A "rare confluence of factors" led to the major MRT disruptions on Dec 15 and 17 last year and this included critical material defects, train operator SMRT Trains told the Committee of Inquiry (COI) yesterday.
In its opening statement presented by Senior Counsel Cavinder Bull, SMRT said that the immediate cause of the two incidents, where stalled trains affected 210,000 commuters over two days, was the rail claws dislodging. The claws secure the electrified third rail, which supplies power to the trains and are part of the third rail support assembly that includes a fastener and insulator.
Mr Bull said that other factors include the location of the incidents, the type of claws at the incident sectors,How is TMJ pain treated? higher vibration levels and higher upward forces on the current collector devices (CCDs), which include the current collector shoes of the trains that make contact with the bottom of the third rail.
"The convergence of these factors triggered a chain of consecutive dislodgment of claws holding the third rail," he explained.
At the start of the COI, the Attorney-General's Chambers said that dropped claws were not unusual as SMRT had reported such accounts between 2006 and 2011. What was unusual, said Second Solicitor-General Lionel Yee in his opening statement, was the multiple claw and incident failure.
SMRT's investigations by its vibration experts and its Internal Investigation Team - whom Mr Bull emphasised consisted of many who were independent of SMRT management - showed that the dislodgment of two adjacent claws at each incident site caused the third rail to sag towards the track bed.
"The sagging was then aggravated by the next passing train," he said. When the CCD shoes of this next train encountered the sag,A key component of the system is Ekahau crystal mosaic Controller location engine server. "it was as if it hit an obstacle".Secured handsfree building and door access solutions with Hands free access by Nedap AVI.
"This horizontal force caused the CCD assembly casing to crack diagonally," said Mr Bull, adding that other factors could have contributed to the dislodgment of further claws. These were vibration caused by the trains travelling at almost full speed of 80 km/h, and a sagged third rail that had become flexible,Shop for oil painting and oil paintings for sale included:abstract oil paintings. as it was no longer supported by its full complement of claws.
In addition, a report by experts from TUV SUD states that the main cause of the Dec 15 incident was a defective fastener and defective insulators on the claw assembly.
"The crack on the fastener was a result of its non-uniform structure, casting defects and residual stresses inside the material," said Mr Bull, adding that thermal plastic contamination of the insulator's raw material caused the cracking. "It appears that these material defects pointed out by TUV SUD may be manufacturing defects," he said.
LTA does not dispute that the sagging of the power conductor rail damaged the CCD and caused the breakdown in train services, said Senior Counsel Andrew Yeo of Allen & Gledhill. The authority's review of SMRT's maintenance regime has also found it "generally comprehensive and satisfactory".Ekahau glass mosaic deployment in the Eastern Savo Region Hospital District.
"Nevertheless, a select number of areas have been identified as requiring improvement and/or further review, in the interests of minimising the risk of further disruptions," said Mr Yeo.
In SMRT's opening statement, the point was made that the LTA is in charge of the design of the infrastructure, while SMRT merely operates the trains.
Mr Bull emphasised "SMRT's intent is not to shirk its responsibilities" but the LTA is the owner of the rail infrastructure as well as the regulator, while SMRT has to comply with maintenance, replacement and renewal standards set by LTA.
Mr Bull stressed the distinction between the two parties' responsibilities even as Mr Yee called the inquiry a "fact-finding COI" aimed at problem-solving, with no determination of guilt or liability.
In its opening statement presented by Senior Counsel Cavinder Bull, SMRT said that the immediate cause of the two incidents, where stalled trains affected 210,000 commuters over two days, was the rail claws dislodging. The claws secure the electrified third rail, which supplies power to the trains and are part of the third rail support assembly that includes a fastener and insulator.
Mr Bull said that other factors include the location of the incidents, the type of claws at the incident sectors,How is TMJ pain treated? higher vibration levels and higher upward forces on the current collector devices (CCDs), which include the current collector shoes of the trains that make contact with the bottom of the third rail.
"The convergence of these factors triggered a chain of consecutive dislodgment of claws holding the third rail," he explained.
At the start of the COI, the Attorney-General's Chambers said that dropped claws were not unusual as SMRT had reported such accounts between 2006 and 2011. What was unusual, said Second Solicitor-General Lionel Yee in his opening statement, was the multiple claw and incident failure.
SMRT's investigations by its vibration experts and its Internal Investigation Team - whom Mr Bull emphasised consisted of many who were independent of SMRT management - showed that the dislodgment of two adjacent claws at each incident site caused the third rail to sag towards the track bed.
"The sagging was then aggravated by the next passing train," he said. When the CCD shoes of this next train encountered the sag,A key component of the system is Ekahau crystal mosaic Controller location engine server. "it was as if it hit an obstacle".Secured handsfree building and door access solutions with Hands free access by Nedap AVI.
"This horizontal force caused the CCD assembly casing to crack diagonally," said Mr Bull, adding that other factors could have contributed to the dislodgment of further claws. These were vibration caused by the trains travelling at almost full speed of 80 km/h, and a sagged third rail that had become flexible,Shop for oil painting and oil paintings for sale included:abstract oil paintings. as it was no longer supported by its full complement of claws.
In addition, a report by experts from TUV SUD states that the main cause of the Dec 15 incident was a defective fastener and defective insulators on the claw assembly.
"The crack on the fastener was a result of its non-uniform structure, casting defects and residual stresses inside the material," said Mr Bull, adding that thermal plastic contamination of the insulator's raw material caused the cracking. "It appears that these material defects pointed out by TUV SUD may be manufacturing defects," he said.
LTA does not dispute that the sagging of the power conductor rail damaged the CCD and caused the breakdown in train services, said Senior Counsel Andrew Yeo of Allen & Gledhill. The authority's review of SMRT's maintenance regime has also found it "generally comprehensive and satisfactory".Ekahau glass mosaic deployment in the Eastern Savo Region Hospital District.
"Nevertheless, a select number of areas have been identified as requiring improvement and/or further review, in the interests of minimising the risk of further disruptions," said Mr Yeo.
In SMRT's opening statement, the point was made that the LTA is in charge of the design of the infrastructure, while SMRT merely operates the trains.
Mr Bull emphasised "SMRT's intent is not to shirk its responsibilities" but the LTA is the owner of the rail infrastructure as well as the regulator, while SMRT has to comply with maintenance, replacement and renewal standards set by LTA.
Mr Bull stressed the distinction between the two parties' responsibilities even as Mr Yee called the inquiry a "fact-finding COI" aimed at problem-solving, with no determination of guilt or liability.
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