Maintenance is a vital part of the system approach: appropriate and timely maintenance forms an integral part of the system approach that needs to be adopted by railways if they are to meet the demanding challenges being put upon them

International Railway Journal, Sept, 2005 by Jay Jaiswal

Railways revolve around the circle of "inspection" followed by "reaction". Now that inspections can be made at higher speeds, earlier intervention should be possible. However, the philosophy is still to "inspect quality in". In other words, the safe and efficient running of the railways cannot be guaranteed without frequent inspections to confirm the condition of the track.

In some industries, the approach is to design out failure mechanisms and regulate inspection on the ability to predict degradation. For railways, the design and operational variables and the response of track components to them are extremely complex and make true predictive condition monitoring difficult. However, some recent advances in sensor technologies, such as the use of fibre optic Bragg gratings, provide a way forward. Harsh conditions in some manufacturing industries have led to the monitoring of deviations from healthy "signature tunes" instead of debating the accuracy of absolute measurements. Such an approach should be applicable to track monitoring.

There is also a need to separate the following types of condition monitoring systems. The most relevant example of operational condition monitoring relates to the operation of switches and the associated mechanisms. Various systems exist. Recent developments of such systems have been in the provision of failure predictive capability based on detection of changes to signals such as motor current. Alarms can then be sent to the maintenance crew. Operational monitoring is also relevant to the operation of level crossing barriers but some recent accidents suggest the need to incorporate further sensors and operational logic.

A key example of policing of compliance to specifications is a wheel impact load detector to identify wheel fiats. Even if a lot of such devices were installed (at great cost), the rogue wheels can still damage the track before they have been detected. However, such devices can be installed at the depots to prevent vehicles with defective wheels from leaving.

Proactive and preventive maintenance enables prediction of residual life and the need for timely intervention to prolong track life. This remains a key challenge and needs further research that is driven by the shrinking time for maintenance (and conversely by the need to increase track availability) and the need to increase worker safety by reducing manual track inspection.

The Intelligent Image Analysis project provides an objective measure of various RCF and running surface characteristics for the entire network so that correlations with track design and traffic characteristics can be established. Equally, the development of a "smart" track capable of monitoring track forces from identified passing vehicles, and undertaking analysis to predict remaining life or the need for maintenance intervention, would be a true application of proactive and predictive condition monitoring. The crunch question that remains is: who should pay for research into the development of such a system?