Technical Reports

Undesired Emergency Brake Applications - Transportation Test Center UDE Tests

  • 01
  • Aug
  • 1990
AUTHOR: Frederick G. Carlson
SUBJECT: Braking Systems
KEYWORDS: Single Car Tests, Brake Pipe Pressure Fluctuations, TTC
ABSTRACT: This report covers the Federal Railroad Administration funded Undesired Emergency Tests performed at the Transportation Test Center in Pueblo, Colorado. This report also covers the AAR research conducted prior to the Transportation Test Center tests. This is necessary in order to provide a background to better understand why the test was designed as it was. The FRA Undesired Emergency Test proved that pressure fluctuations of up to 2 psi can occur due to slack action alone, independent of any intentional brake applications. Brake pipe pressure reduction rates of over 30 psi/sec lasting for about 15 milliseconds were created by harsh slack run-ins. These rates are very close to those necessary to produce Undesired Emergency Brake Applications. A possible cure to Undesired Emergencies was tested. The use of a 0.43 inch dia. choke between the pipe bracket and the emergency portion of the control valve has been proven in lab tests to slightly reduce the sensitivity of a control valve to rapid short duration pressure reductions caused by slack action. The use of this choke in actual train tests resulted in no loss of normal desired emergency braking response.