Investigators from Parsons Brinckerhoff and Meidensha Corporation helped the LTA to identify an ongoing water leak and inadequate maintenance as contributing factors.
The maintenance lapses resulted in a system-wide disruption on the NSEWL for more than two hours during the evening peak period, inconveniencing 413,000 commuters travelling on the MRT network’s most heavily-utilised lines.
The fine will go to the Public Transport Fund to help needy families with their public transport expenditures.
The disruption was caused by intermittent tripping of the rail power system at multiple locations by a safety mechanism. A combination of factors had resulted in weak electrical resistance of one of the third-rail insulators, which in turn activated the mechanism.
The investigators identified the water leak in the tunnel close to the insulator as a contributor to the weak electrical resistance. The leak, and inadequate maintenance, had resulted in extensive mineral deposits on the insulator and trackside equipment. Laboratory tests found high chloride content in samples of the water seepage and in the deposits. The consultants deduced that the conductive mineral deposits, together with the wet tunnel environment, had significantly reduced the effectiveness of the insulator.
As a result, electricity flowed from the insulator to the ground, resulting in a higher than normal voltage between the running rail and the ground. This abnormal voltage, coupled with the usual voltage fluctuation as trains move, activated the safety mechanism and tripped the power system. LTA’s findings are corroborated by the fact that the intermittent tripping stopped after SMRT had replaced the contaminated insulator and rectified the tunnel water seepage.
LTA has concluded that the incident could have been prevented if SMRT had rectified the tunnel water seepage as required under LTA’s Code of Practice for maintenance. Based on SMRT’s records, seepage in the tunnel section in question had been detected during routine track patrols in mid-June. The extent of mineral deposits on the trackside equipment also shows that SMRT’s maintenance measures had been inadequate, said LTA.
SMRT had also failed to meet requirements under the code of practice for incident management, said LTA, including a failure to inform of the intermittent traction power tripping in a timely manner.
LTA chief execturive Chew Men Leong said: “After a full and comprehensive investigation, LTA concludes that the disruption is due to maintenance lapses by SMRT. LTA hence intends to impose a high financial penalty on SMRT in light of the seriousness of the incident, and given that several hundred thousands of train commuters, as well as motorists and bus commuters, were inconvenienced by this disruption. We require SMRT to review and improve their maintenance regime to prevent future occurrences.”