At what pressure is the safety valve set automatically?

Answer: C — 150 psi

The safety valve in an air brake system is typically set to automatically release pressure at a certain threshold to prevent system failure and ensure safe operation. This threshold is generally recognized to be around 150 psi. The purpose of this valve is to provide relief in case of excessive pressure buildup, which can occur due to malfunctioning components or excessive heat. By releasing pressure at this crucial point, the safety valve protects not only the integrity of the system but also the safety of the vehicle and its occupants. Understanding this feature is essential for anyone operating air brake systems, as it highlights the importance of pressure management and the safety mechanisms in place to prevent catastrophic failures.