CDL Air Brake Air Tanks and Drains 2 — Questions and Answers
Question 1: What can happen if water is not drained from air tanks during cold weather?
- The compressor will overheat
- The water can freeze and cause brake failure (Correct answer)
- Air pressure will build up too quickly
- The governor will shut off the compressor
Correct answer: The water can freeze and cause brake failure
Water left in air tanks can freeze in cold temperatures, blocking air lines and valves, which can cause total brake failure.
Question 2: Which air tank typically accumulates the most water and oil contamination?
- Primary service tank
- Secondary service tank
- Supply (wet) tank (Correct answer)
- Trailer reservoir tank
Correct answer: Supply (wet) tank
The supply or wet tank receives air directly from the compressor and therefore collects the most water vapor and oil before air passes to other tanks.
Question 3: What type of drain valve removes moisture from air tanks automatically?
- Manual petcock valve
- Automatic drain valve (Correct answer)
- Spring-loaded pressure valve
- Safety relief valve
Correct answer: Automatic drain valve
Automatic drain valves expel accumulated moisture from air tanks without driver intervention, though they should still be checked during pre-trip inspections.
Question 4: What is the minimum number of air tanks required in a basic single air brake system?
- One tank (Correct answer)
- Two tanks
- Three tanks
- Four tanks
Correct answer: One tank
A basic single air brake system requires at minimum one air tank, though most systems use multiple tanks for reliability and separation of circuits.
Question 5: Where are drain valves typically located on air tanks?
- At the top of the tank
- On the side of the tank near the inlet
- At the bottom of the tank (Correct answer)
- Near the pressure gauge fitting
Correct answer: At the bottom of the tank
Drain valves are located at the bottom of air tanks so that gravity causes water and oil to settle there, making draining effective.
Question 6: During a pre-trip inspection, what should you do with manual drain valves on air tanks?
- Open them to drain moisture, then close them before driving (Correct answer)
- Leave them open while driving to prevent pressure buildup
- Check that they are sealed and never touch them
- Replace them if any moisture comes out
Correct answer: Open them to drain moisture, then close them before driving
During pre-trip inspection, manual drain valves should be opened to release moisture buildup, then closed so the system can build and hold pressure.
Question 7: What substance besides water commonly collects in air tanks and must be drained?
- Brake fluid
- Oil from the air compressor (Correct answer)
- Coolant
- Transmission fluid
Correct answer: Oil from the air compressor
Oil from the air compressor passes into the compressed air supply and accumulates in air tanks, contaminating the brake system if not drained.
CDL Air Brake Air Tanks and Drains 2
What can happen if water is not drained from air tanks during cold weather?