Tracking the cracks

A portable inspection system that could soon be used across the UK’s rail network will be able to spot even the tiniest cracks in track welds, reducing the chance of train derailment, its developers claimed this week.

The system has just completed an evaluation test in which it found cracks in 20 per cent of the 1,000 welds it analysed on lines in the UK.

Developed by Amec Spie Rail, a UK-French joint venture, the radiographic technology used radioactive isotopes to produce images, and was able to detect incredibly small defects in the welds.

Broken welds can cause disruption to services and if left can be a serious safety hazard, said Phil Ransom, contract manager of Amec Spie Rail.

‘Around 20 per cent of the welds we inspected had some form of defect — and around 4-5 per cent had sufficient cracks that they had to be removed from the track,’ said Ransom.

Track welds have a very coarse, crystalline structure, which does not respond well to the ultrasound systems used to inspect the rails themselves, so an alternative imaging technology is needed, said Ransom.

In the Amec system, the radioactive isotopes are exposed to the weld, producing a detailed image that is captured on a digital film and then processed. The image can be studied immediately on the system, saved for review later or transmitted to a remote PC.

The system, which costs £50,000, takes around 15 minutes to inspect each weld, during which time it takes three images, allowing a 3D picture to be built.

Fortunately, a broken weld has not been responsible for a train derailment in the UK since an incident at Bushey in Hertfordshire in 1980, said Ransom. ‘But out of around 500 rails broken in the UK each year, 150-200 are associated with welds, so it is a major area requiring attention,’ he said.

Amec, which developed the system with consultants CoMech, is bidding for a three-year national contract from Network Rail to carry out weld inspections using the equipment. The company said it expects to hear ‘imminently’ whether this bid has been successful.

The technology has also been tested in Australia. As well as track welds, the team is looking into the possibility of using the system to inspect for railhead damage and cracks in ore wagon couplings on the Australian railways.


A monitoring system designed to prevent train delays caused by motorists crashing into railway bridges is to be used on parts of the UK network after a successful trial.

The BridgeGuard system, developed by Ferranti Technologies, has been shadowing normal procedures for dealing with damage to bridges in the northwest of England for the past three years, and will run independently from the end of this month.

The system, which costs around £35,000, consists of a number of sensors attached to the bridge. When a vehicle hits the bridge the sensors detect the fault and notify maintenance engineers of the impact and intensity.

According to Railtrack, now part of Network Rail, hundreds of railway bridges in the UK are hit by vehicles each year, causing extensive delays to trains, road obstructions and in some cases serious damage to the bridges.