At approximately 0428 on 22 May 2007, ballast train 3MR2
derailed near Roopena, SA (between Whyalla and Port Augusta). The
derailment occurred about 28 track kilometres north of Whyalla.
Twenty seven ballast wagons were derailed but there were no
injuries.
The investigation concluded that a number of factors combined to
cause the derailment. A crosslevel track geometry defect caused
body roll on the first wagon to derail which led to dynamic
unloading of the wagon's leading, right-hand wheel. When combined
with a horizontal and vertical alignment defect, wheel unloading
increased further and the right-hand wheel moved into flange
contact with the right-hand rail such that the risk of a
flange-climb increased at the point of derailment. Non-compliant
side bearer gaps, uneven load distribution and the wagon's
sensitivity to spring compression length also combined to cause the
front left-hand suspension springs to become fully compressed
thereby increasing the amount of wheel unloading at the point of
derailment.
All these factors combined to indicate that body roll, spring
compression, train speed, wheel unloading and flange contact at the
point of derailment were of sufficient magnitude that a flangeclimb
derailment would be expected to occur. A range of safety actions
were taken or recommended to seek to prevent similar incidents in
the future.
Rail Safety Recommendations [ RR20080029
] [ RR20080030
]
