12,000 railway wheel sets prone to loosen: TSB
Published: June 5, 2008
Source: Canadian Press

GATINEAU, Que. The Transportation Safety Board of Canada says 12,000 wheel sets still in use by Canadian Pacific Railway, Canadian National Railway and other North American railroads "have a high susceptibility to loosen" and should be replaced.
They were among 43,000 suspect wheel sets produced at the Canadian National Transcona shop, many of which have already been removed from service.

The board said Thursday its finding arose from an investigation into a January 2006 derailment of a Canadian Pacific train near Buckskin, Ont., when a wheel became loose on a curve and shifted inboard on its axle.

The weak wheel set was produced with a modified boring process used between April 1998 and February 2001 at the CN wheel shop in Winnipeg.

The board says at least 18 wheel sets made with the modified pressure-fit technique have been involved in derailments in Canada, plus an unknown number outside the country.

"These wheel sets have a high susceptibility to loosen, particularly in heavy-curvature territory," the board says.

"The risk of failure for these remaining wheel sets continues to increase the longer they remain in service."

It says the Department of Transport should "ensure that all 36-inch Canadian National Transcona wheel shop wheel sets assembled between April 1998 and February 2001 be removed from cars operating in Canada."It also has contacted U.S. rail authorities.

In the Buckskin crash, the board said there was undetected damage to the wheel and its mounting point on the axle, "leading to micro-movement that progressively loosened the wheel until a combination of lateral and rotational forces displaced the wheel inboard."

The derailment damaged 18 kilometres of track as the freight train continued on its way until the loose wheel set hit a switch, causing 11 additional cars to derail and 130 metres of track to be destroyed. There were no hazardous goods involved and no injuries resulted.

The board also said Thursday that the industry has no effective way to track wheel sets once they are removed from their original car, making it hard to locate potentially defective sets. To fix this, it is recommending that the railways be required to keep track of all wheel sets.