CDL Air Brake Air Tanks and Drains 1 — Questions and Answers
Question 1: What is the primary purpose of the safety relief valve on an air tank?
- To release air if the tank pressure gets too high (Correct answer)
- To drain moisture from the tank automatically
- To regulate air flow to the brake chambers
- To equalize pressure between the primary and secondary tanks
Correct answer: To release air if the tank pressure gets too high
The safety relief valve is designed to open and release air if tank pressure exceeds a safe level, protecting the system from over-pressurization.
Question 2: At what pressure is the safety relief valve on an air tank typically set to open?
- 100 psi
- 125 psi
- 150 psi (Correct answer)
- 175 psi
Correct answer: 150 psi
The safety relief valve is set to open at 150 psi to prevent the air tank from being over-pressurized beyond safe limits.
Question 3: How often should air tanks with manual drain valves be drained?
- Once a week
- At the end of each day of use (Correct answer)
- Every 500 miles
- Once a month
Correct answer: At the end of each day of use
Air tanks should be drained at the end of each day of use to remove accumulated water and oil before they can cause problems.
Question 4: Which air tank is the first to receive compressed air from the compressor?
- Primary tank
- Secondary tank
- Supply (wet) tank (Correct answer)
- Rear axle tank
Correct answer: Supply (wet) tank
The supply tank, also called the wet tank, is the first tank air enters after leaving the compressor, where it loses much of its moisture.
Question 5: What is the function of a one-way check valve between air tanks?
- It limits maximum pressure in each tank
- It prevents air from flowing backward from one tank to another (Correct answer)
- It automatically drains water from the tanks
- It controls the rate of air flow to the brakes
Correct answer: It prevents air from flowing backward from one tank to another
A one-way check valve allows air to flow in only one direction, preventing air from flowing back from one tank to another if a line fails.
Question 6: Why is it important to drain air tanks regularly in an air brake system?
- To increase air pressure in the system
- To remove water and oil that can cause brake failure or freeze in cold weather (Correct answer)
- To reset the governor cut-in pressure
- To allow the compressor to build pressure faster
Correct answer: To remove water and oil that can cause brake failure or freeze in cold weather
Water and oil accumulate in air tanks and can lead to brake failure, rust, and freezing in cold temperatures if not drained regularly.
Question 7: What does a drain cock (drain valve) allow you to do on an air tank?
- Manually release air pressure from the tank to drain moisture (Correct answer)
- Adjust the pressure at which the governor cuts out
- Control air flow to the primary circuit only
- Refill the tank with compressed air from an external source
Correct answer: Manually release air pressure from the tank to drain moisture
A drain cock is a manual valve at the bottom of each air tank that lets the driver release air pressure to drain out accumulated water and oil.
CDL Air Brake Air Tanks and Drains 1
What is the primary purpose of the safety relief valve on an air tank?