Technical Reports

Evaluation of Locomotive Cab Air Flow Meters for Train Air Brake Leakage Monitoring

  • 28
  • Apr
  • 1989
AUTHOR: Donald R. Ahlbeck, Steven M. Kiger
SUBJECT: Braking Systems
KEYWORDS: Air Flow Method, Air Flow Indicators, Brake System Test
ABSTRACT: Railroad freight train brake systems must be qualified for safe operation by meeting three brake pipe test criteria: (1) a minimum pressure of 60 psig at the rear of the train, (2) a maximum pressure gradient of 15 psi over the length of the train, and (3) a maximum leakage of 5 psi per minute after applying the brakes. With the advent of the pressure maintaining feature on brake control valves (26L equipment or equivalent), the brake pipe leakage limit became a less critical measure of the controllability of the train brake system. By the addition of an air flow meter or indicator to the locomotive control stand instrumentation, an alternative brake system leakage test, the air flow method (AFM), was possible. This method provides advantages in qualifying train brakes for operation in extreme cold weather, as well as a means for over-the-road monitoring of brake system leakage. This report includes an extensive review of the technical literature and past experience with the AFM. An engineering analysis of air flow meters was conducted in the context of the AFM. This analysis covers the accuracy and reliability of the meters, the required AFM calibration procedures, and the accuracy of the calibration devices themselves.