At about 9am on Wednesday, a faulty first-generation Kawasaki Heavy Industries train that had been in service for more than 35 years was returning to Ulu Pandan Depot when its axle box became dislodged and dropped, said SMRT and LTA.
This caused one bogie to come off the running rail between Dover and Clementi stations.
In turn, this severely damaged the track and track equipment, with 34 rail breaks across 1.6km of westbound tracks between Clementi and Dover stations.
Three machines that are used to divert trains to different tracks, a third rail that supplies power, as well as power cables and rail clips were also damaged.
This is what caused the power trip at about 9.25am on Wednesday, disrupting train services between Boon Lay and Queenstown MRT stations.
When the axle box was dislodged, the train probably became unstable, causing it to move left and right on the rails, said Mr Teo, who is the managing director for Amega Asia.
Using the 34 rail breaks along the 1.6km of track as a gauge, he estimated that the train would have travelled for one to two minutes after the undercarriage came off the rails before stopping.
Typically, the time taken for a train to come to a complete stop after the brake has been applied depends on several factors, including the speed of the train and whether the train is in automatic or manual mode, said Mr Jumaidi.
In this case, the emergency brake should have been applied when the bogie came off the train, he added.
The train was not carrying any passengers since it was on the way to the depot, or the problem might have been caught earlier, said Mr Teo.
As the power lines are typically located right next to the rails, the train’s movements damaged not only the tracks but also the power cables and other equipment, he added.
With over 30 rail breaks and the time needed to conduct repairs, the damage seems “quite serious”, said Mr Teo.
“I can only assume that with the momentum of the train, the bogie that came off would have been dragged along the track, which caused the damage,” added Mr Jumadi.
“However, the investigation currently being conducted will reveal more facts about what actually happened.”
