Circumstances which gave rise to a fire on a Luas tram in Dublin last November had been discovered as far back as December 2008, the Railway Accident Investigation Unit has said.
The unit said the fire which took place on November 7th last, as a four carriage tram approached the Busaras Luas stop, was caused by hydraulic fluid leaking from a worn hose onto a worn power cable.
As a result the unit, which is part of the Department of Transport, has recommended Luas operators Transdev and tram manufacturers Alstom review safety aspects of the of proximity, design and standardisation of hoses and electric cables .
In a further recommendation relating to the handling of the problem since 2008, the unit said Transdev should ensure Alstom review its incident/ accident investigation process.
Both Transdev and Alstom said the recommendations in the report were being addressed and passenger safety was given priority.
Last November’s fire occurred as the tram traversed a bend on the approach to Busáras at about 4.30pm and flames were seen to be shooting from under a carriage.
The railway accident report said the flames reached their peak in the first two seconds of the fire before the driver stopped the tram and emergency services were called. Closed circuit television pictures of the blaze showed flames shooting about six feet from the tram and rising almost to the roof height of the vehicle.
According to the report “fretting” occurred on the hose and the electricity cable as they moved and rubbed off one another.
But under the heading ‘similar occurrences’ the report said in December 2008 an incident occurred in which a tram’s brakes jammed due to a leak in a hydraulic hose. While there was no fire on that occasion an investigation showed that the electric cable adjacent to the hose was exposed to the core.
Subsequent examination of other trams in the fleet identified a further 11 trams with fretting damage in the same location. In addition historical maintenance records showed that fretting between hoses and cables in this area was being recorded at a rate of “ten or more per year”.
However records show this safety concern was “closed” in early 2009 with the comment that the issues raised would be dealt with “through the appropriate channels”.
But the Railway Accident Investigation Unit said it was “ not provided with any further actions taken” on foot of the earlier investigation”.
The unit concluded that the electricity cables were designed to be kept at an angle of fifteen degrees from the hoses, but in a number of cases this separation had not been sustained. It also concluded some of the lengths of cables were longer than designed and this would have given rise to more movement and fretting. In a further conclusion the report said some cables did not contain a protective braid “which may have provided additional protection from fretting”.
The unit made seven recommendations for Transdev and Alstom. The recommendations relate to the design and separation of the cables and hoses, as well as electrical isolation. Also included was a recommendation that Transdev ensure Alstom review its incident / accident investigation process “to ensure that investigations are of sufficient depth and produce clear recommendations”.
In a statement Alstom said the company “takes passenger safety seriously. To ensure that a similar issue will not reoccur, we immediately addressed the root cause of the incident and revised our maintenance procedures. We continue to work closely with Transdev, RAIU and the Railway safety Commission to implement the remaining recommendations in the report and on improving the performance of the Luas fleet on a daily basis.”
The full accident investigation report is available at http://www.raiu.ie
