How the brakes of Fuxing bullet trains are assembled

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With a maximum operating speed of up to 350 km/h, the Fuxing bullet train is considered one of the world's fastest high-speed trains in commercial service.

With such high speeds, the quality of the brake system is vital.

The company that produces the brake system for the Fuxing trains is Beijing Zongheng Electro-Mechanical Technology.

"A full range of brake control products for Fuxing, at 160 km/h, 250 km/h and 350 km/h, are all produced here," said Jin Xiaobo, manager of the urban rail workshop of the company.

Founded in 2014, the workshop consists of two assembly lines and one laboratory.

Wang Lingzhi, the quality engineer who has been working at the workshop since it was established in 2014, introduced five tests to ensure product quality.

The urban rail workshop of Beijing Zongheng Electro-Mechanical Technology. /CGTN Photo

1. Missing parts prevention

Wang said that components are placed on their own trays. After workers in the last assembly process finish their jobs, they will check each tray to make sure there are no missing parts.

"If there is a component left on the tray, the product will be reassembled," she said.

2. Mis-assembly prevention

"Each workbench is equipped with a code scanner," said Wang, adding that before starting the assembly process, workers are required to scan the QR code on the component.

"Assembly is not allowed if the component doesn't match the information in our system."

3. Torque wrench programming

Wang provided an example of how they control the accuracy of assembly through the programming of electronic torque wrenches.

"For example, if we need four torsions on this component, we will set a torque number of four," Wang explained. "The system will know if a worker only torqued three times on the component."

The angle of each torque can also be set.

"When there are four components that need to be torqued but the worker torqued twice on two of the components, the system will realize because the torque angles of the last two times are too small," said the engineer.

4. Mutual inspection

Each worker will check the previous worker's work before starting the next assembly step to prevent loss caused by a mass quality problem.

5. Archiving information

Serial numbers of workers, equipment and components are archived so that they can be traced.

Wang said their principle is "never let quality problem out of the workshop."

For complicated products like Fuxing's brake control unit, the failure rate could be fairly high during the initial period of operation. In order to solve quality problems within the workshop, a 36-hour run-in test is required for all units before delivery.

According to Wang, some inconspicuous problems like microfractures on components and leaky joints can be filtered out by the test.

"The initial failure rate can be significantly reduced during the test," she said.