THE RISK of train accidents rises sharply if rail cannot be maintained at temperatures where it remains stress free, a meeting of the Railway Civil Engineering Association heard this week.
If rail temperature falls out of the neutral range, it is put into tension and can break. If temperature rises, compressive stress can lead to buckling.
Neutral temperature is the temperature of the rail when it is neither in tension nor compression, making it stress free.
Latest figures released by Her Majesty's Railway Inspectorate show the number of rail buckles caused by high temperatures is on the rise.
If this trend is to be reduced, it is essential that more testing of rails is done, and that the track is maintained to a high standard, managing director of Vortok International Peter Shrubsall told the meeting at Great George Street.
In the worst case, rail buckles and breaks can lead to train derailments as well as delays, associated compensation costs and loss of revenue.
Temperature induced stress is a major problem in countries such as Sweden and Finland where winter temperatures can drop to -40degreesC. In the UK, temperatures are relatively constant.
If the ballast, ballast shoulder, clips and sleepers are kept in good condition, the track can resist the extra stress put into it relatively well.
The growth of rail buckling can be turned around by using non destructive testing systems, allowing more rails to be tested more frequently, Shrubsall claimed.
Previously, rail had to be cut and strain gauges attached to obtain a reading. Cutting rails to test was time consuming and costly. Welding up the cut after testing was completed left the rail with a potential point of weakness.
Non destructive systems are now enabling tests to be carried out in minutes, allowing contractors to gauge the condition of track they are responsible for more easily.
Thanks to new technology, engineers are getting a better grasp of track behaviour, Shrubsall said. Thousands of tests are being carried out and will be key to reducing the number of breaks and buckles.