‘Weak chain and jammed springs may have caused escalator accident in Hong Kong mall’

Investigators report cracks in the chain, and a layer of dried grease that prevented a backup safety device from working

PUBLISHED : Wednesday, 19 April, 2017, 4:53pm
UPDATED : Wednesday, 19 April, 2017, 10:30pm

An escalator accident in a Hong Kong mall which injured 18 people may have been caused by a weakened metal chain and jammed springs, government inspectors have said.

A government official said it was the first time this kind of accident had happened in Hong Kong.

The Electrical and Mechanical Services Department confirmed to lawmakers on Wednesday that the metal drive chain – which connects the machine’s motor and main brake to a wheel that moves the steps – had broken, while a safety device that detects that kind of problem failed to activate a backup brake.

On March 25, Hong Kong’s tallest escalator – 45 metres long and 21 metres high – at Langham Place in Mong Kok suddenly reversed at high speed, dumping shoppers quickly to the ground.

Investigators found cracks in segments of the chain, while one of two springs in the “broken chain safety device” was discovered to have been stuck in a layer of dried grease, preventing the device from functioning properly.

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“[Both] the breakage of the driving chain and failure of the safety device to activate [led to the incident], so we are classifying this as a double malfunction,” said assistant director for electrical and mechanical services Eric Pang Yiu-hung. “From our memory, this should be the first time this has happened in Hong Kong.”

The kind of drive chain that the Mong Kok escalator used is designed to withstand weight five times what the escalator can carry at full capacity, Pang added.

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“Since this escalator can accommodate 170 passengers, the chain should have been able to sustain the weight of around 850 passengers,” he said. “At the time [of the incident], there were only about 120 people on the escalator.”

Pang was presenting the latest findings of the investigation to the Legislative Council’s panel on development at a special meeting on lift and escalator safety on Wednesday morning. The probe is expected to be completed next month.