 of an inch (12-20 mm) is a good range. More than 3/4 of an inch (20 mm) means the brake needs adjustment.

1 to 1 1/2 inches (25-38 mm) is a good range, measured at a full application of 90 to 100 psi. More than 1 3/4 inches (45 mm) means the brake needs adjustment.

More than two inches (50 mm) — automatic slack adjusters normally run slightly longer strokes than well-adjusted manual ones, but stroke beyond this limit means the adjuster has failed, is misinstalled, or there is another foundation brake problem.

About 3,000 pounds, based on roughly 30 square inches of effective diaphragm area on a regular Type 30 clamp-type chamber.

It can temporarily shorten stroke while masking an underlying installation, wear, or foundation brake problem that actually needs qualified repair, creating a false sense of security.

Heavy or repeated braking overheats the brakes; hot brake drums expand away from the linings, reducing contact and braking force, so the vehicle takes longer to stop or may not stop at all.

It closes off the trailer air loss so the tractor's own air supply is protected, allowing the tractor to still make a safe stop.

Without a trailer, there is very little weight over the rear drive axles, so relatively light brake applications can lock the rear wheels.

The trailer's wheels must be blocked, because small leaks can reduce or deplete the applied service-brake air pressure holding the trailer, letting it roll away.

Approximately the same 20 psi signal — during normal service braking, the trailer receives a control signal roughly equal to the driver's application pressure.

Gently tugging against the applied tractor or trailer parking brakes in low gear confirms the brakes actually hold the combination before the vehicle is driven.

Apply and maintain firm, continuous brake pressure so the ABS system can modulate individual wheel pressure and help preserve steering control.

The anti-lock feature has a fault and is disabled, but normal service braking remains available. The vehicle needs service.

ATC uses wheel-speed sensors to detect drive-wheel loss of traction; it can apply the brake on a spinning wheel and, in very slippery conditions, reduce engine power to help the wheels regain grip.

Perception time + reaction time + brake lag time + braking time. Perception and reaction are each about 3/4 second; add brake lag time and the braking distance itself.

Brake lag is the roughly 4/10 of a second delay between pressing the brake pedal and the air brakes actually beginning to function. Hydraulic car brakes begin working almost instantly, so air brakes need extra following distance.

Use a lower gear to go down the hill than the gear that was used to climb it; never shift to a higher gear on a downgrade unless speed can be controlled by a retarder or engine compression.

To provide auxiliary slowing, such as controlling speed on long downgrades, without relying on the main air brake system, saving the main brakes for emergency stopping.

A condition where the brakes stop working properly because they are overheated, causing the vehicle to take longer to stop or possibly not stop at all.

Apply slight, continuous brake pressure for a short distance while driving to help dry out the brakes before relying on them fully.

Before the vehicle's first trip of the day, as part of the required daily pre-trip inspection; covered commercial vehicles also need a written trip inspection report.

No more than 4 psi per minute, with the full brake application held at 90 to 100 psi and no audible air leaks.

No more than 6 psi per minute after the initial pressure drop.

No more than 3 psi per minute after the initial pressure drop.

Pump the brakes down to about 80% of maximum system pressure (for example, 100 psi if maximum is 125 psi) and confirm air pressure begins to build again; the compressor must cut in before pressure falls below 80 psi.

With the engine off, the compressor is not adding air, so any hissing or audible leaks in the air brake system can be heard and located clearly.

Code 15, ICBC's air brake endorsement, required for most on-highway air-brake-equipped vehicles and most air-over-hydraulic vehicles.

25 multiple-choice questions, 20 correct answers needed to pass (80%), with a 45-minute maximum time allotment.

7 hours of classroom theory on air brake systems; a certified course adds about 4 hours of practical pre-trip training on top of that.

ICBC requires the applicant to complete or repeat an approved 7-hour air brake training course before attempting the knowledge test again. ICBC's standard knowledge-test retest wait is 7 days after any unsuccessful attempt.

Approved course completion or qualifying experience, the air brake knowledge test, and an air brake pre-trip inspection test are required. A separate road test is not required for this endorsement path.

One year. If the air brake endorsement isn't placed on the driver's licence within one year of passing the knowledge test, it must be retaken.