VIBRATION MONITORING
Test rig keeps transport on the rails
Condition monitoring system keeps check on railway axle vibration and temperature to prevent failures in use
R
ailway operators across the world are faced with a constant challenge of ensuring that wheelsets on rolling stock are monitored, maintained and are always in a safe condition for use.
The wheelsets are made up of a number of critical
components, all of which need to be checked and maintained, including axle boxes and bearings, suspension elements and joints and the wheels themselves, which can suffer damage, wear and flat spots that reduce performance and affect their safe use. Yet it is the axle box and bearings that are most likely to fail and are the hardest in which to detect defects with a purely visual inspection.
AXLE BEARINGS As rotating mechanical assemblies, bearings will always emit a level of vibration and noise during normal operation in good, lubricated condition. As the bearings wear and exhibit defects, the signature of the vibration and the acoustic emissions change. Therefore monitoring these parameters will provide engineers with some idea of the level of wear, the probability of impending failure and the need for lubrication, repair or maintenance.
MAINTENANCE AND MONITORING STRATEGIES Lubrication problems – such as contamination, incorrect or insufficient lubrication and duration between maintenance events – are the most common causes of bearing failure so a planned maintenance schedule is critical to achieving reliable performance over the expected life of the bearing. Bearing condition assessment through loading and monitoring can be performed during
maintenance intervals to determine whether the bearing needs replacing or not and to gauge the remaining expected life. In some critical applications, bearings are replaced at set intervals, regardless of condition. Many operators favour monitoring during
maintenance as a way of assessing axle bearing condition. Another option is to constantly monitor the bearing during operation on the train. While this technique has its advantages in terms of coverage, it requires sensors that can cope with the harsh environment of constant in-service use as well as complex data acquisition and analysis for large numbers of components.
CONDITION MONITORING TEST RIG To ensure the safety of its operations in Asia, one railway company is using a condition monitoring test rig from bearing and noise, vibration & harshness (NVH) specialist, Schaeffler. The operator is using the rig to inspect train wheelsets and gearboxes so as to eliminate unplanned train downtimes and minimise maintenance costs.
22 /// Testing & Test Houses /// December 2019
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