
Some wheels on the Yellow Line monorail trains were defective and their use has been suspended pending thorough inspections, Deputy Transport Minister Surapong Piyachote said on Wednesday.
He said the Yellow Line operator, Eastern Bangkok Monorail Co, had been ordered to make thorough safety checks on all trains before they were put back into service on Wednesday.
A guide wheel fell off one of the trains on Tuesday evening onto Thepharak Road in Samut Prakan, bouncing and then hitting a taxi. The operator on Tuesday night attributed the falling wheel to defective ball bearings.
Mr Surapong said on Wednesday morning that production of a specific batch of guide wheels was defective and their use was suspended immediately.
“It remains uncertain if the wheel fell off because of heat or the ball bearings,” he said. “There must be a thorough examination.
“I assume the problem also affects other wheels. There must be an extensive investigation to determine if it is about ball bearings or heat.”
The expected life of the train wheels is about 300,000 hours, but they have been in use for only about 60,000 hours so far, he said.
He had ordered transport officials to work with Eastern Bangkok Monorail to carefully check the safety of each and every Yellow Line train before they were put back in service on Wednesday. This had caused services to be cut back to once every 30 minutes, instead of the normal 5-10 minutes.
“Today’s service intervals are longer. … The Transport Ministry must guarantee maximum service safety,” Mr Surapong said.
Transport Minister Suriya Jungrungreangkit said he had called EBM representatives in to discuss safety measures on Wednesday afternoon.
At a subsequent press conference to update the public, Mr Suriya said the incident resulted from damaged ball-bearings and that the wheel manufacturer, Alstom, was conducting a thorough investigation into the relevant parts.
At the same press conference, Mr Surapong said that six Yellow Line trains had passed safety checks and were deployed for services on Wednesday. Other units in the fleet of 30 trains were being checked and would be deployed once cleared to gradually increase train frequencies.
While the checks continue from Wednesday to Saturday, the Yellow Line will offer free services to commuters, and regular service intervals of 5-10 minutes should resume by Monday, he said.
EBM is a subsidiary of BSR JV Consortium, a joint venture between three giant SET-listed companies: Bangkok Mass Transit System Group Holding, with a 75% shareholding; Sino-Thai Engineering and Construction, and Ratch Group, a major power producer.
Another subsidiary of the same group operates the Pink Line monorail, on which a four-kilometre length of electrical conductor rail became dislodged and fell onto Tiwanon Road in Nonthaburi on Dec 24.
The Yellow Line runs between eastern Bangkok and Samut Prakan and the Pink Line between northern Bangkok and Nonthaburi. The trains used on both lines were manufactured in China by CRRC Puzhen Bombardier Transportation Systems, a joint venture of Canada-based Bombardier and CRRC Nanjing Puzhen.