The carriages of the affected train being towed to Ulu Pandan Depot on Sept 25. - Photo: ST
SINGAPORE: Train services along a four-station stretch of the East-West Line between Jurong East and Buona Vista will remain disrupted over the weekend, in a breakdown that has affected the commutes of more than 1.3 million passengers so far.
The disruption was caused by a faulty train that was returning to Ulu Pandan Depot on Wednesday (Sept 25).
A defective axle box – a component on a train’s undercarriage – fell out near Dover station. This caused the undercarriage, or bogie, to go off the rails.
It left in its wake extensive damage to the tracks and trackside equipment.
How did the axle box become dislodged from the bogie, and was the incident preventable, given the widespread use of preventive technology in rail maintenance?
These are among the questions that the probe into the serious incident must answer.
Preventive maintenance has been a focus for SMRT.
About nine years ago, for instance, the rail operator adopted a monitoring system that deploys sensors to scan the entire train fleet on the North-South and East-West lines for train wheel and axle defects.
Axles connect the wheels of a train.
While it is unclear if such a system could have detected a defective axle box, the fact is that SMRT has been using technology to shore up its rail maintenance and better predict when parts will fail and need to be replaced.
The North-South and East-West lines have also just undergone a S$2.6 billion renewal programme of its six core systems.
These included replacing sleepers that hold the running rail in place, changing the third rail that supplies power to trains, upgrading the signalling system, and renewing the power-supply system.
Replacement of older trains is also part of the renewal programme, and will be rolled out progressively till the end of 2026.
The faulty train in question was a first-generation Kawasaki Heavy Industries workhorse of more than 35 years, and there are 48 others still in service.
It is the first time a defective axle box has dislodged from an SMRT train, and such occurrences are rare.
Associate Professor Yap Fook Fah, co-director of the Transport Research Centre at the Nanyang Technological University, said it was very unusual for axle box failures to happen.
Train parts, such as axle boxes, are “over-engineered”, and are built to last since they have passed vigorous tests to adhere to international standards, he added.
“This is because axle boxes are designed to be very robust, so it is hard to think of why it fell off,” said Prof Yap, who is also a member of the railway and transportation engineering technical committee at the Institution of Engineers, Singapore.
Mahesh Hariharan, assistant faculty head of rail, transport and logistics at the Technical University of Munich Asia, said one reason could be worn-out axle box bearings that have been exposed to harsh conditions on the tracks.
This could be due to repeated rail vibrations from the wheels coming into contact with the rail, he added, or defects along the rail or on the wheels.
Another question is why the train continued travelling on the westbound track towards Ulu Pandan Depot despite the bogie being derailed, causing severe track and equipment damage.
It is still unclear at what point on Sept 25 did part of the train carriage derail, and what prompted the train driver to stop it on the tracks leading to the depot.
What we do know is that the defective axle box was on the third carriage of the six-carriage train.
Prof Yap said the train driver, located in the first carriage, could have been “quite far away” and may not have noticed immediately that something was wrong. Each carriage is about 22m long.
Hariharan noted that older SMRT trains may also not be fitted with the same advanced condition-monitoring systems present on newer trains.
These systems collect data from onboard sensors so that pre-emptive maintenance can be done before faults happen.
The older trains, therefore, “lack an extra set of eyes” to spot defects, he added.
Whether sufficient checks were done on the defective part before the incident is another issue that the investigation should look at.
For now, Prof Yap suggested doing more checks – over and above the stipulated inspection frequency – to collect up-to-date information about the condition of the trains, especially the older ones.
Hariharan agreed that extra attention could be given to older trains, with more frequent checks and tighter inspections for those in service for longer.
Axle boxes on trains are inspected every three weeks under SMRT’s current maintenance regime.
The operator will discuss with the Land Transport Authority whether the frequency of inspections should be increased.
Apart from shedding light on what went wrong, a thorough investigation will help rail operators and the authorities take steps to learn from this disruption and better manage the aftermath of future incidents.
With the major disruption inconveniencing so many, a full accounting of the incident will also go some way towards restoring public confidence.
Affected commuters deserve no less. - The Straits Times/ANN
