SGI Air Brakes Endorsement Flashcards

What is the purpose of the modulating control valve (spring brake modulator)?

Answer: To allow gradual application of spring brakes for controlled stops

The modulating valve allows the driver to gradually apply the spring brakes as an emergency brake when air pressure is lost.

What does 'compressor cut-in pressure' mean?

Answer: The pressure at which the compressor starts to build air

Cut-in pressure is the minimum level (usually around 100 psi) at which the governor signals the compressor to start building air pressure.

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

Answer: To speed up brake application and release at wheels far from the brake pedal

Relay valves reduce brake response lag by allowing air to flow quickly from nearby reservoirs rather than traveling the full distance from the cab.

How should a driver test the low-pressure warning before a trip?

Answer: Fan the brakes with the engine off until the warning activates around 60 psi

Fanning (rapidly applying and releasing) the brakes with the engine off depletes reservoir pressure until the warning activates, confirming it works.

What is a brake adjustment check, and why is it critical?

Answer: Verifying push rod travel is within limits to ensure effective brake application

Out-of-adjustment brakes have excessive push rod travel, reducing their effectiveness and increasing stopping distance significantly.

When must a driver inspect the brake system during a trip?

Answer: After the first 25 km and every 240 km or 4 hours thereafter

Saskatchewan regulations require an en-route inspection after the first 25 km and then every 240 km or 4 hours to check brakes and other critical systems.