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Sensor failure suspected cause of collapsed gate that killed security guard in Hong Kong

South China Morning Post logo South China Morning Post 17/08/2022 Nadia Lam
  • Engineering expert says falling structure could generate 816kg of force at speed faster than human reaction time
  • Head of industrial accident concern group urges authorities to enforce detailed checks at similar structures citywide

A fatal accident involving the collapse of a motorised metal gate at a government health centre in Hong Kong may have been caused by sensor failure, according to an engineering expert.

On Monday night, a 4.7-by-2.5-metre metal gate at a maternal and child health centre in Yau Ma Tei fell and killed a 43-year-old female security guard. The case has been classified as an industrial accident and a police investigation is under way.

Lo Kok-keung, a retired veteran engineer from Polytechnic University, suggested the accident involved maintenance problems, including rusted or loose parts and sensor failure.

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Hong Kong security guard dies after metal gate collapses on her

"When it is opening, a small part of the gate should still remain on the track ... the entire gate will not come out. If it does, there will be nothing supporting the gate and it will collapse," Lo told a radio programme on Wednesday.

He said a sensor installed within the gate's electric motor would stop the structure from completely moving off the track, suggesting a malfunction could be the cause.

Lo said the gate could generate 1,800 pounds (816kg) of force when it hit the security guard, and injury was inevitable as the falling speed of the electric metal gate ranged from 0.5 to 0.7 seconds, much faster than a human's reaction time of 0.9 seconds.

He suggested pedestrians stay away from moving electric gates, while security guards should notify their manager or maintenance staff if they detected abnormal noises or traction difficulties in the devices.

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The Yaumatei Maternal and Child Health Centre was relocated to Yan Cheung Road in April 2020 due to the construction of the Central Kowloon Route. The scene of the accident was on Tuesday sealed off and guarded by police. People were still able to enter the health centre using a gate next to a car park.

Siu Sin-man, chief executive of the Association for the Rights of Industrial Accident Victims, said a similar accident involving a six-by-two-metre manual gate also happened at a shopping centre in San Tin three years ago, killing a 62-year-old security guard.

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She said she had learned from security guards working at other places that some maintenance companies only conducted checks and tests on their gates once a month instead of once weekly as required by the Electrical and Mechanical Services Department.

Siu urged authorities to review the safety of all electrical gates in the city and require property management companies or building owners to arrange detailed inspections.

"I hope the government can draw a lesson from past accidents and give an account to the public apart from only saying that they are 'highly concerned'," she said.

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This article originally appeared on the South China Morning Post (, the leading news media reporting on China and Asia.

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