LRT axle issue 'may be' related to August 2021 O-Train derailment, OC Transpo says

An Ottawa LRT train on the Confederation Line is seen in this undated photo. (Natalie van Rooy/CTV News Ottawa)

OC Transpo's general manager says the axle hub assembly failure that resulted in several LRT vehicles being pulled from service last month "could be or may be" related to the issue that caused an O-Train vehicle to derail last summer.

On July 23, OC Transpo pulled all O-Train vehicles that have travelled more than 175,000 kilometres from service after a failure was discovered in one of the wheel hub assemblies on a train.  Twenty vehicles taken out of service were scheduled to undergo additional inspection and to have the axle hubs replaced.

In an update to council Thursday evening, Transit Services general manager Renee Amilcar said no further issues have been discovered during the replacement of the axle wheel hubs, adding that a root cause analysis continues into the incident.

“RTG and Alstom categorized this as a unique event," Amilcar said.

"At this time, the ongoing investigation has revealed that the issue of the recent incident could be the same or related to the axle issue that led to the August 8, 2021 derailment. The root cause analysis of the August 2021 incident is also ongoing."

On Aug. 8, 2021, an empty LRT car derailed on a switch near Tunney's Pasture Station. Former OC Transpo general manager John Manconi said shortly after the derailment that the investigation identified a problem in the axle bearing assembly, and that a bolt moved a small amount to damage the bearing inside the unit and wheel.

In its closing submission to Ottawa's light rail transit public inquiry, Alstom, the maker of Ottawa's LRT vehicles, said the derailment was "unexpected" and was caused when an axle hub and its bearings failed.

"Alstom’s preliminary root cause analysis shows that there were excessive transversal loads or forces that were on the axle assembly," Alstom said. "These forces create microscopic movements within the assembly, known as fretting."

Alstom said the "unanticipated loads experienced in Ottawa that have led to the axle hub failure are outside the specified operating parameters" for the project.

"Alstom’s preliminary root cause analysis indicates that the cause of the fretting is a combination of forces arising from the track, the wheel rail interface, and the System’s operating profile," Alstom said.

"Due to the complicated nature of the wheel and rail system, 'The only conclusion that [Alstom] could really draw absolute was that [the trains] were taking excessive loads in the curves.'

"Rather than the wheel taking the brunt of these loads, these forces are being transmitted deeper into the Vehicle and presenting at the wheel bearing, causing excessive heat."

Amilcar says there are "sufficient trains" available to meet daily service requirements while trains are out of service for inspection, and temporary speed restrictions have been put in place while the investigation continues.

"OC Transpo’s number one priority is the safety of our customers and staff. To ensure the ongoing safety and operation of the LRT system while both root cause analyses continue, a number of precautionary measures have been put in place including the replacement of the axle wheel hubs, an enhanced inspection regime, and temporary speed restrictions along sections of the track," Amilcar said.

The Transportation Safety Board continues to investigate.