Saskatchewan Air Brake Knowledge Test

What is the primary purpose of the air compressor in an air brake system?

• ATo cool the brake drums during heavy braking
• BTo pump air into the reservoirs to build system pressure
• CTo release the spring parking brakes directly
• DTo control the amount of force applied to the brake pedal

According to the SGI Air Brake Manual, how far below the cut-out pressure does the governor normally let reservoir pressure fall before it cuts the compressor back in?

• AAbout 5 to 10 psi (34 to 69 kPa)
• BAbout 20 to 25 psi (138 to 172 kPa)
• CAbout 40 to 50 psi (276 to 345 kPa)
• DAbout 60 to 70 psi (414 to 483 kPa)

What is the purpose of the safety valve on the supply reservoir?

• ATo release pressure if the governor fails and pressure exceeds 150 psi
• BTo allow the driver to manually release the parking brakes
• CTo prevent moisture from entering the service tanks
• DTo warn the driver of low air pressure in the system

What colour is the trailer supply line (emergency line) gladhand coupling?

• ABlue
• BYellow
• CRed
• DGreen

What colour is the trailer service line gladhand coupling?

• ARed
• BBlue
• CYellow
• DBlack

What device alerts the driver if the system air pressure falls below 60 psi (414 kPa)?

• AA loud safety pop-off valve on the reservoir
• BA red trailer supply valve popping out from the dashboard
• CA low-pressure warning device (light and buzzer)
• DAn engine automatic shutdown indicator

How should moisture and oil be removed from the air reservoirs?

• ABy adding alcohol to the tanks daily
• BBy running the engine at fast idle for 10 minutes
• CBy opening the drain valves on all reservoirs daily
• DBy replacing the compressor air filter weekly

What does the yellow diamond-shaped knob on the dash control?

• AThe tractor parking brakes
• BThe trailer supply valve
• CThe windshield wipers
• DThe engine governor override

What does the red octagonal-shaped knob on the dash control?

• AThe vehicle's hazard lights
• BThe tractor's front axle brakes only
• CThe trailer supply valve (charges the trailer lines)
• DThe service brake application pressure

What is the purpose of gladhands in a tractor-trailer combination?

• ATo secure the trailer cargo doors
• BTo connect the electrical wiring between tractor and trailer
• CTo connect the tractor and trailer air brake lines
• DTo adjust the slack of the trailer brakes automatically

What is the normal governor cut-out pressure range for most air brake systems?

• A60 to 80 psi (414 to 552 kPa)
• B120 to 145 psi (828 to 1,000 kPa)
• C150 to 180 psi (1,034 to 1,241 kPa)
• D85 to 100 psi (586 to 690 kPa)

What is the minimum air pressure required before driving a vehicle equipped with air brakes?

• A60 psi (414 kPa)
• B100 psi (690 kPa)
• C120 psi (828 kPa)
• D150 psi (1,035 kPa)

What is the primary function of the treadle valve (foot valve)?

• ATo park the vehicle mechanically using cable tension
• BTo regulate the compressor output directly from the cab
• CTo control the flow of air pressure to the service brakes
• DTo automatically adjust the pushrod stroke length

What mechanical force applies the parking/emergency brakes in an air brake system?

• AHigh air pressure acting on the back of the brake chamber
• BA strong steel spring located inside the brake chamber
• CA hydraulic cylinder backup system in the differential housing
• DAn electric solenoid acting on the slack adjuster arm

What is the purpose of chocking the wheels when testing air brakes?

• ATo prevent the air compressor from running during tests
• BTo prevent the vehicle from rolling when parking brakes are released
• CTo increase the speed of the air pressure build-up
• DTo lock the manual slack adjusters in place for measurement

What is the function of the supply reservoir (wet tank)?

• ATo distribute air directly to the front wheel brakes only
• BTo house the low-pressure warning light switch
• CTo collect water and oil condensed from the hot air
• DTo provide auxiliary air to the cabin heater

What is the first tank that receives compressed air from the compressor?

• AThe primary service reservoir
• BThe supply reservoir (wet tank)
• CThe secondary service reservoir
• DThe trailer emergency reservoir

What is the function of a one-way check valve between reservoirs?

• ATo prevent air from flowing back to the supply source if it leaks
• BTo allow the driver to bypass the governor cut-out
• CTo balance pressures between the front and rear brakes during application
• DTo automatically apply the trailer spring brakes

What does the trailer hand control valve (trolley valve) operate?

• AThe tractor parking brakes only
• BThe trailer service brakes independently of the tractor
• CThe automatic engine retarder (Jake brake)
• DThe fifth-wheel slide lock cylinder

What happens to the spring brakes when the driver pulls out the parking brake control valve?

• AHigh air pressure is sent into the chambers to apply the brakes
• BThe caging bolts are automatically unscrewed
• CAir pressure is exhausted from the chambers, letting the springs apply the brakes
• DAn electrical signal locks the mechanical slack adjusters

What holds the spring brakes in the released position?

• AHeavy mechanical springs
• BAir pressure inside the spring chamber
• CThe tractor parking brake dash valve
• DA locking pin on the slack adjuster

What is the purpose of the air dryer in an air brake system?

• ATo cool the compressor oil
• BTo warm up the air lines in sub-zero temperatures
• CTo filter out water and oil vapor before it enters the reservoirs
• DTo dry the brake linings after driving through water

What is the primary purpose of slack adjusters?

• ATo adjust the tension of the engine compressor belt
• BTo regulate the compressor cut-in and cut-out pressures
• CTo adjust the distance (free play) between the brake linings and the brake drums
• DTo control the amount of lubrication sent to the brake chambers

How should you check the operation of the low-pressure warning device?

• ARun the engine at fast idle and check if the pressure gauge needle moves
• BTurn the ignition key on, fan the brakes to drop pressure below 60 psi, and verify that t…
• CDisconnect the red trailer supply line while the engine is running
• DApply the foot brake fully and hold it for one minute while watching for pressure drops

What is the main danger of water freezing in the air brake lines?

• AIt can dilute the brake fluid and reduce braking force
• BIt can block the air lines and prevent the brakes from applying or releasing
• CIt can cause the air compressor to run continuously at fast idle
• DIt can crack the brake drums and rotors due to thermal shock

What type of energy is converted into mechanical force by brake chambers?

• APneumatic energy from compressed air
• BHydraulic pressure from the master cylinder
• CElectrical current from the alternator
• DKinetic energy from the rotating wheels

What is the purpose of the brake drum?

• ATo store spare air pressure at the wheels
• BTo provide a friction surface for the brake shoes to press against to stop the vehicle
• CTo keep dust and dirt off the automatic slack adjusters
• DTo house the return springs for the pushrod

What is a dual air brake system?

• AA system that uses both air and hydraulic lines to stop the vehicle
• BA system with two separate air circuits (primary and secondary) for safety
• CA system that has two compressors running at the same time
• DA system that applies twice the air pressure in an emergency

Even though automatic slack adjusters adjust themselves during normal use, what does the SGI Air Brake Manual require of the driver?

• ANothing, because automatic slack adjusters never need to be inspected
• BCheck them daily to confirm they are maintaining proper push rod travel
• CManually re-adjust them before every trip
• DReplace them every 10,000 km regardless of their condition

Why should you avoid using the trailer hand valve (trolley valve) to park a combination vehicle?

• AIt will damage the tractor's relay valves
• BIt only applies the service brakes, and if air pressure leaks off, the brakes will release
• CIt applies the parking springs with too much force, causing compounding
• DIt bypasses the low-pressure warning buzzer in the tractor

How does the governor command the compressor to stop pumping air?

• ABy disengaging the mechanical clutch drive from the engine
• BBy routing air pressure to the compressor's unloading mechanism to hold the inlet valves…
• CBy shutting off the engine lubrication supply to the compressor cylinders
• DBy closing a butterfly valve in the compressor intake manifold

What pressure does the safety valve on the supply reservoir typically open at?

• A100 psi (690 kPa)
• B120 psi (828 kPa)
• C150 psi (1,035 kPa)
• D175 psi (1,207 kPa)

In a dual air system, what is the role of the primary circuit?

• AIt typically supplies air to control the front axle brakes only
• BIt typically supplies air to control the rear brakes of the tractor
• CIt supplies air to secondary accessories like the air horn and seat
• DIt controls the parking brake caging mechanisms

What is the maximum acceptable air loss rate for a single vehicle during an applied leakage test?

• A1 psi (7 kPa) in one minute
• B2 psi (14 kPa) in one minute
• C3 psi (20 kPa) in one minute
• D4 psi (28 kPa) in one minute

What is the maximum acceptable air loss rate for a combination vehicle during an applied leakage test?

• A2 psi (14 kPa) in one minute
• B3 psi (20 kPa) in one minute
• C4 psi (28 kPa) in one minute
• D5 psi (34 kPa) in one minute

During a pre-trip inspection, what is the maximum time allowed for the air pressure to build from 85 to 100 psi (586 to 690 kPa) at normal engine idle?

• A30 seconds
• BLess than 2 minutes
• C3 minutes
• D5 minutes

What happens to the trailer brakes if the supply (emergency) line breaks?

• AThe trailer service brakes apply using the tractor foot pedal only
• BThe tractor protection valve closes, and the trailer emergency spring brakes apply immedi…
• CThe air compressor switches to fast-pumping mode to compensate
• DThe tractor rear brakes lock up while the trailer continues to roll

What is the purpose of the tractor protection valve?

• ATo limit the pressure applied to the tractor steering axle
• BTo protect the tractor's air supply from venting if the trailer breaks away or leaks
• CTo prevent moisture from traveling from the trailer back to the tractor
• DTo adjust the front-to-rear braking ratio based on vehicle weight

What is the standard pushrod stroke limit for a standard Type 30 clamp-type brake chamber?

• A1 1/2 inches (38 mm)
• B1 3/4 inches (44 mm)
• C2 inches (51 mm)
• D2 1/2 inches (64 mm)

What is the standard pushrod stroke limit for a standard Type 24 clamp-type brake chamber?

• A1 1/2 inches (38 mm)
• B1 3/4 inches (44 mm)
• C2 inches (51 mm)
• D2 1/2 inches (64 mm)

What is the regulation stroke limit for a long-stroke Type 30 clamp-type brake chamber?

• A1 3/4 inches (44 mm)
• B2 inches (51 mm)
• C2 1/2 inches (64 mm)
• D3 inches (76 mm)

What is the regulation stroke limit for a long-stroke Type 24 clamp-type brake chamber?

• A1 3/4 inches (44 mm)
• B2 inches (51 mm)
• C2 1/2 inches (64 mm)
• D3 inches (76 mm)

What is the purpose of a relay valve in an air brake system?

• ATo signal the governor when pressure drops in the tanks
• BTo connect the electrical brake lights when the treadle is applied
• CTo speed up the application and release of the rear brakes
• DTo direct air between the primary and secondary reservoirs

What is the function of a quick release valve?

• ATo allow the driver to quickly discharge all air tanks during parking
• BTo speed up the release of air from the front brake chambers
• CTo quickly isolate the tractor from the trailer during a breakaway
• DTo release the compressor from pumping when cut-out pressure is reached

What does a two-way check valve do in an air brake system?

• AIt allows air to flow only from the compressor to the wet tank
• BIt directs air from the source with higher pressure to a common line while blocking the l…
• CIt allows the driver to apply front and rear brakes independently
• DIt vents air to the atmosphere when tank pressure exceeds 150 psi

What is brake compounding and why is it dangerous?

• AApplying the foot brake too hard, causing the drums to overheat and fade
• BThe simultaneous application of the service and spring parking brakes, which can damage b…
• CMixing oil and water in the reservoirs, causing valve freeze-ups
• DMismatching different sizes of brake chambers on the same axle

How does an automatic slack adjuster (ASA) function?

• AIt monitors wheel speed and releases brake pressure to prevent lockup
• BIt automatically adjusts the camshaft position during brake applications if pushrod strok…
• CIt uses engine vacuum to pull the pushrod back to its starting position
• DIt adjusts the compressor governor pressure to match driver demand

Under what condition will the spring brakes typically apply automatically?

• AWhen system pressure rises above 150 psi (1,035 kPa)
• BWhen system pressure drops to between 20 and 45 psi (138 to 310 kPa)
• CWhen the vehicle exceeds 100 km/h on a downhill grade
• DWhenever the driver activates the engine retarder switch