Following the derailment of train 9T92, Incitec Pivot Limited (IPL) performed in-situ MPIs on the entire GATX wagon fleet. By the end of September 2018, it had detected 17 cracked axles and removed them from service. The company has also increased the frequency of axle non‑destructive inspection and is also introducing an improved axle design for its GATX fleet.
IPL contracted a provider to conduct a crack growth rate study on the 840P1 axles. The study revised previous work with findings based on kilometres travelled. As a result of that study, IPL has increased the inspection frequency to an inspection target of 50,000 km travelled (with an allowable maximum of 65,000 km). The inspection frequency will continue over an expected four year period (or sooner, based on attrition) until the 840P1 axles are replaced with the improved version.
Predicted point of failure graph
Source: Incitec Pivot Limited
The Office of the National Rail Safety Regulator will also work closely with IPL to address the susceptibility of the GATX 840P1 axle to fatigue cracking due to relatively minor damage.
The ATSB notes that the action initiated by IPL, once implemented, should address the safety issue.