Executive summary
On Friday, 31 May 1996, at about 2034 hours Train 404, the Rotorua - Auckland Geyserland Express, derailed at slow speed while crossing from the East Passenger Loop to the West Loop at Hamilton. There were no injuries. The cause of the derailment was an axle failure on the trailing axle of the railcar. Safety issues identified were the need to improve the inspection and testing regime for Silver Fern axles.
Related Recommendations
Ensure all other axles on the Silver Ferns are similarly treated when next in the workshop, and that all spare axles are similarly treated before installation.
Confirm the ability of existing equipment, operators and procedures to detect all cracks over 2 mm deep in the position on the axle where this failure originated, using prepared test pieces as necessary to ensure this can be achieved consistently.
Establish the service stresses being developed in the driven axle of the three axle bogie, and from this determine the related fatigue crack growth rates and implement an inspection regime to detect such cracks and remove any axle from service before it fails.
Dismantle and inspect for fatigue cracks as a matter of urgency all axles under the three axle bogies currently in service on the Silver Fern. Reassembly of uncracked axles should include action to prevent corrosion at the tapered gap between the axle and inner bearing.
Review the procedures during programmed wheel replacement to include monitoring of the condition of the axle surface and the effectiveness of corrosion prevention.