The Transport Accident Investigation Commission’s continuing inquiry into the derailment of a Wellington morning commuter train in May 2013 is pursuing the possibility that two split pins were left off during maintenance allowing a parking brake assembly to work loose, fall and derail the train.
The four-car Ganz Mavag train derailed just south of Kaiwharawhara at 8.06am on Monday 20 May 2013 as it headed in to Wellington with 315 passengers and three crew on board. Four passengers were treated for minor injuries suffered in the accident during which an air compressor was forced up through the floor of the rear passenger car. The train was owned by a subsidiary of Greater Wellington Regional Council, but operated and maintained by KiwiRail.
In a preliminary report released today (24 October 2013) the Commission records an urgent safety recommendation made to KiwiRail in August to tighten maintenance procedures. It also asked the rail industry regulator, the New Zealand Transport Agency, to make sure the company did as recommended.
The report describes how passengers heard scraping sounds for some time before the derailment, and a section of disc pad from the parking brake was found on tracks eight kilometres before the accident site.
The extensively damaged parking brake assembly was found on the track some 113 metres back from the derailed train, however there was no damage to mounting holes on either the assembly or train through which split-pinned bolts were meant to hold the assembly in place. This showed the bolts and split pins were not in place when the train derailed, the report says.
It appears that documentation and miscommunication issues may have resulted in the train being returned to service from routine maintenance in March 2013 with the split pins left off; however the inquiry had yet to reach firm conclusions.
“There were two safety issues identified with the Wellington maintenance depot processes,” Chief Commissioner John Marshall QC said. “First, there were no individual task instructions describing how each safety-critical job was to be done, and secondly there was no check sheet associated with each task to record that important steps and checks for the task had been completed. Instead, the depot relied on the knowledge of the depot staff to complete each task satisfactorily.
“The Commission is concerned that these shortcomings in maintenance control could be indicators of other safety issues within the wider system at KiwiRail’s maintenance depots.
“Because of this, the Commission issued an urgent recommendation for Kiwirail to ensure that its maintenance is in accordance with good railway engineering practice, including documentation of maintenance processes and safety-critical components, and requiring work on safety critical components to be signed off by qualified staff other than the worker who had done the job,” Mr Marshall said.
Mr Marshall said the Commission was pleased that KiwiRail had taken immediate action to address most elements of the recommendation.
The Commission hoped to issue its final inquiry report by mid-2014.
Click through to read the report (.pdf)
(Scroll down to see title on first page.)