Information Technology Reference
In-Depth Information
In case of an alarm, one infrastructure manager has to inform the driver
of a train that a wayside hot box detection system has recognized a temper-
ature exceeding a warning limit. It is also possible to declare two limits of
temperature for warning and for triggering an alarm. In both cases an inspec-
tion of the axle is needed. This will be done by technical inspectors where
available or by the driver of the train. Important for the braking process is
the normal use of brake power and to prevent an emergency brake because
the forces involved could cause a derailment.
Fig. 1. Hot box and hot brake detection system used by Austrian Railways (ÖBB)
Staff (train driver, station inspector or wagon examiner) can only ascer-
tain visually if an axle journal is broken, an axle-bearing is glowing, or an
axle-box case is deformed. Even if none of these indicators can be found,
the train will continue its journey with reduced maximum speed to the next
place where a technical inspector is available. Otherwise - if the driver veri-
fies the defect - the wagon has to be removed even when the alarm has been
generated by the locomotive itself.
Because of the early development of hot box detectors national standards
were mainly used for their design. In accordance to the current standards
of CENELEC [3] the question arises if such systems have to fulfill certain
safety requirements (by means of a tolerable hazard rate and safety integrity
level). For a rough estimation of the recommended safety requirement, the so
called Best Practice Risk (BP-Risk) analysis offers a suitable methodology
to answer this question.
