Intelligent bolt ‘could have saved lives’

A bolt that cannot be loosened by train vibration could have been fitted to the points outside the Potters Bar station for just £12, its makers said this week.

Following our exclusive revelations last week that existing technology could have avoided the Potters Bar tragedy, comes news that a bolt that cannot be loosened by train vibration could have been fitted to the points outside the station for just £12, its makers said this week.

RotaBolt technology, which is already used in the rail industry in Australia, converts existing bolts by installing an indicator that allows it to be tightened to the correct tension.

As the bolt is tightened, a stainless steel cap on the top spins until the bolt has reached the correct tension.

The bolt is designed to achieve a certain level of frictional grip which will not allow the bolt to loosen through fatigue or train vibration, said RotaBolt managing director Rod Corbett. ‘The tension will create sufficient friction grip to withstand the vibration and not loosen,’ he said.

‘If the Potters Bar points had been fitted with RotaBolts set to the correct tension they would not have come undone,’ he added.

The company said Railtrack is already aware of the technology, which would cost around £4 per stretcher bar to install, and had been hoping to run a trial.

‘We contacted them around 12-18 months ago, and were hoping they would issue us with a set of bolts to convert, which we could then fit to a location in the West Midlands, but Railtrack hasn’t got round to it yet.’ The company has also written to the HSE to explain the technology, but has not yet received a reply.

The West Anglia Great Northern train to King’s Lynn derailed when sets of nuts on two stretcher bars were detached. This left the third stretcher bar connecting the tips of the points carrying the load normally shared between the three, and the bar buckled under the stress, causing the points to move as the rear carriage passed over them.

One possible explanation for the Potters Bar crash is that the vibration of trains passing over the points caused the nuts to loosen.

The RotaBolt technology is already used to fasten electronic safety equipment to bogeys on trains in Australia, as the devices had previously had a tendency to fall off with the vibration of trains.

The bolts are also used in industries such as petro-chemical, marine and offshore, defence, mining and structural engineering, where they are often subject to high forces, said Corbett.

The bolts make maintenance quicker and more reliable, as operators can check that the bolts are tightened through finger-feel alone, rather than having to use a large wrench, he said.

‘Maintenance crews are currently having to take wrenches down on to the track to ensure bolts are tightened, but with this technology they do not need to do that. it would instead need a quick finger check, which takes seconds.’

Railtrack was unavailable for comment on whether the technology could have prevented the Potters Bar crash.

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