In response to this occurrence, BHP Billiton (BHPB) conducted an internal investigation that resulted in the following safety action:
1: Re-railing
- A planned re‐railing program was accelerated and during financial years 2016, 2017 and 2018 (to May) covered 260 km, 405 km and 168 km, respectively. Re-railing in the vicinity of the 67 km mark (where the derailment occurred) was completed in April 2016.
Aluminothermic rail welding is being phased out in favour of mobile flash butt welding, in order to reduce the development of rail defects.
2: Prevention of rolling contact fatigue (RCF) cracks developing into transverse defects
- Track grinding capacity is being increased in order to reduce rail grinding debt. An additional grinder is expected by the end of 2018. Grinding intervals are being refined (dynamically over time and location) based on quantifiable data relating to the track material and condition.
- Technology has been introduced to obtain improved data relating to rail track condition. Rail temperature sensors have been installed across the network at hot axle box detector sites to better understand seasonal temperature conditions to allow maintenance windows and activities to suit. Rail is installed to required stress-free temperatures (de-stressing is undertaken where that requirement cannot be met).
- Track redesign across high-risk locations associated with RCF propagation (tight curves and slow speed) is being undertaken. Untestable RCF rails are being tracked to better manage mitigations such as temporary speed restrictions.
3: Rail flaw detection
- An improved methodology to review rail flaw detection data has been introduced. A second rail flaw detection provider has been deployed since June 2017 to verify the incumbent’s performance (no major anomalies have been identified).
- Measures have been introduced to ensure that flaw detection equipment is correctly set up and calibrated. This is partially complete with the second provider independently verifying the incumbent’s calibration processes.
- A longer term project has commenced to use information technology to compare data collected from different flaw detection runs to detect changes requiring human investigation.
BHPB also advised that they were taking action to reduce the occurrence of high wheel impact loading through the introduction of an improved wheel profile and the elimination of track geometry known to result in high impact loads.
Finally, regular and independent audits/reviews of key rail integrity aspects have been established to reduce the risk of derailment.
