2009 – July – Graham – Ensuring Reliability of Track Circuit Operation
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Date presented:
Brent Graham B.Sc. M.Sc., Dipl.T. Project Director, Coffey Rail, Melbourne Track circuits are among the most common and oldest components of railway signaling systems and are one of the major building blocks of railway signaling systems. While the trend today may be towards moving block or communication based systems, conventional track circuits will undoubtedly be around for many years to come. Track circuits were originally developed in the age of steam as a secondary safety device. Trains were pulled by heavy locomotives and rolling stock had poor dynamics by today’s standards. Tread brakes and bogie hunting tended to keep the wheel/rail interface clean and the use of other electrical equipment was minimal. Over the years, the importance of track circuits in railway system safety has increased. At the same time, advances have been made in manufacturing, electronics, and other fields which potentially increases the risk of track circuit failure. High precision wheel lathes and close tolerance manufacturing coupled with the increased use of disk brakes and regenerative braking techniques, while improving ride quality and component life have simultaneously reduced the rail head cleaning characteristics of earlier days. This paper examines how a stringent testing approach can be used to, not only maintain signaling system safety, but also to improve the reliability of the signaling systems and train operations in general. It is important that testing be repeatable, systematic and documented.