Air Breaks

Question 1

In seconds, what is the average reaction time of a driver to hit the brakes after recognizing a hazard

Answer 1

3/4 - 1 1/2 seconds

Question 2

In seconds how long is the average brake lag

Answer 2

4/10 of a second

Question 3

How are spring brakes held in the released position

Answer 3

Spring breaks are held in the release position with air pressure of 70 psi or greater

Question 4

What is the maximum time permitted for the compressor to build from 85 to 100 psi

Answer 4

Less than two minutes from 85 to 100 psi running the engine between 600 and 800 RPM

Question 5

How can trailer brake holding power be tested?

Answer 5

With trailer emergency brakes applied and truck park brakes released, try to gently pull ahead to test emergency application of trailer brakes

Question 6

Name the five basic components of an air brake system

Answer 6

1. Compressor
2. Reservoirs
3. Foot valve(treadle)
4. Brake chambers
5. Brake shoes and drums or brake rotors and pads

Question 7

What is the purpose of a two-way check valve?

Answer 7

Allows control of the trailer brake by use of the hand valve or valve. This valve will permit air to flow from the source that is supplying the greater application pressure.

Question 8

What are the two ways of testing the emergency application of the trailer brakes?

Answer 8

1. Closing supply valve on tractor
2. Disconnecting the supply line between the tractor and trailer with the supply valve in the open position.

Question 9

What is the main purpose of the TRACTOR PROTECTION valve?

Answer 9

To prevent air loss from the tractor when not hooked to a trailer or if a trailer breaks away

Question 10

What is the main purpose of the TRAILER SUPPLY valve?

Answer 10

1. Controls tractor protection valve
2. Serves as a link between the tractor and trailer parking brake system.

Question 11

Three functions of the relay emergency valve

Answer 11

1. The relay part of the valve relays air from the trailer reservoir to the trailer brake chambers during a brake application.
2. The emergency part of the valve direct trailer reservoir, pressure to the trailer brakes causing an emergency application
3. The valve has a one-way check valve that stops air in the reservoir from going back to the source of supply.

Question 12

How are parking brakes held in the release position

Answer 12

With air pressure of 70 psi or greater

Question 13

Describe the function of the spring break modulator valve

Answer 13

If a failure occurs in the primary circuit, control air from the secondary side of the valve is directed to a spring break modulator

Question 14

What is the purpose of a quick release valve?

Answer 14

To allow faster release of the brakes

Question 15

How’s the reservoir protected from over pressurization

Answer 15

By a safety valve