What is the primary purpose of a pressure relief valve in an air brake system?

Answer: B — To prevent excessive pressure buildup in the system

The primary purpose of a pressure relief valve in an air brake system is to prevent excessive pressure buildup in the system. This function is crucial for maintaining the safety and integrity of the air brake system. If the pressure within the system exceeds a predetermined limit, the relief valve opens to release air and reduce the pressure. This helps to protect components of the air brake system from damage due to overpressure, which can lead to failure or malfunctions. In summary, the pressure relief valve acts as a safety device, ensuring that the air brake system operates within its designed pressure range, thereby supporting the reliability and effectiveness of the braking operation.