Friday, 6 July 2012

Train disruption inquiry doesn’t pull any punches

COI report faults SMRT’s inadequate maintenance for the debacle


Guanyu 道 said...

Train disruption inquiry doesn’t pull any punches

COI report faults SMRT’s inadequate maintenance for the debacle

Samuel Lee
05 July 2012

The massive MRT service disruptions on Dec 15 and 17 last year could have been avoided if adequate maintenance measures and checks were carried out. And while SMRT’s response focused on train safety and operations, it should have been on the well-being of passengers in stalled trains and stations instead.

This was the conclusion of the Committee of Inquiry (COI), which submitted its report to the Transport Minister on Tuesday and released it to the public yesterday. Four SMRT trains stalled on Dec 15 when their current collector device (CCD) shoes, which draw power from the electrified third rail, were damaged.

The inquiry, which began on April 16 and lasted six weeks, agreed with the expert witnesses that the damage was initiated by a defective fastener in the third rail support assembly (TRSA). This, in turn, caused the TRSA claw to be dislodged and the third rail to sag by 40 mm. The trains’ CCD shoes have a tolerance of up to 65 mm but the initial sag made the two adjacent TRSAs more vulnerable to vibration.

By coincidence, the insulators of these two adjacent TRSAs were later found to be inherently defective too and over time, the two TRSAs failed gradually and the third rail sagged further.

The COI said that these material defects took time to develop before the Dec 15 incident (the experts were not able to determine how long). But they were not identified and remedied under SMRT’s maintenance regime.

The sagging third rail subsequently damaged the CCD shoes of passing trains. The shoes are designed to break off cleanly in such a situation but some failed to do so and became twisted because of over-tightened bolts. These twisted shoes then went on to rub against third rail covers and further destabilised the third rail system elsewhere along the network.

The forces generated by the CCD shoes of multiple trains dislodged three more claws and caused the third rail to eventually come to rest on the trackbed, thus making this section totally impassable to all trains.

The experts felt that the Dec 15 breakdown was caused by a combination of factors, none of which individually would have resulted in the incident.

But in SMRT’s haste to resume revenue service on Dec 16, the train operator did not conduct a sufficiently thorough check and the CCD shoe damage on the rogue trains went undetected. One or more of these trains, the COI believed, triggered the second service disruption on Dec 17, which might otherwise have been prevented.

The five-hour service disruption on Dec 15 affected some 127,000 commuters, while the seven-hour Dec 17 episode involved 94,000 commuters.

Transport Minister Lui Tuck Yew will go through the COI report and respond during this month’s Parliament sitting.

The report also contained recommendations to address the possible root causes and contributory factors. The key recommendations on engineering and maintenance issues include better detection and rectification of single sags and TRSA defects, and enhanced inspection of TRSAs and the third rail.

Single sags of the third rail are sags caused by the dislodgement of one claw and the report said this must be treated with utmost urgency as they render adjacent TRSAs more vulnerable to failure. The COI suggested that SMRT and the Land Transport Authority (LTA) look at the feasibility of fitting some trains with equipment that can detect such sags and running them across the network daily.

The COI also noted that annual TRSA inspection were not carried out despite being specifically required in the original MRTC Maintenance Manual, and that the Dec 15 incident could have been averted if these checks had been undertaken.

Guanyu 道 said...

To address the issue of an ageing infrastructure’s occasional claw drops, the COI agreed with the experts that SMRT and LTA should develop a new and more robust TRSA with a positive locking mechanism. SMRT and LTA should also continually look out for or develop improved designs for equipment such as TRSAs that can reinforce the network’s reliability.

Turning to incident management, the COI was satisfied that safety was not compromised although it observed a lack of communication between SMRT and LTA on Dec 15.

It said that an integrated land transport emergency plan with clear communications protocols for critical decision making might have been able to prevent the Dec 17 incident and recommends that LTA take the lead in working out such an overall plan with other public transport stakeholders.

In response to the COI report, SMRT said that the December incidents were caused by “a confluence of factors, a key one of which was isolated and latent material defects”, and added that the rogue trains had suffered “not easily detectable CCD shoe damage”.

It also cited challenges posed by an ageing MRT system and increasing ridership. But it admitted that “there are areas we can improve in our maintenance and monitoring regime and our work processes”.

It mentioned improvements in service reliability and incidence response following the December incidents and that these included many of the COI recommendations.

“In some other areas, we have even gone beyond COI recommendations,” said an SMRT spokeswoman. “We will review the COI recommendations to take in further enhancement measures as appropriate, in conjunction with LTA.”

The train operator also pointed out that it has operated “a comprehensive maintenance regime in the past, regularly validated by LTA, which has served us well and placed SMRT among the top performing metro operators, as evidenced by international benchmarking studies and testimonies from the experts at the COI hearings”.