What is the purpose of a "reducing valve" in an air brake system?

The purpose of a reducing valve in an air brake system is to reduce air pressure to a usable level for specific brake components. In an air brake system, different components may require different operating pressures to function effectively and safely. The reducing valve ensures that the air pressure sent to these components is at the appropriate level, preventing damage that could occur from excessive pressure while allowing for efficient operation of the brakes.

This is especially important in systems where certain brake components, such as those on trailers, may be designed to work at lower pressures than the standard supply pressure from the air compressor. By managing this pressure appropriately, the reducing valve helps enhance the reliability and safety of the braking system, allowing it to respond correctly under various load conditions.