Optimising real time rail maintenance efficiency
01 May 2018
Integrating passive UHF RFID technology directly with an IoT philosophy can significantly improve the maintenance procedures of tram and train operators; and maintenance data can be managed on a central system.
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By using RFID to identify key objects, moreover, updates automatically transferred via the internet can be used to optimise inspection scheduling and corrective procedures.
To achieve this, passive UHF on-metal RFID transponders/tags are attached to a rail vehicle’s major components, and harsh rail environment-compatible antennas and readers are deployed trackside, or between the rails, to collect data about when components leave and return to the maintenance depot. Once the required tram or train components are tagged, their serial numbers and history can be entered into the system operating software and paired to the unique ID number encoded to the tag.
The software can then store a parent-child relationship between a vehicle’s tag and those of its components. Operational data can then be collected to learn more about the components’ usage, and consequently, indicate when scheduled maintenance and inspections are required.
The basic concept can be implemented to three levels of IoT complexity, each with increasing benefits:
Automated data collection (1st level IoT)
At its most basic level, data collection using RFID tags and IoT technology will increase depot operating flexibility, due to the availability of real time information on working processes, even where there are multiple maintenance depots. Once all depots on the system are equipped with antennas and readers, operators can gather data from every vehicle equipped with tags. Tests of such systems have shown a 60% reduction in average time spent on operational maintenance processes – and a 20% increase in the efficiency of spare-parts management. This is enough to deliver a 100% return on investment within just a year.
The system works by automating data collection of all regularly-inspected parts when the vehicle enters the maintenance depot. It provides real time event logging for the complete lifecycle of every item and can record configurations of incoming and outgoing trains.
The central management system can then allocate a status to every item (for example, “ready to go”, “needs maintenance” or “maintained and ready to go”). It could even issue alerts if a train leaves the depot with an incorrect status configuration.
Passive UHF on-metal RFID tags are typically attached to axles (RFID tag replacing one lubrication point), wheel sets (tag fitted to a fixing screw), bogies (tag attached to the frame) and wagons (tag attached to the ID plate). Tags have been read in tests at up to 35km/h and can be mechanically protected – even against sand blasting.
The RFID tag becomes the link between the physical component and its corresponding record on the central database.
Predictive maintenance (2nd level IoT)
Once the fleet is tagged and the readers are fully linked to the central maintenance system, data collection can progress to enable predictive maintenance. This is an essential step on the way to condition-based maintenance (CBM), but in itself can deliver dramatic improvement in total cost of ownership (TCO) through fewer, but more focused, maintenance interventions – for better overall results at reduced cost. It can also deliver feedback on product performance to improve vehicle development.
Wear status data can be fed into the operational software system and written to existing or additional tags for future monitor-ing. Measurements of all kinds of important physical values for ongoing lifecycle management – indicating the wear status of key components in relation to the performance of the train – can be used.
Typical monitored components with wear status data written to passive UHF on-metal RFID tags/transponders can include:
• Wheel profile monitoring system – Measures the wheel profile and assesses the condition in comparison to several key markers such as flange height, flat spots and so on.
• Brake pad monitoring system – Issues an alert if a brake pad is missing, and will measure every brake pad thickness, calculate brake pad wear rate and predict when replacement is due.
• Brake disc monitoring system – Measures brake disc thickness, disc profile and maximum wear depth, providing alerts if something is out of operating parameters.
• Wheel damage monitoring system – Measures flat spots on wheels and reports the damage condition of a wheel by a system of thresholds, to determine when it must be sent for wheel re-profiling.
• Video inspection systems – For condition surveillance of critical fasteners, suspension elements, and wheels.
Condition-based maintenance (3rd level IoT)
The third level is condition-based maintenance, which can help maintenance operators regularly track the condition of the constituent parts of a tram/train’s critical components (such as its wheels and axles).
This can be achieved with embedded passive intelligent UHF transponders, which can, for example, monitor the relative rotation of the inner and outer parts of every wheel, and between the wheels and the axle. This is facilitated by the addition of a simple ‘open and closed’ contact on the rotating part with the inputs connected directly via a cable to the transponder.
By direct real time monitoring of such components, which are likely to need regular servicing, operators can save as much as 80% of time required for existing inspection processes and reach 100% accuracy in status control.
Looking to the future, HARTING and other companies are developing a range of new sensor tags to monitor values, such as pressure, temperature and shock and vibration levels, in order to verify their relative impact on operating conditions. It will be possible to integrate all of these into the infrastructure required for first and second level IoT-enabled maintenance systems.
The antennas, readers and RFID tags needed for such maintenance systems are available and in use now. For example, HARTING has recently introduced a new compact ruggedised IP67 mid-range reader (the RF-R300), which is fully compliant with rail standards. This provides tram/train depot maintenance managers with greater RFID installation design flexibility, by providing reader solutions that can satisfy different site performance requirements.
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