CONDITION MONITORING OF RAIL CAR AIR BRAKE SYSTEMS USING ULTRASOUND

摘要

Airbrake reliability during the winter has been an on-going concern for railway operators in North America. Methods to detect air leaks still rely heavily on manual inspection. A noncontact automatic leak detection method may increase airbrake reliability, and save costs associated with prorogated inspection time and delay in schedules. Ultrasound Leakage Detection (ULD) was initially investigated as an alternative to visual inspection and manual testing, with positive results for field trials in a rail yard of a major railway and for bench-scale experiments under idealized cold-room conditions. Simulated leaks using shop air pressure (in the range from 60 to 95 psi) with five different leaking components yielded 100% accurate leak identification and pinpointed faulty components with the initial location of the ULD device being 5 m away and 0° off-axis to the leaks. In laboratory leak classification tests, noises from various leaking components were recorded using the ULD device and digitally processed. Seven parameters in the time and frequency domain were compared among different faulty components. Leak type identification efforts showed no single parameter could unambiguously identify the leak type in the frequency range of heterodyned ultrasound. Distinct trends of Power Spectral Density (PSD) distributions in the entire frequency domain were observed in road noises and distant train noises. Noises from active trains on nearby tracks have large variations, but some noises from sources such as hand brake chains or end-of-train device turbines have unique patterns of PSD distribution. Non-rail noises and distant rail noises can be differentiated from actual leaks in the rail yard environment; however, nearby rail noises interfere greatly with the identification of airbrake system leaks on the train, and so additional knowledge of the train's surroundings is critical for eliminating the false positive results of airbrake leaks. The possibility of using automatic rail side mounted ULD devices is introduced.