Jonathan Newell reports on a condition monitoring system which Transport for London is using to continuously check the health of its Bakerloo Line rolling stock.
One of the main priorities on the London Underground system is to keep the system moving at all times, a task that becomes more difficult as the rolling stock gets older. Despite major upgrade programmes and new trains being delivered across the network, the process takes time and some lines are destined to retain their old stock for another decade.
One such line is the Bakerloo, which runs from central to north-west London. The line itself was built at the turn of the last century and its rolling stock comprises 36 trains using the 1972 Tube Stock (72TS) units. Designed to last four decades, these units are now at the end of their design lifespan but, according to Transport for London’s (TfL) Bakerloo Line Fleet Life Extension Plan, their replacement with new units will not commence until at least 10 years from now.
On September 30 2014, the Mayor of London, Boris Johnson, and Transport for London (TfL) launched a public consultation to seek views on the extension of London Underground’s Bakerloo line, which could run from Elephant & Castle towards New Cross, Lewisham, Bromley and Hayes.
The cost of the extension is estimated at up to £3bn. It is estimated that once the relevant permissions are received, and necessary funding secured, that construction would commence by 2023 and be completed during the 2030s.
Meanwhile, the 72TS trains will continue operating their route, carrying over 100 million passengers every year. Recently, TfL installed a Train Monitoring System (TMS) across the fleet to enable continuous checks to be made on critical parameters to alert maintenance staff to any repairs that need to be made before a failure occurs.
According to TfL, the TMS is designed to monitor a total of 170 parameters throughout the train, with the main focus being on such critical systems as traction and braking as well as door operation. Such comprehensive data collection has never been done previously and when fully rolled out across all of the Bakerloo line trains, it is expected that the TMS will generate around 20 Gbytes of data daily.
The careful analysis of such data will enable TfL to have a clear picture of the condition of each of the trains and what actions are required to prevent them from failing, thereby improving maintenance speed and reliability and reducing passenger delays and unexpected outages.
Consisting of over 30 TMS modules located throughout the train, each module is assigned to the task of monitoring certain inputs that are collected from the train’s main electrical system. The input from these modules goes to a TMS driver alert device which is installed in the cab to inform the driver of any fault that has occurred and where it is located. Some of these problems can be rectified from within the driver’s cabin.
However, each of the modules is also designed to transmit its data wirelessly to a central hub computer fitted to each train. Existing wireless networks within the London Underground infrastructure are used as a conduit for the telematics system so that the status of the modules on the train can be monitored as it passes through the station. For controllers and schedulers to obtain train status is therefore a continuous process, rather than one which can only be achieved during planned stoppages at depots.
By using telematics and collating the monitoring system data in a central database, fault-finding becomes faster and more effective by giving clear information on potential as well as actual failures as they occur and under what conditions.
Using modern levels of telemetry in legacy rolling stock systems is enabling the Bakerloo Line to continue using its old equipment with confidence whilst reducing the risk of unplanned interruptions on a busy and crucial part of the London Underground network.
The Bakerloo Line Train Monitoring System was recently nominated for an award in the British Engineering Excellence Awards in the Electronic Product of the Year category.