What does the duplex air gauge measure?

The duplex air gauge is instrumental in railway operations as it measures two crucial pressures: the straight air pipe (S.A.P) pressure and the brake pipe (B.P.) pressure. The straight air pipe pressure is associated with the direct application of air to the brakes, revealing how much air pressure is available to activate the braking system on a rail vehicle. Conversely, the brake pipe pressure concerns the overall pressure in the main brake line, which is essential for controlling the brakes throughout the entire train.

This dual measurement capability is critical for train operators to ensure that the braking system is functioning correctly, maintaining safe operation and responding effectively when brake application is needed. Monitoring both pressures with a duplex air gauge helps operators quickly diagnose and react to any potential issues within the pneumatic braking system, thereby enhancing safety and operational efficiency.