THE PROSPECT of rail flaw detection at line speed was one of several innovations in condition monitoring and infrastructure assessment held out to delegates at this year’s Railway Engineering conference in London on July 6-7, sponsored by Railway Gazette International.
Rachel Edwards and Steve Dixon of Warwick University have been looking at the use of Rayleigh waves to provide contactless detection of rolling contact fatigue (p495). Elimination of the present wheeled probe arrangement allows the ultrasonic signals to be propagated into the rail much faster, with different frequencies penetrating the rail to the same depth as their respective wavelengths. Laboratory tests on a dozen rail lengths with known defects have established the principle, and the researchers are starting to calibrate their results. They are also looking to form a collaborative venture with rail industry partners to develop a prototype for field trials.
Another high-speed testing unit is taking shape in the USA, where a consortium of Massachussets-based Omtram Inc, BNSF and the Federal Railroad Administration is developing Ground-Penetrating Radar for assessment of subgrade condition. A test unit mounted on a road-rail vehicle has uncovered a growing range of subgrade failure modes following the introduction of heavier freight wagons. However, the test rig is limited to around 50 km/h. Detailed specifications are now being drawn up for a GPR test car able to run at up to 120 km/h, with the aim of placing orders at the end of this year for three vehicles - one for each partner.
Faster and more detailed monitoring generates huge quantities of data to be analysed and stored. As an example, a laser scan of a tunnel bore recently undertaken by Bentley Solutions, Amberg Measuring Technique and Leica Geosystems produced 9 million recording points from a length of just 190m. Bentley has developed a software package that can correlate the results, develop a series of cross-sections and relate them back to the original CAD drawings of the tunnel, based on its MicroStation processing platform.
Railway Engineering 2004 included a session on development of the Citybanan cross-city suburban rail tunnel in Stockholm, looking at track alignment, optimising the capacity of junction layouts, and design of the stations and metro interchanges.
Whilst track and infrastructure issues dominated many of the papers, rolling stock developments included work by the Korean Railway Research Institute on active tilt designs and automatic stepping boards to cover the gaps between trains and curved platforms on the Seoul metro.
The Railway Gazette award for the best paper on innovation went to Rajiv Upadhyay of India’s Northeast Frontier Railway (photo), who has been working on a low-cost vehicle-mounted hotbox detector in conjunction with Northern Railway’s Moradebad workshops. This followed a fatal accident in 1999 when a wagon derailed into the path of an oncoming express due to a bearing failure.
IR ruled out the use of electronic sensors due to the cost and technical problems of fitting them to a large wagon fleet. The Upadhyay Sensor uses a spring-loaded valve attached to the brake pipe, which is held closed by an alloy plug designed to melt at 85íC. In the event of a bearing running dangerously hot, the valve opens and brings the train to a safe halt. A rake of five vehicles has been tested successfully, despite wear problems caused by asymmetric movement of the axle bearings within the bogie. The team are now working on a stainless steel version, which would also eliminate the problem of the prototype brass valves being stolen for their scrap value.
