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Image credit: Kevin_Hsieh / Shutterstock.com
Rail travel continues to grow in popularity with passenger lines in the U.S. alone reporting nearly 30 million riders each year according to Amtrak, the nation’s main passenger line. The amount of freight being shipped across the United Sates has also increased in recent years, with nearly 40 million carloads shipped and $82 billion in freight revenue being generated annually.
According to industry experts, one of the main attributes of using the rail lines for moving both passengers and freight is safety.
Serious railway accidents are rare in comparison to accidents involved in other means of travel, mostly because of the safety standards set by industry leaders. Despite this though, injuries and in some cases deaths do still occur.
According to the European Commission Eurostat, roughly 2,200 people were killed or seriously injured in 137 European rail accidents in 2013; while the United States reported less than 1,000 fatalities during the same time span.
In many of these cases, train-car collisions resulted in the deaths. Other types of accidents included:
- derailment
- train-train collisions
- train-person collisions
- damage to property (buckling, rail damage, etc)
Despite the fact that serious accidents and injuries are rare, train accidents do occur, making inspection a vital aspect of everyday rail maintenance. Rail lines need to be checked constantly for even the slightest defect so that problems can be fixed before trouble ensues.
Rail flaws are usually the cause of derailment accidents, according to the Federal Railroad Administration (U.S. Department of Transportation).
Even the smallest crack can propagate eventually leading to the failure of the rail. Cracks can even spread to interlinking lines and left unchecked, this can lead to a serious accidents.
Although most rail line companies spend a great deal of time and money inspecting their rails for potential problems, not all defects can be found using current detection techniques. For this reason, the Rail Test Facility (PDIF) and the FRA Technology Center (TTC) have increased their efforts to develop faster and more efficient (automated) techniques of detecting internal rail and joint bar defects in recent years.
Using various nondestructive testing techniques, the PDIF and FRA are now testing several rail defect detection methods that will enable the railroad industry to carry out more frequent and thorough inspections, without limiting traffic. The ability to test rails that are in constant use with minimal disruption to train times is also important.
Train Mounted Devices
Track circuits for signaling are currently also used to detect broken rails. While this can be useful, it has been reported that nearly half of all trains do not have track circuits, and those that do rarely use them to detect rail defects.
The FRA is currently working on a train-mounted defect detection system that would find cracked rails and other hazards. Still in testing, this device could help conductors anticipate and react to such things as broken rails or even cars on tracks miles before encountering the danger.
Measuring Rail Stress with Ultrasound Technology
Buckling has long been an issue for rail lines. Stress, heat and other problems can all lead to buckling, which can cause derailments. Although some success has been found in track mounted devices, the FRA continues to research better ways to measure rail stresses and to anticipate problems.
One method that some rail lines use to detect defects is by sending an ultrasonic signal directly into the rail. By measuring the time it takes the signal to bounce back, cracks can be located.
BINDT - Railways and NDT
British Institute of Nondestructive Testing - Railways and NDT.
Video sourced from: YouTube / bindtfilms
Since a crack prevents the signal from reaching the base of the rail, it will bounce back more quickly, alerting the inspector to its presence. Ultrasound does however have its limitations since it must maintain contact with the rails in order to work.
A more reliable source now being studied relies on a Doppler device (which does not require contact with the rails). By studying shifts in sound frequency as the train moves, cracks and other hazards can be found. Defects could also be highlighted by directing an ultra-sonic beam downward at the rail as the train moves forward.
Keeping an Eye on Track Gage Widening Strength
Derailments often occur due to widening of the track gauge. Caused by weakened ties, this widening can create a danger when tracks spread too far apart and allow the wheels of a passing train to slip down between the rails.
To combat this problem, the Deployable Gage Restraint Measuring System (DGRMS), -- developed and patented by ENSCO and Plasser & Theurer of Linz, Austria -- uses a high speed test car to check tracks for problems much quicker and more efficiently than on-site inspectors doing the job on foot.
The DGRMS works by deploying a fifth axle from the frame of a track inspection vehicle. Attached to a custom suspension that is capable of vertically loading, raising and lowering, and properly aligning the vehicle with the track, the axle can operate separately from the four running axles as it is suspended underneath the railroad car. This allows it to detect smaller problems more quickly and alert maintenance workers so that weakened areas can be fixed as quickly as possible.
As worldwide rail lines become busier and busier, it is imperative that the railway industry work with government officials to ensure the safety of passengers and trains alike. Continuing to investigate superior methods of inspecting rail lines, and finding dangerous defects is just one way to ensure that everyone who uses the rail system remains safe, and freight can move quickly and efficiently without the threat of long term delays due to maintenance or accidents.
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