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US rail grinding system could have prevented Hatfield crash

FAILURE OF the broken rail which caused last week's fatal train crash near Hatfield could have been prevented if Railtrack had adopted a North American rail grinding technique.

Railtrack is planning to introduce the grinding technique throughout its network next year, although it has been used in North America since the 1970s.

Four people died on 17 October when GNER's 12.10pm Kings Cross to Leeds service derailed while travelling at 200km/h. The train was travelling around a right hand curve when the middle section snapped away from the front four carriages and rolled over (NCE 19 October).

The track operator said that the cause of the Hatfield railbreak was gauge corner cracking, a problem experts in the UK and US agree can be dramatically reduced by preventative grinding of the rails.

'Tests in Sweden have shown that rail renewals due to gauge corner cracking can be reduced by 80%, ' rail consultant Dr Stuart Grassie told NCE.

Current Railtrack policy - a hangover from British Rail - is to heavily grind the rails on an adhoc basis to remove corrugations in rails and improve ride quality.

Gauge corner cracking - a form of rolling contact fatigue which experts say accounts for 30% of railbreaks - is currently dealt with by replacing the whole rail after intervals as short as five years.

The more systematic North American strategy is to lightly grind the surface of the rails at regular intervals. This removes gauge corner cracks on the rail surface, slowing deterioration (see box overleaf).

Grinding also serves to maintain the rail profile. This stops changes in wheel loading so that existing cracks are prevented from extending and breaking the rail.

Using this technique North American freight rails can typically carry volumes of 1,000M tonnes before they need to be replaced. It is thought that the Hatfield rail failed after only 200M tonnes of traffic had passed over it.

After three years' deliberation Railtrack decided it would introduce preventative grinding next year, after a board meeting last month.

'We are planning a massive increase in rail grinding, ' said David Ventry, Railtrack's head of track asset management.

The investment in grinding will be around £6M over the next two years. Two additional grinding machines will be bought, trebling Railtrack's existing capacity.

Grassie said part of the problem was that 95% of rail breaks caused by gauge corner cracking were not currently recognised as such.

This failure to categorise rail breaks correctly is thought by some experts to have contributed to the slow adoption of preventative grinding.

Most breaks are put down to steel impurities rather than gauge corner cracking.

'There needs to be a big education process for the guys on the track on the cause of rail breaks, ' said Grassie. 'Gauge corner cracking has not been recognised as important.'

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