What happens when the pressure in the air tanks exceeds 150 psi?

Answer: B — Pressure relief valves open

When the pressure in the air tanks exceeds 150 psi, the pressure relief valves are designed to open. This safety feature serves to prevent excessive pressure build-up which could lead to damage to the air tank or other components of the braking system. The purpose of these valves is to release excess air pressure, ensuring that the system operates within safe limits and reducing the risk of potential failure or accidents. It is important to understand the function of the pressure relief valves in maintaining the structural integrity of the air system. Other features, such as the air compressor shut-off mechanism or low-pressure alarms, operate under different conditions and are not directly responsible for releasing excess pressure. Therefore, the primary role of the pressure relief valves is crucial in protecting the overall safety and functionality of the braking system in vehicles.