SGI SGI Air Brakes Endorsement 3

Question 1

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

Accepted Answer

To allow gradual application of spring brakes for controlled stops

Answer

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

Question 2

What does 'compressor cut-in pressure' mean?

Accepted Answer

The pressure at which the compressor starts to build air

Answer

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

Question 3

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

Accepted Answer

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

Answer

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

Question 4

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

Accepted Answer

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

Answer

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

Question 5

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

Accepted Answer

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

Answer

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

SGI - Saskatchewan Government Insurance Corporation Practice Test