At what pressure is the safety valve typically set to open?

Answer: C — 150 psi

The safety valve in an air brake system is typically set to open at 150 psi. This setting is crucial because it serves to prevent excessive pressure buildup within the system, which could potentially lead to component failure or a catastrophic event. The safety valve functions as a fail-safe mechanism, ensuring that, should the pressure exceed the safe operational limits, the excess air is vented safely out of the system. Operating at a pressure of 150 psi provides a reliable balance between maintaining adequate braking power and ensuring the system is protected against overpressure situations. Ensuring that the safety valve opens at this pressure helps maintain the overall integrity and safety of the air brake system during operation.