Lyon english summary
On 26 June 2013 at 13.42, Regional Express Train (TER) No 17929, made up of a Z2-type double-unit railcar, coming from Lyon-Part-Dieu and going to Chambéry, derailed one of its bogies as it was running at about 50 km/h in the Lyon-Guillotière signalbox 15 area.
As he felt abnormal movements, the driver immediately stopped the train.
The derailed vehicle remained on-line and did not leave the track gauge.
No one was injured.
This derailment was caused by a single direct event : the axle of wheelset 5-6 of the railcar broke close to the shimming support of one of its disc brakes.
This breakage was the result of fatigue cracking that developed from a spot of pitting corrosion that was not detected at the time of the mechanical inspection of the train concerned carried out in a maintenance centre.
This situation is the result of the insufficient quality of the maintenance operations performed on the 984-type wheelset involved. On the one hand, the water-soluble paint that had been applied to the axle in 2006 at the Courbessac workshop  did not adhere correctly, allowing chemical corrosion to develop there. On the other hand, at the time of its overhaul in 2012 at the Montigny centre, the criticality of this corrosion was poorly appreciated and the works carried out to eliminate it were not carried out correctly.
Furthermore, the ambiguities in the instructions relating to the elimination of axle defects that applied at the time at SNCF may have played a role in these failures.
The analysis of the causes of this derailment led BEA-TT to make three recommendations to SNCF, respectively covering :
- control of the axle painting process ;
- clarification of the instructions concerning the elimination of axle defects ;
- confirmation of verification, after removal, of the 984-type wheelset overhauled in 2012 by the Montigny centre.
 The Courbessac workship in Gard and the Montigny workshop in Moselle are SNCF repair centres.