Official documents also revealed that tens of thousands of lifts across the city might need additional safety devices to prevent similar mishaps.

Couple in hospital after lift smashes into top of Hong Kong building

How did the accident happen?

At 4pm on Sunday a couple living in Block 2 of private estate Waterside Plaza in Tsuen Wan entered a 27-year-old lift on the ground floor.

The lift was manufactured by Dongyang Elevator, a South Korean firm later taken over by German multinational thyssenkrupp.

The pair pressed the button for the 15th floor, but instead of stopping on the intended level, the lift continued its ascent until it smashed into the top of the building. The couple, both 32, suffered serious head and neck injuries. 

They were rushed to Princess Margaret Hospital and were in a critical state on Monday. By Tuesday they were in a stable condition. 

Following the accident, residents claimed that lifts in the estate were often faulty and had trapped passengers on multiple occasions.

Lift crash estate residents reveal previous incidents at Tsuen Wan complex

A similar incident occurred in Block 1 of the estate in January 2014, but no one was injured. The lift in that case had been under inspection and ascended to the top of the lift shaft. 

Lift incidents involving casualties are not uncommon in the city.

In October 2014, a lift at Selwyn Factory Building in Kwun Tong fell 12 floors, injuring 29 people. An investigation showed it had been overloaded and that the brake system had failed to stop the lift from descending.

What could have caused the latest incident?

An investigation is still under way, but preliminary results from the Electrical and Mechanical Services Department show the suspension ropes of the lift were intact. 

“The cause of the incident might have been insufficient traction between the suspension ropes and the traction sheave or the failure of the braking system,” the department said, adding that such occurrences were “rare”.

Vocational Training Council principal instructor in mechanical and manufacturing engineering, Charles Wong Kai-hon, said the department’s explanation was reasonable.

Wong said all lifts were equipped with “speed reduction devices” that signalled braking systems to slow down passenger compartments before they reached the top of buildings.

Lift that dropped 12 floors in Hong Kong factory was overloaded, report says

“Even if [the compartment] failed to stop at the 15th floor, the device will slow it before it arrives at the 46th floor,” he said of the recent incident.

Wong said the lift compartment in that case “went through” the top floor into the top end of the shaft.

He said he suspected the braking system had been faulty or a signalling issue had stopped the brakes from being activated.

What are registered lift contractors required to do?

Contractors are required by law to maintain and repair lifts every month and conduct a thorough inspection each year.

The lift involved in the Sunday accident is maintained by KONE Elevator (HK), and was last checked on March 26, showing no abnormality.

There are currently 15 contractors in the city that maintain about 300 lifts manufactured by Dongyang Elevator. One of the contractors, Chevalier Group, manages about a third of all Dongyang-made lifts in Hong Kong.

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What safety devices can be installed to prevent the uncontrolled movement of lifts?

Wong said all lifts were equipped with a safety gear preventing a high-speed descent or “free fall”. 

According to the Electrical and Mechanical Services Department’s “guidelines for modernising existing lifts,” the gear can stop a lift compartment from falling even if the suspension cables break.

Wong also said a “rope gripper” device could prevent uncontrolled ascent and unintended movements by holding the compartment in place.

The rope gripper, however, is not required by law on older lifts, such as the one involved in the latest accident.

How many lifts in Hong Kong may have inadequate safety devices?

Under existing laws, lifts installed after 2000 must have a safety device preventing them from ascending at high speed, while lifts installed after 2010 must have a device to stop unintended movements.

According to a document published by the Legislative Council Secretariat, there were 63,651 lifts in the city as of March 2016. It also revealed that 52 per cent, or 33,231 lifts, were over 20 years of age in 2016, with only 19 per cent in use for a decade or less.

Hong Kong lift crash prompts urgent inspections of 300 identical models around city

This means more than half of all lifts in Hong Kong might not be equipped with a safety device to stop uncontrolled ascent, and only about a fifth have devices that guard against unintended movements.

How can such accidents be prevented? 

Chevalier Group chairman Kuok Hoi-sang earlier suggested that landlords of old buildings consider replacing entire lift systems.

Kuok, who is also president of the Lift and Escalator Contractors Association, said the Dongyang lifts were “not that old”.

Charles Wong from the Vocational Training Council believed landlords should consider “modernising” their lift systems. Instead of an overhaul, Wong said new components such as control panels, doors and motors could be added to make the machines more reliable.

The process, however, could cost about HK$1 million (US$127,400) for each lift.

Those with smaller funds could still consider a rope gripper for about HK$100,000, he said.