Friday 8 June 2012

Shedding light on a rail mystery

By Christopher Tan, The Straits Times, 7 Jun 2012

THE Committee of Inquiry's hearing into last December's train breakdowns may have come to a close, but the work of the judges and investigators is far from over.

As they meet to deliberate over the findings of the exercise, they will make a list of useful recommendations that will, hopefully, prevent a repeat of the incidents.

They will have to find clarity in the lengthy statements from more than 110 witnesses, as well as take stock of evidence unearthed on site and from laboratory tests.

Most of all, the committee led by Chief District Judge Tan Siong Thye will have to resolve a few contradictions and discrepancies to arrive at its destination.

It is not an enviable task. Even a team of overseas experts flown in to assist in the inquiry could not arrive at conclusive verdicts on what exactly caused the disruptions, which affected more than 220,000 commuters on Dec 15 and 17 last year.

This is understandable, as forensic evidence had already been 'contaminated' by repair and recovery work done after the breakdowns - a point brought up by the committee in the inquiry.

Led by professor of vibration engineering David Ewins, from Imperial College London's department of mechanical engineering, the team of experts could arrive only at 'probable causes'.

Professor Ewins himself said in court that the disruptions were caused by 'a combination of events that were linked to each other'.

It may not be possible to establish 'the exact sequence of events', he said.

The team of six concurred on a 'likely' scenario for the first breakdown, but were less certain about what triggered the second.

Their scenarios were not a big departure from those of pre-inquiry investigations done by train operator SMRT Corp and the Land Transport Authority (LTA), Singapore's rail developer and regulator.

Structures that support the conductor rail (also known as the third rail), which supplies electricity to the trains, took centrestage in the six-week inquiry that began on April 16.

Since the MRT system was built in the late 1980s, these structures - or more specifically, the metal claws that hold the third rail in place - have fallen off now and then.

Each time a dropped claw was detected, it was put back.

But on Dec 15, a series of these claws dropped, causing the third rail to collapse and the trains to stall.

The sagged third rail also damaged several trains. Investigators suspect that some damaged parts went undetected, and these could have triggered the subsequent breakdown on Dec 17.

Thus, the spotlight has been and is still very much on the third rail claw (right): a simple piece of hardware that belies its complex role in the two breakdowns.

It has been SMRT's assertion that Singapore is one of the first countries to use this particular model of claw to hold up an aluminium composite third rail.

The LTA - whose predecessor MRTC picked this third rail-claw combination - however, maintains that the particular combination has had a proven track record in a number of metros in Germany.

MRTC merged with the LTA when the regulatory body was formed in 1995.

SMRT, citing claw supplier Brecknell Willis, said that while other metros have used this type of claw before, they have all since moved on to more secure designs.

In fact, Brecknell Willis no longer makes the original claw, which has been superseded by several design improvements.

The latest - a fifth-generation claw (left) that is bolted to the third rail - is now used widely, including in Singapore's new Circle Line.

The court also heard evidence from Brecknell Willis. The British manufacturer said it had in 1987 presented to the MRTC a new claw with a split-pin locking system that prevented dislodgement even under 'severe vibration'.

But the company said MRTC felt 'nervous' about using a new design that was untested.

Instead, various methods were employed to keep the old claws from dropping, including the use of plastic cable ties.

The committee will have to weigh all these testimonies and more to arrive at meaningful findings which it will compile in a report to be presented to Transport Minister Lui Tuck Yew - possibly by the end of the month.

And even though Judge Tan has declared more than once that the inquiry is not a trial to establish culpability but a fact-finding exercise, the public will want answers to a few basic questions.

Such as: Were the breakdowns caused by poor maintenance?

Was the system's design flawed in the first place? Is manufacturing defect to blame? Were the breakdowns triggered by a spike in ridership?

Or were they, in the words of another expert witness, caused by a 'confluence of factors'?

Whatever conclusion the committee arrives at, one thing is for sure: There will be a slew of recommended measures that both the rail operator and regulator will have to put in place to make the MRT system more reliable.

Many of these have already been set in motion, such as a $900 million plan to change components and systems of both train and rail infrastructure.

The upgrade will take up to 2019 to complete, but most changes should be in place by 2016.

Among parts to be changed will be the third-rail claw.

All 30,000 pieces of the hardware across the North-South and East-West lines will be replaced by the fifth-generation claws.

This is a vital piece of the puzzle - as the December breakdowns have shown.

But it is just one piece.

Although the latest claw design is said to be far more secure because the device is bolted to the third rail, the entire claw assembly has been known to fail.

In fact there have been half a dozen instances of fifth-generation claw failure recorded along the 6km Changi Airport Extension since it opened in 2001.

So, perhaps the more important question now is: Should SMRT embrace this claw design so quickly, or shop around some more?

As one inquiry panellist, Professor Lim Mong King of the Nanyang Technological University, pointed out so well, if a product is poorly designed or manufactured, no amount of maintenance will make it reliable.

The good professor might have added that there are also engineering structures that should be robust enough to outlast their designed lifespans with little or no maintenance.

Examples of these include building foundations, plumbing, wiring and tunnels.

Should third-rail support structures be built that way too?

Dr Vukan Vuchic of the University of Pennsylvania, who has more than 40 years of experience in the field of urban transport, was surprised when this newspaper asked him to comment on the December breakdowns.

He said 'rapid transit infrastructural failures are not common problems at all', and added that metro systems are typically 'very reliable'.

In fact, SMRT has acknowledged that it has not come across any other case of a third rail collapsing because of dropped claws.

And that adds to the mystery of Dec 15 and 17 - of what happened, how it happened and why.

Will the Committee of Inquiry get to the bottom of things in its report?

Will its findings be more conclusive than the experts'?

Will Singaporeans get answers to their questions?

It is unfair to pre-empt what the inquiry will accomplish at this stage. All will be revealed when its report is out within the next several weeks, and the contents could well be a surprise.



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